Nuclear Theory·nucl-th

Thursday·November 16, 2023

11 papers—6 primary·5 cross-listed

07
[Submitted on 14 Nov 2023] (cross-list from hep-ph)
Relaxation time for the alignment between quark spin and angular velocity in a rotating QCD medium
Alejandro Ayala🇲🇽 · Santiago Bernal-Langarica🇲🇽 · Isabel Domínguez Jiménez🇲🇽 · Ivonne Maldonado🇷🇺 · José Jorge Medina-Serna🇲🇽 · Javier Rendón🇲🇽 · María Elena Tejeda-Yeomans🇲🇽
We compute the relaxation times for massive quarks and anti-quarks to align their spins with the angular velocity in a rigidly rotating medium at finite temperature and baryon density. The rotation effects are implemented using a fermion propagator immersed in a cylindrical rotating environment. The relaxation time is computed as the inverse of the interaction rate to produce an asymmetry between the quark (anti-quark) spin components along and opposite to the angular velocity. For conditions resembling heavy-ion collisions, the relaxation times for quarks are smaller than for anti-quarks. For semi-central collisions the relaxation time is within the possible life-time of the QGP for all collision energies. However, for anti-quarks this happens only for collision energies $s_{N N} ≳ 50$ GeV. The results are quantified in terms of the intrinsic quark and anti-quark polarizations, namely, the probability to build the spin asymmetry as a function of time. Our results show that these intrinsic polarizations tend to 1 with time at different rates given by the relaxation times with quarks reaching a sizable asymmetry at a faster pace. These are key results to further elucidate the mechanisms of hyperon polarization in relativistic heavy-ion collisions.
Comments:
9 pages, 10 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2311.07859 [pdf]
PRD(2024)·8 citations
08
[Submitted on 14 Nov 2023] (cross-list from hep-ph)
Pion distribution functions from low-order Mellin moments
Ya Lu🇨🇳 · Yin-Zhen Xu🇪🇸 · Khépani Raya🇪🇸 · Craig D. Roberts🇨🇳 · José Rodríguez-Quintero🇪🇸
Exploiting an evolution scheme for parton distribution functions (DFs) that is all-orders exact, contemporary lattice-QCD (lQCD) results for low-order Mellin moments of the pion valence quark DF are shown to be mutually consistent. The analysis introduces a means by which key odd moments can be obtained from the even moments in circumstances where only the latter are available. Combining these elements, one arrives at parameter-free lQCD-based predictions for the pointwise behaviour of pion valence, glue, and sea DFs, with sound uncertainty estimates. The behaviour of the pion DFs at large light-front momentum fraction, $x > 0.85$ , is found to be consistent with QCD expectations and continuum analyses of pion structure functions, i.e., damping like $(1 - x)^{β_{parton}}$ , with $β_{valence} \approx 2.4$ , $β_{glue} \approx 3.6$ , $β_{sea} \approx 4.6$ . It may be possible to test these predictions using data from forthcoming experiments.
Comments:
7 pages, 4 figures, 1 table
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2311.08565 [pdf]
PLB(2024)·35 citations
09
[Submitted on 15 Nov 2023] (cross-list from quant-ph)
Identification of a natural fieldlike entanglement resource in trapped-ion chains
Natalie Klco🇺🇸 · D. H. Beck🇺🇸
The electromagnetic trapping of ion chains can be regarded as a process of non-trivial entangled quantum state preparation within Hilbert spaces of the local axial motional modes. To begin uncovering properties of this entanglement resource produced as a byproduct of conventional ion-trap quantum information processing, the quantum continuous-variable formalism is herein utilized to focus on the leading-order entangled ground state of local motional modes in the presence of a quadratic trapping potential. The decay of entanglement between disjoint subsets of local modes is found to exhibit features of entanglement structure and responses to partial measurement reminiscent of the free massless scalar field vacuum. With significant fidelities between the two, even for large system sizes, a framework is established for initializing quantum field simulations via "imaging" extended entangled states from natural sources, rather than building correlations through deep circuits of few-body entangling operators. By calculating probabilities in discrete Fock subspaces of the local motional modes, considerations are presented for locally transferring these pre-distributed entanglement resources to the qudits of ion internal energy levels, improving this procedure's anticipated experimental viability.
Comments:
9 pages, 4 figures, 3 appendices
Subjects:
Quantum Physics (quant-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2311.08842 [pdf]
PRA(2024)·4 citations
