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Femtoscopy Measurement with S$π$RIT TPC in Radioactive BeamHeavy-ion Collisions
Authors:
Y. J. Wang,
C. K. Tam,
Z. G. Xiao,
W. G. Lynch,
C. Y. Tsang,
J. Barney,
G. Jhang,
J. Estee,
M. B. Tsang,
R. S. Wang,
M. Kaneko,
J. W. Lee,
J. Park,
Z. Chajęcki,
G. Verde,
T. Isobe,
M. Kurata-Nishimura,
T. Murakami,
D. S. Ahn,
L. Atar,
T. Aumann,
H. Baba,
K. Boretzky,
J. Brzychczyk,
G. Cerizza
, et al. (42 additional authors not shown)
Abstract:
Femtoscopy is a powerful tool for exploring the dynamic emitting structure in heavy-ion collisions, while radioactive beam heavy-ion collisions enable the investigation of nuclear matter under extreme isospin conditions. Here, we successfully perform femtoscopy measurements using the S$π$RIT Time Projection Chamber (TPC). A dedicated correction scheme for track merging and splitting is proposed, w…
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Femtoscopy is a powerful tool for exploring the dynamic emitting structure in heavy-ion collisions, while radioactive beam heavy-ion collisions enable the investigation of nuclear matter under extreme isospin conditions. Here, we successfully perform femtoscopy measurements using the S$π$RIT Time Projection Chamber (TPC). A dedicated correction scheme for track merging and splitting is proposed, which is well applicable to rectangular TPCs housed inside dipole magnets and effectively improves the reconstructed correlation functions at small relative momenta. Focusing on the proton-proton (p-p) correlation function in the 270 MeV/u $^{132}\text{Sn}+^{124}\text{Sn}$ system, we successfully apply the track merging and splitting correction; additionally, the TPC angular acceptance exhibits a negligible impact on the correlation function. A systematic uncertainty quantification framework is established. The experimental results of the p-p correlation function confirm the feasibility of the S$π$RIT TPC for femtoscopy measurements and provide technical support for high-precision femtoscopy studies using rectangular TPCs in radioactive beam heavy-ion collisions.
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Submitted 15 July, 2026;
originally announced July 2026.
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$l$-forbidden $\mathbf{M1}$ strengths near $^{100}$Sn from knockout reactions in Cd and Sn
Authors:
T. J. Gray,
K. L. Jones,
R. Grzywacz,
B. A. Brown,
A. Gade,
B. C. He,
T. Miyagi,
A. Peter,
M. J. Basson,
T. Beck,
C. M. Campbell,
G. Cerizza,
J. Chung-Jung,
I. Cox,
P. Farris,
R. Ghimire,
S. Gillespie,
M. Grinder,
A. Hill,
S. D. Pain,
A. Palmisano-Kyle,
K. P. Rykaczewski,
D. Weisshaar,
M. Williams
Abstract:
Neutron knockout reactions on beams of $^{104,102}$Cd, and $^{104}$Sn are presented. States in the residual $^{103,101}$Cd and $^{103}$Sn nuclei are populated, including low-lying $7/2^+$ states of $νg_{7/2}$ character. These states have half-lives $\approx 400$ ps due to their low energy and hindered $B(M1; 7/2^+ \rightarrow 5/2^+)$ strengths. The excited-state half-lives were measured using thei…
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Neutron knockout reactions on beams of $^{104,102}$Cd, and $^{104}$Sn are presented. States in the residual $^{103,101}$Cd and $^{103}$Sn nuclei are populated, including low-lying $7/2^+$ states of $νg_{7/2}$ character. These states have half-lives $\approx 400$ ps due to their low energy and hindered $B(M1; 7/2^+ \rightarrow 5/2^+)$ strengths. The excited-state half-lives were measured using their Doppler-shifted lineshapes, and the resulting $B(M1)$ strengths are compared to Valence Space In Medium Similarity Renormalization Group (VS-IMSRG) calculations. The VS-IMSRG calculations under-predict the $l$-forbidden $M1$ strengths in the $^{100}$Sn region, as well as in other regions of the nuclear chart near $^{40}$Ca and $^{208}$Pb.
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Submitted 2 July, 2026;
originally announced July 2026.
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Large amplification of the isospin-dependence of proton emitting source size in radioactive heavy-ion collisions: a signal of n-p correlation
Authors:
Y. J. Wang,
C. K. Tam,
Z. G. Xiao,
W. G. Lynch,
C. Y. Tsang,
J. Barney,
G. Jhang,
J. Estee,
M. B. Tsang,
R. S. Wang,
M. Kaneko,
J. W. Lee,
J. Park,
Z. Chajęcki,
G. Verde,
T. Isobe,
M. Kurata-Nishimura,
T. Murakami,
D. S. Ahn,
L. Atar,
T. Aumann,
H. Baba,
K. Boretzky,
J. Brzychczyk,
G. Cerizza
, et al. (42 additional authors not shown)
Abstract:
We report proton-proton correlation function measurements in central $^{132}$Sn+$^{124}$Sn and $^{108}$Sn+$^{112}$Sn collisions at 270 MeV/nucleon. The proton emitting source sizes are extracted for the systems by using femtoscopic imaging technique. The fast dynamic core radius for the neutron-rich system is found to be $2.22 \pm 0.13\ \text{(stat.)} \pm 0.07\ \text{(syst.)}$ fm, which is approxi…
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We report proton-proton correlation function measurements in central $^{132}$Sn+$^{124}$Sn and $^{108}$Sn+$^{112}$Sn collisions at 270 MeV/nucleon. The proton emitting source sizes are extracted for the systems by using femtoscopic imaging technique. The fast dynamic core radius for the neutron-rich system is found to be $2.22 \pm 0.13\ \text{(stat.)} \pm 0.07\ \text{(syst.)}$ fm, which is approximately 24\% larger than that for the neutron-deficient system, $1.74 \pm 0.08\ \text{(stat.)} \pm 0.05\ \text{(syst.)}$ fm. This difference is an order of magnitude larger than the $\sim$3\% difference in the ground-state charge radii of the projectile nuclei. Transport model simulations based on mean-field dynamics cannot reproduce this amplification. The observation reveals a beyond-mean-field mechanism associated to short-range neutron-proton correlations, which dynamically enhance the proton emitting source in the neutron-rich environment. Our results demonstrate that heavy-ion collisions induced by radioactive beam, combined with femtoscopic precision, provide a new hadronic probe of short-range correlation, and that careful treatment of the beyond-mean-field interactions are required in modeling such processes.
