Nuclear Theory·nucl-th

Tuesday·August 24, 2021

9 papers—4 primary·5 cross-listed

01
[Submitted on 21 Aug 2021]
Evidence of the triaxial structure of $^{129}$ Xe at the Large Hadron Collider
Benjamin Bally🇪🇸 · Michael Bender🇫🇷 · Giuliano Giacalone🇩🇪 · Vittorio Somà🇫🇷
The interpretation of the emergent collective behaviour of atomic nuclei in terms of deformed intrinsic shapes [1] is at the heart of our understanding of the rich phenomenology of their structure, ranging from nuclear energy to astrophysical applications across a vast spectrum of energy scales. A new window onto the deformation of nuclei has been recently opened with the realization that nuclear collision experiments performed at high-energy colliders, such as the CERN Large Hadron Collider (LHC), enable experimenters to identify the relative orientation of the colliding ions in a way that magnifies the manifestations of their intrinsic deformation [2]. Here we apply this technique to LHC data on collisions of $^{129}$ Xe nuclei [3-5] to exhibit the first evidence of non-axiality in the ground state of ions collided at high energy. We predict that the low-energy structure of $^{129}$ Xe is triaxial (a spheroid with three unequal axes), and show that such deformation can be determined from high-energy data. This result demonstrates the unique capabilities of precision collider machines such as the LHC as new means to perform imaging of the collective structure of atomic nuclei.
Comments:
8 pages; 4 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2108.09578 [pdf]
PRL(2022)·105 citations
02
[Submitted on 22 Aug 2021]
Exploring the string shoving model in PYTHIA8 for collective behaviors in $pp$ collisions
Junlee Kim🇰🇷 · Eun-Joo Kim🇰🇷 · SuJeong Ji🇰🇷 · SangHoon Lim🇰🇷
Two-particle correlations have been used to study property of a produced medium called Quark-Gluon Plasma (QGP) in relativistic heavy-ion collisions, and a long-range correlation among produced particles has been considered as a strong evidence of strongly interacting QGP. Strikingly, clear long-range correlations have been also observed in small collision systems like $pp$ and $p$ + $A$ at a wide range of collision energies. A model introducing a repulsive force between flux tubes called string shoving can qualitatively describe the long-range near-side correlations in high multiplicity $pp$ collisions. This model implemented in the PYTHIA Monte Carlo event generator allows us to perform detailed study. In this work, a full data analysis to calculate associated yields and flow coefficients is performed with PYTHIA events, and the results are compared with experimental results. We find that the string shoving model overestimates long-range near-side correlations particularly in low multiplicity events. We also introduce a method to subtract such overestimated correlations in low multiplicity to have a more relevant comparison with the data.
Comments:
12 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2108.09686 [pdf]
J.Korean Phys.Soc.(2021)·9 citations
03
[Submitted on 22 Aug 2021]
Restoring Broken Symmetries for Nuclei and Reaction Fragments
Aurel Bulgac
In typical microscopic approaches, particularly when pairing correlations are present, nuclei and nuclear fragments do not have well defined quantum numbers and symmetries should be restored. I present here a formalism for the simultaneous projection of total particle numbers of a nucleus, particle number of reaction fragments, and of the reaction fragment intrinsic spins and of their correlation, and also for their symmetry restored densities and total energies. These new formulas for the symmetry restored quantities, are free of any singularities, unlike those in the previously introduced prescriptions.
Comments:
10 pages, published version, a number of corrections comlared to intial version
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2108.09846 [pdf]
PRC(2021)·9 citations
04
[Submitted on 23 Aug 2021]
Recent progress on few-body hypernuclei
Avraham Gal🇮🇱
Few-body $Λ$ hypernuclei provide valuable information towards understanding strange matter. Recent experimental progress by the STAR Collaboration at the RHIC facility and by the ALICE Collaboration at the LHC has been matched by theoretical progress reviewed here: (i) lifetimes of the hypertriton $_{Λ}^{3}$ H, $_{Λ}^{3}$ n if particle-stable, $_{Λ}^{4}$ H and $_{Λ}^{4}$ He and their charge symmetry breaking, and (ii) the onset of $ΛΛ$ hypernuclear binding.
Comments:
Invited talk at the 19th International Conference on Strangeness in Quark Matter (SQM 2021), online from BNL Upton NY USA, May 2021. Submitted to EPJ Web of Conferences. v2: Ref.[30] added, errors corrected. v3: updated slightly beyond published version
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2108.10179 [pdf]
EPJ Web Conf.(2022)·8 citations
05
[Submitted on 20 Aug 2021] (cross-list from nucl-ex)
The Physics of Neutrinoless Double Beta Decay: A Primer
B.J.P. Jones🇺🇸
Neutrinoless double beta decay is a hypothetical radioactive process which, if observed, would prove the neutrino to be a Majorana fermion: a particle that is its own antiparticle. In this lecture mini-series I discuss the physics of Majorana fermions and the connection between the nature of neutrino mass and neutrinoless double beta decay. We review Dirac and Majorana spinors, discuss methods of distinguishing between Majorana and Dirac fermions, and derive in outline the connection between neutrino mass and double beta decay rates. We conclude by briefly summarizing the experimental landscape and the challenges associated with searches for this elusive process.