10
[Submitted on 15 Nov 2023] (cross-list from nucl-ex)
Systematic study of the low-lying electric dipole strength in Sn isotopes and its astrophysical implications
M. Markova🇳🇴 · A. C. Larsen🇳🇴 · P. von Neumann-Cosel🇩🇪 · E. Litvinova🇺🇸 · A. Choplin🇧🇪 · S. Goriely🇧🇪 · S. Martinet🇧🇪 · L. Siess🇧🇪 · M. Guttormsen🇳🇴 · F. Pogliano🇳🇴 · S. Siem🇳🇴
The $γ$ -ray strength functions (GSF) and nuclear level densities (NLD) below the neutron threshold have been extracted for $^{111 - 113, 116 - 122, 124}$ Sn from particle- $γ$ coincidence data with the Oslo method. The evolution of bulk properties of the low-lying electric dipole response has been investigated on the basis of the Oslo GSF data and results of a recent systematic study of electric and magnetic dipole strengths in even-even Sn isotopes with relativistic Coulomb excitation. The obtained GSFs reveal a resonance-like peak on top of the tail of the isovector giant dipole resonance, centered at $\approx$ 8 MeV and exhausting $\approx$ 2\% of the classical Thomas-Reiche-Kuhn (TRK) sum. In contrast to predictions of the relativistic quasiparticle random-phase and time-blocking approximation calculations (RQRPA and RQTBA), no monotonous increase in the total low-lying $E 1$ strength was observed in the experimental data from $^{111}$ Sn to $^{124}$ Sn, demonstrating rather similar strength distributions in these nuclei. The Oslo GSFs and NLDs were further used as inputs to constrain the cross sections and Maxwellian-averaged cross sections of $(n, γ)$ reactions in the Sn isotopic chain using TALYS. The obtained results agree well with other available experimental data and the recommended values from the JINA REACLIB, BRUSLIB, and KADoNiS libraries. Despite relatively small exhausted fractions of the TRK sum rule, the low-lying electric dipole strength makes a noticeable impact on the radiative neutron-capture cross sections in stable Sn isotopes. Moreover, the experimental Oslo inputs for the $^{121, 123}$ Sn $(n, γ)$ $^{122, 124}$ Sn reactions were found to affect the production of Sb in the astrophysical $i$ -process, providing new constraints on the uncertainties of the resulting chemical abundances from multi-zone low-metallicity Asymptotic Giant Branch stellar models.
Comments:
27 pages, 14 pages. Submitted to Physical Review C journal on 13 November 2023
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2311.08864 [pdf]
PRC(2024)·23 citations
11
[Submitted on 15 Nov 2023] (cross-list from hep-ph)
Breakdown of collinear factorization in the exclusive photoproduction of a $π^{0} γ$ pair with large invariant mass
Saad Nabeebaccus🇫🇷 · Jakob Schoenleber🇩🇪 · Lech Szymanowski🇵🇱 · Samuel Wallon🇫🇷
We study the exclusive photoproduction of a $π^{0} γ$ pair with large invariant mass $M_{γ π}^{2}$ , which is sensitive to the exchange of either two quarks or two gluons in the $t$ -channel. In this paper, we show that the process involving two-gluon exchanges does not factorize in the Bjorken limit at the leading twist. This can be explicitly demonstrated by the fact that there exist diagrams, which contribute at the leading twist, for which Glauber gluons are trapped, due to the pinching of the contour integration of both the plus and minus component of the Glauber gluon momentum. For the same reason, $π^{0}$ -nucleon scattering to two photons also suffers from the same issue. On the other hand, we stress that there are no issues with respect to collinear factorization for the quark channels. By considering an analysis of all potential reduced diagrams of leading pinch-singular surfaces, we argue that the quark channel is safe from Glauber pinches, and therefore, a collinear factorization in that case follows through without any problems. This means that processes where gluon exchanges are forbidden, such as the exclusive photoproduction of $π^{\pm} γ$ and $ρ^{0, \pm} γ$ , are unaffected by the factorization breaking effects we point out in this paper.
Comments:
23 pages, 12 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2311.09146 [pdf]
PRD(2025)·24 citations

Affiliations

first authorsco-authorsvia INSPIRE

Relaxation time for the alignment between quark spin and angular velocity in a rotating QCD medium

Pion distribution functions from low-order Mellin moments

Identification of a natural fieldlike entanglement resource in trapped-ion chains

Systematic study of the low-lying electric dipole strength in Sn isotopes and its astrophysical implications

Breakdown of collinear factorization in the exclusive photoproduction of a π0γ pair with large invariant mass

Affiliations

Breakdown of collinear factorization in the exclusive photoproduction of a $π^{0} γ$ pair with large invariant mass