Nuclear Theory·nucl-th

Monday·October 10, 2022

7 papers—4 primary·3 cross-listed

01
[Submitted on 6 Oct 2022]
Studying the impact of the nucleon size in relativistic heavy-ion collisions
João Paulo Picchetti🇧🇷
The hydrodynamic stage of relativistic heavy-ion collisions simulations requires an energy density profile of the system as an initial condition. In the process of converting the two colliding nuclei into such an energy distribution, some specification about the $size$ of their constituent nucleons inevitably has to be made. Nucleons are commonly modeled as bidimensional Gaussians, and the Gaussian width (the nucleon-width) is a free parameter of the simulation. A best-fit value of the nucleon-width can be inferred by Bayesian Analyses, where the model is confronted with experimental data. Some of the most recent analyses have obtained surprisingly large values for the nucleon width parameter, exceeding in over 50 % the current value for the proton charged radius. This motivates the development of a better understanding of the role played by this parameter inside the simulation. In this work, we perform simulations of Pb-Pb collisions at $s_{NN}$ = 2.76 TeV using a state-of-the-art hybrid simulation chain, using three different values of the nucleon width inside the initial condition generator T $_{R}$ ENTo, and systematically investigate its effects on the initial condition characteristics and observables. The nucleon-width strongly affects the eccentricity harmonics and the gradients in the initial condition. The $⟨ p_{T} ⟩$ of particles in the simulation using $w$ = 0.5 fm is much larger than experimental data. We associate this to the combination of stronger gradients in the initial condition and the coupling of a conformal pre-equilibrium dynamics to the hydrodynamic simulation. Our findings suggest that the large values of the nucleon width returned by recent Bayesian Analyses were necessary to lower the mean transverse momentum, by damping the gradients in the initial condition.
Comments:
75 pages, 40 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2210.03186 [pdf]
0 citations
02
[Submitted on 7 Oct 2022]
Slope parameters determined from CREX and PREX2 (published in Results in Physics)
Shingo Tagami · Tomotsugu Wakasa · Masanobu Yahiro
[Background] Very lately, the CREX group presents a skin value $Δ R_{skin}^{48} (CREX) = 0.121 \pm 0.026 (exp) \pm 0.024 (model) = 0.071 \sim 0.171$ ~fm. Meanwhile, the PREX group reported a skin value $Δ R_{skin}^{208} (PREX2) = 0.283 \pm 0.071 = 0.212 \sim 0.354$ ~fm. In our previous paper, we determined both the $L$ -- $Δ R_{skin}^{48}$ relation and the $L$ -- $Δ R_{skin}^{208}$ one, using 206 EoSs, where $L$ is a slope parameter. [Purpose] We determine $L$ from $Δ R_{skin}^{48} (CREX)$ and $Δ R_{skin}^{208} (PREX2)$ , using 207 EoSs. [Results] The $Δ R_{skin}^{48} (CREX)$ yields $L (CREX) = 0 \sim 51$ ~MeV and the $Δ R_{skin}^{208} (PREX2)$ does $L (PREX2) = 76 \sim 165$ ~MeV. [Conclusion] There is no overlap between $L (CREX)$ and $L (PREX2)$ . This is a big problem to be solved.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2210.03313 [pdf]
6 citations
03
[Submitted on 7 Oct 2022]
Ab initio calculation of charge symmetry breaking in $A = 7$ and $8$ $Λ$ -hypernuclei
Hoai Le🇩🇪 · Johann Haidenbauer🇩🇪 · Ulf-G. Meißner🇩🇪 · Andreas Nogga🇩🇪
The separation energies of the isospin triplet $_{Λ}^{7} He$ , $_{Λ}^{7} L i^{*}$ , $_{Λ}^{7}$ Be, and the $T = 1/2$ doublet $_{Λ}^{8}$ Li, $_{Λ}^{8}$ Be are investigated within the no-core shell model. Calculations are performed based on a hyperon-nucleon potential derived from chiral effective field theory at next-to-leading order. The potential includes the leading charge-symmetry breaking (CSB) interaction in the $Λ$ N channel, whose strength has been fixed to the experimentally known difference of the $Λ$ separation energies of the mirror hypernuclei $_{Λ}^{4} He$ and $_{Λ}^{4} H$ . It turns out that the CSB predicted for the $A = 7$ systems is small and agrees with the splittings deduced from the empirical binding energies within the experimental uncertainty. In case of the $A = 8$ doublet, the computed CSB is somewhat larger than the available experimental value. Using other experimental input for $A = 4$ can change this prediction moving it closer to experiment.
Comments:
11 pages, 4 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2210.03387 [pdf]
PRC(2023)·26 citations
04
[Submitted on 7 Oct 2022]
Towards a unified treatment of $Δ S = 0$ parity violation in low-energy nuclear processes
Susan Gardner🇺🇸 · Girish Muralidhara🇺🇸
We revisit the unified treatment of low-energy hadronic parity violation espoused by Desplanques, Donoghue, and Holstein to the end of an ab initio treatment of parity violation in low-energy nuclear processes within the Standard Model. We use our improved effective Hamiltonian and precise non-perturbative assessments of the quark charges of the nucleon within lattice QCD to make new assessments of the parity-violating meson-nucleon coupling constants. Comparing with recent, precise measurements of hadronic parity violation in few-body nuclear reactions, we find improved agreement with these experimental results, though some tensions remain. We thus note the broader problem of comparing low-energy constants from nuclear and few-nucleon systems, considering, too, unresolved theoretical issues in connecting an ab initio, effective Hamiltonian approach to chiral effective theories. We note how future experiments and lattice QCD studies could sharpen the emerging picture, promoting the study of hadronic parity violation as a laboratory for testing ``end-to-end'' theoretical descriptions of weak processes in hadrons and nuclei at low energies.
Comments:
13 pages, REVTeX, 1 figure; note partial overlap in content with arXiv:2203.00033v1 (not v2); extended discussion and refs. added, results unchanged
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2210.03567 [pdf]
PRC(2023)·9 citations

Affiliations

first authorsco-authorsvia INSPIRE

Studying the impact of the nucleon size in relativistic heavy-ion collisions

Slope parameters determined from CREX and PREX2 (published in Results in Physics)

Ab initio calculation of charge symmetry breaking in A=7 and 8 Λ-hypernuclei

Towards a unified treatment of ΔS=0 parity violation in low-energy nuclear processes

Affiliations

Ab initio calculation of charge symmetry breaking in $A = 7$ and $8$ $Λ$ -hypernuclei

Towards a unified treatment of $Δ S = 0$ parity violation in low-energy nuclear processes