Nuclear Theory·nucl-th

Friday·May 29, 2015

9 papers—5 primary·4 cross-listed

01
[Submitted on 27 May 2015]
Modeling nuclear weak-interaction processes with relativistic energy density functionals
N. Paar🇨🇭 · T. Marketin🇭🇷 · D. Vale🇭🇷 · D. Vretenar🇭🇷
Relativistic energy density functionals have become a standard framework for nuclear structure studies of ground-state properties and collective excitations over the entire nuclide chart. We review recent developments in modeling nuclear weak-interaction processes: charge-exchange excitations and the role of isoscalar proton-neutron pairing, charged-current neutrino-nucleus reactions relevant for supernova evolution and neutrino detectors, and calculation of beta-decay rates for r-process nucleosynthesis.
Comments:
22 pages, 12 figures, submitted for publication
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
arXiv:
1505.07486 [pdf]
IJMPE(2015)·12 citations
02
[Submitted on 28 May 2015]
Electric Characteristics of Rotational States positive parity in isotopes 170,172,174Yb
P.N.Usmanov · A.A.Okhunov · H. Abu Kassim · U.S. Salikhbaev
Accounting for Coriolis mixing of experimentally known rotational bands with $K^{π} < 3^{+}$ , non-adiabatic effects in energy and electric characteristics of excited states are investigated, within phenomenological model. The energy and wave function structure of excited states are calculated. The finding reveals that the bands mixing has been found to have considerable impact on the wave function of low-lying states $0^{+}$ and $2^{+}$ bands. In addition, the probabilities of $E 2$ -- transitions have been calculated. The values from calculations of $B (E 2)$ -- transitions from $0_{2}^{+}$ , $0_{3}^{+}$ , $2_{1}^{+}$ , and $2_{2}^{+}$ bands are compared with the experimental data.
Comments:
11 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1505.07527 [pdf]
0 citations
03
[Submitted on 28 May 2015]
Sensitivity of $β$ -decay rates to the radial dependence of the nucleon effective mass
A. P. Severyukhin · Jérôme Margueron (IPNL) · I. N. Borzov · Nguyen Van Giai (IPNO)
We analyze the sensitivity of $β$ -decay rates in 78 Ni and 100,132 Sn to a correction term in Skyrme energy-density functionals (EDF) which modifies the radial shape of the nucleon effective mass. This correction is added on top of several Skyrme parametrizations which are selected from their effective mass properties and predictions about the stability properties of 132 Sn. The impact of the correction on high-energy collective modes is shown to be moderate. From the comparison of the effects induced by the surface-peaked effective mass in the three doubly magic nuclei, it is found that 132 Sn is largely impacted by the correction, while 78 Ni and 100 Sn are only moderately affected. We conclude that $β$ -decay rates in these nuclei can be used as a test of different parts of the nuclear EDF: 78 Ni and 100 Sn are mostly sensitive to the particle-hole interaction through the B(GT) values, while 132 Sn is sensitive to the radial shape of the effective mass. Possible improvements of these different parts could therefore be better constrained in the future.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1505.07559 [pdf]
PRC(2015)·7 citations
04
[Submitted on 28 May 2015]
Microscopic evaluation of the hypernuclear chart with $Λ$ -hyperons
E. Khan🇫🇷 · J. Margueron🇫🇷 · F. Gulminelli🇫🇷 · Ad. R. Raduta🇷🇴
A large number of hypernuclei, where a considerable fraction of nucleons is replaced by strange baryons, and even pure hyperonic species are expected to be bound. Though, the hypernuclear landscape remains largely unknown because of scarce constraints on the $N Y$ and $Y Y$ interactions. We want to estimate the number of potentially bound hypernuclei. In order to evaluate realistic error bars within the theoretical uncertainties associated to the spherical mean-field approach, and the present information from already synthetized hypernuclei on the $N - Y$ and $Y - Y$ channels, we limit ourselves to purely $Λ$ -hypernuclei, to magic numbers of $Λ$ 's (for Z $\leq$ 120 and $Λ \leq$ 70), and to even-even-even systems. We consider a density functional approach adjusted to microscopic Bruckner-Hartree-Fock