Nuclear Theory·nucl-th

Friday·May 11, 2018

10 papers—4 primary·6 cross-listed

05
[Submitted on 10 May 2018] (cross-list from hep-lat)
Lattice QCD study of the $H$ dibaryon using hexaquark and two-baryon interpolators
A. Francis🇨🇭 · J.R. Green🇩🇪 · P.M. Junnarkar🇮🇳 · Ch. Miao🇩🇪 · T.D. Rae🇩🇪 · H. Wittig🇩🇪
We present a lattice QCD spectroscopy study in the isospin singlet, strangeness $- 2$ sectors relevant for the conjectured $H$ dibaryon. We employ both local and bilocal interpolating operators to isolate the ground state in the rest frame and in moving frames. Calculations are performed using two flavors of O( $a$ )-improved Wilson fermions and a quenched strange quark. Our initial point-source method for constructing correlators does not allow for bilocal operators at the source; nevertheless, results from using these operators at the sink indicate that they provide an improved overlap onto the ground state in comparison with the local operators. We also present results, in the rest frame, using a second method based on distillation to compute a hermitian matrix of correlators with bilocal operators at both the source and the sink. This method yields a much more precise and reliable determination of the ground-state energy. In the flavor-SU(3) symmetric case, we apply Lüscher's finite-volume quantization condition to the rest-frame and moving-frame energy levels to determine the $S$ -wave scattering phase shift, near and below the two-particle threshold. For a pion mass of 960 MeV, we find that there exists a bound $H$ dibaryon with binding energy $Δ E = (19 \pm 10)$ MeV. In the 27-plet (dineutron) sector, the finite-volume analysis suggests that the existence of a bound state is unlikely.
Comments:
17 pages, 12 figures, expanded discussion of fit ranges and single baryon energy levels, clarification of terminology; version published in Phys. Rev. D
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1805.03966 [pdf]
PRD(2019)·118 citations
06
[Submitted on 10 May 2018] (cross-list from hep-ph)
$N Ω$ interaction: meson exchanges, inelastic channels, and quasibound state
Takayasu Sekihara (JAEA, Ibaraki)🇯🇵 · Yuki Kamiya (Kyoto U., Yukawa Inst., Kyoto)🇯🇵 · Tetsuo Hyodo (Kyoto U., Yukawa Inst., Kyoto)🇯🇵
Based on a baryon-baryon interaction model with meson exchanges, we investigate the origin of the strong attraction in the $N Ω (^{5} S_{2})$ interaction, which was indicated by recent lattice QCD simulations. The long range part of the potential is constructed by the conventional mechanisms, the exchanges of the $η$ meson and of the correlated two mesons in the scalar-isoscalar channel, denoted by " $σ$ " in the literature. The short range part is represented by the contact interaction. We find that the meson exchanges do not provide sufficient attraction. This means that most of the attraction is attributed to the short range contact interaction. We then evaluate the effect of the coupled channels to the $N Ω (^{5} S_{2})$ interaction. We find that, while the $D$ -wave mixing of the $N Ω$ channel is negligible, the inelastic $ΛΞ$ , $ΣΞ$ , and $ΛΞ (1530)$ channels via the $K$ meson exchange give the attraction of the $N Ω (^{5} S_{2})$ interaction to the same level with the elastic meson exchanges. Although the elimination of these channels induces the energy dependence of the single-channel $N Ω$ interaction, this effect is not significant. With the present model parameters fitted to reproduce the scattering length of the HAL QCD result of the nearly physical quark masses, we obtain the $N Ω (^{5} S_{2})$ quasibound state with its eigenenergy $2611.3 - 0.7 i$ MeV, which corresponds to the binding energy $0.1$ MeV and width $1.5$ MeV for the decay to the $ΛΞ$ and $ΣΞ$ channels. From the analysis of the spatial structure and the compositeness, the quasibound state is shown to be the molecular state of $N Ω$ . We also construct an equivalent local potential for the $N Ω (^{5} S_{2})$ system which is useful for various applications.
Comments:
22 pages, 17 eps figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1805.04024 [pdf]
PRC(2018)·43 citations
07
[Submitted on 10 May 2018] (cross-list from hep-th)
Relaxation Times for Chiral Transport Phenomena and Spin Polarization in Strongly Coupled Plasma
Shiyong Li🇺🇸 · Ho-Ung Yee🇺🇸
We compute the dynamical relaxation times for chiral transport phenomena in strongly coupled regime using the AdS/CFT correspondence. These relaxation times can be a useful proxy for the dynamical time scale for achieving equilibrium spin-polarization of quasi-particles in the presence of magnetic field and fluid vorticity. We identify the Kubo relations for these relaxation times and clarify some previous issues regarding time-dependence of the Chiral Vortical Effect. We study the consequences of imposing time-reversal invariance on parity-odd thermal noise fluctuations that are related to chiral transport coefficients by the fluctuation-dissipation relation. We find that time-reversal invariance dictates the equality between some of the chiral transport coefficients as well as their relaxation times.
Comments:
30 pages, 7 figures, More references added
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1805.04057 [pdf]
PRD(2018)·10 citations
08
[Submitted on 10 May 2018] (cross-list from hep-ph)
Geometrical scaling for energies available at the BNL Relativistic Heavy Ion Collider to those at the CERN Large Hadron Collider
M.Petrovici🇷🇴 · A.Lindner🇷🇴 · A.Pop🇷🇴 · M.Tarzila🇷🇴 · I.Berceanu🇷🇴
