Showing 1–50 of 54 results for author: Lin, W

Best Reaction Target To Determine Proton Distribution Radii of Atomic Nuclei

Authors: Jun-Yao Xu, Bao-Hua Sun, Isao Tanihata, Satoru Terashima, Jian-Wei Zhao, Ji-Chao Zhang, Ge Guo, Shi-Tao Wang, Lei Shen, Jun Su, Xiao-Dong Xu, Andrej Prochazka, Guang-Shuai Li, Xiu-Lin Wei, Chang-Jian Wang, Feng Wang, Meng Wang, Jing Wang, Liu-Chun He, Chuan-Ye Liu, Wen-Jian Lin, Wei-Ping Lin, Zhong Liu, Pei-Pei Ren, Yu Zhang , et al. (7 additional authors not shown)

Abstract: We found that a heavy target such as Pb is most suitable for determining the proton distribution radii of unstable nuclei through charge-changing cross-section ($σ_\text{cc}$) measurements. As a heavy ion probe, low-$Z$ targets are routinely used to determine nucleon distribution radii of unstable isotopes. This approach has recently been extended to study proton distribution radii from… ▽ More We found that a heavy target such as Pb is most suitable for determining the proton distribution radii of unstable nuclei through charge-changing cross-section ($σ_\text{cc}$) measurements. As a heavy ion probe, low-$Z$ targets are routinely used to determine nucleon distribution radii of unstable isotopes. This approach has recently been extended to study proton distribution radii from $σ_\text{cc}$ measurements. However, empirical scaling factors have to be introduced to apply the Glauber models. In the present work, we systematically investigated the scaling factor using 39 new $σ_\text{cc}$ data of 18 $p$-shell nuclei on hydrogen, carbon, silver, and lead targets at around 240 MeV/nucleon. Together with the existing data, we reveal a universal dependence of the scaling factor on both the masses of target nuclei and the separation energies of projectile nuclei. The scaling factors decrease with increasing target-nucleus mass and converge to 1 for the highest-$Z$ target, making the scaling unnecessary. We conclude that instead of a low-$Z$ target, employing a heavy target such as Pb in $σ_\text{cc}$ measurements is the best option to determine the proton distribution radii of unstable nuclei. △ Less

Submitted 14 August, 2026; originally announced August 2026.

ePIC Early Science Report

Authors: D. Abbott, N. Abdelrahman, S. Abhijit, I. Abualrob, R. B. Achari, J. Adam, L. Adamczyk, K. Adkins, A. Affolder, K. Agarwal, J. Agarwala, N. Agrawal, C. A. Aidala, W. Akers, A. Al-bataineh, S. N. Alam, M. Alekseev, P. R. Altieri, J. -S. Alvarado Gallenao, S. B. L. Amar, R. Ammendola, I. Amos Cali, G. An, D. Anderson, E. Anderssen , et al. (774 additional authors not shown)

Abstract: This Early Science Report from the ePIC Collaboration outlines the compelling physics program achievable during the first years of operation of the Electron-Ion Collider (EIC), prior to the establishment of the full design luminosity and energy range. The analyses are based on realistic early-running beam configurations and detailed Geant4 ePIC detector simulations, hit digitization and data recon… ▽ More This Early Science Report from the ePIC Collaboration outlines the compelling physics program achievable during the first years of operation of the Electron-Ion Collider (EIC), prior to the establishment of the full design luminosity and energy range. The analyses are based on realistic early-running beam configurations and detailed Geant4 ePIC detector simulations, hit digitization and data reconstruction. The projected studies from the physics working groups of ePIC span inclusive, semi-inclusive, exclusive, diffractive and tagging, as well as jet and heavy flavor measurements in both electron-proton and electron-ion collisions. Even before the collider reaches its full design performance, these measurements will constrain parton distribution functions in nucleons and nuclei, access transverse-momentum-dependent and spin-dependent observables, probe gluon dynamics in nuclei, and initiate a program of imaging of quarks and gluons. Each measurement is directly connected to the core science pillars of the EIC, identified in the 2018 report by the National Academy of Sciences: understanding the origin of the nucleon mass, unraveling the spin structure of the nucleon, and exploring the emergent properties of dense gluonic matter. The results presented here provide examples that demonstrate that the early years of EIC running with ePIC will deliver novel world-leading insights into Quantum Chromodynamics. In addition, the early science program will establish measurement and analysis methodologies that will pave the way to the subsequent full EIC physics program. △ Less

Submitted 5 August, 2026; originally announced August 2026.

Report number: epic-AN-AC-2026-004

Nuclear shell evolution near N = 6, 14, 20 and 28: insights from nuclear charge radii of short-lived nuclei derived from binding energies

Authors: Xingquan Liu, Wanjun Chen, Xing Xu, Yi Hua Lam, Hua Zheng, Jianfeng Han, Weiping Lin, Xi Duan, Xin Zhang, Peipei Ren

Abstract: A deep understanding of the evolution of nuclear shell structure correlating with the nucleon number is crucial for unraveling the fundamental properties of the nuclear structure and for exploring new nuclear physics phenomena far from the $β$-stability line. Although significant progress has been made in probing nuclear shell evolution via the measurements of nuclear root-mean-square charge radii… ▽ More A deep understanding of the evolution of nuclear shell structure correlating with the nucleon number is crucial for unraveling the fundamental properties of the nuclear structure and for exploring new nuclear physics phenomena far from the $β$-stability line. Although significant progress has been made in probing nuclear shell evolution via the measurements of nuclear root-mean-square charge radii, $R_{\text{ch}}$, the scarcity of new data for short-lived and exotic nuclei due to the increasing difficulty of measurements presents a formidable challenge in obtaining deeper and more universal insights into the nature of shell evolution. To mitigate this issue, we develop an improved method, accounting for the exchange term, charge-symmetry breaking effect, and odd-even staggering effect in the Coulomb energy formulation compared with that proposed by Liu et al. [Phys. Lett. B 872, 140046 (2026)], to determine unmeasured $R_{\text{ch}}$ values. Using the improved method, the $R_{\text{ch}}$ values of 59 nuclei are determined from their measured binding energies ($B$) and the respective $B$ and $R_{\text{ch}}$ of their mirror partners. We then systematically study the shell evolution near $N=6$, 14, 20 and 28 (sub)shells by placing the newly obtained $R_{\text{ch}}$ values into the corresponding isotopic chains. More comprehensive insights into the properties of nuclear shell evolution, particularly for the neutron-deficient sectors of the studied shell regions, e.g., $p$, $sd$ and $pf$ shells, are acquired, advancing our understanding of nuclear shell evolution in the light and intermediate mass region. △ Less

Submitted 1 July, 2026; originally announced July 2026.

Comments: 13 pages, 6 figures, 2 tables

Using Neural Networks to Accelerate TALYS-2.0 Nuclear Reaction Simulations

Authors: Wilson Lin, Catherine E Apgar, Lee A Bernstein, YunHsuan Lee, Alan B McIntosh, Dmitri G Medvedev, Ellen M OBrien, Christiaan E Vermeulen, Andrew S Voyles, Jonathan T Morrell

Abstract: Recent efforts to improve the predictability of TALYS-2.0 calculated charged-particle residual product cross sections have focused on adjusting parameters related to the optical model potential and pre-equilibrium process. Although adjusted TALYS-2.0 outputs show marked improvements in agreement with experimental data over the default parameters, the procedure is generally time-consuming due to th… ▽ More Recent efforts to improve the predictability of TALYS-2.0 calculated charged-particle residual product cross sections have focused on adjusting parameters related to the optical model potential and pre-equilibrium process. Although adjusted TALYS-2.0 outputs show marked improvements in agreement with experimental data over the default parameters, the procedure is generally time-consuming due to the need for sequential TALYS-2.0 calculations. Since the models and model parameters must be defined and constrained prior to adjustment, we show in this work that an artificial neural network can serve as a surrogate model to successfully predict TALYS-2.0 outputs within this domain of input parameters. No practical differences were observed in the trained model's performance between uniform random, Latin hypercube and Sobol sequence sampling for generating the training datasets. Once validated, trained neural network models were used to adjust TALYS-2.0 nuclear model parameters, where a multi-parameter fitting procedure was not only feasible but optimal for this process. The neural network approach is >1000x faster at generating residual product cross sections than using TALYS-2.0 directly, and a high-fidelity surrogate model could be implemented with about 1500 TALYS-2.0 files to achieve adjusted cross sections comparable to the previous publication. △ Less

Submitted 13 February, 2026; originally announced February 2026.

Comments: 10 pages, 3 figures, 10 supplementary figures

Characterizing Secondary Neutrons at BLIP for Isotope Production Applications

Authors: Wilson Lin, Michael A. Skulski, Cathy S. Cutler, Dmitri G. Medvedev, Jonathan T. Morrell

Abstract: Fast secondary neutrons created at the Brookhaven Linac Isotope Producer (BLIP) facility following proton irradiation were characterized by the foil activation technique and compared with FLUKA Monte Carlo simulations. The FLUKA-simulated neutron flux was spectrally adjusted following the maximum entropy formalism using the International Reactor Dosimetry and Fusion File (IRDFF-II), with predictio… ▽ More Fast secondary neutrons created at the Brookhaven Linac Isotope Producer (BLIP) facility following proton irradiation were characterized by the foil activation technique and compared with FLUKA Monte Carlo simulations. The FLUKA-simulated neutron flux was spectrally adjusted following the maximum entropy formalism using the International Reactor Dosimetry and Fusion File (IRDFF-II), with predictions agreeing with experimental measurements to within 9% following the adjustment procedure. A multitude of degrader configurations were simulated to assess the feasibility of improving the fast (En > 20 MeV) secondary neutron yield at the proposed neutron target position (N-slot). A configuration where the N-slot is closest to the proton degrader produced the highest fast neutron yield, with tungsten degraders achieving the best performance. Assuming the optimized target-degrader configuration proposed in this work, we discuss potential isotope production opportunities with secondary neutrons. In most cases the yields are in the order of several mCi. △ Less

Submitted 2 February, 2026; originally announced February 2026.

Comments: 20 pages, 5 figures, published in NIMB

Journal ref: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 567 (2025): 165815

The MUSE Target Chamber Post Veto

Authors: R. Ratvasky, T. Rostomyan, M. Ali, H. Atac, F. Barchetti, J. C. Bernauer, W. J. Briscoe, A. Christopher Ndukwe, E. W. Cline, S. Das, K. Deiters, E. J. Downie, Z. Duan, A. Flannery, M. Foster, A. Friebolin, M. Gantert, R. Gilman, A. Golossanov, J. Guo, J. Hirschman, A. Hofer, N. S. Ifat, Y. Ilieva, D. Jayakodige , et al. (24 additional authors not shown)

Abstract: The Muon Scattering Experiment (MUSE) was developed to address the proton radius puzzle through simultaneous electron-proton and muon-proton scattering using the Paul Scherrer Institute's PiM1 secondary beamline. MUSE uses a large-solid-angle, non-magnetic spectrometer to detect beam particles scattering from a liquid hydrogen cell contained within a vacuum chamber. Due to the large scattering win… ▽ More The Muon Scattering Experiment (MUSE) was developed to address the proton radius puzzle through simultaneous electron-proton and muon-proton scattering using the Paul Scherrer Institute's PiM1 secondary beamline. MUSE uses a large-solid-angle, non-magnetic spectrometer to detect beam particles scattering from a liquid hydrogen cell contained within a vacuum chamber. Due to the large scattering windows, the structural integrity of the chamber is supported by posts located at small scattering angles. While out of the acceptance, particles in the tails of the beam distribution can strike these posts, causing a significant trigger background. We describe the design and performance of the Target Chamber Post Veto (TCPV) detector installed inside the vacuum chamber to remove these background events at the trigger level. △ Less

Submitted 26 April, 2026; v1 submitted 10 February, 2026; originally announced February 2026.

