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Polarization-Analyzed Small-Angle Neutron Scattering with an $\textit{in-situ}$ $^{3}$He neutron spin filter at the China Spallation Neutron Source
Authors:
Long Tian,
Han Gao,
Tianhao Wang,
Haiyun Teng,
Jian Tang,
Qingbo Zheng,
Taisen Zuo,
Tengfei Cui,
Bin Wang,
Xu Qin,
Yongxiang Qiu,
Yuchen Dong,
Yujie Zheng,
Zecong Qin,
Zehua Han,
Junpei Zhang,
He Cheng,
Xin Tong
Abstract:
Polarization-analyzed small-angle neutron scattering (PASANS) is an advanced technique that enables the selective investigation of magnetic scattering phenomena in magnetic materials and distinguishes coherent scattering obscured by incoherent backgrounds, making it particularly valuable for cutting-edge research. The successful implementation of PASANS in China was achieved for the first time at…
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Polarization-analyzed small-angle neutron scattering (PASANS) is an advanced technique that enables the selective investigation of magnetic scattering phenomena in magnetic materials and distinguishes coherent scattering obscured by incoherent backgrounds, making it particularly valuable for cutting-edge research. The successful implementation of PASANS in China was achieved for the first time at the newly commissioned Very Small Angle Neutron Scattering (VSANS) instrument at the China Spallation Neutron Source (CSNS). This technique employs a combination of a double-V cavity supermirror polarizer and a radio frequency (RF) neutron spin flipper to manipulate the polarization of the incident neutrons. The scattered neutron polarization is stably analyzed by a specially designed $\textit{in-situ}$ optical pumping $^{3}$He neutron spin filter, which covers a spatially symmetric scattering angle coverage of about 4.8 $^{\circ}$. A comprehensive PASANS data reduction method, aimed at pulsed neutron beams, has been established and validated with a silver behenate powder sample, indicating a maximum momentum transfer coverage of approximately 0.25 Å $^{-1}$.
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Submitted 23 January, 2025;
originally announced January 2025.
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Photo-nuclear reaction rates of $^{157,159}$Ho and $^{163,165}$Tm and their impact in the $γ$--process
Authors:
Hao Cheng,
Bao-Hua Sun,
Li-Hua Zhu,
Motohiko Kusakabe,
Yudong Luo,
Toshitaka Kajino,
Chang-Jian Wang,
Xing-Qun Yao,
Chuang-Ye He,
Fu-Long Liu,
Bing Guo
Abstract:
Reliable photo-nuclear reaction rates at the stellar conditions are essential to understand the origin of the heavy stable neutron-deficient isotopes between $^{74}$Se and $^{196}$Hg-p-nuclei, however, many reaction rates of relevance still have to rely on the Hauser-Feshbach model due to rare experimental progress. One such case is in the mass range of 160 for Dy, Er, Ho and Tm isotopes. In this…
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Reliable photo-nuclear reaction rates at the stellar conditions are essential to understand the origin of the heavy stable neutron-deficient isotopes between $^{74}$Se and $^{196}$Hg-p-nuclei, however, many reaction rates of relevance still have to rely on the Hauser-Feshbach model due to rare experimental progress. One such case is in the mass range of 160 for Dy, Er, Ho and Tm isotopes. In this work we attempt to constrain the Hauser-Feshbach model in the TALYS package by reproducing the available experimental data of $^{160}$Dy($p,γ$)$^{161}$Ho and $^{162}$Er($p,γ$)$^{163}$Tm in the $A\sim 160$ mass region, and examine the effects of level density, gamma strength function and the optical model potential. The constrained model then allows us to calculate the reaction rates of $^{157, 159}$Ho($γ$, $p$) and $^{163,165}$Tm($γ$, $p$) for the $γ$-process nucleosynthesis in carbon-deflagration SNe Ia model. Our recommended rates differ from the JINA REACLIB by more than 1 order of magnitude in the temperature range of 2-3 GK. This results in the changes of final abundance of $p$-nuclei in the $A\sim 160$ mass range by -5.5-3\% from those with JINA, which means that the ($γ$, $p$) reactions uncertainty is not predominant for the synthesis of these nuclei.
