Nuclear Theory·nucl-th

Tuesday·August 2, 2016

9 papers—5 primary·4 cross-listed

01
[Submitted on 30 Jul 2016]
Decay widths of bottomonium states in matter -- a field theoretic model for composite hadrons
Amruta Mishra🇮🇳 · S.P. Misra🇮🇳
We compute the in-medium partial decay widths of the bottomonium states to open bottom mesons ( $B B ˉ$ ) using a field theoretical model for composite hadrons with quark constituents. These decay widths are calculated by using the explicit constructions for the bottomonium states and the open bottom mesons ( $B$ and $B ˉ$ ), and, the quark antiquark pair creation term of the free Dirac Hamiltonian written in terms of the constituent quark field operators. These decay widths in the hadronic medium are calculated as arising from the mass modifications of the bottomonium states and the $B$ and $B ˉ$ mesons, obtained in a chiral effective model. The decay amplitude in the present model is multiplied with a strength parameter for the light quark pair creation, which is fitted from the observed vacuum partial decay width of the bottomonium state, $Υ (4 S)$ to $B B ˉ$ . The effects of the isospin asymmetry, the strangeness fraction of the hadronic matter on the decay widths, arising due to the mass modifications due to these effects, have also been studied. There is observed to be appreciable effects from density, and the effects from isospin asymmetry on the parital decay widths of $Υ \to B B ˉ$ are observed to be quite pronounced at high densities. These effects should show up in the asymmetric heavy ion collisions in Compressed baryonic matter (CBM) experiments planned at the future facility at FAIR. The study of the $Υ$ states will, however, require access to energies higher than the energy regime planned at the CBM experiment. The density effects on the decay widths of the bottomonium states should show up in the production of these states, as well as, in dilepton spectra at the Super Proton Synchrotron (SPS) energies.
Comments:
31 pages, 4 figures (eps files), version published in Phys.Rev.C
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1608.00069 [pdf]
PRC(2017)·27 citations
02
[Submitted on 30 Jul 2016]
Dirac Coupled-channel Analyses of Polarized Proton Scatterings to the 2 $^{+}$ Gamma Vibrational Band in $^{24}$ Mg and $^{26}$ Mg
Sugie Shim
Dirac coupled channel calculations are performed phenomenologically for the high-lying excited states that belong to the 2 $^{+}$ gamma vibrational band at the 800-MeV polarized proton inelastic scatterings from the s-d shell nuclei, $^{24}$ Mg and $^{26}$ Mg. Optical potential model is used and scalar and time-like vector potentials are considered as direct potentials. First-order vibrational collective models are used to obtain the transition optical potentials in order to accommodate the high-lying excited vibrational collective states. The complicated Dirac coupled channel equations are solved phenomenologically to reproduce the differential cross section and analyzing power data by varying the optical potential and deformation parameters. It is found that the relativistic Dirac coupled channel calculation could describe the high-lying excited states of the 2 $^{+}$ gamma vibrational band at the 800-MeV polarized proton inelastic scatterings from s-d shell nuclei $^{24}$ Mg and $^{26}$ Mg reasonably well, showing better agreement with the experimental data compared to the results obtained from the nonrelativistic calculations. Calculated deformation parameters for the excited states are analyzed and compared with those of nonrelativistic calculations.
Comments:
13pages, 6 figures. arXiv admin note: text overlap with arXiv:1501.00650, arXiv:1407.5441, arXiv:1511.01729
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1608.00076 [pdf]
Can.J.Phys.(2017)·2 citations
03
[Submitted on 30 Jul 2016]
A short summary on the search of trineutron and tetraneutron
Roman Ya. Kezerashvili
In light of a new experiment which claims an identification of tetraneutron [3], we discuss the results of experimental search of trineutron and tetraneutron in different nuclear reactions. A summary of theoretical studies for trineutron and tetraneutron within variety of approaches such as variational methods, the method of Faddeev and Faddeev-Yakubovsky equations, and the method of hyperspherical harmonics are presented.
Comments:
5 pages
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1608.00169 [pdf]
Proceedings of the Sixth International Co…·11 citations
04
[Submitted on 31 Jul 2016]
Inclusive breakup of Borromean nuclei
Mahir S. Hussein · Brett V. Carlson · Tobias Frederico
We derive the inclusive breakup cross section of a three-fragment projectile nuclei, $a = b + x_{1} + x_{2}$ , in the spectator model. The resulting four-body cross section for observing $b$ , is composed of the elastic breakup cross section which contains information about the correlation between the two participant fragments, and the inclusive non-elastic breakup cross section. This latter cross section is found to be a non-trivial four-body generalization of the Austern formula \cite{Austern1987}, which is proportional to a matrix element of the form, $⟨ ρ^_{x_{1}, x_{2}} ∣ [W_{x_{1}} + W_{x_{2}} + W_{3 B}] ∣ ρ^_{x_{1}, x_{2}} ⟩$ . The new feature here is the three-body absorption, represented by the imaginary potential, $W_{3 B}$ . We analyze this type of absorption and supply ideas of how to calculate its contribution.
Comments:
4 pages, one page, Contribution to the Proceedings of Cluster16, May 23-27, 2016, Napoli-Italy, to appear in Journal of Physics Conference Series
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1608.00278 [pdf]
J.Phys.Conf.Ser.(2017)·2 citations
05
[Submitted on 1 Aug 2016]
Bounds on the speed of sound in dense matter, and neutron star structure
Ch.C. Moustakidis🇬🇷 · T. Gaitanos🇬🇷 · Ch. Margaritis🇬🇷 · G.A. Lalazissis🇬🇷
The accurate determination of the maximum mass of the neutron stars is one of the most important tasks in astrophysics. It is directly related to the identification of the black holes in the universe, the production of neutron stars from the supernovae explosion, and the equation of state (EoS) of dense matter. However, not only the EoS is directly connected with neutron star masses, but also the speed of sound in dense matter is a crucial quantity which characterizes the stiffness of the EoS. The upper bound of the speed of sound imposes strong constraints on the maximum mass of neutron stars. However, this upper bound remains still an open issue. Recent observations, of binary neutron star systems, offer the possibility of measuring with high accuracy both the mass and the tidal polarizability of the stars. We study possible effects of the upper bound of the speed of sound on the upper bound of the mass and the tidal polarizability. We conclude that these kinds of measurements, combined with recent observations of neutron stars with masses close to $2 M_{⊙}$ , will provide robust constraints on the equation of state of hadronic matter at high densities.
Comments:
17 pages, 11 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
1608.00344 [pdf]
PRC(2017)·86 citations

Affiliations

first authorsco-authorsvia INSPIRE

Decay widths of bottomonium states in matter -- a field theoretic model for composite hadrons

Dirac Coupled-channel Analyses of Polarized Proton Scatterings to the 2+ Gamma Vibrational Band in 24Mg and 26Mg

A short summary on the search of trineutron and tetraneutron

Inclusive breakup of Borromean nuclei

Bounds on the speed of sound in dense matter, and neutron star structure

Affiliations

Dirac Coupled-channel Analyses of Polarized Proton Scatterings to the 2 $^{+}$ Gamma Vibrational Band in $^{24}$ Mg and $^{26}$ Mg