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.
Use of Bayesian Optimization to Understand the Structure of Nuclei
Authors:
J. Hooker,
J. Kovoor,
K. L. Jones,
R. Kanungo,
M. Alcorta,
J. Allen,
C. Andreoiu,
L. Atar,
D. W. Bardayan,
S. S. Bhattacharjee,
D. Blankstein,
C. Burbadge,
S. Burcher,
W. N. Catford,
S. Cha,
K. Chae,
D. Connolly,
B. Davids,
N. Esker,
F. H. Garcia,
S. Gillespie,
R. Ghimire,
A. Gula,
G. Hackman,
S. Hallam
, et al. (19 additional authors not shown)
Abstract:
Monte Carlo simulations are widely used in nuclear physics to model experimental systems. In cases where there are significant unknown quantities, such as energies of states, an iterative process of simulating and fitting is often required to describe experimental data. We describe a Bayesian approach to fitting experimental data, designed for data from a $^{12}$Be(d,p) reaction measurement, using…
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Monte Carlo simulations are widely used in nuclear physics to model experimental systems. In cases where there are significant unknown quantities, such as energies of states, an iterative process of simulating and fitting is often required to describe experimental data. We describe a Bayesian approach to fitting experimental data, designed for data from a $^{12}$Be(d,p) reaction measurement, using simulations made with GEANT4. Q-values from the $^{12}$C(d,p) reaction to well-known states in $^{13}$C are compared with simulations using BayesOpt. The energies of the states were not included in the simulation to reproduce the situation for $^{13}$Be where the states are poorly known. Both cases had low statistics and significant resolution broadening owing to large proton energy losses in the solid deuterium target. Excitation energies of the lowest three excited states in $^{13}$C were extracted to better than 90 keV, paving a way for extracting information on $^{13}$Be.
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Submitted 9 December, 2021;
originally announced December 2021.