Nuclear Theory·nucl-th

Friday·August 19, 2016

10 papers—7 primary·3 cross-listed

01
Examination of strangeness instabilities and effects of strange meson couplings in dense strange hadronic matter and compact stars
James R. Torres🇧🇷 · Francesca Gulminelli🇫🇷 · Debora P. Menezes🇧🇷
Background : The emergence of hyperon degrees of freedom in neutron star matter has been associated to first order phase transitions in some phenomenological models, but conclusions on the possible physical existence of an instability in the strangeness sector are strongly model dependent. Purpose : The purpose of the present study is to assess whether strangeness instabilities are related to specific values of the largely unconstrained hyperon interactions, and to study the effect of the strange meson couplings on phenomenological properties of neutron stars and supernova matter, once these latter are fixed to fulfill the constraints imposed by hypernuclear data. Method : We consider a phenomenological RMF model sufficiently simple to allow a complete exploration of the parameter space. Results : We show that no instability at supersaturation density exists for the RMF model, as long as the parameter space is constrained by basic physical requirements. This is at variance with a non-relativistic functional, with a functional behavior fitted through ab-initio calculations. Once the study is extended to include the full octet, we show that the parameter space allows reasonable radii for canonical neutron stars as well as massive stars above two-solar mass, together with an important strangeness content of the order of 30\%, slightly decreasing with increasing entropy, even in the absence of a strangeness driven phase transition. Conclusions : We conclude that the hyperon content of neutron stars and supernova matter cannot be established with present constraints, and is essentially governed by the unconstrained coupling to the strange isoscalar meson.
nucl-thastro-ph.HEPRC(2017)·26 citations
02
A novel probe of chiral restoration in nuclear medium
Philipp Gubler🇰🇷 · Teiji Kunihiro🇯🇵 · Su Houng Lee🇰🇷
We propose measuring the mass shift and width broadening of the $f_{1} (1285)$ meson together with those of the $ω$ from a nuclear target as a means to experimentally probe the partial restoration of chiral symmetry inside the nuclear matter. The relation between the order parameter of chiral symmetry and the difference in the correlation functions of the $f_{1} (1285)$ current and the $ω$ current is discussed in the limit where the disconnected diagrams are neglected. A QCD sum rule analysis of the $f_{1} (1285)$ meson mass leads to about 100 MeV attraction in nuclear matter, which can be probed in future experiments.
nucl-thhep-phnucl-exPLB(2017)·22 citations
03
Maximal isospin few-body systems of nucleons and $Ξ$ hyperons
H. Garcilazo🇲🇽 · A. Valcarce🇪🇸 · J. Vijande🇪🇸
By using local central Yukawa-type interactions that reproduce the low-energy parameters of the latest updates of the Nijmegen ESC08c potentials we show that the $N Ξ$ , $N N Ξ$ , $N ΞΞ$ and $N N ΞΞ$ systems with maximal isospin are bound. Since in these states the strong decay $N Ξ \to ΛΛ$ is forbidden by isospin conservation, these strange few-body systems will be stable under the strong interaction. These results may suggest that other states with different number of $N$ 's and $Ξ$ 's in the maximal isospin channel could also be bound.
nucl-thhep-phPRC(2016)·24 citations
04
Semihadronic and hadronic decays of $ρ^{0}$ and $ω$ mesons coherently photoproduced in the isoscalar nuclei
Swapan Das🇮🇳
The interference of the $ρ^{0}$ and $ω$ mesons has been studied in the hadronic and leptonic decay channels, i.e., dipion and dilepton decay channels respectively, but this interference is not studied yet in the semihadronic or semileptonic decay channel, e.g., $V \to π^{0} γ$ . $V$ denotes either $ρ^{0}$ or $ω$ meson. To look for the quoted interference in the $π^{0} γ$ decay channel as well as the contribution of $ρ$ meson to the cross section, the correlated $π^{0} γ$ invariant mass distribution spectra are calculated in the photonuclear reaction in the multi-GeV region. It is assumed that these bosons arise in the final state due to the decay of $ρ^{0}$ and $ω$ mesons which are photoproduced coherently in the isoscalar nucleus. The elementary reaction in the nucleus is considered to proceed as $γ N \to V N$ ; $V \to π^{0} γ$ . The forward propagation of the $ρ$ and $ω$ mesons and the near forward emission of pion are considered, so that they can be described by the eikonal form. The meson nucleus interactions are evaluated using $tϱ$ approximation. Replacing the decay vertex $V \to π^{0} γ$ by $V \to π^{+} π^{-}$ in the above formalism, it is also used to study the $ρ - ω$ interference in the $π^{+} π^{-}$ decay channel.
