Nuclear Theory·nucl-th

Friday·December 8, 2017

10 papers—5 primary·5 cross-listed

01
Color superconductivity and charge neutrality in Yukawa theory
Mark G. Alford🇺🇸 · Kamal Pangeni🇺🇸 · Andreas Windisch🇺🇸
It is generally believed that when Cooper pairing occurs between two different species of fermions, their Fermi surfaces become locked together so that the resultant state remains 'neutral', with equal number densities of the two species, even when subjected to a chemical potential that couples to the difference in number densities. This belief is based on mean-field calculations in models with a zero-range interaction, where the anomalous self-energy is independent of energy and momentum. Following up on an early report of a deviation from neutrality in a Dyson-Schwinger calculation of color-flavor-locked quark matter, we investigate the neutrality of a two-species condensate using a Yukawa model which has a finite-range interaction. In a mean field calculation we obtain the full energy-momentum dependence of the self energy and find that the energy dependence leads to a population imbalance in the Cooper-paired phase when it is stressed by a species-dependent chemical potential. This gives some support to the suggestion that the color-flavor-locked phase of quark matter might not be an insulator.
nucl-thhep-phPRL(2018)·10 citations
02
The effect of the fluctuating proton size on the study of chiral magnetic effect in proton-nucleus collisions
Dmitri Kharzeev🇺🇸 · Zhoudunming Tu🇺🇸 · Aobo Zhang🇺🇸 · Wei Li🇺🇸
High energy proton-nucleus (pA) collisions provide an important constraint on the study of the chiral magnetic effect in QCD matter. Naively, in pA collisions one expects no correlation between the orientation of event plane as reconstructed from the azimuthal distribution of produced hadrons and the orientation of magnetic field. If this is the case, any charge-dependent hadron correlations can only result from the background. Nevertheless, in this paper we point out that in high multiplicity pA collisions a correlation between the magnetic field and the event plane can appear. This is because triggering on the high hadron multiplicity amounts to selecting Fock components of the incident proton with a large number of partons that are expected to have a transverse size much larger than the average proton size. We introduce the effect of the fluctuating proton size in the Monte Carlo Glauber model and evaluate the resulting correlation between the magnetic field and the second-order event plane in both pA and nucleus-nucleus (AA) collisions. The fluctuating proton size is found to result in a significant correlation between magnetic field and the event plane in pA collisions, even though the magnitude of the correlation is still much smaller than in AA collisions. This result opens a possibility of studying the chiral magnetic effect in small systems.
nucl-thhep-phnucl-exPRC(2018)·9 citations
03
Systematics of strong nuclear amplification of gluon saturation from exclusive vector meson production in high energy electron-nucleus collisions
Heikki Mäntysaari🇫🇮 · Raju Venugopalan🇺🇸
We show that gluon saturation gives rise to a strong modification of the scaling in both the nuclear mass number $A$ and the virtuality $Q^{2}$ of the vector meson production cross-section in exclusive deep-inelastic scattering off nuclei. We present qualitative analytic expressions for how the scaling exponents are modified as well as quantitative predictions that can be tested at an Electron-Ion Collider.
nucl-thhep-phPLB(2018)·44 citations
04
Repulsion and absorption of the $Σ$ -nucleus potential for $Σ^{-}$ - $^{5}$ He in the $^{6}$ Li( $π^{-}$ , $K^{+}$ ) reaction
Toru Harada · Ryotaro Honda · Yoshiharu Hirabayashi
We study phenomenologically inclusive spectra of the $^{6}$ Li( $π^{-}$ , $K^{+}$ ) reaction at 1.2 GeV/ $c$ within a distorted-wave impulse approximation with the optimal Fermi-averaging $π^{-} p \to K^{+} Σ^{-}$ $t$ matrix. We attempt to clarify the property of a $Σ$ -nucleus potential for $Σ^{-}$ - $^{5}$ He by comparing the calculated spectra with the data of the J-PARC E10 experiment. The result shows that the repulsive and absorptive components of the $Σ^{-}$ - $^{5}$ He potential provide the ability to explain the data of the continuum spectra in $Σ$ and $Λ$ regions; the strengths of $V_{Σ} ≃$ +30 MeV and $W_{Σ} ≃$ $-$ 26 MeV are favored within the Woods-Saxon potential, consistent with analyses for heavier nuclei. Effects of the size and potential range for $Σ^{-}$ - $^{5}$ He in the neutron excess of $(N - Z) / (N + Z) =$ 0.2 are also discussed.
nucl-thPRC(2018)·14 citations
05
Some aspects of global Lambda polarization in heavy-ion collisions
Xiao-Liang Xia🇨🇳 · Hui Li🇨🇳 · Qun Wang🇨🇳
Large orbital angular momentum can be generated in non-central heavy-ion collisions, and part of it is expected to be converted into final particle's polarization due to the spin-orbit coupling. Within the framework of A Multi-Phase Transport (AMPT) model, we studied the vorticity-induced polarization of $Λ$ hyperons at the midrapidity region $∣ η ∣ < 1$ in Au-Au collisions at energies $s_{N N} = 7.7 \sim 200$ GeV. Our results show that the global polarization decreases with the collisional energies and is consistent with the recent STAR measurements. This behavior can be understood by less asymmetry of participant matter in the midrapidity region due to faster expansion of fireball at higher energies. As another evidence, we discuss how much the angular momentum is deposited in different rapidity region. The result supports our asymmetry argument.
nucl-thhep-phPoS(2018)·5 citations
06
Stellar equilibrium configurations of white dwarfs in the $f (R, T)$ gravity
