Nuclear Theory·nucl-th

Tuesday·August 6, 2019

13 papers—6 primary·7 cross-listed

01
[Submitted on 2 Aug 2019]
Calculating n-Point Charge Correlations in Evolving Systems
Scott Pratt🇺🇸
In dynamic systems, charge susceptibilities and local charge correlations change with time. These changes are accompanied by non-local correlations which spread diffusively with time and are constrained by local charge conservation. Assuming the local features of the correlation, which for a gas would be the correlation of charges within the same particle, are equilibrated, a diagrammatic formalism is presented for calculating the evolution of the associated non-local correlations. These provide correlations of $n$ density operators at different positions for arbitrary $n$ . The techniques were developed with an eye towards relativistic heavy-ion collisions, and can account for correlations indexed by up, down and strange charges. Understanding the evolution of such correlations is crucial if one is to interpret measurements of charge fluctuations from the Relativistic Heavy-Ion Collider.
Comments:
14 pages, two figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1908.01053 [pdf]
PRC(2020)·9 citations
02
[Submitted on 3 Aug 2019]
Isospin splitting of pion elliptic flow in relativistic heavy-ion collisions
He Liu🇨🇳 · Feng-Tao Wang🇨🇳 · Kai-Jia Sun🇺🇸 · Jun Xu🇨🇳 · Che Ming Ko🇺🇸
Based on the framework of an extended multiphase transport model with mean-field potentials in both the partonic phase and the hadronic phase, we explain the elliptic flow difference between $π^{+}$ and $π^{-}$ in the beam-energy scan program at the relativistic heavy-ion collider by incorporating the vector-isovector potential for quarks and antiquarks with different isospins. It is found that the isospin splitting of pion elliptic flow favors a strong vector-isovector interaction, and thus serves as a probe of the quark matter equation of state as well as the QCD phase structure at finite baryon and isospin chemical potentials.
Comments:
6 pages, 6 pages
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex)
arXiv:
1908.01156 [pdf]
PLB(2019)·21 citations
03
[Submitted on 4 Aug 2019]
Backward nucleon production by heavy baryonic resonances in proton-nucleus collisions
Oleksandra Panova🇺🇦 · Anton Motornenko🇩🇪 · Mark I. Gorenstein🇺🇦 · Jan Steinheimer🇩🇪 · Horst Stoecker🇩🇪
The production of backward nucleons, $N (18 0^{\circ})$ , at $18 0^{\circ}$ in the nuclear target rest frame in proton-nucleus ( $p + A$ ) collisions is studied. The backward nucleons appearing outside of the kinematically allowed range of proton-nucleon ( $p + N$ ) reactions are shown to be due to secondary reactions of heavy baryonic resonances produced inside the nucleus. Baryonic resonances $R$ created in primary $p + N$ reactions can change their masses and momenta due to successive collisions $R + N \to R + N$ with other nuclear nucleons. Two distinct mechanisms and kinematic restrictions are studied: the reaction $R + N \to N (18 0^{\circ}) + N$ and the resonance decay $R \to N (18 0^{\circ}) + π$ . Simulations of $p + A$ collisions using the Ultra-relativistic Quantum Molecular Dynamics model support these mechanisms and are consistent with available data on proton backward production.
Comments:
16 pages, 15 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1908.01365 [pdf]
PRC(2019)·5 citations
04
[Submitted on 4 Aug 2019]
Decay widths at the scission point in nuclear fission
G.F. Bertsch · L.M. Robledo
An outstanding problem in the theory of nuclear fission is understanding the Hamiltonian dynamics at the scission point. Here we apply the Generator Coordinate Method to calculate decay widths for pre-scission configurations into the two-fragment continuum. Transitions that are allowed under diabatic dynamics can have widths up to several MeV. For non-diabatic decays through the pairing interaction, typical widths to a specific final state channel are 2-3 orders of magnitude smaller. The nucleus U-236 is taken as a representative example in the calculations.