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Submitted 27 April, 2026;
originally announced April 2026.
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Beta-decay Half Lives beyond $^{54}$Ca: A Systematic Survey of Decay Properties approaching the Neutron Dripline
Authors:
W. -J. Ong,
Z. Y. Xu,
R. Grzywacz,
A. Ravlić,
I. Cox,
J. M. Allmond,
T. T. King,
B. C. Rasco,
K. P. Rykaczewski,
H. Schatz,
B. M. Sherrill,
B. Tarasov,
B. A. Brown,
S. Ajayi,
H. Arora,
A. D. Ayangeakaa,
H. C. Berg,
J. M. Berkman,
D. L. Bleuel,
K. Bosmpotinis,
M. P. Carpenter,
G. Cerizza,
A. Chester,
J. M. Christie,
H. L. Crawford
, et al. (61 additional authors not shown)
Abstract:
In an experiment performed at the Facility for Rare Isotope Beams (FRIB) using the FRIB Decay Station initiator (FDSi), 15 new half lives of isotopes near $^{54}$Ca were measured. A new method of extracting lifetimes from experimental data, taking into account the unknown $β$-delayed neutron emission branches of very neutron-rich nuclei, was developed to enable systematic uncertainty analysis. The…
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In an experiment performed at the Facility for Rare Isotope Beams (FRIB) using the FRIB Decay Station initiator (FDSi), 15 new half lives of isotopes near $^{54}$Ca were measured. A new method of extracting lifetimes from experimental data, taking into account the unknown $β$-delayed neutron emission branches of very neutron-rich nuclei, was developed to enable systematic uncertainty analysis. The experiment observed a dramatic change in the half-life systematics for the isotopes with neutron number N =34. Beyond N =34, the decline of nuclear lifetime is much slower, leading to longer than anticipated lifetimes for near-dripline nuclei. State-of-the-art shell-model calculations can explain the experimental results for Z$>$19 nuclei, revealing the imprint of shell effects and the need for modification of single-particle neutron states. The results from a newly developed QRPA model with potential for making global predictions were also tested against the experimental results and good agreement was found.
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Submitted 22 October, 2025;
originally announced October 2025.
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Universal Effective Charges in the $sd$ and $fp$ Shells
Authors:
T. H. Ogunbeku,
J. M. Allmond,
T. J. Gray,
W. -J. Ong,
B. A. Brown,
A. Gargano,
R. Grzywacz,
J. D. Holt,
A. O. Macchiavelli,
T. Miyagi,
S. Neupane,
B. C. Rasco,
H. Schatz,
B. M. Sherrill,
O. B. Tarasov,
H. Arora,
A. D. Ayangeakaa,
H. C. Berg,
J. M. Berkman,
D. L. Bleuel,
K. Bosmpotinis,
M. P. Carpenter,
G. Cerizza,
A. Chester,
J. M. Christie
, et al. (57 additional authors not shown)
Abstract:
The 247-keV state in $^{54}$Sc, populated in the $β$ decay of $^{54}$Ca, is reported here as a nanosecond isomer with a half-life of 26.0(22) ns. The state is interpreted as the $1^+$ member of the $πf_{7/2}\otimesνf_{5/2}$ spin-coupled multiplet, which decays to the $3^+,πf_{7/2} \otimes νp_{1/2}$ ground state. The new half-life corresponds to a pure $E2$ transition with a strength of 1.93(16) W.…
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The 247-keV state in $^{54}$Sc, populated in the $β$ decay of $^{54}$Ca, is reported here as a nanosecond isomer with a half-life of 26.0(22) ns. The state is interpreted as the $1^+$ member of the $πf_{7/2}\otimesνf_{5/2}$ spin-coupled multiplet, which decays to the $3^+,πf_{7/2} \otimes νp_{1/2}$ ground state. The new half-life corresponds to a pure $E2$ transition with a strength of 1.93(16) W.u., providing the most precise, unambiguous $B(E2)$ value in the neutron-rich $fp$ region to date for a nucleus with valence protons above $Z=20$. Notably, it is roughly four times larger than the $B(E2; 1/2^{-} \rightarrow 5/2^{-})$ value in $^{55}$Ca. The results, as compared to semi-empirical and ab initio shell-model calculations, indicate (1) a weak $N=34$ sub-shell gap relative to $N = 32$, (2) a large $E2$ enhancement in Sc as compared to Ca due to $1p-1h$ proton excitations across $Z=28$, and (3) empirical effective proton and neutron charges, $e_π$ = 1.30(8)$e$ and $e_ν$ = 0.452(7)$e$, respectively, that are in contrast to reports of $e_π\approx 1.1-1.15e$ and $e_ν\approx 0.6-0.8e$ for $fp$-shell nuclei near $N = Z$. We demonstrate that these reports are erroneous and that, in fact, a universal set of effective charges can be used across the $sd$ and $fp$ shells.