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Submitted 18 September, 2024;
originally announced September 2024.
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The renormalization of the shell-model GT operator starting from effective field theory for nuclear systems
Authors:
L. Coraggio,
N. Itaco,
G. De Gregorio,
A. Gargano,
Z. H. Cheng,
Y. Z. Ma,
F. R. Xu,
M. Viviani
Abstract:
For the first time, we approach in this work the problem of the renormalization of the Gamow-Teller decay operator for nuclear shell-model calculations by way of many-body perturbation theory, starting from a nuclear Hamiltonian and electroweak currents derived consistently by way of the chiral perturbation theory. These are the inputs we need to construct microscopically the effective shell-model…
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For the first time, we approach in this work the problem of the renormalization of the Gamow-Teller decay operator for nuclear shell-model calculations by way of many-body perturbation theory, starting from a nuclear Hamiltonian and electroweak currents derived consistently by way of the chiral perturbation theory. These are the inputs we need to construct microscopically the effective shell-model Hamiltonians and decay operators. The goal is to assess the role of both electroweak currents and many-body correlations as the origins of the well-known problem of the quenching of the axial coupling constant gA. To this end, the calculation of observables related to the Gamow-Teller transitions has been performed for several nuclear systems outside the 40Ca and 56Ni closed cores and compared with the available data.
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Submitted 22 December, 2023; v1 submitted 24 October, 2023;
originally announced October 2023.
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Comparing pion production in transport simulations of heavy-ion collisions at $270A$ MeV under controlled conditions
Authors:
Jun Xu,
Hermann Wolter,
Maria Colonna,
Mircea Dan Cozma,
Pawel Danielewicz,
Che Ming Ko,
Akira Ono,
ManYee Betty Tsang,
Ying-Xun Zhang,
Hui-Gan Cheng,
Natsumi Ikeno,
Rohit Kumar,
Jun Su,
Hua Zheng,
Zhen Zhang,
Lie-Wen Chen,
Zhao-Qing Feng,
Christoph Hartnack,
Arnaud Le Fèvre,
Bao-An Li,
Yasushi Nara,
Akira Ohnishi,
Feng-Shou Zhang
Abstract:
Within the TMEP, we present a detailed study of the performance of different transport models in Sn+Sn collisions at $270A$ MeV, and put particular emphasis on the production of pions and $Δ$ resonances, which have been used as probes of the nuclear symmetry energy. We prescribe a common and rather simple physics model, and follow in detail the results of 4 BUU models and 6 QMD models. The nucleon…
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Within the TMEP, we present a detailed study of the performance of different transport models in Sn+Sn collisions at $270A$ MeV, and put particular emphasis on the production of pions and $Δ$ resonances, which have been used as probes of the nuclear symmetry energy. We prescribe a common and rather simple physics model, and follow in detail the results of 4 BUU models and 6 QMD models. The nucleonic evolution of the collision and the nucleonic observables in these codes do not completely converge, but the differences among the codes can be understood as being due to several reasons: the basic differences between BUU and QMD models in the representation of the phase-space distributions, computational differences in the mean-field evaluation, and differences in the adopted strategies for the Pauli blocking in the collision integrals. For pionic observables, we find that a higher maximum density leads to an enhanced pion yield and a reduced $π^-/π^+$ yield ratio, while a more effective Pauli blocking generally leads to a slightly suppressed pion yield and an enhanced $π^-/π^+$ yield ratio. We specifically investigate the effect of the Coulomb force, and find that it increases the total $π^-/π^+$ yield ratio but reduces the ratio at high pion energies, although differences in its implementations do not have a dominating role in the differences among the codes. Taking into account only the results of codes that strictly follow the homework specifications, we find a convergence of the codes in the final charged pion yield ratio to a $1σ$ deviation of about $5\%$. However, the uncertainty is expected to be reduced to about $1.6\%$ if the same or similar strategies and ingredients, i.e., an improved Pauli blocking and calculation of the non-linear term in the mean-field potential, are similarly used in all codes.