nucl-thnucl-exPRC(2016)·3 citations
05
Comparison of Yields of neutron rich nuclei in Proton and Photon induced $^{238}$ U fission
F. A. Khan · Debasis Bhowmick · D. N. Basu · M. Farooq · Alok Chakrabarti
A comparative study of fission of actinides specially $^{238}$ U, by proton and bremsstrahlung photon is performed. Relative mass distribution of $^{238}$ U fission fragments have been explored theoretically for both proton and photon induced fission. The integrated yield along with charge distribution of the products are calculated to find out the neutron richness in comparison to the nuclei produced by r-process in nucleosynthesis. Some r-process nuclei in intermediate mass range for symmetric fission mode are found to be produced almost two order of magnitude more for proton induced fission than photofission, although rest of the neutron rich nuclei in the asymmetric mode are produced in comparable proportion for both the processes.
nucl-thPRC(2016)·7 citations
06
Correlations of flow harmonics in 2.76A TeV Pb--Pb collisions
Xiangrong Zhu🇨🇳 · You Zhou🇩🇰 · Haojie Xu🇨🇳 · Huichao Song🇨🇳
Using the event-by-event viscous hydrodynamics VISH2+1 with MC-Glauber, MC-KLN, and AMPT initial conditions, we investigate the correlations of flow harmonics, including the symmetric cumulants $S C^{v} (m, n)$ , the normalized symmetric cumulants $N S C (m, n)$ , and the Pearson correlation coefficients $C (v_{m}^{2}, v_{n}^{2})$ in 2.76A TeV Pb--Pb collisions. We find $S C^{v} (m, n)$ is sensitive to both initial conditions and the specific shear viscosity $η / s$ . A comparison with the recent ALICE data show that our hydrodynamic calculations can qualitatively describe the data of $S C^{v} (3, 2)$ and $S C^{v} (4, 2)$ for various initial conditions, which demonstrate that $v_{2}$ , $v_{4}$ are correlated and $v_{2}$ , $v_{3}$ are anti-correlated. Meanwhile, the predicted symmetric cumulants $S C^{v} (5, 2)$ , $S C^{v} (5, 3)$ , and $S C^{v} (4, 3)$ reveal that $v_{2}$ and $v_{5}$ , $v_{3}$ and $v_{5}$ are correlated, $v_{3}$ and $v_{4}$ are anti-correlated in most centrality classes. We also find $N S C^{v} (3, 2)$ and $C (v_{3}^{2}, v_{2}^{2})$ , which are insensitive to $η / s$ , are mainly determined by corresponding $N S C^{ε} (3, 2)$ and $C (ε_{3}^{2}, ε_{2}^{2})$ correlators from the initial state. In contrast, other $N S C^{v} (m, n)$ and $C (v_{m}^{2}, v_{n}^{2})$ correlators are influenced by both initial conditions and $η / s$ , which illustrates the non-linear mode couplings in higher flow harmonics with $n \geq 4$ .
nucl-thhep-phnucl-exPRC(2017)·68 citations
07
Rapidity Correlation Structures from Causal Hydrodynamics
Sean Gavin🇺🇸 · George Moschelli🇺🇸 · Christopher Zin🇺🇸
Viscous diffusion can broaden the rapidity dependence of two-particle transverse momentum fluctuations. Surprisingly, measurements at RHIC by the STAR collaboration demonstrate that this broadening is accompanied by the appearance of unanticipated structure in the rapidity distribution of these fluctuations in the most central collisions. Although a first order classical Navier-Stokes theory can roughly explain the rapidity broadening, it cannot explain the additional structure. We propose that the rapidity structure can be explained using the second order causal Israel-Stewart hydrodynamics with stochastic noise.
nucl-thhep-phJ.Phys.Conf.Ser.(2016)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE

Examination of strangeness instabilities and effects of strange meson couplings in dense strange hadronic matter and compact stars

A novel probe of chiral restoration in nuclear medium

Maximal isospin few-body systems of nucleons and Ξ hyperons

Semihadronic and hadronic decays of ρ0 and ω mesons coherently photoproduced in the isoscalar nuclei

Comparison of Yields of neutron rich nuclei in Proton and Photon induced 238U fission

Correlations of flow harmonics in 2.76A TeV Pb--Pb collisions

Rapidity Correlation Structures from Causal Hydrodynamics

Affiliations

Maximal isospin few-body systems of nucleons and $Ξ$ hyperons

Semihadronic and hadronic decays of $ρ^{0}$ and $ω$ mesons coherently photoproduced in the isoscalar nuclei

Comparison of Yields of neutron rich nuclei in Proton and Photon induced $^{238}$ U fission