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Submitted 26 June, 2025;
originally announced June 2025.
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Constraining nucleon effective masses with flow and stopping observables from the S$π$RIT experiment
Authors:
C. Y. Tsang,
M. Kurata-Nishimura,
M. B. Tsang,
W. G. Lynch,
Y. X. Zhang,
J. Barney,
J. Estee,
G. Jhang,
R. Wang,
M. Kaneko,
J. W. Lee,
T. Isobe,
T. Murakami,
D. S. Ahn,
L. Atar,
T. Aumann,
H. Baba,
K. Boretzky,
J. Brzychczyk,
G. Cerizza,
N. Chiga,
N. Fukuda,
I. Gasparic,
B. Hong,
A. Horvat
, et al. (30 additional authors not shown)
Abstract:
Properties of the nuclear equation of state (EoS) can be probed by measuring the dynamical properties of nucleus-nucleus collisions. In this study, we present the directed flow ($v_1$), elliptic flow ($v_2$) and stopping (VarXZ) measured in fixed target Sn + Sn collisions at 270 AMeV with the S$π$RIT Time Projection Chamber. We perform Bayesian analyses in which EoS parameters are varied simultane…
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Properties of the nuclear equation of state (EoS) can be probed by measuring the dynamical properties of nucleus-nucleus collisions. In this study, we present the directed flow ($v_1$), elliptic flow ($v_2$) and stopping (VarXZ) measured in fixed target Sn + Sn collisions at 270 AMeV with the S$π$RIT Time Projection Chamber. We perform Bayesian analyses in which EoS parameters are varied simultaneously within the Improved Quantum Molecular Dynamics-Skyrme (ImQMD-Sky) transport code to obtain a multivariate correlated constraint. The varied parameters include symmetry energy, $S_0$, and slope of the symmetry energy, $L$, at saturation density, isoscalar effective mass, $m_{s}^*/m_{N}$, isovector effective mass, $m_{v}^{*}/m_{N}$ and the in-medium cross-section enhancement factor $η$. We find that the flow and VarXZ observables are sensitive to the splitting of proton and neutron effective masses and the in-medium cross-section. Comparisons of ImQMD-Sky predictions to the S$π$RIT data suggest a narrow range of preferred values for $m_{s}^*/m_{N}$, $m_{v}^{*}/m_{N}$ and $η$.
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Submitted 8 December, 2023;
originally announced December 2023.
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Strong evidence for 9N and the limits of existence of atomic nuclei
Authors:
R. J. Charity,
J. Wylie,
S. M. Wang,
T. B. Webb,
K. W. Brown,
G. Cerizza,
Z. Chajecki,
J. M. Elson,
J. Estee,
D. E. M Hoff,
S. A. Kuvin,
W. G. Lynch,
J. Manfredi,
N. Michel,
D. G. McNeel,
P. Morfouace,
W. Nazarewicz,
C. D. Pruitt,
C. Santamaria,
S. Sweany,
J. Smith,
L. G. Sobotka,
M. B. Tsang,
A. H. Wuosmaa
Abstract:
The boundaries of the Chart of Nuclides contain exotic isotopes that possess extreme proton-toneutron asymmetries. Here we report on strong evidence of 9N, one of the most exotic proton-rich isotopes where more than one half of its constitute nucleons are unbound. With seven protons and two neutrons, this extremely proton-rich system would represent the first-known example of a ground-state five-p…
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The boundaries of the Chart of Nuclides contain exotic isotopes that possess extreme proton-toneutron asymmetries. Here we report on strong evidence of 9N, one of the most exotic proton-rich isotopes where more than one half of its constitute nucleons are unbound. With seven protons and two neutrons, this extremely proton-rich system would represent the first-known example of a ground-state five-proton emitter. The invariant-mass spectrum of its decay products can be fit with two peaks whose energies are consistent with the theoretical predictions of an open-quantum-system approach, however we cannot rule out the possibility that only a single resonance-like peak is present in the spectrum.
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Submitted 26 September, 2023;
originally announced September 2023.
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Isoscaling in central Sn+Sn collisions at 270 MeV/u
Authors:
J. W. Lee,
M. B. Tsang,
C. Y. Tsang,
R. Wang,
J. Barney,
J. Estee,
T. Isobe,
M. Kaneko,
M. Kurata-Nishimura,
W. G. Lynch,
T. Murakami,
A. Ono,
S. R. Souza,
D. S. Ahn,
L. Atar,
T. Aumann,
H. Baba,
K. Boretzky,
J. Brzychczyk,
G. Cerizza,
N. Chiga,
N. Fukuda,
I. Gasparic,
B. Hong,
A. Horvat
, et al. (39 additional authors not shown)
Abstract:
Experimental information on fragment emissions is important in understanding the dynamics of nuclear collisions and in the development of transport model simulating heavy-ion collisions. The composition of complex fragments emitted in the heavy-ion collisions can be explained by statistical models, which assume that thermal equilibrium is achieved at collision energies below 100 MeV/u. Our new exp…
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Experimental information on fragment emissions is important in understanding the dynamics of nuclear collisions and in the development of transport model simulating heavy-ion collisions. The composition of complex fragments emitted in the heavy-ion collisions can be explained by statistical models, which assume that thermal equilibrium is achieved at collision energies below 100 MeV/u. Our new experimental data together with theoretical analyses for light particles from Sn+Sn collisions at 270 MeV/u, suggest that the hypothesis of thermal equilibrium breaks down for particles emitted with high transfer momentum. To inspect the system's properties in such limit, the scaling features of the yield ratios of particles from two systems, a neutron-rich system of ${}^{132}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ and a nearly symmetric system of ${}^{108}\mathrm{Sn}+{}^{112}\mathrm{Sn}$, are examined in the framework of the statistical multifragmentation model and the antisymmetrized molecular dynamics model. The isoscaling from low energy particles agree with both models. However the observed breakdown of isoscaling for particles with high transverse momentum cannot be explained by the antisymmetrized molecular dynamics model.