Comments: 23 pages, 22 figures

Realizing the Scientific Program with Polarized Ion Beams at EIC

Authors: Grigor Atoian, Nigel Buttimore, Giuseppe Ciullo, Ian Cloet, Marco Contalbrigo, Jaydeep Datta, Abhay Deshpande, Shubham Dutta, Oleg Eyser, Muhammad Farooq, Renee Fatemi, Ishara Fernando, Michael Finger, Wolfram Fischer, Dave Gaskell, Prakash Gautam, Ralf Gebel, Boxing Gou, Daoning Gu, Yoshitaka Hatta, Mohammad Hattawy, Volker Hejny, Kiel Hock, Georg Hoffstaetter, Haixin Huang , et al. (45 additional authors not shown)

Abstract: Polarized ion beams at the Electron Ion Collider are essential to address some of the most important open questions at the twenty-first century frontiers of understanding of the fundamental structure of matter. Here, we summarize the science case and identify polarized $^2$H, $^3$He, $^6$Li and $^7$Li ion beams as critical technology that will enable experiments which address the most important sc… ▽ More Polarized ion beams at the Electron Ion Collider are essential to address some of the most important open questions at the twenty-first century frontiers of understanding of the fundamental structure of matter. Here, we summarize the science case and identify polarized $^2$H, $^3$He, $^6$Li and $^7$Li ion beams as critical technology that will enable experiments which address the most important science. Further, we discuss the required ion polarimetry and spin manipulation in EIC. The current EIC accelerator design is presented. We identify a significant R\&D effort involving both national laboratories and universities that is required over about a decade to realize the polarized ion beams and estimate (based on previous experience) that it will require about 20 FTE over 10 years (or a total of about 200 FTE-years) of personnel, including graduate students, postdoctoral researchers, technicians and engineers. Attracting, educating and training a new generation of physicists in experimental spin techniques will be essential for successful realization. AI/ML is seen as having significant potential for both acceleration of R\&D and amplification of discovery in optimal realization of this unique quantum technology on a cutting-edge collider. The R\&D effort is synergistic with research in atomic physics and fusion energy science. △ Less

Submitted 12 October, 2025; originally announced October 2025.

Comments: 47 pages, 24 figures; submitted to Phys. Rev. C (PRC)

Vector meson dominance in photon structure functions at small $x$ from holography

Authors: Wei Gao, Siming Liu, Wenbin Lin, Akira Watanabe

Abstract: We investigate the photon structure functions via the photon-photon and photon-vector meson scattering within the framework of holographic QCD, focusing on the small Bjorken $x$ region and assuming that the Pomeron exchange dominates. The quasi-real photon structure functions are formulated as the convolution of the known U(1) vector field wave function with the Brower-Polchinski-Strassler-Tan (BP… ▽ More We investigate the photon structure functions via the photon-photon and photon-vector meson scattering within the framework of holographic QCD, focusing on the small Bjorken $x$ region and assuming that the Pomeron exchange dominates. The quasi-real photon structure functions are formulated as the convolution of the known U(1) vector field wave function with the Brower-Polchinski-Strassler-Tan (BPST) Pomeron exchange kernel in the five-dimensional AdS space. Assuming the vector meson dominance, the photon structure functions can be calculated in a different way with the BPST kernel and vector meson gravitational form factor, which can be obtained in a bottom-up AdS/QCD model, for the Pomeron-vector meson coupling. It is shown that the obtained $F_2$ structure functions in the both ways agree with the experimental data, which implies the realization of the vector meson dominance within the present model setup. Calculations for the longitudinal structure function and the longitudinal-to-transverse ratio are also presented. △ Less

Submitted 27 October, 2025; v1 submitted 11 August, 2025; originally announced August 2025.

Comments: 13 pages, 5 figures, version accepted for publication in Phys. Rev. D

Role of nuclear and electromagnetic fragmentation in the charge-changing reactions of 18O on carbon and lead targets at around 370 MeV/nucleon

Authors: J. R. Liu, B. -H. Sun, J. W. Zhao, G. Guo, G. S. Li, Z. Z. Li, Y. F. Niu, I. Tanihata, S. Terashima, F. Wang, M. Wang, X. L. Wei, J. Y. Xu, J. C. Zhang, L. H. Zhu, L. C. He, C. Y. Liu, C. G. Lu, W. J. Lin, W. P. Lin, Z. Liu, P. P. Ren, Y. Z. Sun, Z. Y. Sun, J. Wang , et al. (5 additional authors not shown)

Abstract: Charge-changing cross sections (CCCSs) of 18O on carbon (C) and lead (Pb) targets have been measured with an uncertainty of less than 4% at around 370MeV/nucleon. We evaluate the contributions of nucleon-nucleon (NN) and electromagnetic (EM) interactions to CCCSs by considering the direct proton removal process, the charged particle evaporation (CPE) after neutron removal, and the EM excitation. W… ▽ More Charge-changing cross sections (CCCSs) of 18O on carbon (C) and lead (Pb) targets have been measured with an uncertainty of less than 4% at around 370MeV/nucleon. We evaluate the contributions of nucleon-nucleon (NN) and electromagnetic (EM) interactions to CCCSs by considering the direct proton removal process, the charged particle evaporation (CPE) after neutron removal, and the EM excitation. We conclude that the CPE accounts for 12.3% and 5% of CCCSs on C and Pb, respectively. Only less than 1% of CCCSs of 18O is attributed to the EM excitation. Further investigation of projectiles from 18O to 197Au on C, silver (Ag) and Pb targets at 300 and 900MeV/nucleon show that the contribution of EM to CCCSs on Ag and Pb increases with projectile mass numbers and incident energies, and can reach 10% for 197Au on Pb at 900MeV/nucleon. In contrast, the EM contribution to CCCS is negligible for all projectiles on C at both energies. △ Less

Submitted 19 June, 2025; originally announced June 2025.

Journal ref: Phys. Rev. C112, 014611(2025)

Enhanced $S$-factor for the $^{14}$N$(p,γ)^{15}$O reaction and its impact on the solar composition problem

Authors: X. Chen, J. Su, Y. P. Shen, L. Y. Zhang, J. J. He, S. Z. Chen, S. Wang, Z. L. Shen, S. Lin, L. Y. Song, H. Zhang, L. H. Wang, X. Z. Jiang, L. Wang, Y. T. Huang, Z. W. Qin, F. C. Liu, Y. D. Sheng, Y. J. Chen, Y. L. Lu, X. Y. Li, J. Y. Dong, Y. C. Jiang, Y. Q. Zhang, Y. Zhang , et al. (23 additional authors not shown)

Abstract: The solar composition problem has puzzled astrophysicists for more than 20 years. Recent measurements of carbon-nitrogen-oxygen (CNO) neutrinos by the Borexino experiment show a $\sim2σ$ tension with the "low-metallicity" determinations. $^{14}$N$(p,γ)^{15}$O, the slowest reaction in the CNO cycle, plays a crucial role in the standard solar model (SSM) calculations of CNO neutrino fluxes. Here we… ▽ More The solar composition problem has puzzled astrophysicists for more than 20 years. Recent measurements of carbon-nitrogen-oxygen (CNO) neutrinos by the Borexino experiment show a $\sim2σ$ tension with the "low-metallicity" determinations. $^{14}$N$(p,γ)^{15}$O, the slowest reaction in the CNO cycle, plays a crucial role in the standard solar model (SSM) calculations of CNO neutrino fluxes. Here we report a direct measurement of the $^{14}$N$(p,γ)^{15}$O reaction, in which $S$-factors for all transitions were simultaneously determined in the energy range of $E_p=110-260$ keV for the first time. Our results resolve previous discrepancies in the ground-state transition, yielding a zero-energy $S$-factor $S_{114}(0) = 1.92\pm0.08$ keV b which is 14% higher than the $1.68\pm0.14$ keV b recommended in Solar Fusion III (SF-III). With our $S_{114}$ values, the SSM B23-GS98, and the latest global analysis of solar neutrino measurements, the C and N photospheric abundance determined by the Borexino experiment is updated to $N_{\mathrm{CN}}=({4.45}^{+0.69}_{-0.61})\times10^{-4}$. This new $N_{\mathrm{CN}}$ value agrees well with latest "high-metallicity" composition, however, is also consistent with the "low-metallicity" determination within $\sim 1σ$ C.L., indicating that the solar metallicity problem remains an open question. In addition, the significant reduction in the uncertainty of $S_{114}$ paves the way for the precise determination of the CN abundance in future large-volume solar neutrino measurements. △ Less

Submitted 21 October, 2024; originally announced October 2024.

The MUSE Beamline Calorimeter

Authors: W. Lin, T. Rostomyan, R. Gilman, S. Strauch, C. Meier, C. Nestler, M. Ali, H. Atac, J. C. Bernauer, W. J. Briscoe, A. Christopher Ndukwe, E. W. Cline, K. Deiters, S. Dogra, E. J. Downie, Z. Duan, I. P. Fernando, A. Flannery, D. Ghosal, A. Golossanov, J. Guo, N. S. Ifat, Y. Ilieva, M. Kohl, I. Lavrukhin , et al. (18 additional authors not shown)

Abstract: The MUon Scattering Experiment (MUSE) was motivated by the proton radius puzzle arising from the discrepancy between muonic hydrogen spectroscopy and electron-proton measurements. The MUSE physics goals also include testing lepton universality, precisely measuring two-photon exchange contribution, and testing radiative corrections. MUSE addresses these physics goals through simultaneous measuremen… ▽ More The MUon Scattering Experiment (MUSE) was motivated by the proton radius puzzle arising from the discrepancy between muonic hydrogen spectroscopy and electron-proton measurements. The MUSE physics goals also include testing lepton universality, precisely measuring two-photon exchange contribution, and testing radiative corrections. MUSE addresses these physics goals through simultaneous measurement of high precision cross sections for electron-proton and muon-proton scattering using a mixed-species beam. The experiment will run at both positive and negative beam polarities. Measuring precise cross sections requires understanding both the incident beam energy and the radiative corrections. For this purpose, a lead-glass calorimeter was installed at the end of the beam line in the MUSE detector system. In this article we discuss the detector specifications, calibration and performance. We demonstrate that the detector performance is well reproduced by simulation, and meets experimental requirements. △ Less

Submitted 23 August, 2024; originally announced August 2024.

Single-proton removal reaction in the IQMD+GEMINI model benchmarked by elemental fragmentation cross sections of $^{29-33}\mathrm{Si}$ on carbon at $\sim$230~MeV/nucleon

Authors: Guang-Shuai Li, Jun Su, Satoru Terashima, Jian-Wei Zhao, Er-Xi Xiao, Ji-Chao Zhang, Liu-Chun He, Ge Guo, Wei-Ping Lin, Wen-Jian Lin, Chuan-Ye Liu, Chen-Gui Lu, Bo Mei, Dan-Yang Pang, Ye-Lei Sun, Zhi-Yu Sun, Meng Wang, Feng Wang, Jing Wang, Shi-Tao Wang, Xiu-Lin Wei, Xiao-Dong Xu, Jun-Yao Xu, Li-Hua Zhu, Yong Zheng , et al. (2 additional authors not shown)

Abstract: We report on the first measurement of the elemental fragmentation cross sections (EFCSs) of $^{29-33}\mathrm{Si}$ on a carbon target at $\sim$230~MeV/nucleon. The experimental data covering charge changes of $ΔZ$ = 1-4 are reproduced well by the isospin-dependent quantum molecular dynamics (IQMD) coupled with the evaporation GEMINI (IQMD+GEMINI) model. We further explore the mechanisms underlying… ▽ More We report on the first measurement of the elemental fragmentation cross sections (EFCSs) of $^{29-33}\mathrm{Si}$ on a carbon target at $\sim$230~MeV/nucleon. The experimental data covering charge changes of $ΔZ$ = 1-4 are reproduced well by the isospin-dependent quantum molecular dynamics (IQMD) coupled with the evaporation GEMINI (IQMD+GEMINI) model. We further explore the mechanisms underlying the single-proton removal reaction in this model framework. We conclude that the cross sections from direct proton knockout exhibit a overall weak dependence on the mass number of $\mathrm{Si}$ projectiles. The proton evaporation induced after the projectile excitation significantly affects the cross sections for neutron-deficient $\mathrm{Si}$ isotopes, while neutron evaporation plays a crucial role in the reactions of neutron-rich $\mathrm{Si}$ isotopes. It is presented that the relative magnitude of one-proton and one-neutron separation energies is an essential factor that influences evaporation processes. △ Less

Submitted 19 July, 2024; originally announced July 2024.