Comments:
To be submitted to Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1908.01368 [pdf]
PRC(2019)·12 citations
05
[Submitted on 5 Aug 2019]
Jet charge in high energy nuclear collisions
Shi-Yong Chen🇨🇳 · Ben-Wei Zhang🇨🇳 · En-Ke Wang🇨🇳
Averaged jet charge characterizes the electric charge for the initiating parton, and provides a powerfull tool to distinguish quark jets from gluon jets. In this paper, we give the first prediction for the medium modification of averaged jet charge in heavy-ion collision at the LHC, where jet productions in p+p collisions are simulated by PYTHIA6, and parton energy loss in QGP are calculated with two Monte Carlo models of jet quenching: PYQUEN and JEWEL. We found that the distribution of averaged jet charge is significantly suppressed by initial state isospin effects due to the participants of neutrons with zero electric charge during nuclear collisions. Considerable enhancement of averaged jet charge in central Pb+Pb collisions relative to peripheral collisions is observed, since jet quenching effect is more pronounced in central collisions. Distinct feature of averaged jet charge between quark and gluon jets, together with the sensitivity of medium modifications on jet charge to flavor dependence of parton energy loss, could be very useful to discriminate the energy loss pattern between quark and gluon jets in heavy-ion collisions.
Comments:
6 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1908.01518 [pdf]
CPC(2020)·32 citations
06
[Submitted on 5 Aug 2019]
Electroweak Current Operators in Chiral Effective Field Theory
Hermann Krebs🇩🇪
In this proceeding I briefly review current status of the construction of nuclear electro-weak currents within chiral effective field theory. I show that gauge and chiral symmetry requirements lead to the well-known continuity equations for the current and charge operators which, however, get modified at higher orders. Regularization of the current will be also discussed. I demonstrate that implementation of a cutoff regulator in a naive way leads to violation of chiral symmetry. To respect the underlying symmetries I propose to use higher derivative regularization in the nuclear forces and currents.
Comments:
10 pages, 4 tables, Contribution to the proceedings of the 9th International workshop on Chiral Dynamics (PoS CD18)
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1908.01538 [pdf]
PoS(2019)·14 citations
07
[Submitted on 23 Jul 2019] (cross-list from hep-lat)
Spectral functions and critical dynamics of the $O (4)$ model from classical-statistical lattice simulations
Sören Schlichting🇩🇪 · Dominik Smith🇩🇪 · Lorenz von Smekal🇩🇪
We calculate spectral functions of the relativistic $O (4)$ model from real-time lattice simulations in classical-statistical field theory. While in the low and high temperature phase of the model, the spectral functions of longitudinal $(σ)$ and transverse $(π)$ modes are well described by relativistic quasi-particle peaks, we find a highly non-trivial behavior of the spectral functions in the cross over region, where additional structures appear. Similarly, we observe a significant broadening of the quasi-particle peaks, when the amount explicit $O (4)$ symmetry breaking is reduced. We further demonstrate that in the vicinity of the $O (4)$ critical point, the spectral functions develop an infrared power law associated with the critical dynamics, and comment on the extraction of the dynamical critical exponent $z$ from our simulations.
Subjects:
High Energy Physics — Lattice (hep-lat); Statistical Mechanics (cond-mat.stat-mech); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1908.00912 [pdf]
NPB(2020)·36 citations
08
[Submitted on 2 Aug 2019] (cross-list from hep-ph)
Hadron and Nuclear Physics on the Light Front
Stanley J. Brodsky🇺🇸 · Alexandre Deur🇺🇸
The QCD light-front (LF) Hamiltonian equation H_{LF}|\Psi> = M^2 |\Psi> derived from quantization at fixed LF time \tau = t+z/c provides a causal, frame-independent, method for computing hadron spectroscopy as well as dynamical observables such as structure functions, transverse momentum distributions, and distribution amplitudes. The LF formalism also leads to novel nuclear phenomena, such as "hidden color", "color transparency", "nuclear-bound quarkonium" and the shadowing and antishadowing of nuclear structure functions. For example, there are five distinct color-singlet Fock state representations of the six color-triplet quarks of the deuteron. The hidden color Fock states become manifest when the deuteron is probed when it has small transverse size, as in measurements of the deuteron form factor at large momentum transfer. The QCD Lagrangian with zero quark mass has no explicit mass scale. However, as shown by de Alfaro, Fubini, and Furlan (dAFF), a mass scale can appear in the equations of motion without affecting the conformal invariance of the Action. When one applies the dAFF procedure to the QCD LF Hamiltonian, it leads to a color confining potential \kappa^4 \zeta^2 for mesons, where \zeta^2 is the LF radial variable conjugate to the qbar-q invariant mass squared. The same result, including spin terms, is obtained using LF holography (AdS/QCD) -- the duality between LF dynamics and AdS_5 -- if one modifies the AdS_5 Action by the dilaton exp{+\kappa^2 z^2} in the fifth dimension z. If this procedure is generalized using superconformal algebra, the resulting LF eigensolutions provide unified Regge spectroscopy of mesons, baryons, and tetraquarks, including remarkable supersymmetric relations between the masses of mesons, baryons and tetraquarks with a universal Regge slope...
Comments:
8 pages, 3 figures. Contribution to the proceedings of 13th International Conference on Nucleus-Nucleus Collisions (NN2018) in Omiya, Japan. Plenary talk given by S. J. Brodsky. arXiv admin note: text overlap with arXiv:1802.08552, arXiv:1709.01191, arXiv:1611.0719
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1908.01043 [pdf]
JPS Conf.Proc.(2020)·1 citation
09
[Submitted on 3 Aug 2019] (cross-list from hep-ph)
Centrality dependence of Electrical and Hall conductivity at RHIC and LHC energies for a Conformal System
Bhaswar Chatterjee🇮🇳 · Rutuparna Rath🇮🇳 · Golam Sarwar🇮🇳 · Raghunath Sahoo🇮🇳
In this work, we study electrical conductivity and Hall conductivity in the presence of electromagnetic field using Relativistic Boltzmann Transport Equation with Relaxation Time Approximation. We evaluate these transport coefficients for a strongly interacting system consisting of nearly massless particles which is similar to Quark-Gluon Plasma and is likely to be formed in heavy-ion collision experiments. We explicitly include the effects of magnetic field in the calculation of relaxation time. The values of magnetic field are obtained for all the centrality classes of Au+Au collisions at $s_{NN} =$ 200 GeV and Pb+Pb collisions at $s_{NN} =$ 2.76 TeV. We consider the three lightest quark flavors and their corresponding antiparticles in this study. We estimate the temperature dependence of the electrical conductivity and Hall conductivity for different strengths of magnetic field. We observe a significant dependence of temperature on electrical and Hall conductivity in the presence of magnetic field.
Comments:
Same as the published version in EPJA
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1908.01121 [pdf]
EPJA(2021)·11 citations
10
[Submitted on 3 Aug 2019] (cross-list from hep-ph)
Modeling of Charged-Neutral Kaon Fluctuations as a Signature of DCC Production in A--A Collisions
Ranjit Nayak🇮🇳 · Sadhana Dash🇮🇳 · Basanata Nandi🇮🇳 · Claude Pruneau🇺🇸
Anomalous event-by-event fluctuations of the relative yields of neutral (K $_{s}^{0}$ ) and charged kaon (K $^{\pm}$ ) have been predicted to yield a signature for the formation of Disoriented Chiral Condensate (DCC) in relativistic heavy-ion collisions. In this work, we model the production and decay of DCCs in the context of heavy-ion collisions at the Large Hadron Collider, and estimate the sensitivity of large acceptance detectors, such as the ALICE detector, towards the identification of such anomalous decays. Our study is based on the robust statistical observable, $ν_{dyn}$ , known for its sensitivity to dynamical fluctuations. We first present simulations without DCCs, based on the HIJING and AMPT models, in order to establish an approximate reference for the magnitude of $ν_{dyn} (K^{\pm}, K_{s}^{0})$ and its centrality evolution in Pb--Pb collisions at the TeV energy scale. We next introduce simple phenomenological models of K $_{s}^{0}$ vs. K $^{\pm}$ event-by-event yield fluctuations, which we use to study the feasibility and sensitivity of detection of the production of DCCs in heavy-ion collisions. Although the precision of models such as HIJING and AMPT limit their use as absolute references and thus render anomalous fluctuations difficult to define precisely, our studies demonstrate that the magnitude of $ν_{dyn} (K^{\pm}, K_{s}^{0})$ is in fact very sensitive to the presence of small admixture of DCCs in normal non-DCC events. Consequently, while large values of $ν_{dyn} (K^{\pm}, K_{s}^{0})$ may not be sufficient to identify the existence of DCCs, nonetheless they constitute a first and necessary condition to signal their possible production in heavy-ion collisions.
