Nuclear Theory·nucl-th

Thursday·June 16, 2016

11 papers—4 primary·7 cross-listed

01
New results for reaction rate of the proton radiative capture on 3H
S.B. Dubovichenko · A.V. Dzhazairov-Kakhramanov · N.V. Afanasyeva
Calculations of the reaction rate of the proton radiative capture on 3H at temperatures from 0.01 T9 up to 5 T9, which are based on the theoretical results for the astrophysical S-factor and take into account the latest experimental data, were carried out. Theoretical results for the S-factor at energies from 1 keV up to 5 MeV were obtained in the framework of the modified potential cluster model with the classification of orbital states according to Young tableaux. On the basis of used nuclear model of the interaction of p and 3H particles there was shown possibility of description the latest experimental data for the S-factor at the energy range from 50 keV up to 5 MeV.
nucl-thNPA(2017)·11 citations
02
Nuclear medium effects in Drell-Yan process
H. Haider🇮🇳 · M. Sajjad Athar🇮🇳 · S. K. Singh🇮🇳 · I. Ruiz Simo🇪🇸
We study the nuclear medium effects in Drell-Yan process using quark parton distribution functions calculated in a microscopic nuclear model which takes into account the effects of Fermi motion, nuclear binding and nucleon correlations through a relativistic nucleon spectral function. The contributions of $π$ and $ρ$ mesons as well as shadowing effects are also included. The beam energy loss is calculated using a phenomenological approach. The present theoretical results are compared with the experimental results of E772 and E886 experiments. These results are applicable to the forthcoming experimental analysis of E906 Sea Quest experiment at Fermi Lab.
nucl-thJ.Phys.G(2017)·12 citations
03
Time-dependent density-functional description of nuclear dynamics
Takashi Nakatsukasa · Kenichi Matsuyanagi · Masayuki Matsuo · Kazuhiro Yabana
We present the basic concepts and recent developments in the time-dependent density functional theory (TDDFT) for describing nuclear dynamics at low energy. The symmetry breaking is inherent in nuclear energy density functionals (EDFs), which provides a practical description of important correlations at the ground state. Properties of elementary modes of excitation are strongly influenced by the symmetry breaking and can be studied with TDDFT. In particular, a number of recent developments in the linear response calculation have demonstrated their usefulness in description of collective modes of excitation in nuclei. Unrestricted real-time calculations have also become available in recent years, with new developments for quantitative description of nuclear collision phenomena. There are, however, limitations in the real-time approach; for instance, it cannot describe the many-body quantum tunneling. Thus, we treat the quantum fluctuations associated with slow collective motions assuming that time evolution of densities are determined by a few collective coordinates and momenta. The concept of collective submanifold is introduced in the phase space associated with the TDDFT and used to quantize the collective dynamics. Selected applications are presented to demonstrate the usefulness and quality of the new approaches. Finally, conceptual differences between nuclear and electronic TDDFT are discussed, with some recent applications to studies of electron dynamics in the linear response and under a strong laser field.
nucl-thRMP(2016)·235 citations
04
Adiabatic fission barriers in superheavy nuclei
P. Jachimowicz · M. Kowal · J. Skalski
Using the microscopic-macroscopic model based on the deformed Woods-Saxon single-particle potential and the Yukawa-plus-exponential macroscopic energy we calculated static fission barriers $B_{f}$ for 1305 heavy and superheavy nuclei $98 \leq Z \leq 126$ , including even - even, odd - even, even - odd and odd - odd systems. For odd and odd-odd nuclei, adiabatic potential energy surfaces were calculated by a minimization over configurations with one blocked neutron or/and proton on a level from the 10-th below to the 10-th above the Fermi level. The parameters of the model that have been fixed previously by a fit to masses of even-even heavy nuclei were kept unchanged. A search for saddle points has been performed by the "Imaginary Water Flow" method on a basic five-dimensional deformation grid, including triaxiality. Two auxiliary grids were used for checking the effects of the mass asymmetry and hexadecapole non-axiallity. The ground states were found by energy minimization over