Comments: 7 pages, 4 figures

Journal ref: Physics Letters B 859 (2024) 139143

Charge radii of $^{11-16}$C, $^{13-17}$N and $^{15-18}$O determined from their charge-changing cross-sections and the mirror-difference charge radii

Authors: J. W. Zhao, B. -H. Sun, I. Tanihata, J. Y. Xu, K. Y. Zhang, A. Prochazka, L. H. Zhu, S. Terashima, J. Meng, L. C. He, C. Y. Liu, G. S. Li, C. G. Lu, W. J. Lin, W. P. Lin, Z. Liu, P. P Ren, Z. Y. Sun, F. Wang, J. Wang, M. Wang, S. T. Wang, X. L. Wei, X. D. Xu, J. C. Zhang , et al. (2 additional authors not shown)

Abstract: Charge-changing cross-sections of $^{11-16}$C, $^{13-17}$N and $^{15-18}$O on a carbon target have been determined at energies around 300 MeV/nucleon. A nucleon separation energy-dependent correction factor has been introduced to the Glauber model calculation for extracting the nuclear charge radii from the experimental CCCSs. The charge radii of $^{11}$C, $^{13,16}$N and $^{15}$O thus were determ… ▽ More Charge-changing cross-sections of $^{11-16}$C, $^{13-17}$N and $^{15-18}$O on a carbon target have been determined at energies around 300 MeV/nucleon. A nucleon separation energy-dependent correction factor has been introduced to the Glauber model calculation for extracting the nuclear charge radii from the experimental CCCSs. The charge radii of $^{11}$C, $^{13,16}$N and $^{15}$O thus were determined for the first time. With the new radii, we studied the experimental mirror-difference charge radii ($ΔR_{\text {ch}}^{\text {mirror}}$) of $^{11}$B-$^{11}$C, $^{13}$C-$^{13}$N, $^{15}$N-$^{15}$O, $^{17}$N-$^{17}$Ne pairs for the first time. We find that the $ΔR_{\text {ch}}^{\text {mirror}}$ values of $^{13}$C-$^{13}$N and $^{15}$N-$^{15}$O pairs follow well the empirical relation to the isospin asymmetry predicted by the $ab$ $initio$ calculations, while $ΔR_{\text {ch}}^{\text {mirror}}$ of $^{11}$B-$^{11}$C and $^{17}$N-$^{17}$Ne pairs deviate from such relation by more than two standard deviations. △ Less

Submitted 16 October, 2024; v1 submitted 14 July, 2024; originally announced July 2024.

Comments: 3 figures, submitted to Physics Letters B

Quantum-number projected generator coordinate method for $^{21}$Ne with a chiral two-nucleon-plus-three-nucleon interaction

Authors: W. Lin, E. F. Zhou, J. M. Yao, H. Hergert

Abstract: We report a study of the low-lying states of deformed $^{21}$Ne within the framework of quantum-number projected generator coordinate method (PGCM), starting from a chiral two-nucleon-plus-three-nucleon (NN+3N) interaction. The wave functions of states are constructed as a linear combination of a set of axially-deformed Hartree-Fock-Bogliubov (HFB) wave functions with different quadrupole deformat… ▽ More We report a study of the low-lying states of deformed $^{21}$Ne within the framework of quantum-number projected generator coordinate method (PGCM), starting from a chiral two-nucleon-plus-three-nucleon (NN+3N) interaction. The wave functions of states are constructed as a linear combination of a set of axially-deformed Hartree-Fock-Bogliubov (HFB) wave functions with different quadrupole deformations. These HFB wave functions are projected onto different angular momenta and the correct neutron and proton numbers for $^{21}$Ne. The results of calculations based on the effective Hamiltonians derived by normal-ordering the 3N interaction with respect to three different reference states, including the quantum-number projected HFB wave functions for $^{20}$Ne, $^{22}$Ne, and an ensemble of them with equal weights, are compared. This study serves as a key step towards ab initio calculations of odd-mass deformed nuclei with the in-medium GCM. △ Less

Submitted 1 October, 2024; v1 submitted 2 March, 2024; originally announced March 2024.

Comments: 22page, 8 figures, an invited contribution to the special issue of Symmetry journal: "Restoration of Broken Symmetries in the Nuclear Many-Body Problem", edited by Prof. Javid Sheikh and Prof. Peter Ring

Journal ref: Symmetry 16, 409 (2024)

Isospin-dependence of the charge-changing cross-section shaped by the charged-particle evaporation process

Authors: J. W. Zhao, B. -H. Sun, I. Tanihata, S. Terashima, A. Prochazka, J. Y. Xu, L. H. Zhu, J. Meng, J. Su, K. Y. Zhang, L. S. Geng, L. C. He, C. Y. Liu, G. S. Li, C. G. Lu, W. J. Lin, W. P. Lin, Z. Liu, P. P Ren, Z. Y. Sun, F. Wang, J. Wang, M. Wang, S. T. Wang, X. L. Wei , et al. (4 additional authors not shown)

Abstract: We present the charge-changing cross sections (CCCS) of $^{11-15}$C, $^{13-17}$N, and $^{15,17-18}$O at around 300 MeV/nucleon on a carbon target, which extends to $p$-shell isotopes with $N < Z$ for the first time. The Glauber model, which considers only the proton distribution of projectile nuclei, underestimates the cross sections by more than 10\%. We show that this discrepancy can be resolved… ▽ More We present the charge-changing cross sections (CCCS) of $^{11-15}$C, $^{13-17}$N, and $^{15,17-18}$O at around 300 MeV/nucleon on a carbon target, which extends to $p$-shell isotopes with $N < Z$ for the first time. The Glauber model, which considers only the proton distribution of projectile nuclei, underestimates the cross sections by more than 10\%. We show that this discrepancy can be resolved by considering the contribution from the charged-particle evaporation process (CPEP) following projectile neutron removal. Using nucleon densities from the deformed relativistic Hartree-Bogoliubov theory in continuum, we investigate the isospin-dependent CPEP contribution to the CCCS for a wide range of neutron-to-proton separation energy asymmetry. Our calculations, which include the CPEP contribution, agree well with existing systematic data and reveal an ``evaporation peak" at the isospin symmetric region where the neutron-to-proton separation energy is close to zero. These results suggest that analysis beyond the Glauber model is crucial for accurately determining nuclear charge radii from CCCSs. △ Less

Submitted 21 October, 2023; originally announced October 2023.

Comments: 5 figures

Journal ref: Phys. Lett. B 847 (2023) 138269

Blinding for precision scattering experiments: The MUSE approach as a case study

Authors: J. C. Bernauer, E. W. Cline, H. Atac, W. J. Briscoe, A. Christopher Ndukwe, E. J. Downie, I. P. Fernando, T. Gautam, R. Gilman, R. Goldin, M. Kohl, I. Lavrukhin, W. Lin, W. Lorenzon, P. Mohanmurthy, S. J. Nazeer, M. Nicol, T. Patel, A. Prosnyakov, R. D. Ransome, R. Ratvasky, H. Reid, P. E. Reimer, G. Ron, T. Rostomyan , et al. (5 additional authors not shown)

Abstract: Human bias is capable of changing the analysis of measured data sufficiently to alter the results of an experiment. It is incumbent upon modern experiments, especially those investigating quantities considered contentious in the broader community, to blind their analysis in an effort to minimize bias. The choice of a blinding model is experiment specific, but should also aim to prevent accidental… ▽ More Human bias is capable of changing the analysis of measured data sufficiently to alter the results of an experiment. It is incumbent upon modern experiments, especially those investigating quantities considered contentious in the broader community, to blind their analysis in an effort to minimize bias. The choice of a blinding model is experiment specific, but should also aim to prevent accidental release of results before an analysis is finalized. In this paper, we discuss common threats to an unbiased analysis, as well as common quantities that can be blinded in different types of nuclear physics experiments. We use the Muon Scattering Experiment as an example, and detail the blinding scheme used therein. △ Less

Submitted 16 October, 2023; originally announced October 2023.

Comments: 6 pages, 3 figures

Instrumental uncertainties in radiative corrections for the MUSE experiment

Authors: L. Li, S. Strauch, J. C. Bernauer, W. J. Briscoe, A. Christopher Ndukwe, E. Cline, D. Cohen, K. Deiters, E. J. Downie, I. P. Fernando, A. Flannery, R. Gilman, Y. Ilieva, M. Kohl, I. Lavrukhin, W. Lin, W. Lorenzon, S. Lunkenheimer, P. Mohanmurthy, J. Nazeer, M. Nicol, T. Patel, A. Prosnyakov, H. Reid, P. E. Reimer , et al. (5 additional authors not shown)

Abstract: The MUSE experiment at the Paul Scherrer Institute is measuring elastic lepton-proton scattering cross sections in a four-momentum transfer range from $Q^2$ of approximately 0.002 to 0.08 GeV$^2$ using positively and negatively charged electrons and muons. The extraction of the Born cross sections from the experimental data requires radiative corrections. Estimates of the instrumental uncertaintie… ▽ More The MUSE experiment at the Paul Scherrer Institute is measuring elastic lepton-proton scattering cross sections in a four-momentum transfer range from $Q^2$ of approximately 0.002 to 0.08 GeV$^2$ using positively and negatively charged electrons and muons. The extraction of the Born cross sections from the experimental data requires radiative corrections. Estimates of the instrumental uncertainties in those corrections have been made using the ESEPP event generator. The results depend in particular on the minimum lepton momentum that contributes to the experimental cross section and the fraction of events with hard initial-state radiation that is detected in the MUSE calorimeter and is excluded from the data. These results show that the angular-dependent instrumental uncertainties in radiative corrections to the electron cross section are better than 0.4 % and are negligible for the muon cross section. △ Less

Submitted 8 January, 2024; v1 submitted 12 July, 2023; originally announced July 2023.

Comments: Accepted version of the manuscript submitted to the EPJ A Topical Collection on radiative corrections

New measurement of the elemental fragmentation cross sections of 218 MeV/nucleon 28 Si on a carbon target

Authors: Guang-Shuai Li, Jun Su, Bao-Hua Sun, Satoru Terashima, Jian-Wei Zhao, Xiao- Dong Xu, Ji-Chao Zhang, Ge Guo, Liu-Chun He, Wei-Ping Lin, Wen-Jian Lin, Chuan-Ye Liu, Chen-Gui Lu, Bo Mei, Zhi-Yu Sun, Isao Tanihata, Meng Wang, Feng Wang, Shi-Tao Wang, Xiu-Lin Wei, Jing Wang, Jun-Yao Xu, Jin-Rong Liu, Mei-Xue Zhang, Yong Zheng , et al. (2 additional authors not shown)

Abstract: Elemental fragmentation cross sections (EFCSs) of stable and unstable nuclides have been investigated with various projectile-target combinations at a wide range of incident energies. These data are critical to constrain and develop the theoretical reaction models and to study the propagation of galactic cosmic rays (GCR). In this work, we present a new EFCS measurement for $^{28}$Si on carbon at… ▽ More Elemental fragmentation cross sections (EFCSs) of stable and unstable nuclides have been investigated with various projectile-target combinations at a wide range of incident energies. These data are critical to constrain and develop the theoretical reaction models and to study the propagation of galactic cosmic rays (GCR). In this work, we present a new EFCS measurement for $^{28}$Si on carbon at 218~MeV/nucleon performed at the Heavy Ion Research Facility (HIRFL-CSR) complex in Lanzhou. The impact of the target thickness has been well corrected to derive an accurate EFCS. Our present results with charge changes $ΔZ$ = 1-6 are compared to the previous measurements and to the predictions from the models modified EPAX2, EPAX3, FRACS, ABRABLA07, NUCFRG2, and IQMD coupled with GEMINI (IQMD+GEMINI). All the models fail to describe the odd-even staggering strength in the elemental distribution, with the exception of the IQMD+GEMINI model, which can reproduce the EFCSs with an accuracy of better than 3.5\% for $ΔZ\leq5$. The IQMD+GEMINI analysis shows that the odd-even staggering in EFCSs occurs in the sequential statistical decay stage rather than in the initial dynamical collision stage. This offers a reasonable approach to understand the underlying mechanism of fragmentation reactions. △ Less

Submitted 18 February, 2023; originally announced February 2023.