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Submitted 14 March, 2024; v1 submitted 10 August, 2023;
originally announced August 2023.
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Transport Model Comparison Studies of Intermediate-Energy Heavy-Ion Collisions
Authors:
Hermann Wolter,
Maria Colonna,
Dan Cozma,
Pawel Danielewicz,
Che Ming Ko,
Rohit Kumar,
Akira Ono,
ManYee Betty Tsang,
Jun Xu,
Ying-Xun Zhang,
Elena Bratkovskaya,
Zhao-Qing Feng,
Theodoros Gaitanos,
Arnaud Le Fèvre,
Natsumi Ikeno,
Youngman Kim,
Swagata Mallik,
Paolo Napolitani,
Dmytro Oliinychenko,
Tatsuhiko Ogawa,
Massimo Papa,
Jun Su,
Rui Wang,
Yong-Jia Wang,
Janus Weil
, et al. (27 additional authors not shown)
Abstract:
Transport models are the main method to obtain physics information from low to relativistic-energy heavy-ion collisions. The Transport Model Evaluation Project (TMEP) has been pursued to test the robustness of transport model predictions in reaching consistent conclusions from the same type of physical model. Calculations under controlled conditions of physical input and set-up were performed with…
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Transport models are the main method to obtain physics information from low to relativistic-energy heavy-ion collisions. The Transport Model Evaluation Project (TMEP) has been pursued to test the robustness of transport model predictions in reaching consistent conclusions from the same type of physical model. Calculations under controlled conditions of physical input and set-up were performed with various participating codes. These included both calculations of nuclear matter in a box with periodic boundary conditions, and more realistic calculations of heavy-ion collisions. In this intermediate review, we summarize and discuss the present status of the project. We also provide condensed descriptions of the 26 participating codes, which contributed to some part of the project. These include the major codes in use today. We review the main results of the studies completed so far. They show, that in box calculations the differences between the codes can be well understood and a convergence of the results can be reached. These studies also highlight the systematic differences between the two families of transport codes, known as BUU and QMD type codes. However, when the codes were compared in full heavy-ion collisions using different physical models, as recently for pion production, they still yielded substantially different results. This calls for further comparisons of heavy-ion collisions with controlled models and of box comparisons of important ingredients, like momentum-dependent fields, which are currently underway. We often indicate improved strategies in performing transport simulations and thus provide guidance to code developers. Results of transport simulations of heavy-ion collisions from a given code will have more significance if the code can be validated against benchmark calculations such as the ones summarized in this review.
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Submitted 4 May, 2022; v1 submitted 14 February, 2022;
originally announced February 2022.
