Nuclear Theory·nucl-th

Monday·December 14, 2020

6 papers—3 primary·3 cross-listed

01
[Submitted on 11 Dec 2020]
Fire streaks, electromagnetic effects, directed flow and lifetime of the plasma at SPS energies
Vitalii Ozvenchuk🇵🇱 · Antoni Szczurek🇵🇱 · Andrzej Rybicki🇵🇱
We present our calculation of electromagnetic effects, induced by the spectator charge on Feynman- $x_{F}$ distributions of charged pions in peripheral $P b + P b$ collisions at CERN SPS energies, including realistic initial space-time-momentum conditions for pion emission. The calculation is performed in the framework of a specific implementation of the fire-streak model, adopted to the production of both $π^{-}$ and $π^{+}$ mesons. Isospin effects are included to take into account the asymmetry in production of $π^{+}$ and $π^{-}$ at high rapidity. A comparison to a simplified model from the literature is made. We obtain a good description of the NA49 data on the $x_{F}$ - and $p_{T}$ -dependence of the ratio of cross sections $π^{+} / π^{-}$ . The experimental data favors short times ( $0.5 < τ < 2$ ~fm/ $c$ ) for fast pion creation in the local fire-streak rest frame. The possibility of the expansion of the spectators is considered in our calculation, and its influence on the electromagnetic effect observed for the $π^{+} / π^{-}$ ratio is discussed. The influence of directed and elliptic flow, and vorticity on the observed effect is also estimated. We conclude that the fire-streak model, which properly describes the centrality dependence of $π^{-}$ rapidity spectra at CERN SPS energies, also provides realistic initial conditions for pion production. Consequently, it provides a quantitative description of the electromagnetic effect on the $π^{+} / π^{-}$ ratio as a function of $x_{F}$ .
Comments:
6 pages, 4 figures. arXiv admin note: substantial text overlap with arXiv:1910.04544
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2012.06243 [pdf]
PoS(2021)·1 citation
02
[Submitted on 11 Dec 2020]
Vector meson mass in the chiral symmetry restored vacuum
Jisu Kim🇰🇷 · Su Houng Lee🇰🇷
We calculate the mass of the vector meson in the chiral symmetry restored vacuum. This is accomplished by separating the four quark operators appearing in the vector and axial vector meson sum rules into chiral symmetric and symmetry breaking parts depending on the contribution of the fermion zero modes. We then identify each part from the fit to the vector and axial vector meson masses. By taking the chiral symmetry breaking part to be zero while keeping the symmetric operator to the vacuum value, we find that the chiral symmetric part of the vector and axial vector meson mass to be between 550 and 600 MeV. This demonstrates that chiral symmetry breaking, while responsible for the mass difference between chiral partner, accounts only for a small fraction of the symmetric part of the mass.
Comments:
5 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2012.06463 [pdf]
PRD(2021)·19 citations
03
[Submitted on 11 Dec 2020]
Microscopic origin of reflection-asymmetric nuclear shapes
Mengzhi Chen · Tong Li · Jacek Dobaczewski · Witold Nazarewicz
Background: The presence of nuclear ground states with stable reflection-asymmetric shapes is supported by rich experimental evidence. Theoretical surveys of odd-multipolarity deformations predict the existence of pear-shaped isotopes in several fairly localized regions of the nuclear landscape in the vicinity of near-lying single-particle shells with $Δ ℓ = Δ j = 3$ . Purpose: We analyze the role of isoscalar, isovector, neutron-proton, neutron-neutron, and proton-proton multipole interaction energies in inducing the onset of reflection-asymmetric ground-state deformations. Methods: The calculations are performed in the framework of axial reflection-asymmetric Hartree-Fock-Bogoliubov theory using two Skyrme energy density functionals and density-dependent pairing force. Results: We show that reflection-asymmetric ground-state shapes of atomic nuclei are driven by the odd-multipolarity neutron-proton (or isoscalar) part of the nuclear interaction energy. This result is consistent with the particle-vibration picture, in which the main driver of octupole instability is the isoscalar octupole-octupole interaction giving rise to large $E 3$ polarizability.
Comments:
11 pages, 12 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2012.06500 [pdf]
PRC(2021)·24 citations
04
[Submitted on 10 Dec 2020] (cross-list from hep-ph)
Pion crystals hosting topologically stable baryons
Fabrizio Canfora🇨🇱 · Stefano Carignano🇪🇸 · Marcela Lagos🇨🇱 · Massimo Mannarelli🇮🇹 · Aldo Vera🇨🇱