Comments: 13 pages, 8 figures

Journal ref: Phys. Rev. C 107, 024609 (2023)

Optimization of generator coordinate method with machine-learning techniques for nuclear spectra and neutrinoless double-beta decay: ridge regression for nuclei with axial deformation

Authors: X. Zhang, W. Lin, J. M. Yao, C. F. Jiao, A. M. Romero, T. R. Rodríguez, H. Hergert

Abstract: The generator coordinate method (GCM) is an important tool of choice for modeling large-amplitude collective motion in atomic nuclei. The computational complexity of the GCM increases rapidly with the number of collective coordinates. It imposes a strong restriction on the applicability of the method. In this work, we propose a subspace-reduction algorithm that employs optimal statistical ML model… ▽ More The generator coordinate method (GCM) is an important tool of choice for modeling large-amplitude collective motion in atomic nuclei. The computational complexity of the GCM increases rapidly with the number of collective coordinates. It imposes a strong restriction on the applicability of the method. In this work, we propose a subspace-reduction algorithm that employs optimal statistical ML models as surrogates for exact quantum-number projection calculations for norm and Hamiltonian kernels. The model space of the original GCM is reduced to a subspace relevant for nuclear low energy spectra and the NME of ground state to ground state $0νββ$ decay based on the orthogonality condition (OC) and the energy-transition-orthogonality procedure (ENTROP), respectively. For simplicity, the polynomial ridge regression (RR) algorithm is used to learn the norm and Hamiltonian kernels of axially deformed configurations. The efficiency and accuracy of this algorithm are illustrated for 76Ge and 76Se by comparing results obtained using the optimal RR models to direct GCM calculations. The low-lying energy spectra of $^{76}$Ge and $^{76}$Se, as well as the $0νββ$-decay NME between their ground states, are computed. The results show that the performance of the GCM+OC/ENTROP+RR is more robust than that of the GCM+RR alone, and the former can reproduce the results of the original GCM calculation accurately with a significantly reduced computational cost. △ Less

Submitted 23 January, 2023; v1 submitted 4 November, 2022; originally announced November 2022.

Comments: 15 pages with 19 figures

Journal ref: Phys. Rev. C107, 024304 (2023)

Deep underground laboratory measurement of $^{13}$C($α$,$n$)$^{16}$O in the Gamow windows of the $s$- and $i$-processes

Authors: B. Gao, T. Y. Jiao, Y. T. Li, H. Chen, W. P. Lin, Z. An, L. H. Ru, Z. C. Zhang, X. D. Tang, X. Y. Wang, N. T. Zhang, X. Fang, D. H. Xie, Y. H. Fan, L. Ma, X. Zhang, F. Bai, P. Wang, Y. X. Fan, G. Liu, H. X. Huang, Q. Wu, Y. B. Zhu, J. L. Chai, J. Q. Li , et al. (50 additional authors not shown)

Abstract: The $^{13}$C($α$,$n$)$^{16}$O reaction is the main neutron source for the slow-neutron-capture (s-) process in Asymptotic Giant Branch stars and for the intermediate (i-) process. Direct measurements at astrophysical energies in above-ground laboratories are hindered by the extremely small cross sections and vast cosmic-ray induced background. We performed the first consistent direct measurement i… ▽ More The $^{13}$C($α$,$n$)$^{16}$O reaction is the main neutron source for the slow-neutron-capture (s-) process in Asymptotic Giant Branch stars and for the intermediate (i-) process. Direct measurements at astrophysical energies in above-ground laboratories are hindered by the extremely small cross sections and vast cosmic-ray induced background. We performed the first consistent direct measurement in the range of $E_{\rm c.m.}=$0.24 MeV to 1.9 MeV using the accelerators at the China Jinping Underground Laboratory (CJPL) and Sichuan University. Our measurement covers almost the entire i-process Gamow window in which the large uncertainty of the previous experiments has been reduced from 60\% down to 15\%, eliminates the large systematic uncertainty in the extrapolation arising from the inconsistency of existing data sets, and provides a more reliable reaction rate for the studies of the s- and i-processes along with the first direct determination of the alpha strength for the near-threshold state. △ Less

Submitted 6 October, 2022; originally announced October 2022.

Journal ref: Physical Review Letters 129, 132701 (2022)

Development of a low-background neutron detector array

Authors: Y. T. Li, W. P. Lin, B. Gao, H. Chen, H. Huang, Y. Huang, T. Y. Jiao, K. A. Li, X. D. Tang, X. Y. Wang, X. Fang, H. X. Huang, J. Ren, L. H. Ru, X. C. Ruan, N. T. Zhang, Z. C. Zhang

Abstract: A low-background neutron detector array was developed to measure the cross section of the $^{13}$C($α$,n)$^{16}$O reaction, which is the neutron source for the $s$-process in AGB stars, in the Gamow window ($E_{c.m.}$ = 190 $\pm$ 40 keV) at the China Jinping Underground Laboratory (CJPL). The detector array consists of 24 $^{3}$He proportional counters embedded in a polyethylene cube. Due to the d… ▽ More A low-background neutron detector array was developed to measure the cross section of the $^{13}$C($α$,n)$^{16}$O reaction, which is the neutron source for the $s$-process in AGB stars, in the Gamow window ($E_{c.m.}$ = 190 $\pm$ 40 keV) at the China Jinping Underground Laboratory (CJPL). The detector array consists of 24 $^{3}$He proportional counters embedded in a polyethylene cube. Due to the deep underground location and a borated polyethylene shield around the detector array, a low background of 4.5(2)/hour was achieved. The $^{51}$V(p, n)$^{51}$Cr reaction was used to determine the neutron detection efficiency of the array for neutrons with energy $E_n$ $<$ 1 MeV. Geant4 simulations, which were shown to well reproduce experimental results, were used to extrapolate the detection efficiency to higher energies for neutrons emitted in the $^{13}$C($α$,n) $^{16}$O reaction. The theoretical angular distributions of the $^{13}$C($α$,n)$^{16}$O reaction were shown to be important in estimating the uncertainties of the detection efficiency. △ Less

Submitted 16 March, 2022; v1 submitted 20 November, 2021; originally announced November 2021.

Characterization of Muon and Electron Beams in the Paul Scherrer Institute PiM1 Channel for the MUSE Experiment

Authors: E. Cline, W. Lin, P. Roy, P. E. Reimer, K. E. Mesick, A. Akmal, A. Alie, H. Atac, A. Atencio, C. Ayerbe Gayoso, N. Benmouna, F. Benmokhtar, J. C. Bernauer, W. J. Briscoe, J. Campbell, D. Cohen, E. O. Cohen, C. Collicott, K. Deiters, S. Dogra, E. Downie, I. P. Fernando, A. Flannery, T. Gautam, D. Ghosal , et al. (35 additional authors not shown)

Abstract: The MUon Scattering Experiment, MUSE, at the Paul Scherrer Institute, Switzerland, investigates the proton charge radius puzzle, lepton universality, and two-photon exchange, via simultaneous measurements of elastic muon-proton and electron-proton scattering. The experiment uses the PiM1 secondary beam channel, which was designed for high precision pion scattering measurements. We review the prope… ▽ More The MUon Scattering Experiment, MUSE, at the Paul Scherrer Institute, Switzerland, investigates the proton charge radius puzzle, lepton universality, and two-photon exchange, via simultaneous measurements of elastic muon-proton and electron-proton scattering. The experiment uses the PiM1 secondary beam channel, which was designed for high precision pion scattering measurements. We review the properties of the beam line established for pions. We discuss the production processes that generate the electron and muon beams, and the simulations of these processes. Simulations of the $π$/$μ$/$e$ beams through the channel using TURTLE and G4beamline are compared. The G4beamline simulation is then compared to several experimental measurements of the channel, including the momentum dispersion at the IFP and target, the shape of the beam spot at the target, and timing measurements that allow the beam momenta to be determined. We conclude that the PiM1 channel can be used for high precision $π$, $μ$, and $e$ scattering. △ Less

Submitted 15 September, 2021; originally announced September 2021.

Comments: 20 pages, 18 figures

Timing Detectors with SiPM read-out for the MUSE Experiment at PSI

Authors: Tigran Rostomyan, Ethan Cline, Ievgen Lavrukhin, Hamza Atac, Ariella Atencio, Jan C. Bernauer, William J. Briscoe, Dan Cohen, Erez O. Cohen, Cristina Collicott, Konrad Deiters, Shraddha Dogra, Evangeline Downie, Werner Erni, Ishara P. Fernando, Anne Flannery, Thir Gautam, Debdeep Ghosal, Ronald Gilman, Alexander Golossanov, Jack Hirschman, Minjung Kim, Michael Kohl, Bernd Krusche, Lin Li , et al. (18 additional authors not shown)

Abstract: The Muon Scattering Experiment at the Paul Scherrer Institut uses a mixed beam of electrons, muons, and pions, necessitating precise timing to identify the beam particles and reactions they cause. We describe the design and performance of three timing detectors using plastic scintillator read out with silicon photomultipliers that have been built for the experiment. The Beam Hodoscope, upstream of… ▽ More The Muon Scattering Experiment at the Paul Scherrer Institut uses a mixed beam of electrons, muons, and pions, necessitating precise timing to identify the beam particles and reactions they cause. We describe the design and performance of three timing detectors using plastic scintillator read out with silicon photomultipliers that have been built for the experiment. The Beam Hodoscope, upstream of the scattering target, counts the beam flux and precisely times beam particles both to identify species and provide a starting time for time-of-flight measurements. The Beam Monitor, downstream of the scattering target, counts the unscattered beam flux, helps identify background in scattering events, and precisely times beam particles for time-of-flight measurements. The Beam Focus Monitor, mounted on the target ladder under the liquid hydrogen target inside the target vacuum chamber, is used in dedicated runs to sample the beam spot at three points near the target center, where the beam should be focused. △ Less

Submitted 15 October, 2020; v1 submitted 23 July, 2020; originally announced July 2020.

Comments: Fixed typos, added references, and rephrased some sections to be clearer. Changed numbering of tables and figures in Appendix

Journal ref: Nucl. Instrum. Meth. A 986 (2021) 164801

Improvement of heavy flavor productions in a multi-phase transport model updated with modern nPDFs

Authors: L. Zheng, C. Zhang, S. S. Shi, Z. W. Lin

Abstract: Recently we have updated a multi-phase transport (AMPT) model with modern parton distribution functions of nuclei (nPDFs). Here we study open charm production in the updated AMPT model and compare to the experimental data from $pp$ and $AA$ collisions over a wide range of collision energies. Besides the update of nPDFs, we have removed the transverse momentum cutoff on initial heavy quark producti… ▽ More Recently we have updated a multi-phase transport (AMPT) model with modern parton distribution functions of nuclei (nPDFs). Here we study open charm production in the updated AMPT model and compare to the experimental data from $pp$ and $AA$ collisions over a wide range of collision energies. Besides the update of nPDFs, we have removed the transverse momentum cutoff on initial heavy quark productions and also included the resultant heavy flavor cross section into the total minijet cross section in the initial condition as described by the HIJING model. We show that the AMPT model with these updates provides a much better description of the yields and transverse momentum spectra of various open charm hadrons in comparison with the experimental data. This lays the foundation for further heavy flavor studies within the transport model approach. △ Less

Submitted 16 April, 2020; v1 submitted 16 September, 2019; originally announced September 2019.

Comments: 11 pages, 10 figures

Journal ref: Phys. Rev. C 101, 034905 (2020)

Constraining the $^{12}$C+$^{12}$C astrophysical S-factors with the $^{12}$C+$^{13}$C measurements at very low energies

Authors: N. T. Zhang, X. Y. Wang, H. Chen, Z. J. Chen, W. P. Lin, W. Y. Xin, S. W. Xu, D. Tudor, A. I. Chilug, I. C. Stefanescu, M. Straticiuc, I. Burducea, D. G. Ghita, R. Margineanu, C. Gomoiu, A. Pantelica, D. Chesneanu, L. Trache, X. D. Tang, B. Bucher, L. R. Gasques, K. Hagino, S. Kubono, Y. J. Li, C. J. Lin , et al. (2 additional authors not shown)

Abstract: We use an underground counting lab with an extremely low background to perform an activity measurement for the $^{12}$C+$^{13}$C system with energies down to $E\rm_{c.m.}$=2.323 MeV, at which the $^{12}$C($^{13}$C,$p$)$^{24}$Na cross section is found to be 0.22(7) nb. The $^{12}$C+$^{13}$C fusion cross section is derived with a statistical model calibrated using experimental data. Our new result o… ▽ More We use an underground counting lab with an extremely low background to perform an activity measurement for the $^{12}$C+$^{13}$C system with energies down to $E\rm_{c.m.}$=2.323 MeV, at which the $^{12}$C($^{13}$C,$p$)$^{24}$Na cross section is found to be 0.22(7) nb. The $^{12}$C+$^{13}$C fusion cross section is derived with a statistical model calibrated using experimental data. Our new result of the $^{12}$C+$^{13}$C fusion cross section is the first decisive evidence in the carbon isotope systems which rules out the existence of the astrophysical S-factor maximum predicted by the phenomenological hindrance model, while confirming the rising trend of the S-factor towards lower energies predicted by other models, such as CC-M3Y+Rep, DC-TDHF, KNS, SPP and ESW. After normalizing the model predictions with our data, a more reliable upper limit is established for the $^{12}$C+$^{12}$C fusion cross sections at stellar energies. △ Less

Submitted 16 September, 2019; originally announced September 2019.

