Nuclear Theory·nucl-th

Tuesday·December 30, 2014

15 papers—7 primary·8 cross-listed

08
Tests of the nuclear equation of state and superfluid and superconducting gaps using the Cassiopeia A neutron star
Wynn C.G. Ho (Univ of Southampton)🇬🇧 · Khaled G. Elshamouty🇨🇦 · Craig O. Heinke (Univ of Alberta)🇨🇦 · Alexander Y. Potekhin (Ioffe Institute)🇷🇺
The observed rapid cooling of the Cassiopeia A neutron star can be interpreted as being caused by neutron and proton transitions from normal to superfluid and superconducting states in the stellar core. Here we present two new Chandra ACIS-S Graded observations of this neutron star and measurements of the neutron star mass M and radius R found from consistent fitting of both the X-ray spectra and cooling behavior. This comparison is only possible for individual nuclear equations of state. We test phenomenological superfluid and superconducting gap models which mimic many of the known theoretical models against the cooling behavior. Our best-fit solution to the Cassiopeia A data is one in which the (M,R) = (1.44 Msun,12.6 km) neutron star is built with the BSk21 equation of state, strong proton superconductor and moderate neutron triplet superfluid gap models, and a pure iron envelope or a thin carbon layer on top of an iron envelope, although there are still large observational and theoretical uncertainties.
↳ astro-ph.HEhep-phnucl-thPRC(2015)·128 citations
09
The same key to different doors - temperature puzzles
Ludwik Turko🇵🇱
The notion of temperature in many body elementary particle processes is in a common use for decades. Thermal models have become simple and universal effective tools to describe particle production -- not only in high energy heavy ion collisions but also in high energy elementary particle collisions. We perform a critical analysis of the temperature concepts in such processes. Although the temperature concept is a very useful tool, nevertheless it should be used with the care, taking into account that usually it is just model dependent fitted parameter.
↳ hep-phnucl-thPhys.Part.Nucl.(2015)·0 citations
10
Ab initio lattice results for Fermi polarons in two dimensions
Shahin Bour🇩🇪 · Dean Lee🇺🇸 · H.-W. Hammer🇩🇪 · Ulf-G. Meißner🇩🇪
We investigate the attractive Fermi polaron problem in two dimensions using non-perturbative Monte Carlo simulations. We introduce a new Monte Carlo algorithm called the impurity lattice Monte Carlo method. This algorithm samples the path integral in a computationally efficient manner and has only small sign oscillations for systems with a single impurity. As a benchmark of the method, we calculate the universal polaron energy in three dimensions in the scale-invariant unitarity limit and find agreement with published results. We then present the first fully non-perturbative calculations of the polaron energy in two dimensions and density correlations between the impurity and majority particles in the limit of zero range interactions. We find evidence for a smooth crossover transition from fermionic quasiparticle to molecular state as a function of interaction strength.
↳ cond-mat.quant-gashep-latnucl-thPRL(2015)·27 citations
11
New Bayesian analysis of hybrid EoS constraints with mass-radius data for compact stars
A. Ayriyan🇷🇺 · D. E. Alvarez-Castillo🇷🇺 · D. Blaschke🇷🇺 · H. Grigorian🇷🇺 · M. Sokolowski🇵🇱
We suggest a new Bayesian analysis using disjunct mass and radius constraints for extracting probability measures for cold, dense nuclear matter equations of state. One of the key issues of such an analysis is the question of a deconfinement transition in compact stars and whether it proceeds as a crossover or rather as a first order transition. The latter question is relevant for the possible existence of a critical endpoint in the QCD phase diagram under scrutiny in present and upcoming heavy-ion collision experiments.
↳ astro-ph.HEhep-phnucl-thPhys.Part.Nucl.(2015)·20 citations
12
Fluctuation of strongly interacting matter in Polyakov Nambu Jona-Lasinio model in finite volume
Abhijit Bhattacharyya🇮🇳 · Rajarshi Ray🇮🇳 · Subrata Sur
