Nuclear Theory·nucl-th

Tuesday·September 8, 2015

10 papers—6 primary·4 cross-listed

01
[Submitted on 5 Sept 2015]
Role of the Three-Body Interactions in the Ground-States of 3H and 4He Nuclei
S. B. Doma🇪🇬 · H. S. El-Gendy
The role of the three-body interactions in the ground-states of 3H and 4He nuclei has been investigated by using two different methods. Accordingly, the ground-state nuclear wave functions, the binding energies, the root mean-square radii and the first excited-state energies of the 3H and 4He nuclei are investigated by applying the translation invariant shell model with basis functions corresponding to even number of quanta of excitations in the range 0 less than or equal to N less than or equal to 20 and using two residual two-body interactions, given by the first author, together with three-body interaction in the form of a delta force. Furthermore, we have calculated the binding energy and the root mean-square radius of these nuclei by applying the variational Monte Carlo method and using the Reid V_8 two-body potential together with the Urbana model of the three-nucleon interaction.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1509.01730 [pdf]
0 citations
02
[Submitted on 6 Sept 2015]
Predictions for squeezed back-to-back correlations of $ϕϕ$ and $K^{+} K^{-}$ in high-energy heavy-ion collisions by event-by-event hydrodynamics
Yong Zhang🇨🇳 · Wei-Ning Zhang🇨🇳
We calculate the squeezed back-to-back correlation (BBC) functions of $ϕϕ$ and $K^{+} K^{-}$ for heavy-ion collisions at RHIC and LHC energies, using ( $2 + 1$ )-dimensional hydrodynamics with fluctuating initial conditions. The BBC functions averaged over event-by-event calculations for many events for the hydrodynamic sources are smoothed as a function of the particle momentum. For heavy-ion collisions of Au+Au at $s_{N N} = 200$ GeV, the BBC functions are larger than those for collisions of Pb+Pb at $s_{N N} = 2.76$ TeV. The BBC of $ϕϕ$ may possibly be observed in peripheral collisions at the RHIC and LHC energies. It is large for the smaller sources of Cu+Cu collisions at $s_{N N} = 200$ GeV.
Comments:
16 pages, 11 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1509.01826 [pdf]
EPJC(2016)·14 citations
03
[Submitted on 7 Sept 2015]
Neutrinoless double electron capture
J. Kotila🇺🇸 · J. Barea🇨🇱 · F. Iachello🇺🇸
Direct determination of the neutrino mass is at the present time one of the most important aims of experimental and theoretical research in nuclear and particle physics. A possible way of detection is through neutrinoless double electron capture, $0 ν E C E C$ . This process can only occur when the energy of the initial state matches precisely that of the final state. We present here a calculation of prefactors (PF) and nuclear matrix elements (NME) within the framework of the microscopic interacting boson model (IBM-2) for $^{124}$ Xe, $^{152}$ Gd, $^{156}$ Dy, $^{164}$ Er, and $^{180}$ W. From PF and NME we calculate the expected half-lives and obtain results that are of the same order as those of $0 ν β^{+} β^{+}$ decay, but considerably longer than those of $0 ν β^{-} β^{-}$ decay.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1509.01927 [pdf]
PRC(2014)·52 citations
04
[Submitted on 7 Sept 2015]
Charge-exchange resonances and restoration of the Wigner SU(4)-symmetry in heavy and superheavy nuclei
Yu.S. Lutostansky · V.N. Tikhonov
Energies of the giant Gamow-Teller and analog resonances - $E_{G}$ and $E_{A}$ , are presented, calculated using the microscopic theory of finite Fermi system. The calculated differences $Δ E_{G - A} = E_{G} - E_{A}$ go to zero in heavier nuclei indicating the restoration of Wigner SU(4)-symmetry. The calculated $Δ E_{G - A}$ values are in good agreement with the experimental data. The average deviation is 0.30 MeV for the 33 considered nuclei for which experimental data is available. The $Δ E_{G - A}$ values were calculated for heavy and superheavy nuclei up to the mass number $A$ = 290. Using the experimental data for the analog resonances energies, the isotopic dependence of the difference of the Coulomb energies of neighboring nuclei isobars analyzed within the SU(4)-approach for more than 400 nuclei in the mass number range of $A$ = 3 - 244. The Wigner SU(4)-symmetry restoration for heavy and superheavy nuclei is confirmed. It is shown that the restoration of SU(4)-symmetry does not contradict the possibility of the existence of the "island of stability" in the region of superheavy nuclei.