calculations, where the $ΛΛ$ term is corrected in a phenomenological way, to reproduce present experimental constraints. The number of bound even-even-even $Λ$ -hypernuclei is estimated to 491680 $\pm$ 34400. This relatively low uncertainty is due to the fact that the well constrained low density and highly unconstrained high density behavior of the energy functional turn out to be largely decoupled. Results in $Λ$ -hypernuclei appear to be almost independent of the choice for the high-density part of the $ΛΛ$ interaction. The location of the $Λ$ -hyperdriplines is also evaluated. Significant deviations from Iron-Nickel elements can be found for $Λ$ -hypernuclei with the largest binding energy per baryon. Proton, neutron and $Λ$ -hyperon magicity evolution and triple magic $Λ$ -hypernuclei are studied. Possible bubbles and haloes effect in $Λ$ -hypernuclei are also discussed.
Comments:
16 pages, 16 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1505.07678 [pdf]
PRC(2015)·29 citations
05
[Submitted on 28 May 2015]
The impact of individual nuclear masses on $r$ -process abundances
M. R. Mumpower · R. Surman · D.-L. Fang · M. Beard · P. Moller · T. Kawano · A. Aprahamian
We have performed for the first time a comprehensive study of the sensitivity of $r$ -process nucleosynthesis to individual nuclear masses across the chart of nuclides. Using the latest version (2012) of the Finite-Range Droplet Model, we consider mass variations of $\pm 0.5$ MeV and propagate each mass change to all affected quantities, including $Q$ -values, reaction rates, and branching ratios. We find such mass variations can result in up to an order of magnitude local change in the final abundance pattern produced in an $r$ -process simulation. We identify key nuclei whose masses have a substantial impact on abundance predictions for hot, cold, and neutron star merger $r$ -process scenarios and could be measured at future radioactive beam facilities.
Comments:
8 pages, 3 figures, submitted
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
1505.07789 [pdf]
PRC(2015)·98 citations
06
[Submitted on 28 May 2015] (cross-list from astro-ph.HE)
Angular Momentum Role in the Hypercritical Accretion of Binary-Driven Hypernovae
L. Becerra · F. Cipolletta · C. L. Fryer · Jorge A. Rueda · R. Ruffini
The induced gravitational collapse (IGC) paradigm explains a class of energetic, $E_{iso} ≳ 1 0^{52}$ ~erg, long-duration gamma-ray bursts (GRBs) associated with Ic supernovae, recently named binary-driven hypernovae (BdHNe). The progenitor is a tight binary system formed of a carbon-oxygen (CO) core and a neutron star companion. The supernova ejecta of the exploding CO core triggers a hypercritical accretion process onto the neutron star, which reaches in a few seconds the critical mass, and gravitationally collapses to a black hole emitting a GRB. In our previous simulations of this process we adopted a spherically symmetric approximation to compute the features of the hypercritical accretion process. We here present the first estimates of the angular momentum transported by the supernova ejecta, $L_{acc}$ , and perform numerical simulations of the angular momentum transfer to the neutron star during the hyperaccretion process in full general relativity. We show that the neutron star: i) reaches in a few seconds either mass-shedding limit or the secular axisymmetric instability depending on its initial mass; ii) reaches a maximum dimensionless angular momentum value, $[c J / (G M^{2})]_{max} \approx 0.7$ ; iii) can support less angular momentum than the one transported by supernova ejecta, $L_{acc} > J_{NS, max}$ , hence there is an angular momentum excess which necessarily leads to jetted emission.
Comments:
Accepted for publication in Astrophysical Journal
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
1505.07580 [pdf]
ApJ(2015)·60 citations
07
[Submitted on 28 May 2015] (cross-list from hep-ph)
QCD Equation of State and Cosmological Parameters in Early Universe
Paolo Castorina🇮🇹 · Vincenzo Greco🇮🇹 · Salvatore Plumari🇮🇹