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Submitted 5 November, 2022;
originally announced November 2022.
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Using spin alignment of inelastically-excited fast beams to make spin assignments: the spectroscopy of 13O as a test case
Authors:
R. J. Charity,
T. B. Webb,
J. M. Elson,
D. E. M. Hoff,
C. D. Pruitt,
L. G. Sobotka,
P. Navratil,
G. Hupin,
K. Kravvaris,
S. Quaglioni,
K. W. Brown,
G. Cerizza,
J. Estee,
W. G. Lynch,
J. Manfredi,
P. Morfouace,
C. Santamaria,
S. Sweany,
M. B. Tsang,
T. Tsang,
K. Zhu,
S. A. Kuvin,
D. McNeel,
J. Smith,
A. H. Wousmaa
, et al. (1 additional authors not shown)
Abstract:
Excited states in 13O were investigated using inelastic scattering of an E/A=69.5-MeV 13O beam off of a 9Be target. The excited states were identified in the invariant-mass spectra of the decay products. Both single proton and sequential two-proton decays of the excited states were examined. For a number of the excited states, the protons were emitted with strong anisotropy where emissions transve…
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Excited states in 13O were investigated using inelastic scattering of an E/A=69.5-MeV 13O beam off of a 9Be target. The excited states were identified in the invariant-mass spectra of the decay products. Both single proton and sequential two-proton decays of the excited states were examined. For a number of the excited states, the protons were emitted with strong anisotropy where emissions transverse to the beam axis are favored. The measured proton-decay angular distributions were compared to predictions from distorted-wave born-approximation (DWBA) calculations of the spin alignment which was shown to be largely independent of the excitation mechanism. The deduced $^{13}$O level scheme is compared to ab initio no-core shell model with continuum (NCSMC) predictions. The lowest-energy excited states decay isotropically consistent with predictions of strong proton 1s1/2 structure. Above these states in the level scheme, we observed a number of higher-spin states not predicted within the model. Possibly these are associated with rotational bands built on deformed cluster configurations predicted by antisymmetrized molecular dynamics (AMD) calculations. The spin alignment mechanism is shown to be useful for making spin assignments and may have widespread use.
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Submitted 7 July, 2021;
originally announced July 2021.
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Probing the Symmetry Energy with the Spectral Pion Ratio
Authors:
J. Estee,
W. G. Lynch,
C. Y. Tsang,
J. Barney,
G. Jhang,
M. B. Tsang,
R. Wang,
M. Kaneko,
J. W. Lee,
T. Isobe,
M. Kurata-Nishimura,
T. Murakami,
D. S. Ahn,
L. Atar,
T. Aumann,
H. Baba,
K. Boretzky,
J. Brzychczyk,
G. Cerizza,
N. Chiga,
N. Fukuda,
I. Gasparic,
B. Hong,
A. Horvat,
K. Ieki
, et al. (38 additional authors not shown)
Abstract:
Many neutron star (NS) properties, such as the proton fraction within a NS, reflect the symmetry energy contributions to the Equation of State that dominate when neutron and proton densities differ strongly. To constrain these contributions at supra-saturation densities, we measure the spectra of charged pions produced by colliding rare isotope tin (Sn) beams with isotopically enriched Sn targets.…
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Many neutron star (NS) properties, such as the proton fraction within a NS, reflect the symmetry energy contributions to the Equation of State that dominate when neutron and proton densities differ strongly. To constrain these contributions at supra-saturation densities, we measure the spectra of charged pions produced by colliding rare isotope tin (Sn) beams with isotopically enriched Sn targets. Using ratios of the charged pion spectra measured at high transverse momenta, we deduce the slope of the symmetry energy to be $42 < L < 117$ MeV. This value is slightly lower but consistent with the $L$ values deduced from a recent measurement of the neutron skin thickness of $^{208}$Pb.
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Submitted 11 March, 2021;
originally announced March 2021.
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Symmetry energy investigation with pion production from Sn+Sn systems
Authors:
G. Jhang,
J. Estee,
J. Barney,
G. Cerizza,
M. Kaneko,
J. W. Lee,
W. G. Lynch,
T. Isobe,
M. Kurata-Nishimura,
T. Murakami,
C. Y . Tsang,
M. B. Tsang,
R. Wang,
D. S. Ahn,
L. Atar,
T. Aumann,
H. Baba,
K. Boretzky,
J. Brzychczyk,
N. Chiga,
N. Fukuda,
I. Gasparic,
B. Hong,
A. Horvat,
K. Ieki
, et al. (55 additional authors not shown)
Abstract:
In the past two decades, pions created in the high density regions of heavy ion collisions have been predicted to be sensitive at high densities to the symmetry energy term in the nuclear equation of state, a property that is key to our understanding of neutron stars. In a new experiment designed to study the symmetry energy, the multiplicities of negatively and positively charged pions have been…
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In the past two decades, pions created in the high density regions of heavy ion collisions have been predicted to be sensitive at high densities to the symmetry energy term in the nuclear equation of state, a property that is key to our understanding of neutron stars. In a new experiment designed to study the symmetry energy, the multiplicities of negatively and positively charged pions have been measured with high accuracy for central $^{132}$Sn+$^{124}$Sn, $^{112}$Sn+$^{124}$Sn, and $^{108}$Sn+$^{112}$Sn collisions at $E/A=270~\mathrm{MeV}$ with the S$π$RIT Time Projection Chamber. While the uncertainties of individual pion multiplicities are measured to 4\%, those of the charged pion multiplicity ratios are measured to 2\%. We compare these data to predictions from seven major transport models. The calculations reproduce qualitatively the dependence of the multiplicities and their ratios on the total neutron to proton number in the colliding systems. However, the predictions of the transport models from different codes differ too much to allow extraction of reliable constraints on the symmetry energy from the data. This finding may explain previous contradictory conclusions on symmetry energy constraints obtained from pion data in Au+Au system. These new results call for better understanding of the differences among transport codes, and new observables that are more sensitive to the density dependence of the symmetry energy.
