Nuclear Theory·nucl-th

Thursday·March 9, 2017

11 papers—6 primary·5 cross-listed

01
Improved Quark Coalescence for a Multi-Phase Transport Model
Yuncun He🇨🇳 · Zi-Wei Lin🇺🇸
The string melting version of a multi-phase transport model is often applied to high-energy heavy-ion collisions since the dense matter thus formed is expected to be in parton degrees of freedom. In this work we improve its quark coalescence component, which describes the hadronization of the partonic matter to a hadronic matter. We removed the previous constraint that forced the numbers of mesons, baryons, and antibaryons in an event to be separately conserved through the quark coalescence process. A quark now could form either a meson or a baryon depending on the distance to its coalescence partner(s). We then compare results from the improved model with the experimental data on hadron $d N / d y$ , $p_{_{T}}$ spectra, and $v_{2}$ in heavy-ion collisions from $s_{_{NN}} = 62.4$ GeV to $5.02$ TeV. We show that, besides being able to describe these observables for low- $p_{_{T}}$ pions and kaons, the improved model also better describes the low- $p_{_{T}}$ baryon observables in general, especially the baryon $p_{_{T}}$ spectra and antibaryon-to-baryon ratios for multistrange baryons.
nucl-thnucl-exPRC(2017)·103 citations
02
Compositeness of hadron resonances in finite volume
Yujiro Tsuchida🇯🇵 · Tetsuo Hyodo🇯🇵
We develop a theoretical framework to quantify the structure of unstable hadron resonances. With the help of the corresponding system in a finite volume, we define the compositeness of resonance states which can be interpreted as a probability. This framework is used to study the structure of the scalar mesons f_0(980) and a_0(980). In both mesons, the Kbar K component dominates about a half of the wave function. The method is also applied to the Lambda(1405) resonance. We argue that a single energy level in finite volume represents the two eigenstates in infinite volume. The KbarK N component of Lambda(1405), including contributions from both eigenstates, is found to be 58%, and the rest is composed of the pi Sigma and other channels.
nucl-thhep-phPRC(2018)·9 citations
03
High-mass twin stars with a multi-polytrope EoS
D.E. Alvarez-Castillo · D.B. Blaschke
We show that in the 3-polytropes model of Hebeler et al. \cite{Hebeler:2013nza} for the neutron star equation of state at supersaturation densities a third family of compact stars can be obtained which confirms the possibility of high-mass twin stars that have coincident masses $M_{1} = M_{2} \approx 2 M_{⊙}$ and significantly different radii $∣ R_{1} - R_{2} ∣ > 2 - 3$ km. We show that the causality constraint puts severe limitations on the maximum mass of the third family sequence which can be relaxed when this scheme is extended to four polytropes thus mimicking a realistic high-density matter EoS.
nucl-thastro-ph.HEPRC(2017)·87 citations
04
Quantum tunneling with friction
M. Tokieda · K. Hagino
Using the phenomenological quantum friction models introduced by Caldirola-Kanai, Kostin, and Albrecht, we study quantum tunneling of a one-dimensional potential in the presence of energy dissipation. To this end, we calculate the tunneling probability using a time-dependent wave packet method. The friction reduces the tunneling probability. We show that the three models provide similar penetrabilities to each other, among which the Caldirola-Kanai model requires the least numerical effort. We also discuss the effect of energy dissipation on quantum tunneling in terms of barrier distributions.
nucl-thnucl-exquant-phPRC(2017)·18 citations
05
Spectral functions for $D ˉ$ meson and $D ˉ_{0}^{*}$ meson in nuclear matter with partial restoration of chiral symmetry
Daiki Suenaga🇯🇵 · Shigehiro Yasui🇯🇵 · Masayasu Harada🇯🇵
We investigate the in-medium masses of a $D ˉ (0^{-})$ meson and a $D ˉ_{0}^{*} (0^{+})$ meson and spectral functions for $D ˉ$ and $D ˉ_{0}^{*}$ meson channels in nuclear matter. These mesons are introduced as chiral partner in the chiral symmetry broken vacuum, hence they are useful to explore the partial restoration of the broken chiral symmetry in nuclear matter. We consider the linear sigma model to describe the chiral symmetry breaking. Our study shows that the loop corrections to $D ˉ$ and $D ˉ_{0}^{*}$ meson masses provide a smaller mass splitting at finite density than that in vacuum, whose result indicates a tendency of the restoration of the chiral symmetry. We investigate also the spectral function for $D ˉ_{0}^{*}$ meson channel, and find three peaks. The first peak which corresponds to the resonance of $D ˉ_{0}^{*}$ meson is broadened by collisions with nucleons in medium, and the peak position shifts to lower mass due to the partial restoration of chiral symmetry as the density increases. The second peak is identified as a threshold enhancement which shows a remarkable enhancement as the density increase. The third peak is Landau damping. The obtained properties of $D ˉ$ and $D ˉ_{0}^{*}$ mesons in nuclear matter will provide useful information for experiments.
nucl-thhep-phPRC(2017)·21 citations
06
Onset of $η$ -nuclear binding in a pionless EFT approach
N. Barnea🇮🇱 · B. Bazak🇫🇷 · E. Friedman🇮🇱 · A. Gal🇮🇱