configurations and deformations. We find that the non-axiallity significantly changes first and second fission barrier in many nuclei. The effect of the mass - asymmetry, known to lower the second, very deformed barriers in actinides, in the heaviest nuclei appears at the less deformed saddles in more than 100 nuclei. It happens for those saddles in which the triaxiallity does not play any role, what suggests a decoupling between effects of the mass-asymmetry and triaxiality. We studied also the influence of the pairing interaction strength on the staggering of $B_{f}$ for odd- and even-particle numbers. Finally, we provide a comparison of our results with other theoretical fission barrier evaluations and with available experimental estimates.
nucl-thPRC(2017)·65 citations
05
An effective-field-theory analysis of Efimov physics in heteronuclear mixtures of ultracold atomic gases
Bijaya Acharya · Chen Ji · Lucas Platter
We use an effective-field-theory framework to analyze the Efimov effect in heteronuclear three-body systems consisting of two species of atoms with a large interspecies scattering length. In the leading-order description of this theory, various three-body observables in heteronuclear mixtures can be universally parameterized by one three-body parameter. We present the next-to-leading corrections, which include the effects of the finite interspecies effective range and the finite intraspecies scattering length, to various three-body observables. We show that only one additional three-body parameter is required to render the theory predictive at this order. By including the effective range and intraspecies scattering length corrections, we derive a set of universal relations that connect the different Efimov features near the interspecies Feshbach resonance. Furthermore, we show that these relations can be interpreted in terms of the running of the three-body counterterms that naturally emerge from proper renormalization. Finally, we make predictions for recombination observables of a number of atomic systems that are of experimental interest.
↳ cond-mat.quant-gasnucl-thPRA(2016)·8 citations
06
An electroweak basis for neutrinoless double $β$ decay
Michael L. Graesser🇺🇸
A discovery of neutrinoless double- $β$ decay would be profound, providing the first direct experimental evidence of $Δ L = 2$ lepton number violating processes. While a natural explanation is provided by an effective Majorana neutrino mass, other new physics interpretations should be carefully evaluated. At low--energies such new physics could manifest itself in the form of color and $S U (2)_{L} \times U (1)_{Y}$ invariant higher dimension operators. Here we determine a complete set of electroweak invariant dimension--9 operators, and our analysis supersedes those that only impose $U (1)_{e m}$ invariance. Imposing electroweak invariance implies: 1) a significantly reduced set of leading order operators compared to only imposing $U (1)_{e m}$ invariance; and 2) other collider signatures. Prior to imposing electroweak invariance we find a minimal basis of 24 dimension-9 operators, which is reduced to 11 electroweak invariant operators at leading order in the expansion in the Higgs vacuum expectation value. We set up a systematic analysis of the hadronic realization of the 4-quark operators using chiral perturbation theory, and apply it to determine which of these operators have long-distance pion enhancements at leading order in the chiral expansion. We also find at dimension--11 and dimension--13 the electroweak invariant operators that after electroweak symmetry breaking produce the remaining $Δ L = 2$ operators that would appear at dimension--9 if only $U (1)_{e m}$ is imposed.
↳ hep-phnucl-exnucl-thJHEP(2017)·75 citations
07
$K ˉ$ -induced formation of the $f_{2} (1270)$ and $f_{2}^{^{'}} (1525)$ resonances on proton targets
Yin Huang🇨🇳 · Ju-jun Xie🇨🇳 · Jun He🇨🇳 · Xurong Chen🇨🇳 · Hong-fei Zhang🇨🇳
We investigate the productiong of $f_{2} (1270)$ and $f_{2}^{^{'}} (1525)$ mesons in the $K^{-} p \to Λ f_{2} (1270)$ , $K^{-} p \to Λ f_{2}^{^{'}} (1525)$ and $K^{-} p \to K^{+} K^{-} Λ$ reactions within an effective Lagrangian approach. For $K^{-} p \to f_{2} Λ$ reaction, by considering the contributions from the $t$ -channel $K^{+}$ exchange and $u$ -channel nucleon pole, we get a fairly good description of the experimental measurements about the total and differential cross sections. Based on the studies of the $K^{-} p \to f_{2} Λ$ reaction, we investigate $K^{-} p \to K^{+} K^{-} Λ$ reaction including the contributions from the $f_{2} (1270)$ and $f_{2}^{'} (1525)$ mesons decaying into $K^{+} K^{-}$ pair. The total cross sections and invariant mass distribution of the $K p \to K^{+} K^{-} Λ$ reaction are predicted. The results can be tested in future experiments and therefore offer new clues on the nature of these tensor states.
