Nuclear Theory·nucl-th

Tuesday·April 18, 2017

26 papers—15 primary·11 cross-listed

16
Effective Field Theory Models for Thermal QCD
Sourendu Gupta🇮🇳 · Rishi Sharma🇮🇳
We present an effective field theory model for QCD at finite temperature with quarks. We discuss the mean field theory, the fixing of parameters, and a prediction for the curvature of the critical line. We proceed to write down a pionic theory of fluctuations around the mean field, and discuss how the parameters of this pionic effective theory descend from the model with quarks.
↳ hep-phhep-lathep-thnucl-thNPA(2017)·1 citation
17
Structure of virtual photon polarization in ultrarelativistic heavy-ion collisions
Gordon Baym🇺🇸 · Tetsuo Hatsuda🇯🇵 · Michael Strickland🇺🇸
Anisotropy in heavy-ion collisions leads to polarization of both direct and virtual photons, the latter detected via internal conversion to dileptons pairs. Thus measurement of photon polarization probes the anisotropy at all stages of collisions. In order to characterize the polarization of virtual photons, we derive here the general structure of the photon polarization operator, rho^(mu nu), in an anisotropic medium, in terms of the four spectral functions, two transverse and one longitudinal, as usual, plus a new spectral function that reflects anisotropy in asymmetric collisions; and derive the local production rate of dilepton pairs in terms of these four functions.
↳ hep-phnucl-thNPA(2017)·5 citations
18
PHENIX Overview
D. McGlinchey (for the PHENIX Collaboration)🇺🇸
These proceedings present highlighted results from PHENIX shown at the Quark Matter 2017 conference.
↳ nucl-exnucl-thNPA(2017)·3 citations
19
A Unified Description for Comprehensive Sets of Jet Energy Loss Observables with CUJET3
Shuzhe Shi🇺🇸 · Jiechen Xu🇺🇸 · Jinfeng Liao🇺🇸 · Miklos Gyulassy🇺🇸
Jet energy loss in heavy ion collisions, as quantified by the traditional observable of high $p_{T}$ hadron's nuclear modification factor $R_{AA}$ , provides highly informative "imaging" of the hot medium created in heavy ion collisions. There are now comprehensive sets of available data, from average suppression to azimuthal anisotropy, from light to heavy flavors, from RHIC 200GeV to LHC 2.76TeV as well as 5.02TeV collisions. A unified description of such comprehensive data presents a stringent vetting of any viable model for jet quenching phenomenology. In this contribution we report such a systematic and successful test of CUJET3, a jet energy loss simulation framework built upon a nonperturbative microscopic model for the hot medium as a semi-quark-gluon-monopole plasma (sQGMP) which integrates two essential elements of confinement, i.e. the Polyakov-loop suppression of quarks/gluons and emergent magnetic monopoles.
↳ hep-phnucl-exnucl-thNPA(2017)·9 citations
20
Spontaneous Spin Polarization due to Tensor Selfenergies in Quark Matter
Tomoyuki Maruyama🇯🇵 · Toshitaka Tatsumi🇯🇵
We study the magnetic properties of quark matter in the NJL model with the tensor interaction. The spin-polarized phase given by the tensor interaction remains even when the quark mass is zero, while the phase given by the axial vector interaction disappears. There are two kinds of spin-polarized phases: one appears in the chiral-broken phase, and the other appears in the chiral-restored phase where the quark mass is zero. The latter phase can appear independently of the strength of the tensor interaction.
↳ hep-phnucl-thPRD(2017)·9 citations
21
Exact Self-Dual Skyrmions
L.A. Ferreira🇧🇷 · Ya. Shnir🇷🇺
We introduce a Skyrme type model with the target space being the 3-sphere S^3 and with an action possessing, as usual, quadratic and quartic terms in field derivatives. The novel character of the model is that the strength of the couplings of those two terms are allowed to depend upon the space-time coordinates. The model should therefore be interpreted as an effective theory, such that those couplings correspond in fact to low energy expectation values of fields belonging to a more fundamental theory at high energies. The theory possesses a self-dual sector that saturates the Bogomolny bound leading to an energy depending linearly on the topological charge. The self-duality equations are conformally invariant in three space dimensions leading to a toroidal ansatz and exact self-dual Skyrmion solutions. Those solutions are labelled by two integers and, despite their toroidal character, the energy density is spherically symmetric when those integers are equal and oblate or prolate otherwise.
↳ hep-thmath-phmath.MPnlin.SI+1PLB(2017)·21 citations
22
Jet Measurements with Neutral and Di-jet Triggers in Central Au+Au Collisions at $s_{N N}$ = 200 GeV with STAR
Nihar Ranjan Sahoo (for the STAR Collaboration)🇺🇸
We present two measurements related to jet production in p+p and central Au+Au collisions at $s_{N N}$ =200 GeV. Firstly, a study of semi-inclusive charged recoil jets coincident with high- $p_{T}$ direct-photon and neutral pions, and secondly, the hadron correlations with respect to reconstructed di-jet triggers. Indication of medium effects is observed by comparing $γ$ +jet and $π^{0}$ +jet measurements. The di-jet+hadron study shows signs that the medium-induced modifications of an imbalanced set of di-jets with "hard cores" primarily affect the recoil jet.
↳ nucl-exhep-exhep-phnucl-thNPA(2017)·1 citation
23
In-Medium Bottomonium Production in Heavy-Ion Collisions
Xiaojian Du🇺🇸 · Min He🇨🇳 · Ralf Rapp🇺🇸
We study bottomonium production in heavy-ion collisions using a transport model which utilizes kinetic-rate and Boltzmann equations to calculate the energy, centrality and transverse-momentum ( $p_{T}$ ) dependence of the yields. Both gluo-dissociation and inelastic parton-induced break-up including interference effects are improved over previous work by using in-medium binding energies from a thermodynamic $T$ -matrix approach. A coalescence model with bottom-quark spectra from Langevin simulations is implemented to account for thermal off-equilibrium effects in the $p_{T}$ -spectra of the regeneration contribution. We also update the equation of state for the bulk medium by extracting it from lattice-QCD results. A systematic analysis of bottomonium observables is conducted in comparison to RHIC and LHC data. In particular, the off-equilibrium bottom-quark spectra are found to play an important role in the bottomonium $p_{T}$ spectra.
↳ hep-phnucl-thNPA(2017)·10 citations
24
Charmed Baryon $Λ_{c}$ in Nuclear Matter
Keisuke Ohtani🇯🇵 · Ken-ji Araki🇯🇵 · Makoto Oka🇯🇵
Density dependences of the mass and self-energies of $Λ_{c}$ in nulear matter are studied in the parity projected QCD sum rule. Effects of nuclear matter are taken into account through the quark and gluon condensates. It is found that the four-quark condensates give dominant contributions. As the density dependences of the four-quark condensates are not known well, we examine two hypotheses. One is based on the factorization hypothesis (F-type) and the other is derived from the perturbative chiral quark model (QM-type). The F-type strongly depends on density, while the QM-type gives a weaker dependence. It is found that, for the F-type dependence, the energy of $Λ_{c}$ increases as the density of nuclear matter grows, that is, $Λ_{c}$ feels repulsion. On the other hand, the QM-type predicts a weak attraction ( $\sim 20$ MeV at the normal nuclear density) for $Λ_{c}$ in nuclear matter. We carry out a similar analysis of the $Λ$ hyperon and find that the F-type density dependence is too strong to explain the observed binding energy of $Λ$ in nuclei. Thus we conclude that the weak density dependence of the four-quark condensate is more realistic. The scalar and vector self-energies of $Λ_{c}$ for the QM-type dependence are found to be much smaller than those of the light baryons.
↳ hep-phnucl-thPRC(2017)·12 citations
25
Topology in the SU(N_f) chiral symmetry restored phase of unquenched QCD and axion cosmology II
Vicente Azcoiti🇪🇸
We investigate the physical consequences of the survival of the effects of the U(1)_A anomaly in the chiral symmetric phase of QCD, and show that the free energy density is a singular function of the quark mass m, in the chiral limit, and that the $σ$ and $π ˉ$ susceptibilities diverge in this limit at any $T \geq T_{c}$ . We also show that the difference between the $π ˉ$ and $δ ˉ$ susceptibilities diverges in the chiral limit at any $T \geq T_{c}$ , a result which seems to be excluded by recent results of Tomiya et al. from numerical simulations of two-flavor QCD. We also discuss on the generalization of these results to the $N_{f} \geq 3$ model.
↳ hep-lathep-phhep-thnucl-thPRD(2017)·11 citations
26
Patterns and partners for chiral symmetry restoration
A. Gomez Nicola🇪🇸 · J. Ruiz de Elvira🇩🇪
We present and analyze a new set of Ward Identities which shed light on the distinction between different patterns of chiral symmetry restoration in QCD, namely $O (4)$ vs $O (4) \times U (1)_{A}$ . The degeneracy of chiral partners for all scalar and pseudoscalar meson nonet members are studied through their corresponding correlators. Around chiral symmetry degeneration of $O (4)$ partners, our analysis predicts that $U (1)_{A}$ partners are also degenerated. Our analysis also leads to $I = 1/2$ scalar-pseudoscalar partner degeneration at exact chiral restoration, and supports ideal mixing between the $η$ - $η^{'}$ and the $f_{0} (500)$ - $f_{0} (980)$ mesons at $O (4) \times U (1)_{A}$ restoration, with a possible range where the pseudoscalar mixing vanishes if the two transitions are well separated. We test our results with lattice data and provide further relevant observables regarding chiral and $U (1)_{A}$ restoration for future lattice and model analyses.
↳ hep-phhep-lathep-thnucl-thPRD(2018)·36 citations

Affiliations

first authorsco-authorsvia INSPIRE