Comments:
5 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1509.02014 [pdf]
EPJ Web Conf.(2016)·7 citations
05
[Submitted on 7 Sept 2015]
Weakly bound states with spin-isospin symmetry
A. Kievsky🇮🇹 · M. Gattobigio🇫🇷
We discuss weakly bound states of a few-fermion system having spin-isospin symmetry. This corresponds to the nuclear physics case in which the singlet, $a_{0}$ , and triplet, $a_{1}$ , $n - p$ scattering lengths are large with respect to the range of the nuclear interaction. The ratio of the two is about $a_{0} / a_{1} \approx - 4.31$ . This value defines a plane in which $a_{0}$ and $a_{1}$ can be varied up to the unitary limit, $1/ a_{0} = 0$ and $1/ a_{1} = 0$ , maintaining its ratio fixed. Using a spin dependant potential model we estimate the three-nucleon binding energy along that plane. This analysis can be considered an extension of the Efimov plot for three bosons to the case of three $1/2$ -spin-isospin fermions.
Comments:
Proceedings of the 21st International Conference on Few-Body Problems in Physics. May 18-22, 2015. Chicago, Illinois, USA
Subjects:
Nuclear Theory (nucl-th); Quantum Gases (cond-mat.quant-gas)
arXiv:
1509.02059 [pdf]
EPJ Web Conf.(2016)·3 citations
06
[Submitted on 7 Sept 2015]
Small radii of neutron stars as an indication of novel in-medium effects
Wei-Zhou Jiang · Bao-An Li · F. J. Fattoyev
At present, neutron star radii from both observations and model predictions remain very uncertain. Whereas different models can predict a wide range of neutron star radii, it is not possible for most models to predict radii that are smaller than about 10 km, thus if such small radii are established in the future they will be very difficult to reconcile with model estimates. By invoking a new term in the equation of state that enhances the energy density, but leaves the pressure unchanged we simulate the current uncertainty in the neutron star radii. This new term can be possibly due to the exchange of the weakly interacting light U-boson with appropriate in-medium parameters, which does not compromise the success of the conventional nuclear models. The validity of this new scheme will be tested eventually by more precise measurements of neutron star radii.
Comments:
EPJA (2015) in press
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
1509.02128 [pdf]
EPJA(2015)·15 citations
07
[Submitted on 7 Sept 2015] (cross-list from hep-ph)
Limits on sterile neutrino contributions to neutrinoless double beta decay
J. Barea🇨🇱 · J. Kotila🇫🇮 · F. Iachello🇺🇸
Nuclear matrix elements (NME) for exchange of arbitrary mass neutrinos are calculated in the interacting boson model (IBM-2). By combining the NME with the phase space factors (PSF), expected half-lives for neutrinos of mass $m_{N}$ and coupling $U_{e N}$ are estimated. Limits on sterile neutrinos with masses in the eV, keV, MeV-GeV, and TeV range are given.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1509.01925 [pdf]
PRD(2015)·55 citations
08
[Submitted on 7 Sept 2015] (cross-list from hep-ph)
Baryon effects on the location of QCD's critical end point
Gernot Eichmann🇩🇪 · Christian S. Fischer🇩🇪 · Christian A. Welzbacher🇩🇪
The location of the critical end point of QCD has been determined in previous studies of $N_{f} = 2 + 1$ and $N_{f} = 2 + 1 + 1$ dynamical quark flavors using a (truncated) set of Dyson-Schwinger equations for the quark and gluon propagators of Landau-gauge QCD. A source for systematic errors in these calculations has been the omission of terms in the quark-gluon interaction that can be parametrized in terms of baryonic degrees of freedom. These have a potentially large dependence on chemical potential and therefore may affect the location of the critical end point. In this exploratory study we estimate the effects of these contributions, both in the vacuum and at finite temperature and chemical potential. We find only a small influence of baryonic contributions on the location of the critical end point. We estimate the robustness of this result by parameterizing further dependencies on chemical potential.
Comments:
12 pages, 8 figures, v2: minor changes, version accepted by PRD
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1509.02082 [pdf]
PRD(2016)·90 citations
09
[Submitted on 7 Sept 2015] (cross-list from astro-ph.SR)