We have estimated the susceptibilities of conserved charges for 2-flavor strongly interacting matter with varying system sizes, using the Polyakov loop enhanced Nambu Jona-Lasinio model. The susceptibilities for vanishing baryon densities are found to show a scaling with the system volume in the hadronic as well as partonic phase. This scaling breaks down for a temperature range of about 30-50 MeV around the cross-over region. Simultaneous measurements of the various susceptibilities may thus indicate how close to the cross-over region the freeze-out occurs for the fireball created in heavy-ion collision experiments.
↳ hep-phnucl-thPRD(2015)·69 citations
13
Electromagnetic baryon form factors in the Poincare-covariant Faddeev approach
Reinhard Alkofer🇦🇹 · Gernot Eichmann🇩🇪 · Helios Sanchis-Alepuz🇩🇪 · Richard Williams🇩🇪
Baryons are treated as three-quark systems using QCD degrees of freedom in Poincare-covariant bound-state equations. The quark self-energy as well as the interaction between quarks are approximated by a vector-vector interaction via a single dressed-gluon exchange (rainbow-ladder truncation), thereby allowing a unified study of quark, meson and baryon properties. Here we will focus on the calculation of electromagnetic properties of spin-1/2 and spin-3/2 ground state baryons.
↳ hep-phnucl-thHyperfine Interact.(2015)·6 citations
14
New Power to Measure Supernova $ν_{e}$ with Large Liquid Scintillator Detectors
Ranjan Laha🇺🇸 · John F. Beacom🇺🇸 · Sanjib Kumar Agarwalla🇮🇳
We examine the prospects for detecting supernova $ν_{e}$ in JUNO, RENO-50, LENA, or other approved or proposed large liquid scintillator detectors. The main detection channels for supernova $ν_{e}$ in a liquid scintillator are its elastic scattering with electrons and its charged-current interaction with the $^{12}$ C nucleus. In existing scintillator detectors, the numbers of events from these interactions are too small to be very useful. However, at the 20-kton scale planned for the new detectors, these channels become powerful tools for probing the $ν_{e}$ emission. We find that the $ν_{e}$ spectrum can be well measured, to better than $\sim 40%$ precision for the total energy and better than $\sim 25%$ precision for the average energy. This is adequate to distinguish even close average energies, e.g., 11 MeV and 14 MeV, which will test the predictions of supernova models. In addition, it will help set constraints on neutrino mixing effects in supernovae by testing non-thermal spectra. Without such large liquid scintillator detectors (or Super-Kamiokande with added gadolinium, which has similar capabilities), supernova $ν_{e}$ will be measured poorly, holding back progress on understanding supernovae, neutrinos, and possible new physics.
↳ hep-phastro-ph.HEastro-ph.SRhep-ex+134 citations
15
Mixed phase effects on high-mass twin stars
D. E. Alvarez-Castillo🇷🇺 · D. Blaschke🇷🇺
Recently it has been found that a certain class of hybrid star equations of state with a large latent heat (strong first order phase transition obtained by a Maxwell construction) between stiff hadronic hadronic and stiff quark matter phases allows for the appearance of a third family of compact stars (including "twins") at high mass of $\sim 2 M_{⊙}$ . We investigate how robust this high-mass twin phenomenon is against a smoothing of the transition which would occur, e.g., due to pasta structures in the mixed phase. To this end we propose a simple construction of a pasta-like equation of state with a parameter that quantifies the degree of smoothing of the transition and could eventually be related to the surface tension of the pasta structures. It is interesting to note that the range of energy densities for the transition as well as the pressure at the onset of the transition of this class of hybrid star matter at zero temperature corresponds well to values of the same quantities found in finite temperature lattice QCD simulations for the 1 $σ$ region at the pseudocritical temperature $T_{c} = 154 \pm 9$ MeV. The pattern of the speed of sound as a function of energy density is very different.
↳ astro-ph.HEhep-phnucl-thPhys.Part.Nucl.(2015)·42 citations

Affiliations

first authorsco-authorsvia INSPIRE