The time evolution of cosmological parameters in early Universe at the deconfinement transition is studied by an equation of state (EoS) which takes into account the finite baryon density and the background magnetic field. The non perturbative dynamics is described by the Field Correlator Method (FCM) which gives, with a small number of free parameters, a good fit of lattice data. The entire system has two components, i.e. the quark-gluon plasma and the electroweak sector, and the solutions of the Friedmann equation show that the scale factor, $a (t)$ , and $H (t) = (1/ a) d a / d t$ are weakly dependent on the EoS, but the deceleration parameter, $q (t)$ , and the jerk, $j (t)$ , are strongly modified above the critical temperature $T_{c}$ , corresponding to a critical time $t_{c} ≃ 20 - 25 μ s$ . The time evolution of the cosmological parameters suggest that above and around $T_{c}$ there is a transient state of acceleration typical of a matter dominated Universe; this is entailed by the QCD strong interaction driven by the presence of massive colored objects.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Nuclear Theory (nucl-th)
arXiv:
1505.07655 [pdf]
PRD(2015)·13 citations
08
[Submitted on 28 May 2015] (cross-list from gr-qc)
Quantum corrections to the stress-energy tensor in thermodynamic equilibrium with acceleration
F. Becattini🇮🇹 · E. Grossi (University of Florence, Italy)🇮🇹
We show that the stress-energy tensor has additional terms with respect to the ideal form in states of global thermodynamic equilibrium in flat spacetime with non-vanishing acceleration and vorticity. These corrections are of quantum origin and their leading terms are second order in the gradients of the thermodynamic fields. Their relevant coefficients can be expressed in terms of correlators of the stress-energy tensor operator and the generators of the Lorentz group. With respect to previous assessments, we find that there are more second order coefficients and that all thermodynamic functions including energy density receive acceleration and vorticity dependent corrections. Notably, also the relation between \rho and p, that is the equation of state, is affected by acceleration and vorticity. We have calculated the corrections for a free real scalar field -- both massive and massless -- and we have found that they increase, particularly for a massive field, at very high acceleration and vorticity and very low temperature. Finally, these non-ideal terms depend on the explicit form of the stress-energy operator, implying that different stress-energy tensor of the scalar field -- canonical or improved -- are thermodynamically inequivalent.
Comments:
18 pages, 1 figure. Minor changes, to appear in PRD
Subjects:
General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1505.07760 [pdf]
PRD(2015)·77 citations
09
[Submitted on 28 May 2015] (cross-list from nucl-ex)
Azimuthal anisotropy in U+U and Au+Au collisions at RHIC
STAR Collaboration: L. Adamczyk · J. K. Adkins · G. Agakishiev · M. M. Aggarwal · Z. Ahammed · I. Alekseev · J. Alford · A. Aparin · D. Arkhipkin · E. C. Aschenauer · G. S. Averichev · V. Bairathi and 320 other authors
Collisions between prolate uranium nuclei are used to study how particle production and azimuthal anisotropies depend on initial geometry in heavy-ion collisions. We report the two- and four-particle cumulants, $v_{2} {2}$ and $v_{2} {4}$ , for charged hadrons from U+U collisions at $s_{NN}$ = 193 GeV and Au+Au collisions at $s_{NN}$ = 200 GeV. Nearly fully overlapping collisions are selected based on the amount of energy deposited by spectators in the STAR Zero Degree Calorimeters (ZDCs). Within this sample, the observed dependence of $v_{2} {2}$ on multiplicity demonstrates that ZDC information combined with multiplicity can preferentially select different overlap configurations in U+U collisions. An initial-state model with gluon saturation describes the slope of $v_{2} {2}$ as a function of multiplicity in central collisions better than one based on Glauber with a two-component multiplicity model.
Comments:
Final paper version accepted for publication in Phys. Rev. Lett. New version includes comparisons to a constituent quark glauber model
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1505.07812 [pdf]
PRL(2015)·169 citations

Affiliations

first authorsco-authorsvia INSPIRE