Nuclear Theory·nucl-th

Monday·October 5, 2015

12 papers—8 primary·4 cross-listed

01
Dilepton emission in high-energy heavy-ion collisions with dissipative hydrodynamics
Gojko Vujanovic🇨🇦 · Gabriel S. Denicol🇺🇸 · Chun Shen🇨🇦 · Matthew Luzum🇪🇸 · Bjoern Schenke🇺🇸 · Sangyoung Jeon🇨🇦 · Charles Gale🇨🇦
In this contribution we study the effects of three transport coefficients of dissipative hydrodynamics on thermal dilepton anisotropic flow observables. The first two transport coefficients investigated influence the overall size and growth rate of shear viscous pressure, while the last transport coefficient governs the magnitude of net baryon number diffusion in relativistic dissipative fluid dynamics. All calculations are done using state-of-the-art 3+1D hydrodynamical simulations. We show that thermal dileptons are sensitive probes of the transport coefficients of dissipative hydrodynamics.
nucl-thhep-phnucl-ex3 citations
02
Properties of hot and dense matter from relativistic heavy ion collisions
Peter Braun-Munzinger🇩🇪 · Volker Koch🇺🇸 · Thomas Schaefer🇺🇸 · Johanna Stachel🇩🇪
We review the progress achieved in extracting the properties of hot and dense matter from relativistic heavy ion collisions at the relativistic heavy ion collider (RHIC) at Brookhaven National Laboratory and the large hadron collider (LHC) at CERN. We focus on bulk properties of the medium, in particular the evidence for thermalization, aspects of the equation of state, transport properties, as well as fluctuations and correlations. We also discuss the in-medium properties of hadrons with light and heavy quarks, and measurements of dileptons and quarkonia. This review is dedicated to the memory of Gerald E. Brown.
nucl-thhep-phnucl-exPhys.Rept.(2016)·385 citations
03
Microscopically constrained mean field models from chiral nuclear thermodynamics
Ermal Rrapaj🇺🇸 · Alessandro Roggero🇺🇸 · Jeremy W. Holt🇺🇸
We explore the use of mean field models to approximate microscopic nuclear equations of state derived from chiral effective field theory across the densities and temperatures relevant for simu- lating astrophysical phenomena such as core-collapse supernovae and binary neutron star mergers. We consider both relativistic mean field theory with scalar and vector meson exchange as well as energy density functionals based on Skyrme phenomenology and compare to thermodynamic equa- tions of state derived from chiral two- and three-nucleon forces in many-body perturbation theory. Quantum Monte Carlo simulations of symmetric nuclear matter and pure neutron matter are used to determine the density regimes in which perturbation theory with chiral nuclear forces is valid. Within the theoretical uncertainties associated with the many-body methods, we find that select mean field models describe well microscopic nuclear thermodynamics. As an additional consistency requirement, we study as well the single-particle properties of nucleons in a hot/dense environment, which affect e.g., charged-current weak reactions in neutron-rich matter. The identified mean field models can be used across a larger range of densities and temperatures in astrophysical simulations than more computationally expensive microscopic models.
nucl-thPRC(2016)·42 citations
04
Lightest Kaonic Nuclear Clusters
Roman Ya. Kezerashvili🇺🇸 · Shalva M. Tsiklauri🇺🇸 · Nurgali Zh. Takibayev🇰🇿
We present our study of kaonic three-body $K_N N$ , $K_K_N$ and $K K K_$ and four-body $K_$ , and $K_K_N N$ clusters within the framework of a potential model using the method of hyperspherical functions in momentum representation. To perform a numerical calculations for the bound state energy of the light kaonic system, we use a set of different potentials for the nucleon-nucleon and $K_N$ interactions, as well as for the kaon-kaon interaction. The calculations show that a quasibound state energy is not sensitive to the $N N$ interaction, and it shows very strong dependence on the $K_N$ potential. We also compare our results with those obtained using different theoretical approaches. The theoretical discrepancies in the binding energy and width for the lightest kaonic system related to the different $N N$ and $\overset{\_% }{K}N$ interactions are addressed.
nucl-thPhys.Sci.Tech.(2017)·6 citations
05
Electron capture rates in stars studied with heavy ion charge exchange reactions
C.A. Bertulani
Indirect methods using nucleus-nucleus reactions at high energies (here, high energies mean $\sim$ 50 MeV/nucleon and higher) are now routinely used to extract information of interest for nuclear astrophysics. This is of extreme relevance as many of the nuclei involved in stellar evolution are short-lived. Therefore, indirect methods became the focus of recent studies carried out in major nuclear physics facilities. Among such methods, heavy ion charge exchange is thought to be a useful tool to infer Gamow-Teller matrix elements needed to describe electron capture rates in stars and also double beta-decay experiments. In this short review, I provide a theoretical guidance based on a simple reaction model for charge exchange reactions.
nucl-thastro-ph.SRnucl-exJ.Phys.Conf.Ser.(2018)·1 citation
06
Chemically non-equilibrated QGP and thermal photon elliptic flow
Akihiko Monnai🇺🇸
It has been discovered in recent heavy-ion experiments that elliptic and triangular flow of direct photons are underpredicted by most hydrodynamic models. I discuss possible enhancement mechanisms based on late chemical equilibration of the QGP and in-medium modification of parton distributions. Numerical hydrodynamic analyses indicate that they suppress early photon emission and visibly enhance thermal photon elliptic flow.
nucl-thNucl.Part.Phys.Proc.(2016)·5 citations
07
The Octet Meson and Octet Baryon Interaction with strangeness and the $Λ (1405)$
Jun He🇨🇳 · Pei-Liang Lu🇨🇳