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Submitted 13 December, 2020;
originally announced December 2020.
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The S$π$RIT Time Projection Chamber
Authors:
J. Barney,
J. Estee,
W. G. Lynch,
T. Isobe,
G. Jhang,
M. Kurata-Nishimura,
A. B. McIntosh,
T. Murakami,
R. Shane,
S. Tangwancharoen,
M. B. Tsang,
G. Cerizza,
M. Kaneko,
J. W. Lee,
C. Y. Tsang,
R. Wang,
C. Anderson,
H. Baba,
Z. Chajecki,
M. Famiano,
R. Hodges-Showalter,
B. Hong,
T. Kobayashi,
P. Lasko,
J. Łukasik
, et al. (15 additional authors not shown)
Abstract:
The SAMURAI Pion Reconstruction and Ion-Tracker Time Projection Chamber (S$π$RIT TPC) was designed to enable measurements of heavy ion collisions with the SAMURAI spectrometer at the RIKEN Radioactive Isotope Beam Factory and provide constraints on the Equation of State of neutron-rich nuclear matter. The S$π$RIT TPC has a 50.5 cm drift length and an 86.4 cm $\times$ 134.4 cm pad plane with 12,096…
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The SAMURAI Pion Reconstruction and Ion-Tracker Time Projection Chamber (S$π$RIT TPC) was designed to enable measurements of heavy ion collisions with the SAMURAI spectrometer at the RIKEN Radioactive Isotope Beam Factory and provide constraints on the Equation of State of neutron-rich nuclear matter. The S$π$RIT TPC has a 50.5 cm drift length and an 86.4 cm $\times$ 134.4 cm pad plane with 12,096 pads that are equipped with the Generic Electronics for TPCs readout electronics. The S$π$RIT TPC allows excellent reconstruction of particles and provides isotopic resolution for pions and other light charged particles across a wide range of energy losses and momenta. Details of the S$π$RIT TPC are presented, along with discussion of the TPC performance based on cosmic ray and experimental data.
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Submitted 21 May, 2020;
originally announced May 2020.
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Charged particle track reconstruction with S$π$RIT Time Projection Chamber
Authors:
J. W. Lee,
G. Jhang,
G. Cerizza,
J. Barney,
J. Estee,
T. Isobe,
M. Kaneko,
M. Kurata-Nishimura,
W. G. Lynch,
T. Murakami,
C. Y. Tsang,
M. B. Tsang,
R. Wang,
B. Hong,
A. B. McIntosh,
H. Sakurai,
C. Santamaria,
R. Shane,
S. Tangwancharoen,
S. J. Yennello,
Y. Zhang
Abstract:
In this paper, we present a software framework, S$π$RITROOT, which is capable of track reconstruction and analysis of heavy-ion collision events recorded with the S$π$RIT time projection chamber. The track-fitting toolkit GENFIT and the vertex reconstruction toolkit RAVE are applied to a box-type detector system. A pattern recognition algorithm which performs helix track finding and handles overla…
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In this paper, we present a software framework, S$π$RITROOT, which is capable of track reconstruction and analysis of heavy-ion collision events recorded with the S$π$RIT time projection chamber. The track-fitting toolkit GENFIT and the vertex reconstruction toolkit RAVE are applied to a box-type detector system. A pattern recognition algorithm which performs helix track finding and handles overlapping pulses is described. The performance of the software is investigated using experimental data obtained at the Radioactive Isotope Beam Facility (RIBF) at RIKEN. This work focuses on data from $^{132}$Sn + $^{124}$Sn collision events with beam energy of 270 AMeV. Particle identification is established using $\left<dE/dx\right>$ and magnetic rigidity, with pions, hydrogen isotopes, and helium isotopes.
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Submitted 10 January, 2020;
originally announced January 2020.
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Space Charge Effects in the S$π$RIT Time Projection Chamber
Authors:
C. Y. Tsang,
J. Estee,
R. Wang,
J. Barney,
G. Jhang,
W. G. Lynch,
Z. Q. Zhang,
G. Cerizza,
T. Isobe,
M. Kaneko,
M. Kurata-Nishimura,
J. W. Lee,
T. Murakami,
M. B. Tsang,
S$π$RIT collaboration
Abstract:
Time projection chambers (TPCs) are widely used in nuclear and particle physics. They are particularly useful when measuring reaction products from heavy ion collisions. Most nuclear experiments at low energy are performed in a fixed target configuration, in which the unreacted beam will pass through the detection volume. As the beam intensity increases, the buildup of positive ions created from t…
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Time projection chambers (TPCs) are widely used in nuclear and particle physics. They are particularly useful when measuring reaction products from heavy ion collisions. Most nuclear experiments at low energy are performed in a fixed target configuration, in which the unreacted beam will pass through the detection volume. As the beam intensity increases, the buildup of positive ions created from the ionization of the detector gas by the beam creates the main source of space charge, distorting the nominal electric field of the TPC. This has a profound effect on the accuracy of the measured momenta of the emitted particles. In this paper we will discuss the magnitude of the effects and construct an observable more appropriate for fixed target experiments to study the effects. We also will present an algorithm for correcting the space charge and some of the implications it has on the momentum determination.
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Submitted 29 January, 2020; v1 submitted 23 December, 2019;
originally announced December 2019.
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Development of a novel MPGD-based drift chamber for the NSCL/FRIB S800 spectrometer
Authors:
M. Cortesi,
J. Pereira,
D. Bazin,
Y. Ayyad,
G. Cerizza,
R. Fox,
R. G. T. Zegers
Abstract:
The performance of a novel tracking detector developed for the focal plane of the NSCL/FRIB S800 magnetic spectrometer is presented. The detector comprises a large-area drift chamber equipped with a hybrid Micro-Pattern Gaseous Detector (MPGD)-based readout. The latter consists of a position-sensitive Micromegas detector preceded by a two-layer M-THGEM multiplier as a pre-amplification stage. The…
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The performance of a novel tracking detector developed for the focal plane of the NSCL/FRIB S800 magnetic spectrometer is presented. The detector comprises a large-area drift chamber equipped with a hybrid Micro-Pattern Gaseous Detector (MPGD)-based readout. The latter consists of a position-sensitive Micromegas detector preceded by a two-layer M-THGEM multiplier as a pre-amplification stage. The signals from the Micromegas readout are processed by a data acquisition system based on the General Electronics for TPC (GET). The drift chamber has an effective area of around 60x30 cm^2, which matches to the very large acceptance of the S800 spectrometer. This work discusses in detail the results of performance evaluation tests carried out with a low-energy alpha-particles source and with high-energy heavy-ion beams with the detector installed at the S800 focal plane. In this latter case, the detector was irradiated with a 150 MeV/u 78Kr36+ beam as well as a heavy-ion fragmentation cocktail beam produced by the 78Kr36+ beam impinging on a thin beryllium target. Sub-millimeter position resolution is obtained in both dispersive and non-dispersive directions.
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Submitted 7 December, 2019;
originally announced December 2019.
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Particle decays of levels in $^{11,12}$N and $^{12}$O investigated with the invariant-mass method
Authors:
T. B. Webb,
R. J. Charity,
J. M. Elson,
D. E. M Hoff,
C. D. Pruitt,
L. G. Sobotka,
K. W. Brown,
J. Barney,
G. Cerizza,
J. Estee,
G. Jhang,
W. G. Lynch,
J. Manfredi,
P. Morfouace,
C. Santamaria,
S. Sweany,
M. B. Tsang,
T. Tsang,
S. M. Wang,
Y. Zhang,
K. Zhu,
S. A. Kuvin,
D. McNeel,
J. Smith,
A. H. Wuosmaa
, et al. (1 additional authors not shown)
Abstract:
Particle-decaying states of the light nuclei $^{11,12}$N and $^{12}$O were studied using the invariant-mass method. The decay energies and intrinsic widths of a number of states were measured, and the momentum correlations of three-body decaying states were considered. A second 2$p$-decaying 2$^+$ state of $^{12}$O was observed for the first time, and a higher energy $^{12}$O state was observed in…
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Particle-decaying states of the light nuclei $^{11,12}$N and $^{12}$O were studied using the invariant-mass method. The decay energies and intrinsic widths of a number of states were measured, and the momentum correlations of three-body decaying states were considered. A second 2$p$-decaying 2$^+$ state of $^{12}$O was observed for the first time, and a higher energy $^{12}$O state was observed in the 4$p$+2$α$ decay channel. This 4$p$+2$α$ channel also contains contributions from fission-like decay paths, including $^6$Be$_{g.s.}$+$^{6}$Be$_{g.s.}$. Analogs to these states in $^{12}$O were found in $^{12}$N in the 2$p$+$^{10}$B and 2$p$+$α$+$^6$Li channels. The momentum correlations for the prompt 2$p$ decay of $^{12}$O$_{g.s.}$ were found to be nearly identical to those of $^{16}$Ne$_{g.s.}$, and the correlations for the new 2$^+$ state were found to be consistent with sequential decay through excited states in $^{11}$N. The momentum correlations for the 2$^+_1$ state in $^{12}$O provide a new value for the $^{11}$N ground-state energy. The states in $^{12}$N/$^{12}$O that belong to the $A$=12 isobaric sextet do not deviate from the quadratic isobaric multiplet mass equation (IMME) form.
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Submitted 10 April, 2020; v1 submitted 26 June, 2019;
originally announced June 2019.
