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
06
[Submitted on 1 Aug 2016] (cross-list from hep-ph)
Charmonium spectrum and their electromagnetic transitions with higher multipole contributions
Wei-Jun Deng🇨🇳 · Hui Liu🇨🇳 · Long-Cheng Gui🇨🇳 · Xian-Hui Zhong🇨🇳
The charmonium spectrum is calculated with two nonrelativistic quark models, the linear potential model and the screened potential model. Using the obtained wavefunctions, we evaluate the electromagnetic transitions of charmonium states up to $4 S$ multiplet. The higher multipole contributions are included by a multipole expansion of the electromagnetic interactions. Our results are in reasonable agreement with the measurements. As conventional charmonium states, the radiative decay properties of the newly observed charmonium-like states, such as $X (3823)$ , $X (3872)$ , $X (4140/4274)$ , are discussed. The $X (3823)$ as $ψ_{2} (1 D)$ , its radiative decay properties well agree with the observations. From the radiative decay properties of $X (3872)$ , one can not exclude it as a $χ_{c 1} (2 P)$ dominant state. We also give discussions of possibly observing the missing charmonium states in radiative transitions, which might provide some useful references to look for them in forthcoming experiments. The higher multipole contributions to the electromagnetic transitions are analyzed as well. It is found that the higher contribution from the magnetic part could give notable corrections to some E1 dominant processes by interfering with the E1 amplitudes. Our predictions for the normalized magnetic quadrupole amplitudes $M_{2}$ of the $χ_{c 1, 2} (1 P) \to J / ψ γ$ processes are in good agreement with the recent CLEO measurements.
Comments:
20 pages, 1 figure. Large improvement was done according to the referee's suggestions. To be published in PRD. arXiv admin note: text overlap with arXiv:1510.08269
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1608.00287 [pdf]
PRD(2017)·150 citations
07
[Submitted on 1 Aug 2016] (cross-list from hep-ph)
Virtual states and generalized completeness relation in the Friedrichs Model
Zhiguang Xiao🇨🇳 · Zhi-Yong Zhou🇨🇳
We study the well-known Friedrichs model, in which a discrete state is coupled to a continuum state. By examining the pole behaviors of the Friedrichs model in a specific form factor thoroughly, we find that, in general, when the bare discrete state is below the threshold of the continuum state, there should also be a virtual-state pole accompanying the bound-state pole originating from the bare discrete state as the coupling is turned on. There are also other second-sheet poles originating from the singularities of the form factor. We give a general argument for the existence of these two kinds of states. As the coupling is increased to a certain value, the second-sheet poles may merge and become higher-order poles. We then discuss the completeness relations incorporating bound states, virtual states, and resonant states corresponding to higher-order poles.
Comments:
15 pages, 8 figures; Minor modifications, imporved figures, version to appear in Phys. Rev. D
Subjects:
High Energy Physics — Phenomenology (hep-ph); Mathematical Physics (math-ph); math.MP (math.MP); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
1608.00468 [pdf]
PRD(2016)·27 citations
08
[Submitted on 1 Aug 2016] (cross-list from hep-ph)
Hot origin of the Little Bang
S.V. Akkelin🇺🇦
Ultrarelativistic heavy ion collisions produce a quark-gluon matter which lies in the future light cone originating from given points on the $t = z = 0$ plane of the Minkowski spacetime manifold. We show that in a weak coupling regime the Minkowski vacuum of massless fields presents itself in the "Little Bang" region as a thermal state of low $p_{T}$ particles, in close analogy to the Unruh effect for uniformly accelerated observers which are causally restricted to a Rindler wedge. It can shed some light on the mechanisms of early time thermalization in ultrarelativistic heavy ion collisions.
Comments:
17 pages
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1608.00472 [pdf]
EPJA(2017)·2 citations
09
[Submitted on 1 Aug 2016] (cross-list from nucl-ex)
Analysis of Neutron Stars Observations Using a Correlated Fermi Gas Model
O. Hen · A.W. Steiner · E. Piasetzky · L.B. Weinstein
Background: The nuclear symmetry energy is a fundamental ingredient in determining the equation of state (EOS) of neutron stars (NS). Recent terrestrial experiments constrain both its value and slope at nuclear saturation density, however, its value at higher densities is unknown. Assuming a Free Fermi-gas (FFG) model for the kinetic symmetry energy, the high-density extrapolation depends on a single parameter, the density dependence of the potential symmetry energy. The Correlated Fermi-gas (CFG) model improves on the FFG model by including the effects of short-range, correlated, high-momentum, nucleons in nuclear matter. Using the CFG model for the kinetic symmetry energy along with constraints from terrestrial measurements leads to a much softer density dependence for the potential symmetry energy. Purpose: Examine the ability of the FFG and CFG models to describe NS observables that are directly sensitive to the symmetry energy at high-density. Specifically, examine the ability of the CFG model, with its softer density dependence of the potential symmetry energy, to describe a two solar-mass NS. Methods: Using a Bayesian analysis of NS observables we compare the CFG and FFG models and examine the resulting parameters in the NS EOS and the density dependence of the potential symmetry energy. Results: Despite the large difference in the density dependence of the potential part of the symmetry energy, both models can describe the NS data and support a two solar-mass NS. The different density dependences has only a small effect on the NS EOS. Conclusions: While sensitive to the high-density values of the symmetry energy, NS observables alone are not enough to distinguish between the CFG and FFG models. This indicates that the NS EOS, obtain from Bayesian analysis of NS observables, is robust and is not sensitive to the exact nuclear model used for the kinetic symmetry energy.
Comments:
5 pages, 3 figures
Subjects:
Nuclear Experiment (nucl-ex); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
1608.00487 [pdf]
13 citations

Affiliations

first authorsco-authorsvia INSPIRE