Comments:
A write-up of a lecture series given at the Theoretical Advanced Study Institute: The Obscure Universe: Neutrinos and Other Dark Matters - TASI2020 summer school v2: Fix some typos from v1
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2108.09364 [pdf]
35 citations
06
[Submitted on 21 Aug 2021] (cross-list from hep-ph)
3-dimensional QCD phase diagram with pion condensate in the NJL model
Lu-Meng Liu🇨🇳 · Jun Xu🇨🇳 · Guang-Xiong Peng🇨🇳
With the isovector coupling constants adjusted to reproduce the physical pion mass and lattice QCD results in baryon-free quark matter, we have carried out rigourous calculations for the pion condensate in the 3-flavor Nambu-Jona-Lasinio model, and studied the 3-dimensional QCD phase diagram. With the increasing isospin chemical potential $μ_{I}$ , we have observed two nonzero solutions of the pion condensate at finite baryon chemical potentials $μ_{B}$ , representing respectively the pion superfluid phase and the Sarma phase, and their appearance and disappearance correspond to a second-order (first-order) phase transition at higher (lower) temperatures $T$ and lower (higher) $μ_{B}$ . Calculations by assuming equal constituent mass of $u$ and $d$ quarks would lead to large errors of the QCD phase diagram within $μ_{B} \in (500, 900)$ MeV, and affect the position of the critical end point.
Comments:
14 pages, 10 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2108.09477 [pdf]
PRD(2021)·17 citations
07
[Submitted on 22 Aug 2021] (cross-list from hep-ph)
Chiral vortical catalysis
Yin Jiang🇨🇳
Gluon interaction introduces remarkable corrections to the magnetic polarization effects on the chiral fermions, which is known as the inverse magnetic catalysis. It is a natural speculation that the vorticity, which has many similar properties as magnetic field, would bring non-negligible contribution to the chiral rotational suppression. Using the intuitive semi-classical background field method we studied the rotation dependence of the effective strong interaction coupling. Contrary to the magnetic field case the rotation increases the effective coupling which leads to slowing down the condensate melting procedure with temperature. This could be named as the chiral vortical catalysis or inverse rotation suppression. Imposing such dependence to the coupling in the NJL model, we numerically checked this analysis qualitatively. The pseudo critical temperature is shown to rise with the rotation and approach saturation eventually which may be induced by the model cutoff.
Comments:
6 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2108.09622 [pdf]
EPJC(2022)·20 citations
08
[Submitted on 22 Aug 2021] (cross-list from hep-ph)
Femtoscopic study of coupled-channel $N Ξ$ and $ΛΛ$ interactions
Y. Kamiya🇨🇳 · K. Sasaki🇯🇵 · T. Fukui🇯🇵 · T. Hyodo🇯🇵 · K. Morita🇯🇵 · K. Ogata🇯🇵 · A. Ohnishi🇯🇵 · T. Hatsuda🇯🇵
The momentum correlation functions of S = -2 baryon pairs (p Xi^- and Lambda Lambda) produced in high-energy pp and pA collisions are investigated on the basis of the coupled-channel formalism. The strong interaction is described by the coupled-channel HAL QCD potential obtained by the lattice QCD simulations near physical quark masses, while the hadronic source function is taken to be a static Gaussian form. The coupled-channel effect, the threshold difference, the realistic strong interaction, and the Coulomb interaction are fully taken into account for the first time in the femtoscopic analysis of baryon-baryon correlations. The characteristic features of the experimental data for the p Xi^- and Lambda Lambda pairs at LHC are reproduced quantitatively with a suitable choice of non-femtoscopic parameters and the source size. The agreement between theory and experiment indicates that the N Xi (Lambda Lambda) interaction is moderately (weakly) attractive without having a quasi-bound (bound) state.
Comments:
13 pages, 10 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2108.09644 [pdf]
PRC(2022)·68 citations
09
[Submitted on 23 Aug 2021] (cross-list from physics.data-an)
Pileup Correction on Higher-order Cumulants with Unfolding Approach
Yu Zhang🇨🇳 · Yige Huang🇨🇳 · Toshihiro Nonaka🇯🇵 · Xiaofeng Luo🇨🇳
Higher-order cumulants of conserved charge distributions are sensitive observables to probe the critical fluctuations near QCD critical point in heavy-ion collisions. Due to high interaction rate, pileup event can be one of the major sources of background in the measurements of higher-order cumulants. In this paper, we studied the effects of pileup events on higher-order cumulants of proton multiplicity distributions using UrQMD model. It is found that the proposed pileup correction fails if the correction parameters are determined by the Glauber fitting of charged particle multiplicities, which is usually done in the real heavy-ion experiment. To address this, we propose a model independent unfolding approach to determine the parameters in the pileup correction. This approach can be applied in the pileup correction for the future measurement of higher-order cumulants in heavy-ion collision experiment.
Comments:
14 pages, 6 figures
Subjects:
Data Analysis, Statistics and Probability (physics.data-an); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2108.10134 [pdf]
Nucl.Instrum.Meth.A(2022)·13 citations

Affiliations

first authorsco-authorsvia INSPIRE