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First observation of unbound $^{11}$O, the mirror of the halo nucleus $^{11}$Li
Authors:
T. B. Webb,
S. M. Wang,
K. W. Brown,
R. J. Charity,
J. M. Elson,
J. Barney,
G. Cerizza,
Z. Chajecki,
J. Estee,
D. E. M. Hoff,
S. A. Kuvin,
W. G. Lynch,
J. Manfredi,
D. McNeel,
P. Morfouace,
W. Nazarewicz,
C. D. Pruitt,
C. Santamaria,
J. Smith,
L. G. Sobotka,
S. Sweany,
C. Y. Tsang,
M. B. Tsang,
A. H. Wuosmaa,
Y. Zhang
, et al. (1 additional authors not shown)
Abstract:
The structure of the extremely proton-rich nucleus $^{11}_{~8}$O$_3$, the mirror of the two-neutron halo nucleus $^{11}_{~3}$Li$_8$, has been studied experimentally for the first time. Following two-neutron knockout reactions with a $^{13}$O beam, the $^{11}$O decay products were detected after two-proton emission and used to construct an invariant-mass spectrum. A broad peak of width $\sim$3\,MeV…
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The structure of the extremely proton-rich nucleus $^{11}_{~8}$O$_3$, the mirror of the two-neutron halo nucleus $^{11}_{~3}$Li$_8$, has been studied experimentally for the first time. Following two-neutron knockout reactions with a $^{13}$O beam, the $^{11}$O decay products were detected after two-proton emission and used to construct an invariant-mass spectrum. A broad peak of width $\sim$3\,MeV was observed. Within the Gamow coupled-channel approach, it was concluded that this peak is a multiplet with contributions from the four-lowest $^{11}$O resonant states: $J^π$=3/2$^-_1$, 3/2$^-_2$, 5/2$^+_1$, and 5/2$^+_2$. The widths and configurations of these states show strong, non-monotonic dependencies on the depth of the $p$-$^9$C potential. This unusual behavior is due to the presence of a broad threshold resonant state in $^{10}$N, which is an analog of the virtual state in $^{10}$Li in the presence of the Coulomb potential. After optimizing the model to the data, only a moderate isospin asymmetry between ground states of $^{11}$O and $^{11}$Li was found.
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Submitted 20 March, 2019; v1 submitted 20 December, 2018;
originally announced December 2018.
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Pion Production in Rare Isotope Collisions
Authors:
M. B. Tsang,
J. Estee,
H. Setiawan,
W. G. Lynch,
J. Barney,
M. B. Chen,
G. Cerizza,
P. Danielewicz,
J. Hong,
P. Morfouace,
R. Shane,
S. Tangwancharoen,
K. Zhu,
T. Isobe,
M. Kurata-Nishimura,
J. Lukasik,
T. Murakami,
the SπRIT collaboration
Abstract:
Pion energy spectra are presented for central collisions of neutron-rich 132Sn+124Sn and neutron-deficient 108Sn+112Sn systems using simulations with Boltzmann-Uehling-Uhlenbeck transport model. These calculations, which incorporate isospin-dependent mean field potentials for relevant baryons and mesons, display a sensitivity to the pion spectra that could allow significant constraints on the dens…
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Pion energy spectra are presented for central collisions of neutron-rich 132Sn+124Sn and neutron-deficient 108Sn+112Sn systems using simulations with Boltzmann-Uehling-Uhlenbeck transport model. These calculations, which incorporate isospin-dependent mean field potentials for relevant baryons and mesons, display a sensitivity to the pion spectra that could allow significant constraints on the density dependence of the symmetry energy and its mean field potential at supra-saturation densities. The predicted sensitivity increases with the isospin asymmetry of the total system and decreases with incident energy.
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Submitted 12 March, 2017; v1 submitted 20 December, 2016;
originally announced December 2016.
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KATANA - a charge-sensitive triggering system for the S$π$RIT experiment
Authors:
P. Lasko,
M. Adamczyk,
J. Brzychczyk,
P. Hirnyk,
J. Łukasik,
P. Pawłowski,
K. Pelczar,
A. Snoch,
A. Sochocka,
Z. Sosin,
J. Barney,
G. Cerizza,
J. Estee,
T. Isobe,
G. Jhang,
M. Kaneko,
M. Kurata-Nishimura,
W. G. Lynch,
T. Murakami,
C. Santamaria,
M. B. Tsang,
Y. Zhang
Abstract:
KATANA - the Krakow Array for Triggering with Amplitude discrimiNAtion - has been built and used as a trigger and veto detector for the S$π$RIT TPC at RIKEN. Its construction allows operating in magnetic field and providing fast response for ionizing particles, giving the approximate forward multiplicity and charge information. Depending on this information, trigger and veto signals are generated.…
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KATANA - the Krakow Array for Triggering with Amplitude discrimiNAtion - has been built and used as a trigger and veto detector for the S$π$RIT TPC at RIKEN. Its construction allows operating in magnetic field and providing fast response for ionizing particles, giving the approximate forward multiplicity and charge information. Depending on this information, trigger and veto signals are generated. The article presents performance of the detector and details of its construction. A simple phenomenological parametrization of the number of emitted scintillation photons in plastic scintillator is proposed. The effect of the light output deterioration in the plastic scintillator due to the in-beam irradiation is discussed.
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Submitted 13 January, 2017; v1 submitted 21 October, 2016;
originally announced October 2016.
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Recent direct reaction experimental studies with radioactive tin beams
Authors:
K. L. Jones,
S. Ahn,
J. M. Allmond,
A. Ayres,
D. W. Bardayan,
T. Baugher,
D. Bazin,
J. S. Berryman,
A. Bey,
C. Bingham,
L. Cartegni,
G. Cerizza,
K. Y. Chae,
J. A. Cizewski,
A. Gade,
A. Galindo-Uribarri,
R. F. Garcia-Ruiz,
R. Grzywacz,
M. E. Howard,
R. L. Kozub,
J. F. Liang,
B. Manning,
M. Matos,
S. McDaniel,
D. Miller
, et al. (18 additional authors not shown)
Abstract:
Direct reaction techniques are powerful tools to study the single-particle nature of nuclei. Performing direct reactions on short-lived nuclei requires radioactive ion beams produced either via fragmentation or the Isotope Separation OnLine (ISOL) method. Some of the most interesting regions to study with direct reactions are close to the magic numbers where changes in shell structure can be track…
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Direct reaction techniques are powerful tools to study the single-particle nature of nuclei. Performing direct reactions on short-lived nuclei requires radioactive ion beams produced either via fragmentation or the Isotope Separation OnLine (ISOL) method. Some of the most interesting regions to study with direct reactions are close to the magic numbers where changes in shell structure can be tracked. These changes can impact the final abundances of explosive nucleosynthesis. The structure of the chain of tin isotopes is strongly influenced by the Z=50 proton shell closure, as well as the neutron shell closures lying in the neutron-rich, N=82, and neutron-deficient, N=50, regions. Here we present two examples of direct reactions on exotic tin isotopes. The first uses a one-neutron transfer reaction and a low-energy reaccelerated ISOL beam to study states in 131Sn from across the N=82 shell closure. The second example utilizes a one-neutron knockout reaction on fragmentation beams of neutron-deficient 106,108Sn. In both cases, measurements of gamma rays in coincidence with charged particles proved to be invaluable.