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Measurements of $^{160}$Dy($p,γ$) at energies relevant for astrophysical $γ$ process
Authors:
Hao Cheng,
Bao-Hua Sun,
Li-Hua Zhu,
Motohiko Kusakabe,
Yun Zheng,
Liu-Chun He,
Toshitaka Kajino,
Zhong-Ming Niu,
Tian-Xiao Li,
Cong-Bo Li,
Dong-Xi Wang,
Meng Wang,
Guang-Shuai Li,
Kang Wang,
Lin Song,
Ge Guo,
Zhi-Yong Huang,
Xiu-Lin Wei,
Fu-WeI Zhao,
Xiao-Guang Wu,
Yimuran Abulikemu,
Jian-Cheng Liu,
Ping Fan
Abstract:
Rare information on photodisintegration reactions of nuclei with mass numbers $A \approx 160$ at astrophysical conditions impedes our understanding of the origin of $p$-nuclei. Experimental determination of the key ($p,γ$) cross sections has been playing an important role to verify nuclear reaction models and to provide rates of relevant ($γ,p$) reactions in $γ$-process. In this paper we report th…
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Rare information on photodisintegration reactions of nuclei with mass numbers $A \approx 160$ at astrophysical conditions impedes our understanding of the origin of $p$-nuclei. Experimental determination of the key ($p,γ$) cross sections has been playing an important role to verify nuclear reaction models and to provide rates of relevant ($γ,p$) reactions in $γ$-process. In this paper we report the first cross section measurements of $^{160}$Dy($p,γ$)$^{161}$Ho and $^{161}$Dy($p,n$)$^{161}$Ho in the beam energy range of 3.4 - 7.0 MeV, partially covering the Gamow window. Such determinations are possible by using two targets with various isotopic fractions. The cross section data can put a strong constraint on the nuclear level densities and gamma strength functions for $A \approx$ 160 in the Hauser-Feshbach statistical model. Furthermore, we find the best parameters for TALYS that reproduce the A $\thicksim$ 160 data available, $^{160}$Dy($p,γ$)$^{161}$Ho and $^{162}$Er($p,γ$)$^{163}$Tm, and recommend the constrained $^{161}$Ho($γ,p$)$^{160}$Dy reaction rates over a wide temperature range for $γ$-process network calculations. Although the determined $^{161}$Ho($γ$, p) stellar reaction rates at the temperature of 1 to 2 GK can differ by up to one order of magnitude from the NON-SMOKER predictions, it has a minor effect on the yields of $^{160}$Dy and accordingly the $p$-nuclei, $^{156,158}$Dy. A sensitivity study confirms that the cross section of $^{160}$Dy($p$, $γ$)$^{161}$Ho is measured precisely enough to predict yields of $p$-nuclei in the $γ$-process.
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Submitted 24 September, 2021; v1 submitted 15 May, 2021;
originally announced May 2021.
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Intrinsic radiation background of LaBr$_3$(Ce) detector via coincidence measurements and simulations
Authors:
Hao Cheng,
Bao-Hua Sun,
Li-Hua Zhu,
Tian-Xiao Li,
Guang-Shuai Li,
Cong-Bo Li,
Xiao-Guang Wu,
Yun Zheng
Abstract:
The LaBr$_3$(Ce) detector has attracted much attention in recent years for its superior characteristics to other scintillating materials in terms of resolution and efficiency. However, it has relatively high intrinsic radiation background due to the naturally occurring radioisotope in lanthanum, actinium and their daughter nuclei. This limits its applications in low counting rate experiments. In t…
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The LaBr$_3$(Ce) detector has attracted much attention in recent years for its superior characteristics to other scintillating materials in terms of resolution and efficiency. However, it has relatively high intrinsic radiation background due to the naturally occurring radioisotope in lanthanum, actinium and their daughter nuclei. This limits its applications in low counting rate experiments. In this paper, we identified the radioactive isotopes in the $\phi3''\times 3''$ Saint-Gobain B380 detector by a coincidence measurement using a Clover detector in a low-background shielding system. Moreover, we carried out a Geant4 simulation to the experimental spectra to evaluate the activities of the main internal radiation components. % by means of the $α$, $γ$ and $β$ decays from the $^{138}$La and $^{227}$Ac. The activity of radiation background of B380 is determined to be 1.480 (69) Bq/cm$^3$, the main sources of which include $^{138}$La of 1.425 (59) Bq/cm$^3$, $^{211}$Bi of 0.0136 (15) Bq/cm$^3$, $^{219}$Rn of 0.0125 (17) Bq/cm$^3$, $^{223}$Ra of 0.0127 (14) Bq/cm$^3$, and $^{227}$Th of 0.0158 (22) Bq/cm$^3$.