G. A. Carvalho · R. V. Lobato · P. H. R. S. Moraes · José D. V. Arbañil · R. M. Marinho Jr · E. Otoniel · M. Malheiro
In this work we investigate the equilibrium configurations of white dwarfs in a modified gravity theory, na\-mely, $f (R, T)$ gravity, for which $R$ and $T$ stand for the Ricci scalar and trace of the energy-momentum tensor, respectively. Considering the functional form $f (R, T) = R + 2 λ T$ , with $λ$ being a constant, we obtain the hydrostatic equilibrium equation for the theory. Some physical properties of white dwarfs, such as: mass, radius, pressure and energy density, as well as their dependence on the parameter $λ$ are derived. More massive and larger white dwarfs are found for negative values of $λ$ when it decreases. The equilibrium configurations predict a maximum mass limit for white dwarfs slightly above the Chandrasekhar limit, with larger radii and lower central densities when compared to standard gravity outcomes. The most important effect of $f (R, T)$ theory for massive white dwarfs is the increase of the radius in comparison with GR and also $f (R)$ results. By comparing our results with some observational data of massive white dwarfs we also find a lower limit for $λ$ , namely, $λ > - 3 \times 1 0^{- 4}$ .
↳ gr-qcastro-ph.SRhep-thnucl-thEPJC(2017)·126 citations
07
Towards the full realization of the RIBLL2 beam line at the HIRFL-CSR complex
Bao-Hua Sun🇨🇳 · Jian-Wei Zhao🇨🇳 · Xue-Heng Zhang🇨🇳 · Li-Na Sheng🇨🇳 · Zhi-Yu Sun🇨🇳 · Isao Tanihata🇨🇳 · Satoru Terashima🇨🇳 · Yong Zheng🇨🇳 · Li-Hua Zhu🇨🇳 · Li-Min Duan🇨🇳 · Liu-Chun He🇨🇳 · Rong-Jiang Hu🇨🇳 and 22 other authors
The RIBLL2 in-flight separator at IMP, the secondary beam line between two storage rings at the \blue{\uwave{Heavy Ion Research Facility in Lanzhou (HIRFL-CSR)}}, has been commissioned to study the rare-isotope beam (RIB) physics at around 300 MeV/nucleon for the first time, in combination of the external target facility (ETF). The unambiguous particle identification in mass and charge states for $^{18}$ O and $^{40}$ Ar fragments has been achieved in recent experiments. A full realization of RIBLL2 will open many potentials to address important RIB physics problems at around 300 MeV/nucleon.
↳ physics.acc-phnucl-exnucl-thSci.Bull.(2018)·38 citations
08
Wounded quark emission function at the top RHIC energy
Michał Barej🇵🇱 · Adam Bzdak🇵🇱 · Paweł Gutowski🇵🇱
The wounded nucleon and quark emission functions are extracted for different centralities in d+Au collisions at $s = 200 GeV$ using Monte Carlo simulations and experimental data. The shape of the emission function depends on centrality in the wounded nucleon model, whereas it is practically universal (within uncertainties) in the wounded quark model. Predictions for $d N_{c h} / d η$ distributions in p+Au and $^{3}$ He+Au collisions are presented.
↳ hep-phhep-exnucl-exnucl-thPRC(2018)·19 citations
09
Effect of an anisotropic escape mechanism on elliptic flow in relativistic heavy-ion collisions
Amaresh Jaiswal🇮🇳 · Partha Pratim Bhaduri🇮🇳
We study the effect of anisotropic escape mechanism on elliptic flow in relativistic heavy-ion collisions. We use Glauber model to generate initial conditions and ignore hydrodynamic expansion in the transverse direction. We employ Beer-Lambert law to allow for the transmittance of produced hadrons in the medium and calculate the anisotropy generated due to the suppression of particles traversing through the medium. In order to separate non-flow contribution due to surface bias effects, we ignore hydrodynamic expansion in the transverse direction and consider purely longitudinal boost-invariant expansion. We calculate the transverse momentum dependence of elliptic flow, generated from anisotropic escape mechanism due to surface bias effects, for various centralities in $s_{N N} = 200$ GeV Au $+$ Au collisions at RHIC and $s_{N N} = 2.76$ TeV Pb $+$ Pb collisions at LHC. We find that the surface bias effects have a sizable contribution to the total elliptic flow observed in heavy-ion collisions indicating that the viscosity of the QCD matter extracted from hydrodynamic simulations may be underestimated.
↳ hep-phnucl-thPRC(2018)·7 citations
10
Resurgence and Hydrodynamic Attractors in Gauss-Bonnet Holography
Jorge Casalderrey-Solana🇬🇧 · Nikola I. Gushterov🇬🇧 · Ben Meiring🇬🇧
We study the convergence of the hydrodynamic series in the gravity dual of Gauss-Bonnet gravity in five dimensions with negative cosmological constant via holography. By imposing boost invariance symmetry, we find a solution to the Gauss-Bonnet equation of motion in inverse powers of the proper time, from which we can extract high order corrections to Bjorken flow for different values of the Gauss-Bonnet parameter $λ_{GB}$ . As in all other known examples the gradient expansion is, at most, an asymptotic series which can be understood through applying the techniques of Borel-Padé summation. As expected from the behaviour of the quasi-normal modes in the theory, we observe that the singularities in the Borel plane of this series show qualitative features that interpolate between the infinitely strong coupling limit of $N = 4$ Super Yang Mills theory and the expectation from kinetic theory. We further perform the Borel resummation to constrain the behaviour of hydrodynamic attractors beyond leading order in the hydrodynamic expansion. We find that for all values of $λ_{GB}$ considered, the convergence of different initial conditions to the resummation and its hydrodynamization occur at large and comparable values of the pressure anisotropy.
↳ hep-thhep-phnucl-thJHEP(2018)·62 citations

Affiliations

first authorsco-authorsvia INSPIRE