Nuclear Theory·nucl-th

Monday·January 5, 2015

11 papers—4 primary·7 cross-listed

01
Quark-gluon plasma phenomenology from anisotropic lattice QCD
Jon-Ivar Skullerud🇮🇪 · Gert Aarts🇬🇧 · Chris Allton🇬🇧 · Alessandro Amato🇬🇧 · Yannis Burnier🇨🇭 · P. Wynne M. Evans🇬🇧 · Pietro Giudice🇩🇪 · Simon Hands🇬🇧 · Tim Harris🇮🇪 · Aoife Kelly🇮🇪 · Seyong Kim🇰🇷 · Maria Paola Lombardo🇮🇹 and 3 other authors
The FASTSUM collaboration has been carrying out simulations of N_f=2+1 QCD at nonzero temperature in the fixed-scale approach using anisotropic lattices. Here we present the status of these studies, including recent results for electrical conductivity and charge diffusion, and heavy quarkonium (charm and beauty) physics.
nucl-thhep-lathep-phAIP Conf.Proc.(2016)·8 citations
02
1D inelastic relativistic-collision
Ryosuke Yano · Arnaud Martin
In this paper, we discuss one dimensional inelastic relativistic-collisions in the framework of the relativistic kinetic theory. In particular, we focus on the relativistic effects on time evolutions of the temperature and flow velocity under the spatially homogeneous state. As a result of the relativistic effects, we obtain the characteristic time evolutions of the temperature and flow velocity, which are never obtained under the nonrelativistic limit.
nucl-th0 citations
03
Investigation of $^{23}$ N in a three-body model
Liuyang Zhang · Zhongzhou Ren · Mengjiao Lyu · Chen Ji
The neutron-drip-line nucleus $^{23}$ N is investigated in a three-body model consisting of a $^{21}$ N core and two valence neutrons. By solving the Faddeev equations with the realistic neutron-neutron potentials and the neutron-core potentials, we calculate the ground state properties of $^{23}$ N and also find that there is a new excited state with two-neutron separation energy at about 0.18 MeV. The properties, such as the two-neutron separation energies, are obtained with a good agreement with experiments. By calculating the root-mean-square matter radii, the average distances between the valence neutrons, and the average distances between the core and the center-of-mass of the neutron pair, we show that the excited state of $^{23}$ N has a clear halo structure. The correlation density distributions of the three-body system are also calculated to analyze its geometric configuration. At last, we find that the excited state of $^{23}$ N has a very small binding energy, a large radius and distribution, and a triangular shape similar with the ground state. These roperties of the excited state indicate that it can be an Efimov state.
nucl-thPRC(2015)·4 citations
04
The role of pion exchange in $η$ meson photo production on the deuteron
A. Fix🇷🇺 · H. Arenhövel🇩🇪 · M. Levchuk🇧🇾 · M. Tammam🇪🇬
Incoherent $η$ photoproduction on the deuteron is studied with the main emphasis on the role of final state interactions. In addition to the previously studied mechanisms of $N N$ and $η N$ rescatterings, the role of an intermediate pion exchange is considered in detail, where first a pion is photoproduced on one nucleon and then rescatters into an $η$ meson on the other, the spectator nucleon. It is found, that the role of this pion mediated contribution is comparable in size to that of $η N$ rescattering. Results for total and semi-inclusive differential cross sections and associated polarization observables are presented. In particular polarization observables show a significant sensititvity to final state interactions.
nucl-thPRC(2015)·3 citations
05
Probing the neutron star interior and the Equation of State of cold dense matter with the SKA
Anna Watts · Renxin Xu · Cristobal Espinoza · Nils Andersson · John Antoniadis · Danai Antonopoulou · Sarah Buchner · Shi Dai · Paul Demorest · Paulo Freire · Jason Hessels · Jerome Margueron and 6 other authors
With an average density higher than the nuclear density, neutron stars (NS) provide a unique test-ground for nuclear physics, quantum chromodynamics (QCD), and nuclear superfluidity. Determination of the fundamental interactions that govern matter under such extreme conditions is one of the major unsolved problems of modern physics, and -- since it is impossible to replicate these conditions on Earth -- a major scientific motivation for SKA. The most stringent observational constraints come from measurements of NS bulk properties: each model for the microscopic behaviour of matter predicts a specific density-pressure relation (its `Equation of state', EOS). This generates a unique mass-radius relation which predicts a characteristic radius for a large range of masses and a maximum mass above which NS collapse to black holes. It also uniquely predicts other bulk quantities, like maximum spin frequency and moment of inertia. The SKA, in Phase 1 and particularly in Phase 2 will, thanks to the exquisite timing precision enabled by its raw sensitivity, and surveys that dramatically increase the number of sources: 1) Provide many more precise NS mass measurements (high mass NS measurements are particularly important for ruling out EOS models); 2) Allow the measurement of the NS moment of inertia in highly relativistic binaries such as the Double Pulsar; 3) Greatly increase the number of fast-spinning NS, with the potential discovery of spin frequencies above those allowed by some EOS models; 4) Improve our knowledge of new classes of binary pulsars such as black widows and redbacks (which may be massive as a class) through sensitive broad-band radio observations; and 5) Improve our understanding of dense matter superfluidity and the state of matter in the interior through the study of rotational glitches, provided that an ad-hoc campaign is developed.