Based on the recent RHIC and LHC experimental results, the $⟨ p_{T} ⟩$ dependence of identified light flavour charged hadrons on $(\frac{d N}{d y}) / S_{⊥}$ , relevant scale in gluon saturation picture, is studied from $s_{N N}$ =7.7 GeV up to 5.02 TeV. This study is extended to the slopes of the $⟨ p_{T} ⟩$ dependence on the particle mass and the $⟨ β_{T} ⟩$ parameter from Boltzmann-Gibbs Blast Wave (BGBW) fits of the $p_{T}$ spectra. A systematic decrease of the slope of the $⟨ p_{T} ⟩$ dependence on $(\frac{d N}{d y}) / S_{⊥}$ from BES to the LHC energies is evidenced. While for the RHIC energies, within the experimental errors, the $⟨ p_{T} ⟩$ / $(\frac{d N}{d y}) / S_{⊥}$ does not depend on centrality, at the LHC energies a deviation from a linear behaviour is observed towards the most central collisions. The influence of the corona contribution to the observed trends is discussed. The slopes of the $⟨ p_{T} ⟩$ particle mass dependence and the $⟨ β_{T} ⟩$ parameter from BGBW fits scale well with $(\frac{d N}{d y}) / S_{⊥}$ . Similar systematic trends for pp at $s$ =7 TeV are in a good agreement with the ones corresponding to Pb-Pb collisions at $s_{N N}$ =2.76 TeV and 5.02 TeV pointing to a system size independent behaviour.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1805.04060 [pdf]
PRC(2018)·13 citations
09
[Submitted on 10 May 2018] (cross-list from hep-ph)
Opacity dependence of elliptic flow in kinetic theory
Aleksi Kurkela🇨🇭 · Urs Achim Wiedemann🇨🇭 · Bin Wu🇨🇭
The observation of large azimuthal anisotropies $v_{n}$ in the particle spectra of proton-proton (pp) and proton-nucleus (pA) collisions challenges fluid dynamic interpretations of $v_{n}$ , as it remains unclear how small collision systems can hydrodynamize and to what extent hydrodynamization is needed to build up $v_{n}$ . Here, we study in a simple kinetic theory how the same physics that leads to hydrodynamization in large systems represents itself in small systems. We observe that one third to one half of the elliptic flow signal seen in fully hydrodynamized systems can be built up in collisions that extend over only one mean free path $l_{mfp}$ and that do not hydrodynamize. This is qualitatively in line with observing a sizeable $v_{2}$ in $pp$ collisions for which other characteristics of soft multi-particle production seem well-described in a free-streaming picture. We further expose a significant system size dependence in the accuracy of hybrid approaches that match kinetic theory to viscous fluid dynamics. The implications of these findings for a reliable extraction of shear viscosity are discussed.
Comments:
5 pages, 5 figures, version accepted for publication in EPJC
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1805.04081 [pdf]
EPJC(2019)·88 citations
10
[Submitted on 10 May 2018] (cross-list from hep-ph)
Third family of compact stars within a nonlocal chiral quark model equation of state
D.E. Alvarez-Castillo🇷🇺 · D.B. Blaschke🇷🇺 · A.G. Grunfeld🇦🇷 · V.P. Pagura🇪🇸
A class of hybrid compact star equations of state is investigated that joins by a Maxwell construction a low-density phase of hadronic matter, modeled by a relativistic meanfield approach with excluded nucleon volume, with a high-density phase of color superconducting two-flavor quark matter, described within a nonlocal covariant chiral quark model. We find the conditions on the vector meson coupling in the quark model under which a stable branch of hybrid compact stars occurs in the cases with and without diquark condensation. We show that these hybrid stars do not form a third family disconnected from the second family of ordinary neutron stars unless additional (de)confining effects are introduced with a density-dependent bag pressure. A suitably chosen density dependence of the vector meson coupling assures that at the same time the $2$ M $_{⊙}$ maximum mass constraint is fulfilled on the hybrid star branch. A twofold interpolation method is realized which implements both, the density dependence of a confining bag pressure at the onset of the hadron-to-quark matter transition as well as the stiffening of quark matter at higher densities by a density-dependent vector meson coupling. For three parametrizations of this class of hybrid equation of state the properties of corresponding compact star sequences are presented, including mass twins of neutron and hybrid stars at 2.00, 1.39 and 1.20 $M_{⊙}$ , respectively. The sensitivity of the hybrid equation of state and the corresponding compact star sequences to variations of the interpolation parameters at the 10% level is investigated and it is found that the feature of third family solutions for compact stars is robust against such a variation. This advanced description of hybrid star matter allows to interpret GW170817 as a merger not only of two neutron stars but also of a neutron star with a hybrid star or of two hybrid stars.
Comments:
20 pages, 17 figures, 2 tables, largely extended version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1805.04105 [pdf]
PRD(2019)·129 citations

Affiliations

first authorsco-authorsvia INSPIRE

Lattice QCD study of the H dibaryon using hexaquark and two-baryon interpolators

NΩ interaction: meson exchanges, inelastic channels, and quasibound state

Relaxation Times for Chiral Transport Phenomena and Spin Polarization in Strongly Coupled Plasma

Geometrical scaling for energies available at the BNL Relativistic Heavy Ion Collider to those at the CERN Large Hadron Collider

Opacity dependence of elliptic flow in kinetic theory

Third family of compact stars within a nonlocal chiral quark model equation of state

Affiliations

Lattice QCD study of the $H$ dibaryon using hexaquark and two-baryon interpolators

$N Ω$ interaction: meson exchanges, inelastic channels, and quasibound state