Nuclear Theory·nucl-th

Tuesday·January 5, 2016

16 papers—11 primary·5 cross-listed

01
Spinodal Instabilities of Baryon-Rich Quark-gluon Plasma in the PNJL Model
Feng Li🇺🇸 · Che Ming Ko🇺🇸
Using the Polyakov-Nambu-Jona-Lasinia (PNJL) model, we study the spinodal instability of a baryon-rich quark-gluon plasma in the linear response theory. We find that the spinodal unstable region in the temperature and density plane shrinks with increasing wave number of the unstable mode and is also reduced if the effect of Polyakov loop is not included. In the small wave number or long wavelength limit, the spinodal boundaries in both cases of with and without the Polyakov loop coincide with those determined from the isothermal spinodal instability in the thermodynamic approach. Also, the vector interactions among quarks is found to suppress unstable modes of all wave numbers. Moreover, the growth rate of unstable modes initially increases with the wave number but is reduced when the wave number becomes large. Including the collisional effect from quark scattering via the linearized Boltzmann equation, we further find that it decreases the growth rate of unstable modes of all wave numbers. Relevance of these results to relativistic heavy ion collisions is discussed.
nucl-thPRC(2016)·31 citations
02
Nonlinear hydrodynamic response confronts LHC data
Li Yan🇫🇷 · Subrata Pal🇮🇳 · Jean-Yves Ollitrault🇫🇷
Higher order harmonic flow $v_{n}$ (with $n \geq 4$ ) in heavy-ion collisions can be measured either with respect to their own plane, or with respect to a plane constructed using lower-order harmonics. By assuming that higher flow harmonics are the superposition of medium nonlinear and linear responses to initial anisotropies, we propose a set of nonlinear response coefficients $χ_{n}$ 's, which are independent of initial state by construction. In experiments, $χ_{n}$ 's can be extracted as the ratio between higher order harmonic flow measured in the plane constructed by $v_{2}$ and $v_{3}$ , and moments of lower order harmonic flow. Simulations with single-shot hydrodynamics and AMPT model lead to results of these nonlinear response coefficients in good agreement with the experimental data at the LHC energy. Predictions for $v_{7}$ and $v_{8}$ measured with respect to plane of lower order harmonics are given accordingly.
nucl-thnucl-exNPA(2016)·8 citations
03
An Evidence of Mass Dependent Differential Kinetic Freeze-out Scenario Observed in Pb-Pb Collisions at 2.76 TeV
Hai-Ling Lao🇨🇳 · Hua-Rong Wei🇨🇳 · Fu-Hu Liu🇨🇳 · Roy A. Lacey🇺🇸
Transverse momentum spectra of different particles produced in mid-rapidity interval in lead-lead (Pb-Pb) collisions with different centrality intervals, measured by the ALICE Collaboration at center-of-mass energy per nucleon pair $s_{N N} = 2.76$ TeV, are conformably and approximately described by the Tsallis distribution. The dependences of parameters (effective temperature, entropy index, and normalization factor) on event centrality and particle rest mass are obtained. The source temperature at the kinetic freeze-out is obtained to be the intercept in the linear relation between effective temperature and particle rest mass, while the particle transverse flow velocity is approximately extracted to be the slope in the linear relation between mean transverse momentum and particle rest mass. It is shown that the source temperature increases with increase of particle rest mass, which exhibits an evidence of mass dependent differential kinetic freeze-out scenario or multiple kinetic freeze-out scenario.
nucl-thhep-exhep-phnucl-exEPJA(2016)·46 citations
04
Fractionized Skyrmions in Dense Compact-Star Matter
Masayasu Harada🇯🇵 · Hyun Kyu Lee🇰🇷 · Yong-Liang Ma🇨🇳 · Mannque Rho🇫🇷
The hadronic matter described as a skyrmion matter embedded in an FCC crystal is found to turn into a half-skyrmion matter with vanishing (in the chiral limit) quark condensate and {\it non-vanishing} pion decay constant { $f_{π}$ } at a density $n_{1/2}$ lower than or near the critical density $n_{c}$ at which hadronic matter changes over to a chiral symmetry restored phase with possibly deconfined quarks. When hidden local gauge fields and a dilaton scalar of spontaneously broken scale symmetry with decay constant $f_{χ}$ are incorporated, this half-skyrmion phase is characterized by $f_{χ} \approx f_{π} \neq = 0$ with the hidden gauge coupling $g \neq = 0$ but $≪ 1$ . While chiral symmetry is restored {\it globally} in this region in the sense that space-averaged, $\la q ˉ q \ra$ vanishes, quarks are still confined in massive hadrons and massless pions. This phase is shown to play a crucial role in the model for a smooth transition from a soft EoS at low density to a stiffer EoS at high density, the changeover taking place at $n_{1/2} \sim 2 n_{0}$ . It resembles the "quarkyonic phase" predicted in large $N_{c}$ QCD and represents the "hadronic freedom" regime which figures as a doorway to chiral restoration. The fractionization of skyrmion matter into half-skyrmion matter has a tantalizing analogy to what appears to happen in condensed matter in (2+1) dimensions where half-skyrmions or "merons" enter as relevant degrees of freedom at the interface.