↳ hep-phnucl-exnucl-th2 citations
08
Instantaneous Bethe-Salpeter View of Goldstone-Type Pseudoscalar Mesons
Wolfgang Lucha🇦🇹 · Franz F. Schöberl🇦🇹
Describing the lightest pseudoscalar mesons as bound states of quark and antiquark within the framework of an instantaneous Bethe-Salpeter formalism constructed such as to retain (in contrast to Salpeter's equation) as much information on the relativistic effects provided by the full quark propagator as conceivable allows for a surprisingly simple implementation of their near masslessness mandatory for their interpretability as pseudo-Goldstone bosons related to the spontaneous breaking of the chiral symmetries of quantum chromodynamics.
↳ hep-phnucl-thInt.J.Mod.Phys.A(2016)·7 citations
09
Energy versus centrality dependence of the jet quenching parameter $q^$ at RHIC and LHC: a new puzzle?
Carlota Andrés🇪🇸 · Néstor Armesto🇪🇸 · Matthew Luzum🇪🇸 · Carlos A. Salgado🇪🇸 · Pía Zurita🇪🇸
The central goal of jet quenching studies in high-energy nuclear collisions is the characterization of those QCD medium properties that are accessible by these probes. Most of the discussion in the last years has been focused on the determination of the jet quenching parameter, $q^$ . We present here an extraction of this parameter using data of inclusive particle suppression at RHIC and LHC energies for different centralities. Our approach consists of fitting a $K$ factor that quantifies the departure of this parameter from an ideal estimate, $K \equiv q^/ (2 ϵ^{3/4})$ , where $q^$ is determined by the local medium quantities as provided by hydrodynamical calculations. We find that this $K$ factor is larger at RHIC than at the LHC, as obtained already in previous analyses, but, surprisingly, it is almost independent of the centrality of the collision. Taken at face value, the $K$ factor would not depend on the local properties of the medium as energy density or temperature, but on global collision quantities such as the center of mass energy. This is a very intriguing, unexpected possibility for which we cannot yet provide a clear interpretation. We also comment on the limitations of the formalism that may affect this conclusion.
↳ hep-phnucl-exnucl-thEPJC(2016)·105 citations
10
The internal composition of proto-neutron stars under strong magnetic fields
B. Franzon · V. Dexheimer · S. Schramm
In this work, we study the effects of magnetic fields and rotation on the structure and composition of proto-neutron stars (PNS's). A hadronic chiral SU(3) model is applied to cold neutron stars (NS) and proto-neutron stars with trapped neutrinos and at fixed entropy per baryon. We obtain general relativistic solutions for neutron and proto-neutron stars endowed with a poloidal magnetic field by solving Einstein-Maxwell field equations in a self-consistent way. As the neutrino chemical potential decreases in value over time, this alters the chemical equilibrium and the composition inside the star, leading to a change in the structure and in the particle population of these objects. We find that the magnetic field deforms the star and significantly alters the number of trapped neutrinos in the stellar interior, together with strangeness content and temperature in each evolution stage.
↳ astro-ph.HEnucl-thPRD(2016)·33 citations
11
Vortex pinning and dynamics in the neutron star crust
Gabriel Wlazłowski · Kazuyuki Sekizawa · Piotr Magierski · Aurel Bulgac · Michael McNeil Forbes
The nature of the interaction between superfluid vortices and the neutron star crust, conjectured by Anderson and Itoh in 1975 to be at the heart vortex creep and the cause of glitches, has been a long-standing question in astrophysics. Using a qualitatively new approach, we follow the dynamics as superfluid vortices move in response to the presence of "nuclei" (nuclear defects in the crust). The resulting motion is perpendicular to the force, similar to the motion of a spinning top when pushed. We show that nuclei repel vortices in the neutron star crust, and characterize the force as a function of the vortex-nucleus separation.
↳ astro-ph.HEastro-ph.SRcond-mat.supr-connucl-thPRL(2016)·79 citations

Affiliations

first authorsco-authorsvia INSPIRE