$η N N N$ and $η N N N N$ bound states are explored in stochastic variational method (SVM) calculations within a pionless effective field theory (EFT) approach at leading order. The theoretical input consists of regulated $N N$ and $N N N$ contact terms, and a regulated energy dependent $η N$ contact term derived from coupled-channel models of the $N^{*} (1535)$ nucleon resonance plus a regulated $η N N$ contact term. A self consistency procedure is applied to deal with the energy dependence of the $η N$ subthreshold input, resulting in a weak dependence of the calculated $η$ -nuclear binding energies on the EFT regulator. It is found, in terms of the $η N$ scattering length $a_{η N}$ , that the onset of binding $η^{3}$ He requires a minimal value of Re $a_{η N}$ close to 1 fm, yielding then a few MeV $η$ binding in $η^{4}$ He. The onset of binding $η^{4}$ He requires a lower value of Re $a_{η N}$ , but exceeding 0.7 fm.
nucl-thhep-phnucl-exPLB(2017)·37 citations
07
Extended soft-wall model for the QCD phase diagram
Rico Zöllner🇩🇪 · Falk Wunderlich🇩🇪 · Burkhard Kampfer🇩🇪
The soft-wall model, emerging as bottom-up holographic scenario anchored in the AdS/CFT correspondence, displays the disappearance of normalisable modes referring to vector mesons at a temperature $T_{\dis}$ depending on the chemical potential $μ$ , $T_{\dis} (μ)$ . We explore options for making $T_{\dis} (μ)$ consistent with the freeze-out curve $T_{f.o.} (μ)$ from relativistic heavy-ion collisions and the cross-over curve $T_{c} (μ)$ from QCD at small values of $μ$ .
↳ hep-thhep-phnucl-thActa Phys.Polon.Supp.B(2017)·6 citations
08
Effective kinetic description of the expanding overoccupied Glasma
Naoto Tanji🇩🇪 · Raju Venugopalan🇺🇸
We report on a numerical study of the Boltzmann equation including $2 \leftrightarrow 2$ scatterings of gluons and quarks in an overoccupied Glasma undergoing longitudinal expansion. We find that when a cascade of gluon number to the infrared occurs, corresponding to an infrared enhancement analogous to a transient Bose-Einstein condensate, gluon distributions qualitatively reproduce the results of classical-statistical simulations for the expanding Glasma. These include key features of the distributions that are not anticipated in the "bottom-up" thermalization scenario. We also find that quark distributions, like those of gluons, satisfy self-similar scaling distributions in the overoccupied Glasma. We discuss the implications of these results for a deeper understanding of the self-similarity and universality of parton distributions in the Glasma.
↳ hep-phnucl-thPRD(2017)·37 citations
09
Recent status of the understanding of neutrino-nucleus cross section
H. Haider🇮🇳 · M. Sajjad Athar🇮🇳 · S. K. Singh🇮🇳
In this work we have presented current understanding of neutrino-nucleon/nucleus cross sections in the few GeV energy region relevant for a precise determination of neutrino oscillation parameters and CP violation in the leptonic sector. In this energy region various processes like quasielastic and inelastic production of single and multipion production, coherent pion production, kaon, eta, hyperon production, associated particle production as well as deep inelastic scattering processes contribute to the neutrino event rates.
↳ hep-phnucl-thSpringer Proc.Phys.(2018)·0 citations
10
Nuclear parton density functions from jet production in DIS at the EIC
M. Klasen🇩🇪 · K. Kovarik🇩🇪 · J. Potthoff🇩🇪
We investigate the potential of inclusive-jet production in deep-inelastic scattering (DIS) at a future Electron-Ion Collider (EIC) to improve our current knowledge of nuclear parton density functions (PDFs). We demonstrate that the kinematic reach is extended similarly to inclusive DIS, but that the uncertainty of the nuclear PDFs, in particular of the gluon density at low Bjorken-x, is considerably reduced, by up to an order of magnitude compared to the present situation. Using an approximate next-to-next-to-leading order (aNNLO) calculation implemented in the program JetViP, we also make predictions for three different EIC designs and for four different light and heavy nuclei.
↳ hep-phhep-exnucl-exnucl-thPRD(2017)·36 citations
11
Phase Transitions, Inhomogeneous Horizons and Second-Order Hydrodynamics
Maximilian Attems🇪🇸 · Yago Bea🇪🇸 · Jorge Casalderrey-Solana🇬🇧 · David Mateos🇪🇸 · Miquel Triana🇪🇸 · Miguel Zilhao🇪🇸
We use holography to study the spinodal instability of a four-dimensional, strongly-coupled gauge theory with a first-order thermal phase transition. We place the theory on a cylinder in a set of homogeneous, unstable initial states. The dual gravity configurations are black branes afflicted by a Gregory-Laflamme instability. We numerically evolve Einstein's equations to follow the instability until the system settles down to a stationary, inhomogeneous black brane. The dual gauge theory states have constant temperature but non-constant energy density. We show that the time evolution of the instability and the final states are accurately described by second-order hydrodynamics. In the static limit, the latter reduces to a single, second-order, non-linear differential equation from which the inhomogeneous final states can be derived.
↳ hep-thgr-qchep-phnucl-thJHEP(2017)·53 citations

Affiliations

first authorsco-authorsvia INSPIRE