nucl-thhep-ph5 citations
05
The shell model Monte Carlo approach to level densities: recent developments and perspectives
Y. Alhassid
We review recent advances in the shell model Monte Carlo approach for the microscopic calculation of statistical and collective properties of nuclei. We discuss applications to the calculation of (i) level densities in nickel isotopes, implementing a recent method to circumvent the odd-particle sign problem; (ii) state densities in heavy nuclei; (iii) spin distributions of nuclear levels; and (iv) finite-temperature quadrupole distributions.
nucl-thEPJA(2015)·10 citations
06
Microsopic nuclear level densities by the shell model Monte Carlo method
Y. Alhassid · G.F. Bertsch · C.N. Gilbreth · H. Nakada · C. Özen
The configuration-interaction shell model approach provides an attractive framework for the calculation of nuclear level densities in the presence of correlations, but the large dimensionality of the model space has hindered its application in mid-mass and heavy nuclei. The shell model Monte Carlo (SMMC) method permits calculations in model spaces that are many orders of magnitude larger than spaces that can be treated by conventional diagonalization methods. We discuss recent progress in the SMMC approach to level densities, and in particular the calculation of level densities in heavy nuclei. We calculate the distribution of the axial quadrupole operator in the laboratory frame at finite temperature and demonstrate that it is a model-independent signature of deformation in the rotational invariant framework of the shell model. We propose a method to use these distributions for calculating level densities as a function of intrinsic deformation.
nucl-thProceedings of the 14th International Con…·0 citations
07
Color transparency in $π^{-}$ -induced dilepton production on nuclei
A.B. Larionov🇩🇪 · M. Strikman🇺🇸 · M. Bleicher🇩🇪
We argue that the observation of the color transparency effect in the semiexclusive $A (π^{-}, l^{+} l^{-})$ process is important for determining whether it is possible to extract the generalized parton distributions of the nucleon from the elementary reaction $π^{-} p \to l^{+} l^{-} n$ at $p_{lab} = 15 - 20$ GeV/c at small $∣ t ∣$ and large invariant mass of the dilepton pair $l^{+} l^{-}$ . Assuming that the transverse size of the pionic $q q ˉ$ pair in the hard interaction point is similar to the one in the reaction $γ^{*} p \to π^{+} n$ studied at JLab we predict large color transparency effects in the discussed kinematic range. We also suggest that the semiexclusive $ρ^{0}$ production in $π^{-}$ -induced reactions in the same beam momentum region may provide new information on the dynamics of the interaction in the non-vacuum channel, while the $J / ψ$ production can be used to get information on $J / ψ N$ total interaction cross section.,
nucl-thhep-exhep-phnucl-exPRC(2016)·10 citations
08
The subtle interplay of elastic and inelastic collisions in the thermalization of the quark-gluon plasma
Jean-Paul Blaizot🇫🇷 · Jinfeng Liao🇺🇸 · Yacine Mehtar-Tani🇺🇸
Using kinetic theory, we analyze the interplay of elastic and inelastic collisions in the thermalization of the quark-gluon plasma. The main focus is the dynamics and equilibration of long wavelength modes.
nucl-thNPA(2016)·9 citations
09
Chiral Magnetic Effect in Heavy Ion Collisions
Jinfeng Liao🇺🇸
The Chiral Magnetic Effect (CME) is a remarkable phenomenon that stems from highly nontrivial interplay of QCD chiral symmetry, axial anomaly, and gluonic topology. It is of fundamental importance to search for the CME in experiments. The heavy ion collisions provide a unique environment where a hot chiral-symmetric quark-gluon plasma is created, gluonic topological fluctuations generate chirality imbalance, and very strong magnetic fields $∣ B ∣ \sim m_{π}^{2}$ are present during the early stage of such collisions. Significant efforts have been made to look for CME signals in heavy ion collision experiments. In this contribution we give a brief overview on the status of such efforts.
nucl-thhep-phnucl-exNPA(2016)·20 citations
10
Hyperons in neutron stars and supernova cores
M. Oertel🇫🇷 · F. Gulminelli🇫🇷 · C. Providencia🇵🇹 · A.R. Raduta🇷🇴
The properties of compact stars and their formation processes depend on many physical ingredients. The composition and the thermodynamics of the involved matter is one of them. We will investigate here uniform strongly interacting matter at densities and temperatures, where potentially other components than free nucleons appear such as hyperons, mesons or even quarks. In this paper we will put the emphasis on two aspects of stellar matter with non-nucleonic degrees of freedom. First, we will study the phase diagram of baryonic matter with strangeness, showing that the onset of hyperons, as that of quark matter, could be related to a very rich phase structure with a large density domain covered by phase coexistence. Second, we will investigate thermal effects on the equation of state (EoS), showing that they favor the appearance of non-nucleonic particles. We will finish by reviewing some recent results on the impact of non-nucleonic degrees freedom in compact star mergers and core-collapse events, where thermal effects cannot be neglected.