The octet meson and baryon interaction with strangeness $S = - 1$ is studied fully relativistically with chiral Lagrangian. In this work, a Bethe-Salpeter equation approach with spectator quasipotential approximation is applied to study the reactions $K^{-} p \to M B$ with $M B = K^{-} p, K ˉ^{0} n, π^{-} Σ^{+}, π^{0} Σ^{0}, π^{+} Σ^{-}$ and $η Λ$ with all possible partial waves and theoretical results are comparable with experimental data. It is found that the Weinberg-Tomozawa potential derived from the lowest order chiral Lagrangian only provides the contributions from partial waves with spin-parities $J^{P} = 1/ 2^{+}$ and $1/ 2^{-}$ . Two-pole structure of the $Λ (1405)$ is confirmed with poles at $1383 + 99 i$ and $1423 + 14 i$ MeV. The lower and higher poles originate from $Σ π$ interaction as a resonance and $K ˉ N$ interaction as a bound state, respectively.
nucl-thIJMPE(2015)·18 citations
08
The baryon spectrum and the hypercentral Constituent Quark Model
M.M. Giannini🇮🇹 · E. Santopinto🇮🇹
The description of the baryon spectrum is performed using the hypercentral Consituent Quark Model (hCQM), mainly in comparison with the harmonic oscillator (h.o.). Recentlly many new states, at various levels of confidence have been observed, leading to a softening of the missing resonance problem in the case of positive parity states. However, the number of negative states is higher that predicted by the commonly used h.o. scheme and therefore one is forced to take into account also the higher energy shells, which contain an overall number of states much greater than the observed one. It is shown that, thanks to the peculiar level scheme of the hCQM, the recently observed negative parity states can be considered as belonging to the lower shells, keeping the missing resonance problem within more acceptable limits.
nucl-th4 citations
09
Pinning down the superfluid and measuring masses using pulsar glitches
Wynn C. G. Ho · Cristobal M. Espinoza · Danai Antonopoulou · Nils Andersson
Pulsars are known for their superb timing precision, although glitches can interrupt the regular timing behavior when the stars are young. These glitches are thought to be caused by interactions between normal and superfluid matter in the crust of the star. However, glitching pulsars such as Vela have been shown to require a superfluid reservoir that greatly exceeds that available in the crust. We examine a model in which glitches tap the superfluid in the core. We test a variety of theoretical superfluid models against the most recent glitch data and find that only one model can successfully explain up to 45 years of observational data. We develop a new technique for combining radio and X-ray data to measure pulsar masses, thereby demonstrating how current and future telescopes can probe fundamental physics such as superfluidity near nuclear saturation.
↳ astro-ph.SRastro-ph.HEnucl-thScience Adv. 1, e1500578 (2015)·65 citations
10
Majorana Neutrino Magnetic Moment and Neutrino Decoupling in Big Bang Nucleosynthesis
N. Vassh (Wisconsin U., Madison)🇺🇸 · E. Grohs ( Michigan U.)🇺🇸 · A.B. Balantekin (Wisconsin U., Madison)🇺🇸 · G.M. Fuller (UC, San Diego)🇺🇸
We examine the physics of the early universe when Majorana neutrinos (electron neutrino, muon neutrino, tau neutrino) possess transition magnetic moments. These extra couplings beyond the usual weak interaction couplings alter the way neutrinos decouple from the plasma of electrons/positrons and photons. We calculate how transition magnetic moment couplings modify neutrino decoupling temperatures, and then use a full weak, strong, and electromagnetic reaction network to compute corresponding changes in Big Bang Nucleosynthesis abundance yields. We find that light element abundances and other cosmological parameters are sensitive to magnetic couplings on the order of 10^{-10} Bohr magnetons. Given the recent analysis of sub-MeV Borexino data which constrains Majorana moments to the order of 10^{-11} Bohr magnetons or less, we find that changes in cosmological parameters from magnetic contributions to neutrino decoupling temperatures are below the level of upcoming precision observations.
↳ astro-ph.COhep-phnucl-thPRD(2015)·31 citations
11
Massive Yang-Mills for Vector and Axial-Vector Spectral Functions at Finite Temperature
Paul M. Hohler🇺🇸 · Ralf Rapp🇺🇸
The hadronic mechanism which leads to chiral symmetry restoration is explored in the context of the rho-pi-a_1 system using Massive Yang-Mills, a hadronic effective theory which governs their microscopic interactions. In this approach, vector and axial-vector mesons are implemented as gauge bosons of a local chiral gauge group. We have previously shown that this model can describe the experimentally measured vector and axial-vector spectral functions in vacuum. Here, we carry the analysis to finite temperatures by evaluating medium effects in a pion gas and calculating thermal spectral functions. We find that the spectral peaks in both channels broaden along with a noticeable downward mass shift in the a_1 spectral peak and negligible movement of the rho peak. The approach toward spectral function degeneracy is accompanied by a reduction of chiral order parameters, i.e., the pion decay constant and scalar condensate. Our findings suggest a mechanism where the chiral mass splitting induced in vacuum is burned off. We explore this mechanism and identify future investigations which can further test it.
↳ hep-phnucl-thAnnals Phys.(2016)·18 citations
12
The light-front energy-momentum tensor
Cédric Lorcé (CPHT, Ecole Polytechnique)🇧🇪
We present the first complete parametrization for the matrix elements of the generic light-front gauge-invariant energy-momentum tensor, derive the expressions giving separately the spin and orbital angular momentum of quarks and gluons as probed in high-energy scattering experiments, and discuss the relations with two-parton generalized and transverse-momentum dependent distributions. As a by-product, we recovered the Burkardt sum rule, clarified its physical meaning and obtained similar new sum rules for higher-twist distributions.
↳ hep-phnucl-thPoS(2015)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE