Nuclear Theory·nucl-th

Thursday·March 30, 2023

8 papers—4 primary·4 cross-listed

05
[Submitted on 28 Mar 2023] (cross-list from hep-ph)
High-energy dipole scattering amplitude from evolution of low-energy proton light-cone wave functions
Adrian Dumitru🇺🇸 · Heikki Mäntysaari🇫🇮 · Risto Paatelainen🇫🇮
The forward scattering amplitude of a small dipole at high energies is given in the mean field approximation by the Balitsky-Kovchegov (BK) evolution equation. It requires an initial condition $N (r; x_{0})$ describing the scattering of a dipole with size $r$ off the target that is probed at momentum fraction $x_{0}$ . Rather than using ad hoc parameterizations tuned to high-energy data at $x ≪ x_{0}$ , here we attempt to construct an initial scattering amplitude that is consistent with low-energy, large- $x$ properties of the proton. We start from a non-perturbative three quark light-cone model wave function from the literature. We add $O (g)$ corrections due to the emission of a gluon, and $O (g^{2})$ virtual corrections due to the exchange of a gluon, computed in light-cone perturbation theory with exact kinematics. We provide numerical data as well as analytic parameterizations of the resulting $N (r; x_{0})$ for $x_{0} = 0.01 - 0.05$ . Solving the BK equation in the leading logarithmic (LL) approximation towards lower $x$ , we obtain a fair description of the charm cross section in deeply inelastic scattering measured at HERA by fitting one parameter, the coupling constant $α_{s} ≃ 0.2$ . However, without the option to tune the initial amplitude at $x_{0}$ , the fit of the high precision data results in $χ^{2} / N_{dof} = 2.3$ at $N_{dof} = 38$ , providing clear statistical evidence for the need of systematic improvement e.g. of the photon wave function, evolution equation, and initial condition.
Comments:
11 pages, 10 figures. Obtained dipole-proton amplitudes at different x are included in the ancillary files, v2 matches published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2303.16339 [pdf]
PRD(2023)·15 citations
06
[Submitted on 29 Mar 2023] (cross-list from quant-ph)
Degeneracy in excited-state quantum phase transitions of two-level bosonic models and its influence on system dynamics
J. Khalouf-Rivera · Qian Wang · Lea F. Santos · J.E. García Ramos · M. Carvajal · F. Pérez-Bernal
Excited-state quantum phase transitions (ESQPTs) strongly influence the spectral properties of collective many-body quantum systems, changing degeneracy patterns in different quantum phases. Level degeneracies, in turn, affect the system's dynamics. We analyze the degeneracy dependence on the size of two-level boson models with a $u (n + 1)$ dynamical algebra, where $n$ is the number of collective degrees of freedom. Below the ESQPT critical energy of these models, the energy gap between neighboring levels that belong to different symmetry sectors gets close to zero as the system size increases. We report and explain why this gap goes to zero exponentially for systems with one collective degree of freedom, but algebraically in models with more than one degree of freedom. As a consequence, we show that the infinite-time average of out-of-time-order correlators is an ESQPT order parameter in finite systems with $n = 1$ , but in systems with $n > 1$ , this average only works as an order parameter in the mean-field limit.
Subjects:
Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech); Nuclear Theory (nucl-th)
arXiv:
2303.16551 [pdf]
PRA(2024)·8 citations
07
[Submitted on 29 Mar 2023] (cross-list from hep-ph)
Heavy quarkonium with finite three momentum near $T_{c}$
HyungJoo Kim🇰🇷 · Seokwoo Yeo🇰🇷 · Sungtae Cho🇰🇷 · Su Houng Lee🇰🇷
We investigate the non-trivial 3-momentum effects on the masses of heavy quarkonium states that are moving in a hot medium using QCD sum rules. For all charmonium states, we observe a negative mass shift near $T_{c}$ that is less than 3 $%$ at a momentum of 1 $GeV$ . Specifically, we first investigate the difference between the longitudinal and transverse modes of both $J / ψ$ and $χ_{c 1}$ . We find that the transverse mode of the $J / ψ$ experiences larger modification than the longitudinal mode, while the $χ_{c 1}$ has the opposite behavior. By comparing the $η_{c}$ and $χ_{c 0}$ , and also the unpolarized $J / ψ$ and $χ_{c 1}$ , we recognize that the P-wave particles have stronger momentum dependencies on their masses than the S-wave ones. We also find $Υ$ (1S) has negligible 3-momentum dependence compared to the charmonium states, e.g. less than 0.01 $%$ even at 1.4 $T_{c}$ and at a momentum of 4 $GeV$ .
Comments:
6 pages, 7 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2303.16731 [pdf]
PRD(2023)·3 citations
08
[Submitted on 29 Mar 2023] (cross-list from hep-ph)
Effects of finite volume and magnetic fields on thermodynamic properties of quark matter and fluctuations of conserved charges
Nisha Chahal🇮🇳 · Suneel Dutt🇮🇳 · Arvind Kumar🇮🇳
In the current work, we present the influence of finite volume and magnetic field on the thermodynamic properties of isospin asymmetric quark matter using the Polyakov loop extended chiral SU(3) quark mean field (PCQMF) model at finite chemical potential and temperature. Within the PCQMF model, we use the scalar and vector field values in mean-field approximation to obtain the thermodynamic properties: pressure density, entropy density and energy density. The susceptibilities of conserved charges for strongly interacting matter for different system sizes as well as for different values of the magnetic field have been studied. A sizable shift in phase boundary towards the higher values of quark chemical potential ( $μ_{q}$ ) and temperature (T) has been observed for decreasing values of system volume as well as an opposite shift towards lower temperature and quark chemical potential for increasing magnetic field. We observe an enhancement in fluctuations of conserved charges in the regime of the transition temperature. These studies may have a significant role in understanding the thermodynamic observables extracted from heavy-ion collisions data.
Comments:
42 pages, 15 figures (Accepted for publication in Physical Review C)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2303.16840 [pdf]
PRC(2023)·17 citations

Affiliations

first authorsco-authorsvia INSPIRE

High-energy dipole scattering amplitude from evolution of low-energy proton light-cone wave functions

Degeneracy in excited-state quantum phase transitions of two-level bosonic models and its influence on system dynamics

Heavy quarkonium with finite three momentum near Tc​

Effects of finite volume and magnetic fields on thermodynamic properties of quark matter and fluctuations of conserved charges

Affiliations

Heavy quarkonium with finite three momentum near $T_{c}$