The scenario of two families of compact stars 1. Equations of state, mass-radius relations and binary systems
Alessandro Drago🇮🇹 · Andrea Lavagno🇮🇹 · Giuseppe Pagliara🇮🇹 · Daniele Pigato🇮🇹
We present several arguments which favor the scenario of two coexisting families of compact stars: hadronic stars and quark stars. Besides the well known hyperon puzzle of the physics of compact stars, a similar puzzle exists also when considering delta resonances. We show that these particles appear at densities close to twice saturation density and must be therefore included in the calculations of the hadronic equation of state. Such an early appearance is strictly related to the value of the L parameter of the symmetry energy that has been found, in recent phenomenological studies, to lie in the range $40 < L < 62$ MeV. We discuss also the threshold for the formation of deltas and hyperons for hot and lepton rich hadronic matter. Similarly to the case of hyperons, also delta resonances cause a softening of the equation of state which makes it difficult to obtain massive hadronic stars. Quark stars, on the other hand, can reach masses up to $2.75 M_{⊙}$ as predicted by perturbative QCD calculations. We then discuss the observational constraints on the masses and the radii of compact stars. The tension between the precise measurements of high masses and the indications of the existence of very compact stellar objects (with radii of the order of $10$ km) is relieved when assuming that very massive compact stars are quark stars and very compact stars are hadronic stars. Finally, we discuss recent interesting measurements of the eccentricities of the orbits of millisecond pulsars in low mass X-ray binaries. The high values of the eccentricities found in some cases could be explained by assuming that the hadronic star, initially present in the binary system, converts to a quark star due to the increase of its central density.
Comments:
11 pages, 9 figures, prepared for the 2015 EPJA Topical Issue on "Exotic Matter in Neutron Stars". Revised version
Subjects:
Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1509.02131 [pdf]
EPJA(2016)·114 citations
10
[Submitted on 7 Sept 2015] (cross-list from astro-ph.SR)
The scenario of two families of compact stars 2. Transition from hadronic to quark matter and explosive phenomena
Alessandro Drago🇮🇹 · Giuseppe Pagliara🇮🇹
We will follow the two-families scenario described in the accompanying paper, in which compact stars having a very small radius and masses not exceeding about 1.5 $M_{⊙}$ are made of hadrons, while more massive compact stars are quark stars. In the present paper we discuss the dynamics of the transition of a hadronic star into a quark star. We will show that the transition takes place in two phases: a very rapid one, lasting a few milliseconds, during which the central region of the star converts into quark matter and the process of conversion is accelerated by the existence of strong hydrodynamical instabilities, and a second phase, lasting about ten seconds, during which the process of conversion proceeds till the surface of the star via production and diffusion of strangeness. We will show that these two steps play a crucial role in the phenomenological implications of the model. We will discuss the possible implications of this scenario both for long and for short Gamma Ray Bursts, using the proto-magnetar model as the reference frame of our discussion. We will show that the process of quark deconfinement can be connected to specific observed features of the GRBs. In the case of long GRBs we will discuss the possibility that quark deconfinement is at the origin of the second peak present in quite a large fraction of bursts. Also we will discuss the possibility that long GRBs can take place in binary systems without being associated with a SN explosion. Concerning short GRBs, quark deconfinement can play the crucial role in limiting their duration. Finally we will shortly revisit the possible relevance of quark deconfinement in some specific type of Supernova explosions, in particular in the case of very massive progenitors.
Comments:
15 pages, 9 figures, prepared for the 2015 EPJA Topical Issue on "Exotic Matter in Neutron Stars". Revised version
Subjects:
Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1509.02134 [pdf]
EPJA(2016)·84 citations

Affiliations

first authorsco-authorsvia INSPIRE