Improvement of charge resolution for radioactive heavy ions at relativistic energies using a hybrid detector system

Authors: J. W. Zhao, B. H. Sun, L. C. He, G. S. Li, W. J. Lin, C. Y. Liu, Z. Liu, C. G. Lu, D. P. Shen, Y. Z. Sun, Z. Y. Sun, I. Tanihata, S. Terashima, D. T. Tran, F. Wang, J. Wang, S. T. Wang, X. L. Wei, X. D. Xu, L. H. Zhu, J. C. Zhang, X. H. Zhang, Y. Zhang, Z. T. Zhou, Z. T. Zhou

Abstract: In typical nuclear physics experiments with radioactive ion beams (RIBs) selected by the in-flight separation technique, Si detectors or ionization chambers are usually equipped for the charge determination of RIBs. The obtained charge resolution relies on the performance of these detectors for energy loss determination, and this affects the particle identification capability of RIBs. We present a… ▽ More In typical nuclear physics experiments with radioactive ion beams (RIBs) selected by the in-flight separation technique, Si detectors or ionization chambers are usually equipped for the charge determination of RIBs. The obtained charge resolution relies on the performance of these detectors for energy loss determination, and this affects the particle identification capability of RIBs. We present an approach on improving the resolution of charge measurement for heavy ions by using the abundant energy loss information from different types of existing detectors along the beam line. Without altering the beam line and detectors, this approach can improve the charge resolution by more than 12\% relative to the multiple sampling ionization chamber of the best resolution. △ Less

Submitted 9 January, 2019; originally announced January 2019.

Comments: 8 pages, 5 figures

Journal ref: NIMA 930(2019)95

Statistical analysis of experimental multifragmentation events in $^{64}$Zn + $^{112}$Sn at 40 MeV/nucleon

Authors: W. Lin, H. Zheng, P. Ren, X. Liu, M. Huang, R. Wada, Z. Chen, J. Wang, G. Q. Xiao, G. Qu

Abstract: A statistical multifragmentation model (SMM) is applied to the experimentally observed multifragmentation events in an intermediate heavy ion reaction.Using the temperature and symmetry energy extracted from the isobaric yield ratio (IYR) method based on the Modified Fisher Model (MFM), SMM is applied to the reaction $^{64}$Zn + $^{112}$Sn at 40 MeV/nucleon. The experimental isotope distribution a… ▽ More A statistical multifragmentation model (SMM) is applied to the experimentally observed multifragmentation events in an intermediate heavy ion reaction.Using the temperature and symmetry energy extracted from the isobaric yield ratio (IYR) method based on the Modified Fisher Model (MFM), SMM is applied to the reaction $^{64}$Zn + $^{112}$Sn at 40 MeV/nucleon. The experimental isotope distribution and mass distribution of the primary reconstructed fragments are compared without afterburner and they are well reproduced. The extracted temperature $T$ and symmetry energy coefficient $a_{sym}$ from SMM simulated events, using the IYR method, are also consistent with those from the experiment. These results strongly suggest that in the multifragmentation process there is a freezeout volume, in which the thermal and chemical equilibrium is established before or at the time of the intermediate-mass fragments emission. △ Less

Submitted 29 May, 2018; originally announced May 2018.

Journal ref: Phys. Rev. C 97, 044603 (2018)

Towards the full realization of the RIBLL2 beam line at the HIRFL-CSR complex

Authors: Bao-Hua Sun, Jian-Wei Zhao, Xue-Heng Zhang, Li-Na Sheng, Zhi-Yu Sun, Isao Tanihata, Satoru Terashima, Yong Zheng, Li-Hua Zhu, Li-Min Duan, Liu-Chun He, Rong-Jiang Hu, Guang-Shuai Li, Wen-Jian Lin, Wei-Ping Lin, Chuan-Ye Liu, Zhong Liu, Chen-Gui Lu, Xin-Wen Ma, Li-Jun Mao, Yi Tian, Feng Wang, Meng Wang, Shi-Tao Wang, Jia-Wen Xia , et al. (9 additional authors not shown)

Abstract: The RIBLL2 in-flight separator at IMP, the secondary beam line between two storage rings at the \blue{\uwave{Heavy Ion Research Facility in Lanzhou (HIRFL-CSR)}}, has been commissioned to study the rare-isotope beam (RIB) physics at around 300 MeV/nucleon for the first time, in combination of the external target facility (ETF). The unambiguous particle identification in mass and charge states for… ▽ More The RIBLL2 in-flight separator at IMP, the secondary beam line between two storage rings at the \blue{\uwave{Heavy Ion Research Facility in Lanzhou (HIRFL-CSR)}}, has been commissioned to study the rare-isotope beam (RIB) physics at around 300 MeV/nucleon for the first time, in combination of the external target facility (ETF). The unambiguous particle identification in mass and charge states for $^{18}$O and $^{40}$Ar fragments has been achieved in recent experiments. A full realization of RIBLL2 will open many potentials to address important RIB physics problems at around 300 MeV/nucleon. △ Less

Submitted 11 February, 2018; v1 submitted 7 December, 2017; originally announced December 2017.

Comments: 3 pages, 2 figures

Journal ref: Science Bulletin 63 (2018) 78-80

Technical Design Report for the Paul Scherrer Institute Experiment R-12-01.1: Studying the Proton "Radius" Puzzle with μp Elastic Scattering

Authors: R. Gilman, E. J. Downie, G. Ron, S. Strauch, A. Afanasev, A. Akmal, J. Arrington, H. Atac, C. Ayerbe-Gayoso, F. Benmokhtar, N. Benmouna, J. Bernauer, A. Blomberg, W. J. Briscoe, D. Cioffi, E. Cline, D. Cohen, E. O. Cohen, C. Collicott, K. Deiters, J. Diefenbach, B. Dongwi, D. Ghosal, A. Golossanov, R. Gothe , et al. (34 additional authors not shown)

Abstract: The difference in proton radii measured with $μp$ atoms and with $ep$ atoms and scattering remains an unexplained puzzle. The PSI MUSE proposal is to measure $μp$ and $e p$ scattering in the same experiment at the same time. The experiment will determine cross sections, two-photon effects, form factors, and radii independently for the two reactions, and will allow $μp$ and $ep$ results to be compa… ▽ More The difference in proton radii measured with $μp$ atoms and with $ep$ atoms and scattering remains an unexplained puzzle. The PSI MUSE proposal is to measure $μp$ and $e p$ scattering in the same experiment at the same time. The experiment will determine cross sections, two-photon effects, form factors, and radii independently for the two reactions, and will allow $μp$ and $ep$ results to be compared with reduced systematic uncertainties. These data should provide the best test of lepton universality in a scattering experiment to date, about an order of magnitude improvement over previous tests. Measuring scattering with both particle polarities will allow a test of two-photon exchange at the sub-percent level, about a factor of four improvement on uncertainties and over an order of magnitude more data points than previous low momentum transfer determinations, and similar to the current generation of higher momentum transfer electron experiments. The experiment has the potential to demonstrate whether the $μp$ and $ep$ interactions are consistent or different, and whether any difference results from novel physics or two-photon exchange. The uncertainties are such that if the discrepancy is real it should be confirmed with $\approx$5$σ$ significance, similar to that already established between the regular and muonic hydrogen Lamb shift. △ Less

Submitted 27 September, 2017; originally announced September 2017.

Evidence for Z=6 `magic number' in neutron-rich carbon isotopes

Authors: D. T. Tran, H. J. Ong, G. Hagen, T. D. Morris, N. Aoi, T. Suzuki, Y. Kanada-En'yo, L. S. Geng, S. Terashima, I. Tanihata, T. T. Nguyen, Y. Ayyad, P. Y. Chan, M. Fukuda, H. Geissel, M. N. Harakeh, T. Hashimoto, T. H. Hoang, E. Ideguchi, A. Inoue, G. R. Jansen, R. Kanungo, T. Kawabata, L. H. Khiem, W. P. Lin , et al. (15 additional authors not shown)

Abstract: The nuclear shell structure, which originates in the nearly independent motion of nucleons in an average potential, provides an important guide for our understanding of nuclear structure and the underlying nuclear forces. Its most remarkable fingerprint is the existence of the so-called `magic numbers' of protons and neutrons associated with extra stability. Although the introduction of a phenomen… ▽ More The nuclear shell structure, which originates in the nearly independent motion of nucleons in an average potential, provides an important guide for our understanding of nuclear structure and the underlying nuclear forces. Its most remarkable fingerprint is the existence of the so-called `magic numbers' of protons and neutrons associated with extra stability. Although the introduction of a phenomenological spin-orbit (SO) coupling force in 1949 helped explain the nuclear magic numbers, its origins are still open questions. Here, we present experimental evidence for the smallest SO-originated magic number (subshell closure) at the proton number 6 in 13-20C obtained from systematic analysis of point-proton distribution radii, electromagnetic transition rates and atomic masses of light nuclei. Performing ab initio calculations on 14,15C, we show that the observed proton distribution radii and subshell closure can be explained by the state-of-the-art nuclear theory with chiral nucleon-nucleon and three-nucleon forces, which are rooted in the quantum chromodynamics. △ Less

Submitted 11 September, 2017; originally announced September 2017.

Comments: 7 pages, 5 figures

Plastic scintillation detectors for precision time-of-flight measurements of relativistic heavy ions

Authors: Wen-Jian Lin, Jian-Wei Zhao, Bao-Hua Sun, Liu-Chun He, Wei-Ping Lin, Chuan-Ye Liu, Isao Tanihata, Satoru Terashima, Yi Tian, Feng Wang, Meng Wang, Guang-Xin Zhang, Xue-Heng Zhang, Li-Hua Zhu, Li-Min Duan, Rong-Jiang Hu, Zhong Liu, Chen-Gui Lu, Pei-Pei Ren, Li-Na Sheng, Zhi-Yu Sun, Shi-Tao Wang, Tao-Feng Wang, Zhi-Guo Xu, Duo Yan , et al. (2 additional authors not shown)

Abstract: Plastic scintillation detectors for Time-of-Flight (TOF) measurements are almost essential for event-by-event identification of relativistic rare isotopes. In this work, a pair of plastic scintillation detectors of 50 $\times$ 50 $\times$ 3$^{t}$ mm$^3$ and 80 $\times$ 100 $\times$ 3$^{t}$ mm$^3$ have been set up at the external target facility (ETF), Institute of Modern Physics. Their time, energ… ▽ More Plastic scintillation detectors for Time-of-Flight (TOF) measurements are almost essential for event-by-event identification of relativistic rare isotopes. In this work, a pair of plastic scintillation detectors of 50 $\times$ 50 $\times$ 3$^{t}$ mm$^3$ and 80 $\times$ 100 $\times$ 3$^{t}$ mm$^3$ have been set up at the external target facility (ETF), Institute of Modern Physics. Their time, energy and position responses are measured with $^{18}$O primary beam at 400 MeV/nucleon. After the off-line walk-effect and position corrections, the time resolution of the two detectors are determined to be 27 ps ($σ$) and 36 ps ($σ$), respectively. Both detectors have nearly the same energy resolution of 3$\%$ ($σ$) and position resolution of 2 mm ($σ$). The detectors have been used successfully in nuclear reaction cross section measurements, and will be be employed for upgrading RIBLL2 beam line at IMP as well as for the high energy branch at HIAF. △ Less

Submitted 27 September, 2016; originally announced September 2016.