↳ astro-ph.SRastro-ph.HEastro-ph.IMnucl-thPoS(2015)·60 citations
06
Highlights from COMPASS in hadron spectroscopy
Fabian Krinner (for the COMPASS collaboration)🇩🇪
Since Quantum Choromdynamics allows for gluon self-coupling, quarks and gluons cannot be observed as free particles, but only their bound states, the hadrons. This so-called confinement phenomenon is responsible for $98%$ of the mass in the visible universe. The measurement of the hadron excitation spectra therefore gives valuable input for theory and phenomenology to quantitatively understand this phenomenon. One simple model to describe hadrons is the Constituent Quark Model (CQM), which knows two types of hadrons: mesons, consisting of a quark and an antiquark, and baryons, which are made out of three quarks. More advanced models, which are inspired by QCD as well as calculations within Lattice QCD predict the existence of other types of hadrons, which may be e.g. described solely by gluonic excitations (glueballs) or mixed quark and gluon excitations (hybrids). In order to search for such states, the COMPASS experiment at the Super Proton Synchrotron at CERN has collected large data sets, which allow to study the light-quark meson and baryon spectra in unmatched precision. The overview shown here focuses on the light meson sector, presenting a detailed Partial-Wave Analysis of the processes: $π^{-} p \to π^{-} π^{+} π^{-} p$ and $π^{-} p \to π^{-} π^{0} π^{0} p$ . A new state, the $a_{1} (1420)$ with $J^{P C} = 1^{++}$ is observed. Its Breit-Wigner parameters are found to be in the ranges: $m = 1412 - 1422 MeV / c^{2}$ and $Γ = 130 - 150 MeV / c^{2}$ . In the same analysis, a signal in a wave with $J^{P C} = 1^{-+}$ is observed. A resonant origin of this signal would not be explicable within the CQM. In addition to this possibility of an exotic state, a possible non resonant origin of this signal is discussed.
↳ hep-exhep-phnucl-exnucl-thEPJ Web Conf.(2015)·4 citations
07
NLO Dispersion Laws for Slow-Moving Quarks in HTL QCD
Abdessamad Abada🇩🇿 · Karima Benchallal🇩🇿 · Karima Bouakaz🇩🇿
We determine the next-to-leading order dispersion laws for slow-moving quarks in hard-thermal-loop perturbation of high-temperature QCD where weak coupling is assumed. Real-time formalism is used. The next-to-leading order quark self-energy is written in terms of three and four HTL-dressed vertex functions. The hard thermal loops contributing to these vertex functions are calculated ab initio and expressed using the Feynman parametrization which allows the calculation of the solid-angle integrals involved. We use a prototype of the resulting integrals to indicate how finite results are obtained in the limit of vanishing regularizer.
↳ hep-phnucl-thJHEP(2015)·6 citations
08
Collective Modes of Chiral Kinetic Theory in Magnetic Field
Mikhail Stephanov🇺🇸 · Ho-Ung Yee🇺🇸 · Yi Yin🇺🇸
We study collective excitations in systems described by chiral kinetic theory in external magnetic field. We consider high-temperature weak-coupling plasma, as well as high-density Landau Fermi liquid with interaction not restricted to be weak. We show that chiral magnetic wave (CMW) emerges in hydrodynamic regime (at frequencies smaller than collision relaxation rate) and the CMW velocity is determined by thermodynamic properties only. We find that in a plasma of opposite chiralities, at frequencies smaller than the chirality-flipping rate, the CMW excitation turns into a vector-like diffusion mode. In the interacting Fermi liquid, the CMW turns into the Landau zero sound mode in the high-frequency collisionless regime.
↳ hep-thhep-phnucl-thPRD(2015)·40 citations
09
Hyperfine splitting in muonic hydrogen constrains new pseudoscalar interactions
W.-Y. Keung🇺🇸 · D. Marfatia🇺🇸
We constrain the possibility of a new pseudoscalar coupling between the muon and proton using a recent measurement of the 2S hyperfine splitting in muonic hydrogen.
↳ hep-phhep-exnucl-exnucl-thPLB(2015)·2 citations
10
Caloron correction to the effective potential in thermal gluodynamics
Chris P. Korthals Altes🇫🇷 · Alfonso Sastre🇩🇪
The effective potential in thermal gluodynamics has stable minima in perturbation theory. There the Wilson line is center group valued and eigenvalues of the Wilson line stay clustered. Calorons with non-trivial holonomy contribute to one loop order a linear term in the holonomy. The sign is such that the center group minimum stays stable.
↳ hep-thhep-lathep-phnucl-th2 citations
11
Mott-hadron resonance gas and lattice QCD thermodynamics
D. Blaschke🇷🇺 · A. Dubinin🇵🇱 · L. Turko🇵🇱
We present an effective model for the generic behaviour of hadron masses and phase shifts at finite temperature which shares basic features with recent developments within the PNJL model for correlations in quark matter. On this basis we obtain the transition between a hadron resonance gas phase and the quark gluon plasma in the spirit of the generalized Beth-Uhlenbeck approach where the Mott dissociation of hadrons is encoded in the hadronic phase shifts. Here we restrict ourselves to low-lying hadronic channels and perform a discussion of recent lattice QCD thermodynamics results from this perspective. We find agreement in the asymptotic regions while for the description of the transition itself the inclusion of further hadronic channels as well as a selfconsistent determination of the continuum thresholds is required.
↳ hep-phnucl-thPhys.Part.Nucl.(2015)·12 citations

Affiliations

first authorsco-authorsvia INSPIRE