Nuclear Theory·nucl-th

Tuesday·May 1, 2018

13 papers—7 primary·6 cross-listed

08
Color screening in (2+1)-flavor QCD
TUMQCD collaboration: Alexei Bazavov (1)🇺🇸 · Nora Brambilla (2,3)🇩🇪 · Peter Petreczky (4)🇺🇸 · Antonio Vairo (2)🇩🇪 · Johannes Heinrich Weber (1,2,5) ((1) Department of Computational Mathematics, Science and Engineering and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA (2) Physik Department, Technische Universit ät München, D-85748 Garching, Germany (3) Institute of Advanced Studies, Technische Universität München, D-85748 Garching, Germany (4) Physics Department, Brookhaven National Laboratory, Upton, New York 11973, USA (5) Exzellenzcluster Universe, Technische Universität M ünchen, D-85748 Garching, Germany)🇩🇪
We study correlation functions of spatially separated static quark-antiquark pairs in (2+1)-flavor QCD in order to investigate onset and nature of color screening at high temperatures. We perform lattice calculations in a wide temperature range, $140 \leq T \leq 5814 MeV$ , using the highly improved staggered quark action and several lattice spacings to control discretization effects. By comparing at high temperatures our lattice results to weak-coupling calculations as well as to the zero temperature result for the energy of a static quark-antiquark pair, we observe that color screening sets in at $r T \approx 0.3$ . Furthermore, we also observe that in the range $0.3 ≲ r T ≲ 0.6$ weak-coupling calculations in the framework of suitable effective field theories provide an adequate picture of color screening.
↳ hep-lathep-phhep-thnucl-thPRD(2018)·104 citations
09
Isotopic Symmetry Breaking in the $η (1405) \to f_{0} (980) π^{0} \to π^{+} π^{-} π^{0}$ . Decay through a $K K ˉ$ Loop Diagram and the Role of Anomalous Landau Thresholds
N.N. Achasov🇷🇺 · G.N. Shestakov🇷🇺
Anomalous isotopic symmetry breaking in the $η (1405) \to f_{0} (980) π^{0} \to π^{+} π^{-} π^{0}$ decay through a mechanism featuring anomalous Landau thresholds in the form of logarithmic triangle singularities, i.e., through the $η (1405) \to (K^{*} K ˉ + K ˉ^{*} K) \to (K^{+} K^{-} + K^{0} K ˉ^{0}) π^{0} \to f_{0} (980) π^{0} \to π^{+} π^{-} π^{0}$ transition, has been analyzed. It has been shown that this effect can be correctly quantified only by taking into account the nonzero $K^{*}$ width. Different scales of isotopic symmetry breaking associated with the $K^{+} - K^{0}$ mass difference are compared.
↳ hep-phhep-exnucl-thJETP Lett.(2018)·15 citations
10
Predictions for azimuthal anisotropy in Xe+Xe collisions at $s_{N N}$ = 5.44 TeV using a multiphase transport model
Sushanta Tripathy🇮🇳 · Sudipan De🇮🇳 · Mohammed Younus🇮🇳 · Raghunath Sahoo🇮🇳
Xe+Xe collision at relativistic energies may provide us with a partonic system whose size is approximately in between those produced by p+p and Pb+Pb collisions. The experimental results on anisotropic flow in Xe+Xe and Pb+Pb collisions should provide us with an opportunity to study system size dependence of $v_{2}$ . In the present work, we have used AMPT transport model to calculate charged particles' $v_{2}$ for Xe+Xe collisions at $s_{N N}$ =5.44 TeV. We have also tried to demonstrate the no. of constituent quark, $N_{q}$ , and $m_{T}$ scaling of the elliptic flow. We find that $n_{q}$ scaling of $v_{2}$ is not observed for the identified hadrons. The $v_{2}$ results from Xe+Xe collisions have also been compared to Pb+Pb collisions at $s_{N N}$ = 5.02 TeV. We find that flow of charged particles in (50-60)\% central collisions for Xenon nuclei is almost 30\% less than particle flow developed in lead ion collisions, implying the important role the system size play in development of particle collective motion in relativistic heavy ion collisions.
↳ hep-phhep-exnucl-exnucl-thPRC(2018)·23 citations
11
Connection formulas between Coulomb wave functions
David Gaspard