We construct analytic (3+1)-dimensional inhomogeneous and topologically non-trivial pion systems using chiral perturbation theory. We discuss the effect of isospin asymmetry with vanishing electromagnetic interactions as well as some particular configurations with non-vanishing electromagnetic interactions. The inhomogeneous configurations of the pion fields are characterized by a non-vanishing topological charge that can be identified with baryons surrounded by a cloud of pions. This system supports a topologically protected persistent superflow. When the electromagnetic field is turned on the superflow corresponds to an electromagnetic supercurrent.
Comments:
v2: extended discussion and added references; matches published version on Physical Review D
Subjects:
High Energy Physics — Phenomenology (hep-ph); Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th)
arXiv:
2012.05921 [pdf]
PRD(2021)·36 citations
05
[Submitted on 11 Dec 2020] (cross-list from hep-ph)
Collisional energy loss and the Chiral Magnetic Effect
Jeremy Hansen🇺🇸 · Kirill Tuchin🇺🇸
Collisional energy loss of a fast particle in a medium is mostly due to the medium polarization by the electromagnetic fields of the particle. A small fraction of energy is carried away by the Cherenkov radiation. In chiral medium there is an additional contribution to the energy loss due to induction of the anomalous current proportional to the magnetic field. It causes the particle to lose energy mostly in the form of the \emph{chiral} Cherenkov radiation. We employ classical electrodynamics, adequate in a wide range of particle energies, to compute the collisional energy loss by a fast particle in a homogenous chiral plasma and apply the results to Quark-Gluon Plasma and a Weyl semimetal. In the later case photon spectrum is strongly enhanced in the ultraviolet and X-ray regions which makes it amenable to experimental investigation. Our main observation is that while the collisional energy loss in a non-chiral medium is a slow, at most logarithmic, function of energy $E$ , the chiral Cherenkov radiation is proportional to $E^{2}$ when the recoil is neglected and to $E$ when it is taken into account.
Comments:
13 pages, 2 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Nuclear Theory (nucl-th)
arXiv:
2012.06089 [pdf]
PRC(2021)·12 citations
06
[Submitted on 11 Dec 2020] (cross-list from hep-ph)
Dijet Acoplanarity in CUJET3 as a Probe of the Nonperturbative Color Structure of QCD Perfect Fluids
M. Gyulassy🇺🇸 · P.M. Jacobs🇺🇸 · J. Liao🇺🇸 · S. Shi🇨🇦 · X.N. Wang🇺🇸 · F.Yuan🇺🇸
Using the CUJET3=DGLV+VISHNU jet-medium interaction framework, we show that dijet azimuthal acoplanarity in high energy $A + A$ collisions is sensitive to possible non-perturbative enhancement of the jet transport coefficient, $q^(T, E)$ , in the QCD crossover temperature $T \sim 150 - 300$ MeV range. With jet-medium couplings constrained by global RHIC\& LHC $χ^{2}$ fits to nuclear modification data on $R_{AA}$ , we compare predictions of the medium induced dijet transverse momentum squared, $Q_{s}^{2} \sim ⟨ q^L ⟩ \sim Δ ϕ^{2} E^{2}$ , in two models of the temperature, $T$ , and jet energy $E$ dependence of the jet medium transport coefficient, $q^(T, E)$ . In one model, wQGP, only perturbative quark and gluon dof are assumed. In the second model, sQGMP, nonperturbative three component semi-Quark-Gluon and Magnetic Monopole dof are asssumed. We show that the dijet path averaged medium induced azimuthal acoplanarity, $Δ ϕ^{2}$ , in sQGMP is robustly a factor of $\sim 2$ larger than in perturbative wQGP while the radiative energy loss in both models is nearly identical as required to fit the same single jet nuclear modification $R_{AA}$ data. Future A+A dijet acoplanarity measurements correlated with $R_{AA}$ and azimuthal asymmetry $v_{n}$ measurements therefore appears to be a promising strategy to search for possible signatures of critical opalescence like phenomena in the QCD confinement temperature range.
Comments:
4 pages, 5 figures, Published in the Proceedings of XXVIIIth International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2019)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2012.06151 [pdf]
NPA(2021)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE

Fire streaks, electromagnetic effects, directed flow and lifetime of the plasma at SPS energies

Vector meson mass in the chiral symmetry restored vacuum

Microscopic origin of reflection-asymmetric nuclear shapes

Pion crystals hosting topologically stable baryons

Collisional energy loss and the Chiral Magnetic Effect

Dijet Acoplanarity in CUJET3 as a Probe of the Nonperturbative Color Structure of QCD Perfect Fluids

Affiliations