Comments: 6 pages, 11 figures

Journal ref: Chinese Physics C 41 (2017) 066001

Charge-changing-cross-section measurements of $^{12-16}$C at around $45A$ MeV and development of a Glauber model for incident energies $10A-2100A$ MeV

Authors: D. T. Tran, H. J. Ong, T. T. Nguyen, I. Tanihata, N. Aoi, Y. Ayyad, P. Y. Chan, M. Fukuda, T. Hashimoto, T. H. Hoang, E. Ideguchi, A. Inoue, T. Kawabata, L. H. Khiem, W. P. Lin, K. Matsuta, M. Mihara, S. Momota, D. Nagae, N. D. Nguyen, D. Nishimura, A. Ozawa, P. P. Ren, H. Sakaguchi, J. Tanaka , et al. (4 additional authors not shown)

Abstract: We have measured for the first time the charge-changing cross sections ($σ_{\text{CC}}$) of $^{12-16}$C on a $^{12}$C target at energies below $100A$ MeV. To analyze these low-energy data, we have developed a finite-range Glauber model with a global parameter set within the optical-limit approximation which is applicable to reaction cross section ($σ_{\text{R}}$) and $σ_{\text{CC}}$ measurements a… ▽ More We have measured for the first time the charge-changing cross sections ($σ_{\text{CC}}$) of $^{12-16}$C on a $^{12}$C target at energies below $100A$ MeV. To analyze these low-energy data, we have developed a finite-range Glauber model with a global parameter set within the optical-limit approximation which is applicable to reaction cross section ($σ_{\text{R}}$) and $σ_{\text{CC}}$ measurements at incident energies from 10$A$ to $2100A$ MeV. Adopting the proton-density distribution of $^{12}$C known from the electron-scattering data, as well as the bare total nucleon-nucleon cross sections, and the real-to-imaginary-part ratios of the forward proton-proton elastic scattering amplitude available in the literatures, we determine the energy-dependent slope parameter $β_{\rm pn}$ of the proton-neutron elastic differential cross section so as to reproduce the existing $σ_{\text{R}}$ and interaction-cross-section data for $^{12}$C+$^{12}$C over a wide range of incident energies. The Glauber model thus formulated is applied to calculate the $σ_{\text{\tiny R}}$'s of $^{12}$C on a $^9$Be and $^{27}$Al targets at various incident energies. Our calculations show excellent agreement with the experimental data. Applying our model to the $σ_{\text{\tiny R}}$ and $σ_{\text{\tiny CC}}$ for the "neutron-skin" $^{16}$C nucleus, we reconfirm the importance of measurements at incident energies below $100A$ MeV. The proton root-mean-square radii of $^{12-16}$C are extracted using the measured $σ_{\text{CC}}$'s and the existing $σ_{\text{R}}$ data. The results for $^{12-14}$C are consistent with the values from the electron scatterings, demonstrating the feasibility, usefulness of the $σ_{\text{CC}}$ measurement and the present Glauber model. △ Less

Submitted 28 June, 2016; originally announced June 2016.

Comments: 8 pages, 4 figures

Journal ref: Phys. Rev. C 94, 064604 (2016)

Participant and spectator scaling of spectator fragments in Au+Au and Cu+Cu collisions at sqrt(sNN) = 19.6 and 22.4 GeV

Authors: B. Alver, B. B. Back, M. D. Baker, M. Ballintijn, D. S. Barton, R. R. Betts, A. A. Bickley, R. Bindel, A. Budzanowski, W. Busza, A. Carroll, Z. Chai, V. Chetluru, M. P. Decowski, E. Garcia, T. Gburek, N. George, K. Gulbrandsen, S. Gushue, C. Halliwell, J. Hamblen, I. Harnarine, G. A. Heintzelman, C. Henderson, D. J. Hofman , et al. (57 additional authors not shown)

Abstract: Spectator fragments resulting from relativistic heavy ion collisions, consisting of single protons and neutrons along with groups of stable nuclear fragments up to Nitrogen (Z=7), are measured in PHOBOS. These fragments are observed in Au+Au (sqrt(sNN)=19.6 GeV) and Cu+Cu (22.4 GeV) collisions at high pseudorapidity ($η$). The dominant multiply-charged fragment is the tightly bound Helium ($α$), w… ▽ More Spectator fragments resulting from relativistic heavy ion collisions, consisting of single protons and neutrons along with groups of stable nuclear fragments up to Nitrogen (Z=7), are measured in PHOBOS. These fragments are observed in Au+Au (sqrt(sNN)=19.6 GeV) and Cu+Cu (22.4 GeV) collisions at high pseudorapidity ($η$). The dominant multiply-charged fragment is the tightly bound Helium ($α$), with Lithium, Beryllium, and Boron all clearly seen as a function of collision centrality and pseudorapidity. We observe that in Cu+Cu collisions, it becomes much more favorable for the $α$ fragments to be released than Lithium. The yields of fragments approximately scale with the number of spectator nucleons, independent of the colliding ion. The shapes of the pseudorapidity distributions of fragments indicate that the average deflection of the fragments away from the beam direction increases for more central collisions. A detailed comparison of the shapes for $α$ and Lithium fragments indicates that the centrality dependence of the deflections favors a scaling with the number of participants in the collision. △ Less

Submitted 24 November, 2015; originally announced November 2015.

Comments: To be submitted to PRC 17 pages, 19 figures

Journal ref: Phys. Rev. C 94, 024903 (2016)

Nucleon-Gold Collisions at 200 AGeV Using Tagged d+Au Interactions in PHOBOS

Authors: B. B. Back, M. D. Baker, M. Ballintijn, D. S. Barton, B. Becker, R. R. Betts, A. A. Bickley, R. Bindel, W. Busza, A. Carroll, M. P. Decowski, E. García, T. Gburek, N. George, K. Gulbrandsen, S. Gushue, C. Halliwell, J. Hamblen, A. S. Harrington, C. Henderson, D. J. Hofman, R. S. Hollis, R. Hołyński, B. Holzman, A. Iordanova , et al. (36 additional authors not shown)

Abstract: Forward calorimetry in the PHOBOS detector has been used to study charged hadron production in d+Au, p+Au and n+Au collisions at sqrt(s_nn) = 200 GeV. The forward proton calorimeter detectors are described and a procedure for determining collision centrality with these detectors is detailed. The deposition of energy by deuteron spectator nucleons in the forward calorimeters is used to identify p+A… ▽ More Forward calorimetry in the PHOBOS detector has been used to study charged hadron production in d+Au, p+Au and n+Au collisions at sqrt(s_nn) = 200 GeV. The forward proton calorimeter detectors are described and a procedure for determining collision centrality with these detectors is detailed. The deposition of energy by deuteron spectator nucleons in the forward calorimeters is used to identify p+Au and n+Au collisions in the data. A weighted combination of the yield of p+Au and n+Au is constructed to build a reference for Au+Au collisions that better matches the isospin composition of the gold nucleus. The p_T and centrality dependence of the yield of this improved reference system is found to match that of d+Au. The shape of the charged particle transverse momentum distribution is observed to extrapolate smoothly from pbar+p to central d+Au as a function of the charged particle pseudorapidity density. The asymmetry of positively- and negatively-charged hadron production in p+Au is compared to that of n+Au. No significant asymmetry is observed at mid-rapidity. These studies augment recent results from experiments at the LHC and RHIC facilities to give a more complete description of particle production in p+A and d+A collisions, essential for the understanding the medium produced in high energy nucleus-nucleus collisions. △ Less

Submitted 25 May, 2015; originally announced May 2015.

Comments: 17 pages, 18 figures

Measurement of Leakage Neutron Spectra for Tungsten with D-T Neutrons and Validation of Evaluated Nuclear Data

Authors: S. Zhanga, Z. Chen, Y. Nie, R. Wada, X. Ruan, R. Han, X. Liu, W. Lin, J. Liu, F. Shi, P. Ren, G. Tian, F. Luo, J. Ren, J. Bao

Abstract: Integral neutronics experiments have been investigated at Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS) in order to validate evaluated nuclear data related to the design of Chinese Initiative Accelerator Driven Systems (CIADS). In present paper, the accuracy of evaluated nuclear data for Tungsten has been examined by comparing measured leakage neutron spectra with calculated… ▽ More Integral neutronics experiments have been investigated at Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS) in order to validate evaluated nuclear data related to the design of Chinese Initiative Accelerator Driven Systems (CIADS). In present paper, the accuracy of evaluated nuclear data for Tungsten has been examined by comparing measured leakage neutron spectra with calculated ones. Leakage neutron spectra from the irradiation of D-T neutrons on Tungsten slab sample were experimentally measured at 60$^{\circ}$ and 120$^{\circ}$ by using a time-of-flight method. Theoretical calculations are carried out by Monte Carlo neutron transport code MCNP-4C with evaluated nuclear data of the ADS-2.0, ENDF/B-VII.0, ENDF/B-VII.1, JENDL-4.0 and CENDL-3.1 libraries. From the comparisons, it is found that the calculations with ADS-2.0 and ENDF/B-VII.1 give good agreements with the experiments in the whole energy regions at 60$^{\circ}$, while a large discrepancy is observed at 120$^{\circ}$ in the elastic scattering peak, caused by a slight difference in the oscillation pattern of the elastic angular distribution at angles larger than 20$^{\circ}$. However, the calculated spectra using data from ENDF/B-VII.0, JENDL-4.0 and CENDL-3.1 libraries showed larger discrepancies with the measured ones, especially around 8.5-13.5 MeV. Further studies are presented for these disagreements. △ Less

Submitted 19 November, 2014; originally announced November 2014.

Comments: 10pages, 7figures

Neutron Time-Of-Flight Spectrometer Based on HIRFL for Studies of Spallation Reactions Related to ADS Project

Authors: Suyalatu Zhang, Zhiqiang Chen, Rui Han, Roy Wada, Xingquan Liu, Weiping Lin, Jianli Liu, Fudong Shi, Peipei Ren, Guoyu Tian, Fei Luo

Abstract: A Neutron Time-Of-Flight (NTOF) spectrometer based on Heavy Ion Research Facility in Lanzhou (HIRFL) is developed for studies of neutron production of proton induced spallation reactions related to the ADS project. After the presentation of comparisons between calculated spallation neutron production double-differential cross sections and the available experimental one, a detailed description of N… ▽ More A Neutron Time-Of-Flight (NTOF) spectrometer based on Heavy Ion Research Facility in Lanzhou (HIRFL) is developed for studies of neutron production of proton induced spallation reactions related to the ADS project. After the presentation of comparisons between calculated spallation neutron production double-differential cross sections and the available experimental one, a detailed description of NTOF spectrometer is given. Test beam results show that the spectrometer works well and data analysis procedures are established. The comparisons of the test beam neutron spectra with those of GEANT4 simulations are presented. △ Less

Submitted 19 November, 2014; originally announced November 2014.

Comments: 9 pages, 7 figures

Characterization and Performance of Germanium Detectors with sub-keV Sensitivities for Neutrino and Dark Matter Experiments

Authors: The TEXONO Collaboration, A. K. Soma, M. K. Singh, L. Singh, G. Kiran Kumar, F. K. Lin, Q. Du, H. Jiang, S. K. Liu, J. L. Ma, V. Sharma, L. Wang, Y. C. Wu, L. T. Yang, W. Zhao, M. Agartioglu, G. Asryan, Y. Y. Chang, J. H. Chen, Y. C. Chuang, M. Deniz, C. L. Hsu, Y. H. Hsu, T. R. Huang, L. P. Jia , et al. (24 additional authors not shown)

Abstract: Germanium ionization detectors with sensitivities as low as 100 eVee (electron-equivalent energy) open new windows for studies on neutrino and dark matter physics. The relevant physics subjects are summarized. The detectors have to measure physics signals whose amplitude is comparable to that of pedestal electronic noise. To fully exploit this new detector technique, various experimental issues in… ▽ More Germanium ionization detectors with sensitivities as low as 100 eVee (electron-equivalent energy) open new windows for studies on neutrino and dark matter physics. The relevant physics subjects are summarized. The detectors have to measure physics signals whose amplitude is comparable to that of pedestal electronic noise. To fully exploit this new detector technique, various experimental issues including quenching factors, energy reconstruction and calibration, signal triggering and selection as well as evaluation of their associated efficiencies have to be attended. The efforts and results of a research program to address these challenges are presented. △ Less

Submitted 1 September, 2016; v1 submitted 18 November, 2014; originally announced November 2014.