The mathematical relations between the regular Coulomb function $F_{η ℓ} (ρ)$ and the irregular Coulomb functions $H_{η ℓ}^{\pm} (ρ)$ and $G_{η ℓ} (ρ)$ are obtained in the complex plane of the variables $η$ and $ρ$ for integer or half-integer values of $ℓ$ . These relations, referred to as "connection formulas", form the basis of the theory of Coulomb wave functions, and play an important role in many fields of physics, especially in the quantum theory of charged particle scattering. As a first step, the symmetry properties of the regular function $F_{η ℓ} (ρ)$ are studied, in particular under the transformation $ℓ \mapsto - ℓ - 1$ , by means of the modified Coulomb function $Φ_{η ℓ} (ρ)$ , which is entire in the dimensionless energy $η^{- 2}$ and the angular momentum $ℓ$ . Then, it is shown that, for integer or half-integer $ℓ$ , the irregular functions $H_{η ℓ}^{\pm} (ρ)$ and $G_{η ℓ} (ρ)$ can be expressed in terms of the derivatives of $Φ_{η, ℓ} (ρ)$ and $Φ_{η, - ℓ - 1} (ρ)$ with respect to $ℓ$ . As a consequence, the connection formulas directly lead to the description of the singular structures of $H_{η ℓ}^{\pm} (ρ)$ and $G_{η ℓ} (ρ)$ at complex energies in their whole Riemann surface. The analysis of the functions is supplemented by novel graphical representations in the complex plane of $η^{- 1}$ .
↳ math-phmath.MPnucl-thJ.Math.Phys.(2018)·18 citations
12
Vector mesons as dynamical resonances in the Bethe-Salpeter framework
Richard Williams🇩🇪
We present the first dynamical calculation of the $ρ$ -meson as a resonance in the Dyson-Schwinger/Bethe-Salpeter framework by including explicit two-pion exchange in addition to the t-channel one-gluon exchange of rainbow-ladder in the interaction kernel. The width is determined from the imaginary part of the resonance pole and is generated by the singularity structure of the integrand, treated by means of suitable path deformations. We find the resonant mass and width to be $640$ MeV and $100$ MeV respectively, corresponding to a coupling constant $g_{ρ π π} = 5.7$ ; repulsive corrections beyond rainbow-ladder are known to bring these in alignment with experiment. Furthermore we present the dependence of these parameters on the pion mass and compare with results from lattice QCD.
↳ hep-phhep-latnucl-thPLB(2019)·51 citations
13
General structure of gauge boson propagator and its spectra in a hot magnetized medium
Bithika Karmakar🇮🇳 · Aritra Bandyopadhyay🇧🇷 · Najmul Haque🇮🇳 · Munshi G Mustafa🇮🇳
Based on transversality condition of gauge boson self-energy we have systematically constructed the general structure of the gauge boson two-point functions using four linearly independent basis tensors in presence of a nontrivial background, i.e., hot magnetized material medium. The hard thermal loop approximation has been used for the heat bath to compute various form factors associated with the gauge boson's two point functions both in strong and weak field approximation. We have also analyzed the dispersion of a gauge boson (e.g., gluon) using the effective propagator both in strong and weak magnetic field approximation. The formalism is also applicable to QED. The presence of only thermal background leads to a longitudinal (plasmon) mode and a two-fold degenerate transverse mode. In presence of a hot magnetized background medium the degeneracy of the two transverse modes is lifted and one gets three quasiparticle modes. In weak field approximation one gets two transverse modes and one plasmon mode. On the other hand, in strong field approximation also one gets the three modes in Lowest Landau Level. The general structure of two-point function may be useful for computing the thermo-magnetic correction of various quantities associated with a gauge boson.
↳ hep-phnucl-thEPJC(2019)·49 citations

Affiliations

first authorsco-authorsvia INSPIRE

Color screening in (2+1)-flavor QCD

Isotopic Symmetry Breaking in the η(1405)→f0​(980)π0→π+π−π0. Decay through a KKˉ Loop Diagram and the Role of Anomalous Landau Thresholds

Predictions for azimuthal anisotropy in Xe+Xe collisions at sNN​​ = 5.44 TeV using a multiphase transport model

Connection formulas between Coulomb wave functions

Vector mesons as dynamical resonances in the Bethe-Salpeter framework

General structure of gauge boson propagator and its spectra in a hot magnetized medium

Affiliations

Isotopic Symmetry Breaking in the $η (1405) \to f_{0} (980) π^{0} \to π^{+} π^{-} π^{0}$ . Decay through a $K K ˉ$ Loop Diagram and the Role of Anomalous Landau Thresholds

Predictions for azimuthal anisotropy in Xe+Xe collisions at $s_{N N}$ = 5.44 TeV using a multiphase transport model