Comments:
7 pages, 5 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1908.01130 [pdf]
PRC(2020)·11 citations
11
[Submitted on 3 Aug 2019] (cross-list from hep-ph)
Nucleon resonances in $γ p \to ω p$ reaction
N.C. Wei🇨🇳 · F. Huang🇨🇳 · K. Nakayama🇺🇸 · D. M. Li🇨🇳
The most recent high-precision data on spin observables $Σ$ , $T$ , $P^{'}$ , $E$ , $F$ and $H$ reported by the CLAS Collaboration together with the previous data on differential cross sections and spin-density-matrix elements reported by the CLAS, A2, GRAAL, SAPHIR and CBELSA/TAPS Collaborations for the reaction $γ p \to ω p$ are analyzed within an effective Lagrangian approach. The reaction amplitude is constructed by considering the $t$ -channel $π$ and $η$ exchanges, the $s$ -channel nucleon and nucleon resonances exchanges, the $u$ -channel nucleon exchange and the generalized contact current. The latter accounts effectively for the interaction current and ensures that the full photoproduction amplitude is gauge invariant. It is shown that all the available CLAS data can be satisfactorily described by considering the $N (1520) 3/ 2^{-}$ , $N (1700) 3/ 2^{-}$ , $N (1720) 3/ 2^{+}$ , $N (1860) 5/ 2^{+}$ , $N (1875) 3/ 2^{-}$ , $N (1895) 1/ 2^{-}$ and $N (2060) 5/ 2^{-}$ resonances in the $s$ -channel. The parameters of these resonances are extracted and compared with those quoted by PDG.
Comments:
22 pages, 17 figures, version to appear in PRD
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1908.01139 [pdf]
PRD(2019)·23 citations
12
[Submitted on 3 Aug 2019] (cross-list from hep-ph)
Pion off-shell electromagnetic form factors: data extraction and model analysis
Ho-Meoyng Choi🇰🇷 · T. Frederico🇧🇷 · Chueng-Ryong Ji🇺🇸 · J. P. B. C. de Melo🇧🇷
We investigate the pion electromagnetic half off-shell form factors, which parametrize the matrix element of the charged pion electromagnetic current with one leg off-mass-shell and the other leg on-mass-shell, using an exactly solvable manifestly covariant model of a $(3 + 1)$ dimensional fermion field theory. The model provides a 3D imaging of the two off-shell pion form factors $F_{1}$ and $F_{2}$ as a function of $(Q^{2}, t)$ , which are related to each other satisfying the Ward-Takahashi identity. The normalization of the renormalized charge form factor $F_{1}$ is fixed by $F_{1} (Q^{2} = 0, t = m_{π}^{2}) = 1$ while the other form factor $F_{2}$ vanishes, i.e. $F_{2} (Q^{2}, t = m_{π}^{2}) = 0$ for any value of $Q^{2}$ due to the time-reversal invariance of the strong interaction. We define the new form factor $g (Q^{2}, t) = F_{2} (Q^{2}, t) / (t - m_{π}^{2})$ and find that $g (Q^{2}, t)$ can be measurable in the on-mass-shell limit. In particular, $g (Q^{2} = 0, t = m_{π}^{2})$ is related with the pion charge radius. We also compare our form factors with the data extracted from the pion electroproduction reaction for both the off-shell region ( $t < 0$ ) and the on-shell limit ( $t \to m_{π}^{2}$ ).
Comments:
typo corrected; revision for the discussion in Sec. III.; 11pages, 10 figures; version to appear in Physical Review D
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1908.01185 [pdf]
PRD(2019)·14 citations
13
[Submitted on 4 Aug 2019] (cross-list from hep-ph)
On the stability of two-flavor and three-flavor quark stars
Qianyi Wang🇨🇳 · Tong Zhao🇨🇳 · Hongshi Zong🇨🇳
Following our recenty proposed self-consistent mean-field approximation approach, we have done some researches on the chiral phase transition of strong interaction matter within the framework of Nambu-Jona-Lasinio (NJL) model. The chiral susceptibility and equation of state (EOS) are computed in this work for both two-flavor and three-flavor quark matter for contrast. The Pauli-Villars scheme, which can preserve gauge invariance, is used in this paper. Moreover, whether the three-flavor quark matter is more stable than the two-flavor quark matter or not in quark stars is discussed in this work. In our model, when the bag constant are the same, the two-flavor quark matter has a higher pressure than the three-flavor quark matter, which is different from what Witten proposed in his pioneering work.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1908.01325 [pdf]
10 citations

Affiliations

first authorsco-authorsvia INSPIRE