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Submitted 15 July, 2020;
originally announced July 2020.
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Development and prospect of Very Small Angle Neutron Scattering (VSANS) Techniques
Authors:
Taisen Zuo,
He Cheng,
Yuan-Bo Chen,
Fang-Wei Wang
Abstract:
Very Small Angle Neutron Scattering (VSANS) is an upgrade of the traditional Small Angle Neutron Scattering (SANS) technique which can cover three orders of magnitude of length scale from one nanometer to one micrometer. It is a powerful tool for structure calibration in polymer science, biology, material science and condensed matter physics. Since the first VSANS instrument, D11 in Grenoble, was…
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Very Small Angle Neutron Scattering (VSANS) is an upgrade of the traditional Small Angle Neutron Scattering (SANS) technique which can cover three orders of magnitude of length scale from one nanometer to one micrometer. It is a powerful tool for structure calibration in polymer science, biology, material science and condensed matter physics. Since the first VSANS instrument, D11 in Grenoble, was built in 1972, new collimation techniques, focusing optics (multi-beam converging apertures, material or magnetic lenses, and focusing mirrors) and higher resolution detectors combined with the long flight paths and long incident neutron wavelengths have been developed. In this paper, a detailed review is given of the development, principles and application conditions of various VSANS techniques. Then, beam current gain factors are calculated to evaluate those techniques. A VSANS design for the China Spallation Neutron Source (CSNS) is thereby presented.
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Submitted 16 March, 2016;
originally announced March 2016.
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Measurement of the Reactor Antineutrino Flux and Spectrum at Daya Bay
Authors:
Daya Bay Collaboration,
F. P. An,
A. B. Balantekin,
H. R. Band,
M. Bishai,
S. Blyth,
I. Butorov,
D. Cao,
G. F. Cao,
J. Cao,
W. R. Cen,
Y. L. Chan,
J. F. Chang,
L. C. Chang,
Y. Chang,
H. S. Chen,
Q. Y. Chen,
S. M. Chen,
Y. X. Chen,
Y. Chen,
J. H. Cheng,
J. Cheng,
Y. P. Cheng,
J. J. Cherwinka,
M. C. Chu
, et al. (200 additional authors not shown)
Abstract:
This Letter reports a measurement of the flux and energy spectrum of electron antineutrinos from six 2.9~GW$_{th}$ nuclear reactors with six detectors deployed in two near (effective baselines 512~m and 561~m) and one far (1,579~m) underground experimental halls in the Daya Bay experiment. Using 217 days of data, 296,721 and 41,589 inverse beta decay (IBD) candidates were detected in the near and…
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This Letter reports a measurement of the flux and energy spectrum of electron antineutrinos from six 2.9~GW$_{th}$ nuclear reactors with six detectors deployed in two near (effective baselines 512~m and 561~m) and one far (1,579~m) underground experimental halls in the Daya Bay experiment. Using 217 days of data, 296,721 and 41,589 inverse beta decay (IBD) candidates were detected in the near and far halls, respectively. The measured IBD yield is (1.55 $\pm$ 0.04) $\times$ 10$^{-18}$~cm$^2$/GW/day or (5.92 $\pm$ 0.14) $\times$ 10$^{-43}$~cm$^2$/fission. This flux measurement is consistent with previous short-baseline reactor antineutrino experiments and is $0.946\pm0.022$ ($0.991\pm0.023$) relative to the flux predicted with the Huber+Mueller (ILL+Vogel) fissile antineutrino model. The measured IBD positron energy spectrum deviates from both spectral predictions by more than 2$σ$ over the full energy range with a local significance of up to $\sim$4$σ$ between 4-6 MeV. A reactor antineutrino spectrum of IBD reactions is extracted from the measured positron energy spectrum for model-independent predictions.
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Submitted 18 August, 2015;
originally announced August 2015.