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Submitted 26 August, 2015;
originally announced August 2015.
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Neutron Knockout on Beams of $^{108,106}$Sn and $^{106}$Cd
Authors:
Giordano Cerizza
Abstract:
Characterizing the nature of single-particle states outside of double shell closures is essential to a fundamental understanding of nuclear structure. This is especially true for those doubly magic nuclei that lie far from stability and where the shell closures influence nucleo-synthetic pathways. The region around $^{100}$Sn is one of the most important due to the proximity of the N=Z=50 magic nu…
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Characterizing the nature of single-particle states outside of double shell closures is essential to a fundamental understanding of nuclear structure. This is especially true for those doubly magic nuclei that lie far from stability and where the shell closures influence nucleo-synthetic pathways. The region around $^{100}$Sn is one of the most important due to the proximity of the N=Z=50 magic numbers, the proton-drip line, and the end of the rp-process. However, owing to the low production rates, there is a lack of spectroscopic information and no firm spin-parity assignment for ground states of odd-A isotopes close to $^{100}$Sn. Neutron knockout reaction experiments on beams of $^{108,106}$Sn and $^{106}$Cd have been performed at the NSCL. By measuring gamma rays and momentum distributions from reaction residues, the spin of ground state and first excited state for $^{107,105}$Sn have been established. The results also show a degree of mixing in the ground states of the isotopes $^{108,106}$Sn between the d$_{5/2}$ and g$_{7/2}$ single particle-states and they are compared to reaction calculations. Single-, double-, and triple-neutron knockout reactions on the $^{106}$Cd beam have been observed. The spin-parity of $^{105}$Cd is already known, therefore, the measurement of the momentum distributions of the ground and first excited states of this residue is an important validation of the technique used for the light tin isotopes.
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Submitted 5 January, 2015;
originally announced January 2015.
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The Physics of the B Factories
Authors:
A. J. Bevan,
B. Golob,
Th. Mannel,
S. Prell,
B. D. Yabsley,
K. Abe,
H. Aihara,
F. Anulli,
N. Arnaud,
T. Aushev,
M. Beneke,
J. Beringer,
F. Bianchi,
I. I. Bigi,
M. Bona,
N. Brambilla,
J. B rodzicka,
P. Chang,
M. J. Charles,
C. H. Cheng,
H. -Y. Cheng,
R. Chistov,
P. Colangelo,
J. P. Coleman,
A. Drutskoy
, et al. (2009 additional authors not shown)
Abstract:
This work is on the Physics of the B Factories. Part A of this book contains a brief description of the SLAC and KEK B Factories as well as their detectors, BaBar and Belle, and data taking related issues. Part B discusses tools and methods used by the experiments in order to obtain results. The results themselves can be found in Part C.
Please note that version 3 on the archive is the auxiliary…
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This work is on the Physics of the B Factories. Part A of this book contains a brief description of the SLAC and KEK B Factories as well as their detectors, BaBar and Belle, and data taking related issues. Part B discusses tools and methods used by the experiments in order to obtain results. The results themselves can be found in Part C.
Please note that version 3 on the archive is the auxiliary version of the Physics of the B Factories book. This uses the notation alpha, beta, gamma for the angles of the Unitarity Triangle. The nominal version uses the notation phi_1, phi_2 and phi_3. Please cite this work as Eur. Phys. J. C74 (2014) 3026.
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Submitted 31 October, 2015; v1 submitted 24 June, 2014;
originally announced June 2014.
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Study of the Bs->J/psi phi decay in pp collisions at sqrt(s)=7 TeV with the CMS detector
Authors:
Giordano Cerizza
Abstract:
B-hadrons are an ideal tool for advancing our current understanding of the flavor sector of the Standard Model (SM). The study of B-meson production and decays is one of the key physics themes at the Large Hadron Collider (LHC) thanks to the large production rate and the fact that B-hadrons are relatively easy to trigger on and identify due to their long lifetime and decays to muons. This talk pre…
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B-hadrons are an ideal tool for advancing our current understanding of the flavor sector of the Standard Model (SM). The study of B-meson production and decays is one of the key physics themes at the Large Hadron Collider (LHC) thanks to the large production rate and the fact that B-hadrons are relatively easy to trigger on and identify due to their long lifetime and decays to muons. This talk presents the cross section measurement for the exclusive final state Bs->J/psi phi and an evaluation of the decay branching fraction from the previously published exclusive-B production cross sections. Besides probing the heavy quark properties for the first time at the LHC energy, these measurements are also important tools for understanding and calibrating the detector, giving input for Monte Carlo tuning, and providing results for direct comparison with other experiments.
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Submitted 29 September, 2011;
originally announced September 2011.