nucl-thEPJA(2016)·70 citations
11
Towards the QCD phase diagram from analytical continuation
R. Bellwied🇺🇸 · S. Borsanyi🇩🇪 · Z. Fodor🇭🇺 · J. Gunther🇩🇪 · S. D. Katz🇭🇺 · A. Pasztor🇩🇪 · C. Ratti🇺🇸 · K. K. Szabo🇩🇪
We calculate the QCD cross-over temperature, the equation of state and fluctuations of conserved charges at finite density by analytical continuation from imaginary to real chemical potentials. Our calculations are based on new continuum extrapolated lattice simulations using the 4stout staggered actions with a lattice resolution up to $N_{t} = 16$ . The simulation parameters are tuned such that the strangeness neutrality is maintained, as it is in heavy ion collisions.
nucl-thhep-latNPA(2016)·17 citations
12
Two Cold Atoms in a Time-Dependent Harmonic Trap in One Dimension
M. Ebert · A. Volosniev · H.-W. Hammer
We analyze the dynamics of two atoms with a short-ranged pair interaction in a one-dimensional harmonic trap with time-dependent frequency. Our analysis is focused on two representative cases: (i) a sudden change of the trapping frequency from one value to another, and (ii) a periodic trapping frequency. In case (i), the dynamics of the interacting and the corresponding non-interacting systems turn out to be similar. In the second case, however, the interacting system can behave quite differently, especially close to parametric resonance. For instance, in the regions where such resonance occurs we find that the interaction can significantly reduce the rate of energy increase. The implications for applications of our findings to cool or heat the system are also dicussed.
↳ cond-mat.quant-gasnucl-thquant-phAnnalen Phys.(2016)·7 citations
13
Soft-collinear effective theory for hadronic and nuclear collisions: The evolution of jet quenching from RHIC to the highest LHC energies
Ivan Vitev🇺🇸
In the framework of soft-collinear effective theory with Glauber gluons, results and predictions for inclusive hadron suppression, based upon in-medium parton shower evolution, are presented for Au+Au and Pb+Pb collisions at RHIC and LHC energies $s = 200$ AGeV and $s = 2.76, 5.1$ ATeV, respectively. The $SCE T_{G}$ medium-induced splitting kernels are further implemented to evaluate the attenuation of reconstructed jet cross in such reactions and to examine their centrality and radius $R$ dependence. Building upon a previously developed method to systematically resum the jet shape at next-to-leading logarithmic accuracy, a quantitative understanding of the jet shape modification measurement in Pb+Pb collisions at $s = 2.76$ ATeV at the LHC can be achieved. Predictions for photon-tagged jet cross sections and shapes, that can shed light on the parton flavor dependence of in-medium parton shower modification, are also given.
↳ hep-phnucl-thNPA(2016)·0 citations
14
Heavy Quark and Quarkonium Transport in High Energy Nuclear Collisions
Kai Zhou🇨🇳 · Wei Dai🇨🇳 · Nu Xu🇺🇸 · Pengfei Zhuang🇨🇳
The strong interaction between heavy quarks and the quark gluon plasma makes the open and hidden charm hadrons be sensitive probes of the deconfinement phase transition in high energy nuclear collisions. Both the cold and hot nuclear matter effects change with the colliding energy and significantly influence the heavy quark and charmonium yield and their transverse momentum distributions. The ratio of averaged quarkonium transverse momentum square and the elliptic flow reveal the nature of the QCD medium created in heavy ion collisions at SPS, RHIC and LHC energies.
↳ hep-phnucl-thNPA(2016)·4 citations
15
Massive dark photons in a Higgs portal model
Dimiter Hadjimichef🇧🇷
An extension of the Standard Model with a hidden sector which consists of gauge singlets (a Dirac fermion $χ$ and a scalar $S$ ) plus a vector boson $V_{μ}$ (dark massive photon) is studied. The singlet scalar interacts with the Standard Model sector through the triple and quartic scalar interactions, while the singlet fermion and vector boson field interact with the Standard Model only via the singlet scalar. The scalar field generates the vector boson's mass. Perspectives for future $e^{-} e^{+}$ colliders is considered.
↳ hep-phnucl-thAIP Conf.Proc.(2015)·3 citations
16
Zero energy scattering calculation in Euclidean space
J. Carbonell🇫🇷 · V.A. Karmanov🇷🇺
We show that the Bethe-Salpeter equation for the scattering amplitude in the limit of zero incident energy can be transformed into a purely Euclidean form, as it is the case for the bound states. The decoupling between Euclidean and Minkowski amplitudes is only possible for zero energy scattering observables and allows determining the scattering length from the Euclidean Bethe-Salpeter amplitude. Such a possibility strongly simplifies the numerical solution of the Bethe-Salpeter equation and suggests an alternative way to compute the scattering length in Lattice Euclidean calculations without using the Luscher formalism. The derivations contained in this work were performed for scalar particles and one-boson exchange kernel. They can be generalized to the fermion case and more involved interactions.
↳ hep-phhep-lathep-thnucl-thPLB(2016)·9 citations

Affiliations

first authorsco-authorsvia INSPIRE