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A new measurement of antineutrino oscillation with the full detector configuration at Daya Bay
Authors:
Daya Bay Collaboration,
F. P. An,
A. B. Balantekin,
H. R. Band,
M. Bishai,
S. Blyth,
I. Butorov,
G. F. Cao,
J. Cao,
W. R. Cen,
Y. L. Chan,
J. F. Chang,
L. C. Chang,
Y. Chang,
H. S. Chen,
Q. Y. Chen,
S. M. Chen,
Y. X. Chen,
Y. Chen,
J. H. Cheng,
J. Cheng,
Y. P. Cheng,
J. J. Cherwinka,
M. C. Chu,
J. P. Cummings
, et al. (194 additional authors not shown)
Abstract:
We report a new measurement of electron antineutrino disappearance using the fully-constructed Daya Bay Reactor Neutrino Experiment. The final two of eight antineutrino detectors were installed in the summer of 2012. Including the 404 days of data collected from October 2012 to November 2013 resulted in a total exposure of 6.9$\times$10$^5$ GW$_{\rm th}$-ton-days, a 3.6 times increase over our pre…
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We report a new measurement of electron antineutrino disappearance using the fully-constructed Daya Bay Reactor Neutrino Experiment. The final two of eight antineutrino detectors were installed in the summer of 2012. Including the 404 days of data collected from October 2012 to November 2013 resulted in a total exposure of 6.9$\times$10$^5$ GW$_{\rm th}$-ton-days, a 3.6 times increase over our previous results. Improvements in energy calibration limited variations between detectors to 0.2%. Removal of six $^{241}$Am-$^{13}$C radioactive calibration sources reduced the background by a factor of two for the detectors in the experimental hall furthest from the reactors. Direct prediction of the antineutrino signal in the far detectors based on the measurements in the near detectors explicitly minimized the dependence of the measurement on models of reactor antineutrino emission. The uncertainties in our estimates of $\sin^{2}2θ_{13}$ and $|Δm^2_{ee}|$ were halved as a result of these improvements. Analysis of the relative antineutrino rates and energy spectra between detectors gave $\sin^{2}2θ_{13} = 0.084\pm0.005$ and $|Δm^{2}_{ee}|= (2.42\pm0.11) \times 10^{-3}$ eV$^2$ in the three-neutrino framework.
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Submitted 10 September, 2015; v1 submitted 13 May, 2015;
originally announced May 2015.
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On the Momentum Dependence of the Flavor Structure of the Nucleon Sea
Authors:
Jen-Chieh Peng,
Wen-Chen Chang,
Hai-Yang Cheng,
Tie-Jiun Hou,
Keh-Fei Liu,
Jian-Wei Qiu
Abstract:
Difference between the $\bar u$ and $\bar d$ sea quark distributions in the proton was first observed in the violation of the Gottfried sum rule in deep-inelastic scattering (DIS) experiments. The parton momentum fraction $x$ dependence of this difference has been measured over the region $0.02 < x < 0.35$ from Drell-Yan and semi-inclusive DIS experiments. The Drell-Yan data suggested a possible s…
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Difference between the $\bar u$ and $\bar d$ sea quark distributions in the proton was first observed in the violation of the Gottfried sum rule in deep-inelastic scattering (DIS) experiments. The parton momentum fraction $x$ dependence of this difference has been measured over the region $0.02 < x < 0.35$ from Drell-Yan and semi-inclusive DIS experiments. The Drell-Yan data suggested a possible sign-change for $\bar d(x)-\bar u(x)$ near $x \sim 0.3$, which has not yet been explained by existing theoretical models. We present an independent evidence for the $\bar d(x)-\bar u(x)$ sign-change at $x \sim 0.3$ from an analysis of the DIS data. We further discuss the $x$-dependence of $\bar d(x)-\bar u(x)$ in the context of meson cloud model and the lattice QCD formulation.
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Submitted 28 July, 2014; v1 submitted 8 January, 2014;
originally announced January 2014.