Comments: 18 pages, 18 figures, 3 table; v3 -- Published Version

Journal ref: Nuclear Instruments and Methods A 836, 67-82 (2016)

Fast neutron scattering on Gallium target at 14.8 MeV

Authors: R. Han, R. Wada, Z. Chen, Y. Nie, X. Liu, S. Zhang, P. Ren, B. Jia, G. Tian, F. Luo, W. Lin, J. Liu, F. Shi, M. Huang, X. Ruan, J. Ren, Z. Zhou, H. Huang, J. Bao, K. Zhang, B. Hu

Abstract: Benchmarking of evaluated nuclear data libraries was performed for $\sim 14.8$ MeV neutrons on Gallium targets. The experiments were performed at China Institute of Atomic Energy(CIAE). Solid samples of natural Gallium (3.2 cm and 6.4 cm thick) were bombarded by $\sim 14.8$ MeV neutrons and leakage neutron energy spectra were measured at 60$^{\circ}$ and 120$^{\circ}$. The measured spectra are rat… ▽ More Benchmarking of evaluated nuclear data libraries was performed for $\sim 14.8$ MeV neutrons on Gallium targets. The experiments were performed at China Institute of Atomic Energy(CIAE). Solid samples of natural Gallium (3.2 cm and 6.4 cm thick) were bombarded by $\sim 14.8$ MeV neutrons and leakage neutron energy spectra were measured at 60$^{\circ}$ and 120$^{\circ}$. The measured spectra are rather well reproduced by MCNP-4C simulations with the CENDL-3.1, ENDF/B-VII and JENDL-4.0 evaluated nuclear data libraries, except for the inelastic contributions around $E_{n} = 10-13$ MeV. All three libraries significantly underestimate the inelastic contributions. The inelastic contributions are further studied, using the Talys simulation code and the experimental spectra are reproduced reasonably well in the whole energy range by the Talys calculation, including the inelastic contributions. △ Less

Submitted 3 November, 2014; originally announced November 2014.

Comments: 12 pages, 7 figures

Reconstructed primary fragments and symmetry energy, temperature and density of the fragmenting source in $^{64}$Zn + $^{112}$Sn at 40 MeV/nucleon

Authors: X. Liu, W. Lin, R. Wada, M. Huang, S. Zhang, P. Ren, Z. Chen, J. Wang, G. Q. Xiao, R. Han, J. Liu, F. Shi, M. R. D. Rodrigues, S. Kowalski, T. Keutgen, K. Hagel, M. Barbui, H. Zheng, A. Bonasera, J. B. Natowitz

Abstract: Symmetry energy, temperature and density at the time of the intermediate mass fragment formation are determined in a self-consistent manner, using the experimentally reconstructed primary hot isotope yields and anti-symmetrized molecular dynamics (AMD) simulations. The yields of primary hot fragments are experimentally reconstructed for multifragmentation events in the reaction system $^{64}$Zn +… ▽ More Symmetry energy, temperature and density at the time of the intermediate mass fragment formation are determined in a self-consistent manner, using the experimentally reconstructed primary hot isotope yields and anti-symmetrized molecular dynamics (AMD) simulations. The yields of primary hot fragments are experimentally reconstructed for multifragmentation events in the reaction system $^{64}$Zn + $^{112}$Sn at 40 MeV/nucleon. Using the reconstructed hot isotope yields and an improved method, based on the modified Fisher model, symmetry energy values relative to the apparent temperature, $a_{sym}/T$, are extracted. The extracted values are compared with those of the AMD simulations, extracted in the same way as that for the experiment, with the Gogny interaction with three different density-dependent symmetry energy terms. $a_{sym}/T$ values change according to the density-dependent symmetry energy terms used. Using this relation, the density of the fragmenting system is extracted first. Then symmetry energy and apparent temperature are determined in a self consistent manner in the AMD model simulations. Comparing the calculated $a_{sym}/T$ values and those of the experimental values from the reconstructed yields, $ρ/ρ_{0} = 0.65 \pm 0.02 $, $a_{sym} = 23.1 \pm 0.6$ MeV and $T= 5.0 \pm 0.4$ MeV are evaluated for the fragmenting system experimentally observed in the reaction studied. △ Less

Submitted 14 October, 2014; v1 submitted 14 September, 2014; originally announced September 2014.

Comments: 28 pages, 7 figures. arXiv admin note: text overlap with arXiv:1405.6911, Nucl. Phys. A (2014)

Experimental reconstruction of primary hot isotopes and characteristic properties of the fragmenting source in the heavy ion reactions near the Fermi energy

Authors: W. Lin, X. Liu, M. R. D. Rodrigues, S. Kowalski, R. Wada, M. Huang, S. Zhang, Z. Chen, J. Wang, G. Q. Xiao, R. Han, Z. Jin, J. Liu, P. Ren, F. Shi, T. Keutgen, K. Hagel, M. Barbui, C. Bottosso, A. Bonasera, J. B. Natowitz, T. Materna, L. Qin, P. K. Sahu, H. Zheng

Abstract: The characteristic properties of the hot nuclear matter existing at the time of fragment formation in the multifragmentation events produced in the reaction $^{64}$Zn + $^{112}$Sn at 40 MeV/nucleon are studied. A kinematical focusing method is employed to determine the multiplicities of evaporated light particles, associated with isotopically identified detected fragments. From these data the prim… ▽ More The characteristic properties of the hot nuclear matter existing at the time of fragment formation in the multifragmentation events produced in the reaction $^{64}$Zn + $^{112}$Sn at 40 MeV/nucleon are studied. A kinematical focusing method is employed to determine the multiplicities of evaporated light particles, associated with isotopically identified detected fragments. From these data the primary isotopic yield distributions are reconstructed using a Monte Carlo method. The reconstructed yield distributions are in good agreement with the primary isotope distributions obtained from AMD transport model simulations. Utilizing the reconstructed yields, power distribution, Landau free energy, characteristic properties of the emitting source are examined. The primary mass distributions exhibit a power law distribution with the critical exponent, $A^{-2.3}$, for $A \geq 15$ isotopes, but significantly deviates from that for the lighter isotopes. Landau free energy plots show no strong signature of the first order phase transition. Based on the Modified Fisher Model, the ratios of the Coulomb and symmetry energy coefficients relative to the temperature, $a_{c}/T$ and $a_{sym}/T$, are extracted as a function of A. The extracted $a_{sym}/T$ values are compared with results of the AMD simulations using Gogny interactions with different density dependencies of the symmetry energy term. The calculated $a_{sym}/T$ values show a close relation to the symmetry energy at the density at the time of the fragment formation. From this relation the density of the fragmenting source is determined to be $ρ/ρ_{0} = (0.63 \pm 0.03 )$. Using this density, the symmetry energy coefficient and the temperature of fragmenting source are determined in a self-consistent manner as $a_{sym} = (24.7 \pm 3.4) MeV$ and $T=(4.9 \pm 0.2)$ MeV. △ Less

Submitted 14 September, 2014; v1 submitted 27 May, 2014; originally announced May 2014.

QCD and strongly coupled gauge theories: challenges and perspectives

Authors: N. Brambilla, S. Eidelman, P. Foka, S. Gardner, A. S. Kronfeld, M. G. Alford, R. Alkofer, M. Butenschoen, T. D. Cohen, J. Erdmenger, L. Fabbietti, M. Faber, J. L. Goity, B. Ketzer, H. W. Lin, F. J. Llanes-Estrada, H. Meyer, P. Pakhlov, E. Pallante, M. I. Polikarpov, H. Sazdjian, A. Schmitt, W. M. Snow, A. Vairo, R. Vogt , et al. (24 additional authors not shown)

Abstract: We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to strongly-coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standar… ▽ More We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to strongly-coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments. △ Less

Submitted 18 May, 2014; v1 submitted 14 April, 2014; originally announced April 2014.

Comments: 246 pp, around 128 figures; v2 adds material, references, and corrections suggested by readers of v1 -- to be submitted to EPJC

Report number: CCQCN-2014-24, CCTP-2014-5, CERN-PH-TH/2014-033, DF-1-2014, FERMILAB-PUB-14-024/T, HIP-2014-03/TH, ITEP-LAT-2014-1, JLAB-THY-14-1865, LLNL-JRNL-651216, MITP/14-016, NT@UW 14-04, RUB-TPII-01/2014, TUM-EFT 46/14, UWThPh-2014-006

Journal ref: Eur. Phys. J. C 74:2981 (2014) 1

A novel determination of density, temperature and symmetry energy for nuclear multi-fragmentation through primary fragment yield reconstruction

Authors: W. Lin, X. Liu, M. R. D. Rodrigues, S. Kowalski, R. Wada, M. Huang, S. Zhang, Z. Chen, J. Wang, G. Q. Xiao, R. Han, Z. Jin, J. Liu, F. Shi, T. Keutgen, K. Hagel, M. Barbui, C. Bottosso, A. Bonasera, J. B. Natowitz, E. J. Kim, T. Materna, L. Qin, P. K. Sahu, K. J. Schmidt , et al. (2 additional authors not shown)

Abstract: For the first time primary hot isotope distributions are experimentally reconstructed in intermediate heavy ion collisions and used with antisymmetrized molecular dynamics (AMD) calculations to determine density, temperature and symmetry energy coefficient in a self-consistent manner. A kinematical focusing method is employed to reconstruct the primary hot fragment yield distributions for multifra… ▽ More For the first time primary hot isotope distributions are experimentally reconstructed in intermediate heavy ion collisions and used with antisymmetrized molecular dynamics (AMD) calculations to determine density, temperature and symmetry energy coefficient in a self-consistent manner. A kinematical focusing method is employed to reconstruct the primary hot fragment yield distributions for multifragmentation events observed in the reaction system $^{64}$Zn + $^{112}$Sn at 40 MeV/nucleon. The reconstructed yield distributions are in good agreement with the primary isotope distributions of AMD simulations. The experimentally extracted values of the symmetry energy coefficient relative to the temperature, $a_{sym}/T$, are compared with those of the AMD simulations with different density dependence of the symmetry energy term. The calculated $a_{sym}/T$ values changes according to the different interactions. By comparison of the experimental values of $a_{sym}/T$ with those of calculations, the density of the source at fragment formation was determined to be $ρ/ρ_{0} = (0.63 \pm 0.03 )$. Using this density, the symmetry energy coefficient and the temperature are determined in a self-consistent manner as $a_{sym} = (24.7 \pm 1.9) MeV$ and $T=(4.9 \pm 0.2)$ MeV △ Less

Submitted 17 February, 2014; v1 submitted 1 January, 2014; originally announced January 2014.

A Lattice Study of Quark and Glue Momenta and Angular Momenta in the Nucleon

Authors: M. Deka, T. Doi, Y. B. Yang, B. Chakraborty, S. J. Dong, T. Draper, M. Glatzmaier, M. Gong, H. W. Lin, K. F. Liu, D. Mankame, N. Mathur, T. Streuer

Abstract: We report a complete calculation of the quark and glue momenta and angular momenta in the proton. These include the quark contributions from both the connected and disconnected insertions. The quark disconnected insertion loops are computed with $Z_4$ noise, and the signal-to-noise is improved with unbiased subtractions. The glue operator is comprised of gauge-field tensors constructed from the ov… ▽ More We report a complete calculation of the quark and glue momenta and angular momenta in the proton. These include the quark contributions from both the connected and disconnected insertions. The quark disconnected insertion loops are computed with $Z_4$ noise, and the signal-to-noise is improved with unbiased subtractions. The glue operator is comprised of gauge-field tensors constructed from the overlap operator. The calculation is carried out on a $16^3 \times 24$ quenched lattice at $β= 6.0$ for Wilson fermions with $κ=0.154, 0.155$, and $0.1555$ which correspond to pion masses at $650, 538$, and $478$~MeV, respectively. The chirally extrapolated $u$ and $d$ quark momentum/angular momentum fraction is found to be $0.64(5)/0.70(5)$, the strange momentum/angular momentum fraction is $0.024(6)/0.023(7)$, and that of the glue is $0.33(6)/0.28(8)$. The previous study of quark spin on the same lattice revealed that it carries a fraction of $0.25(12)$ of proton spin. The orbital angular momenta of the quarks are then obtained from subtracting the spin from their corresponding angular momentum components. We find that the quark orbital angular momentum constitutes $0.47(13)$ of the proton spin with almost all of it coming from the disconnected insertions. △ Less

Submitted 12 February, 2015; v1 submitted 17 December, 2013; originally announced December 2013.

Comments: Renormalization section is expanded to include more details. There are slight changes in the final numbers. A few modification and corrections are made in the rest of the text

Report number: RIKEN-QHP-109

Journal ref: Phys.Rev. D91 (2015) 1, 014505

Breaking the EOS-Gravity Degeneracy with Masses and Pulsating Frequencies of Neutron Stars

Authors: Weikang Lin, Bao-An Li, Lie-Wen Chen, De-Hua Wen, Jun Xu

Abstract: A thorough understanding of many astrophysical phenomena associated with compact objects requires reliable knowledge about both the equation of state (EOS)of super-dense nuclear matter and the theory of strong-field gravity simultaneously because of the EOS-gravity degeneracy. Currently, variations of the neutron star (NS) mass-radius correlation from using alternative gravity theories are much la… ▽ More A thorough understanding of many astrophysical phenomena associated with compact objects requires reliable knowledge about both the equation of state (EOS)of super-dense nuclear matter and the theory of strong-field gravity simultaneously because of the EOS-gravity degeneracy. Currently, variations of the neutron star (NS) mass-radius correlation from using alternative gravity theories are much larger than those from changing the NS matter EOS within known constraints. At least two independent observables are required to break the EOS-gravity degeneracy. Using model EOSs for hybrid stars and a Yukawa-type non-Newtonian gravity, we investigate both the mass-radius correlation and pulsating frequencies of NSs. While the maximum mass of NSs increases, the frequencies of the $f$, $p_1$, $p_2$, and $w_I$ pulsating modes are found to decrease with the increasing strength of the Yukawa-type non-Newtonian gravity, providing a useful reference for future determination simultaneously of both the strong-field gravity and the supranuclear EOS by combining data of x-ray and gravitational wave emissions of neutron stars. △ Less

Submitted 21 March, 2014; v1 submitted 13 November, 2013; originally announced November 2013.

Comments: Added new results and discussions. Version accepted by J. of Phys. G. arXiv admin note: text overlap with arXiv:1101.1504

Journal ref: J. of Phys. G41, 075203 (2014)

Imprints of Nuclear Symmetry Energy on Properties of Neutron Stars

Authors: Bao-An Li, Lie-Wen Chen, Michael Gearheart, Joshua Hooker, Che Ming Ko, Plamen G. Krastev, Wei-Kang Lin, William G. Newton, De-Hua Wen, Chang Xu, Jun Xu

Abstract: Significant progress has been made in recent years in constraining the density dependence of nuclear symmetry energy using terrestrial nuclear laboratory data. Around and below the nuclear matter saturation density, the experimental constraints start to merge in a relatively narrow region. At supra-saturation densities, there are, however, still large uncertainties. After summarizing the latest ex… ▽ More Significant progress has been made in recent years in constraining the density dependence of nuclear symmetry energy using terrestrial nuclear laboratory data. Around and below the nuclear matter saturation density, the experimental constraints start to merge in a relatively narrow region. At supra-saturation densities, there are, however, still large uncertainties. After summarizing the latest experimental constraints on the density dependence of nuclear symmetry energy, we highlight a few recent studies examining imprints of nuclear symmetry energy on the binding energy, energy release during hadron-quark phase transitions as well as the $w$-mode frequency and damping time of gravitational wave emission of neutron stars. △ Less

Submitted 23 March, 2011; originally announced March 2011.

Comments: 10 pages. Invited talk given in the Nuclear Astrophysics session of INPC2010, July 4-9, 2010, Vancouver, Canada; Journal of Physics: Conference Series (2011)

Journal ref: J.Phys.Conf.Ser.312:042006,2011

Present Constraints on the H-dibaryon at the Physical Point from Lattice QCD

Authors: S. R. Beane, E. Chang, W. Detmold, B. Joo, H. W. Lin, T. C. Luu, K. Orginos, A. Parreno, M. J. Savage, A. Torok, A. Walker-Loud

Abstract: The current constraints from lattice QCD on the existence of the H-dibaryon are discussed. With only two significant lattice QCD calculations of the H-dibaryon binding energy at approximately the same lattice spacing, the forms of the chiral and continuum extrapolations to the physical point are not determined. In this brief report, we consider the constraints on the H-dibaryon imposed by two simp… ▽ More The current constraints from lattice QCD on the existence of the H-dibaryon are discussed. With only two significant lattice QCD calculations of the H-dibaryon binding energy at approximately the same lattice spacing, the forms of the chiral and continuum extrapolations to the physical point are not determined. In this brief report, we consider the constraints on the H-dibaryon imposed by two simple chiral extrapolations. In both instances, the extrapolation to the physical pion mass allows for a bound H-dibaryon or a near-threshold scattering state. Further lattice QCD calculations are required to clarify this situation. △ Less

Submitted 13 September, 2011; v1 submitted 14 March, 2011; originally announced March 2011.

Comments: 8 pages, 2 figures, 1 table; revised for the journal

Report number: UNH-11-1; ICCUB-11-125; JLAB-THY-11-1326; NT@UW-11-02; IUHET-558; UCB-NPAT-11-003; NT-LBNL-11-005

Journal ref: Mod. Phys. Lett. A26: 2587, 2011

Energy release from hadron-quark phase transition in neutron stars and the axial $w$-mode of gravitational waves

Authors: Weikang Lin, Bao-An Li, Jun Xu, Che Ming Ko, De-Hua Wen

Abstract: Describing the hyperonic and quark phases of neutron stars with an isospin- and momentum-dependent effective interaction for the baryon octet and the MIT bag model, respectively, and using the Gibbs conditions to construct the mixed phase, we study the energy release due to the hadron-quark phase transition. Moreover, the frequency and damping time of the first axial $w$-mode of gravitational wave… ▽ More Describing the hyperonic and quark phases of neutron stars with an isospin- and momentum-dependent effective interaction for the baryon octet and the MIT bag model, respectively, and using the Gibbs conditions to construct the mixed phase, we study the energy release due to the hadron-quark phase transition. Moreover, the frequency and damping time of the first axial $w$-mode of gravitational waves are studied for both hyperonic and hybrid stars. We find that the energy release is much more sensitive to the bag constant than the density dependence of the nuclear symmetry energy. Also, the frequency of the $w$-mode is found to be significantly different with or without the hadron-quark phase transition and depends strongly on the value of the bag constant. Effects of the density dependence of the nuclear symmetry energy become, however, important for large values of the bag constant that lead to higher hadron-quark transition densities. △ Less

Submitted 28 November, 2010; originally announced November 2010.

Comments: 17 pages including 7 figures

Journal ref: Phys.Rev.C83:045802,2011

Phobos results on charged particle multiplicity and pseudorapidity distributions in Au+Au, Cu+Cu, d+Au, and p+p collisions at ultra-relativistic energies

Authors: B. Alver, B. B. Back, M. D. Baker, M. Ballintijn, D. S. Barton, R. R. Betts, A. A. Bickley, R. Bindel, A. Budzanowski, W. Busza, A. Carroll, Z. Chai, V. Chetluru, M. P. Decowski, E. Garcıa, T. Gburek, N. George, K. Gulbrandsen, S. Gushue, C. Halliwell, J. Hamblen, G. A. Heintzelman, C. Henderson, D. J. Hofman, R. S. Hollis , et al. (54 additional authors not shown)

Abstract: Pseudorapidity distributions of charged particles emitted in $Au+Au$, $Cu+Cu$, $d+Au$, and $p+p$ collisions over a wide energy range have been measured using the PHOBOS detector at RHIC. The centrality dependence of both the charged particle distributions and the multiplicity at midrapidity were measured. Pseudorapidity distributions of charged particles emitted with $|η|<5.4$, which account for b… ▽ More Pseudorapidity distributions of charged particles emitted in $Au+Au$, $Cu+Cu$, $d+Au$, and $p+p$ collisions over a wide energy range have been measured using the PHOBOS detector at RHIC. The centrality dependence of both the charged particle distributions and the multiplicity at midrapidity were measured. Pseudorapidity distributions of charged particles emitted with $|η|<5.4$, which account for between 95% and 99% of the total charged-particle emission associated with collision participants, are presented for different collision centralities. Both the midrapidity density, $dN_{ch}/dη$, and the total charged-particle multiplicity, $N_{ch}$, are found to factorize into a product of independent functions of collision energy, $\sqrt{s_{_{NN}}}$, and centrality given in terms of the number of nucleons participating in the collision, $N_{part}$. The total charged particle multiplicity, observed in these experiments and those at lower energies, assumes a linear dependence of $(\ln s_{_{NN}})^2$ over the full range of collision energy of $\sqrt{s_{_{NN}}}$=2.7-200 GeV. △ Less

Submitted 8 November, 2010; originally announced November 2010.

Comments: 25 pages, 29 figures, 8 tables

Journal ref: Phys.Rev.C83:024913,2011

Scaling properties in bulk and p$_{\rm T}$-dependent particle production near midrapidity in relativistic heavy ion collisions

Authors: PHOBOS Collaboration, B. Alver, B. B. Back, M. D. Baker, M. Ballintijn, D. S. Barton, R. R. Betts, R. Bindel, W. Busza, Z. Chai, V. Chetluru, E. Garcia, T. Gburek, K. Gulbrandsen, J. Hamblen, I. Harnarine, C. Henderson, D. J. Hofman, R. S. Hollis, R. Holynski, B. Holzman, A. Iordanova, J. L. Kane, P. Kulinich, C. M. Kuo , et al. (34 additional authors not shown)

Abstract: The centrality dependence of the midrapidity charged-particle multiplicity density ($|η|$$<$1) is presented for Au+Au and Cu+Cu collisions at RHIC over a broad range of collision energies. The multiplicity measured in the Cu+Cu system is found to be similar to that measured in the Au+Au system, for an equivalent N$_{\rm part}$, with the observed factorization in energy and centrality still persi… ▽ More The centrality dependence of the midrapidity charged-particle multiplicity density ($|η|$$<$1) is presented for Au+Au and Cu+Cu collisions at RHIC over a broad range of collision energies. The multiplicity measured in the Cu+Cu system is found to be similar to that measured in the Au+Au system, for an equivalent N$_{\rm part}$, with the observed factorization in energy and centrality still persistent in the smaller Cu+Cu system. The extent of the similarities observed for bulk particle production is tested by a comparative analysis of the inclusive transverse momentum distributions for Au+Au and Cu+Cu collisions near midrapidity. It is found that, within the uncertainties of the data, the ratio of yields between the various energies for both Au+Au and Cu+Cu systems are similar and constant with centrality, both in the bulk yields as well as a function of p$_{\rm T}$, up to at least 4 GeV/$c$. The effects of multiple nucleon collisions that strongly increase with centrality and energy appear to only play a minor role in bulk and intermediate transverse momentum particle production. △ Less

Submitted 13 August, 2008; originally announced August 2008.

Comments: Submitted for publication in Phys. Rev. C, 5 pages, 3 figures

Journal ref: Phys.Rev.C80:011901,2009

System size, energy, centrality and pseudorapidity dependence of charged-particle density in Au+Au and Cu+Cu collisions at RHIC

Authors: PHOBOS Collaboration, G. I. Veres, B. Alver, B. B. Back, M. D. Baker, M. Ballintijn, D. S. Barton, R. R. Betts, A. A. Bickley, R. Bindel, W. Busza, A. Carroll, Z. Chai, V. Chetluru, M. P. Decowski, E. García, T. Gburek, N. George, K. Gulbrandsen, C. Halliwell, J. Hamblen, I. Harnarine, M. Hauer, C. Henderson, D. J. Hofman , et al. (44 additional authors not shown)

Abstract: Charged particle pseudorapidity distributions are presented from the PHOBOS experiment at RHIC, measured in Au+Au and Cu+Cu collisions at sqrt{s_NN}=19.6, 22.4, 62.4, 130 and 200 GeV, as a function of collision centrality. The presentation includes the recently analyzed Cu+Cu data at 22.4 GeV. The measurements were made by the same detector setup over a broad range in pseudorapidity, |eta|<5.4,… ▽ More Charged particle pseudorapidity distributions are presented from the PHOBOS experiment at RHIC, measured in Au+Au and Cu+Cu collisions at sqrt{s_NN}=19.6, 22.4, 62.4, 130 and 200 GeV, as a function of collision centrality. The presentation includes the recently analyzed Cu+Cu data at 22.4 GeV. The measurements were made by the same detector setup over a broad range in pseudorapidity, |eta|<5.4, allowing for a reliable systematic study of particle production as a function of energy, centrality and system size. Comparing Cu+Cu and Au+Au results, we find that the total number of produced charged particles and the overall shape (height and width) of the pseudorapidity distributions are determined by the number of nucleon participants, N_part. Detailed comparisons reveal that the matching of the shape of the Cu+Cu and Au+Au pseudorapidity distributions over the full range of eta is better for the same N_part/2A value than for the same N_part value, where A denotes the mass number. In other words, it is the geometry of the nuclear overlap zone, rather than just the number of nucleon participants that drives the detailed shape of the pseudorapidity distribution and its centrality dependence. △ Less

Submitted 17 June, 2008; originally announced June 2008.

Comments: 5 pages, 4 figures. Presented at the 20th International Conference on Nucleus-Nucleus Collisions (Quark Matter 2008), Jaipur, Rajasthan, India, 4-10 February 2008

Journal ref: Indian J.Phys.85:1015-1019,2011