Nuclear Theory·nucl-th

Friday·August 16, 2019

9 papers—6 primary·3 cross-listed

01
Toward an accurate strongly-coupled many-body theory within the equation of motion framework
Elena Litvinova🇺🇸 · Peter Schuck🇫🇷
Non-perturbative aspects of the quantum many-body problem are revisited, discussed and advanced in the equation of motion framework. We compare the approach to the two-fermion response function truncated on the two-body level by the cluster expansion of the dynamical interaction kernel to the approach known as time blocking approximation. Such a comparison leads to an extended many-body theory with non-perturbative treatment of high-order configurations. The present implementation of the advanced theory introduces a new class of solutions for the response functions, which include explicitly beyond-mean-field correlations between up to six fermions. The novel approach, which includes configurations with two quasiparticles coupled to two phonons (2q $\otimes$ 2phonon), is discussed in detail for the particle-hole nuclear response and applied to medium-mass nuclei. The proposed developments are implemented numerically on the basis of the relativistic effective meson-nucleon Lagrangian and compared to the models confined by two-fermion and four-fermion configurations, which are considered as state-of-the-art for the response theory in nuclear structure calculations. The results obtained for the dipole response of $^{42, 48}$ Ca and $^{68}$ Ni nuclei in comparison to available experimental data show that the higher configurations are necessary for a successful description of both gross and fine details of the spectra in both high-energy and low-energy sectors.
nucl-thnucl-exPRC(2019)·48 citations
02
Probing $ΩΩ$ and $p Ω$ dibaryons with femtoscopic correlations in relativistic heavy-ion collisions
Kenji Morita🇯🇵 · Shinya Gongyo🇯🇵 · Tetsuo Hatsuda🇯🇵 · Tetsuo Hyodo🇯🇵 · Yuki Kamiya🇨🇳 · Akira Ohnishi🇯🇵
The momentum correlation functions of baryon pairs, which reflects the baryon-baryon interaction at low energies, are investigated for multi-strangeness pairs ( $ΩΩ$ and $N Ω$ ) produced in relativistic heavy-ion collisions. We calculate the correlation functions based on an expanding source model constrained by single-particle distributions. The interaction potentials are taken from those obtained from recent lattice QCD calculations at nearly physical quark masses. Experimental measurements of these correlation functions for different system sizes will help to disentangle the strong interaction between baryons and to unravel the possible existence of strange dibaryons.
nucl-thhep-lathep-phnucl-exPRC(2020)·80 citations
03
Ab Initio Treatment of Collective Correlations and the Neutrinoless Double Beta Decay of $^{48}$ Ca
J. M. Yao🇺🇸 · B. Bally🇺🇸 · J. Engel🇺🇸 · R. Wirth🇺🇸 · T. R. Rodríguez🇪🇸 · H. Hergert🇺🇸
Working with Hamiltonians from chiral effective field theory, we develop a novel framework for describing arbitrary deformed medium-mass nuclei by combining the in-medium similarity renormalization group with the generator coordinate method. The approach leverages the ability of the first method to capture dynamic correlations and the second to include collective correlations without violating symmetries. We use our scheme to compute the matrix element that governs the neutrinoless double beta decay of $^{48}$ Ca to $^{48}$ Ti, and find it to have the value $0.61$ , near or below the predictions of most phenomenological methods. The result opens the door to ab initio calculations of the matrix elements for the decay of heavier nuclei such as $^{76}$ Ge, $^{130}$ Te, and $^{136}$ Xe.
nucl-thhep-phnucl-exPRL(2020)·195 citations
04
Impact of the initial fluctuations on the dissipative dynamics of interacting Fermi systems: A model case study
Ibrahim Ulgen🇹🇷 · Bulent Yilmaz🇹🇷 · Denis Lacroix🇫🇷
Standard methods used for computing the dynamics of a quantum many-body system are the mean-field (MF) approximations such as the time-dependent Hartree-Fock (TDHF) approach. Even though MF approaches are quite successful, they suffer some well-known shortcomings, one of which is insufficient dissipation of collective motion. The stochastic mean-field approach (SMF), where a set of MF trajectories with random initial conditions are considered, is a good candidate to include dissipative effects beyond mean field. In this approach, the one-body density matrix elements are treated initially as a set of stochastic Gaussian c numbers that are adjusted to reproduce first and second moments of collective one-body observables. It is shown that the predictive power of the SMF approach can be further improved by relaxing the Gaussian assumption for the initial probabilities. More precisely, using Gaussian or uniform distributions for the matrix elements generally leads to overdamping for long times, whereas distributions with smaller kurtosis lead to much better reproduction of the long time evolution.
nucl-thcond-mat.str-elphysics.chem-phPRC(2019)·13 citations
05
Reaction Rate Of p14N --> 15Ogamma Capture To All Bound States In Potential Cluster Model
Sergey Dubovichenko · Nataliya Burkova · Albert Dzhazairov-Kakhramanov · Bekmurza Beysenov
Review of calculation results for astrophysical S-factor of the 14N(p,gamma)15O capture reaction in the p14N channel of 15O was presented. It was carried out in the frame of the modified potential cluster model, taking into account resonances in the 15O spectrum up to 3.2 MeV at energy of incident protons varying from 30 keV to 5 MeV. It is possible to describe experimental data for the astrophysical S-factors of the radiative proton capture on 14N to five excited states of 15O at excitation energies from 5.18 MeV to 6.86 MeV, only under assumption, that all five resonances are D scattering waves. Quality new physical interpretation of the capture mechanism is discussed in this channel to the ground state of 15O. Carried out by us assumption that the ground state of 15O is determined by the p14N* channel with excited 14N* cluster, immediately allowed us to correctly describe order of values of the experimental S-factor for capture to this state. Taking into account these results, the total S-factor of the proton capture on 14N and the reaction rates to the ground and five excited states of 15O were determined at temperatures from 0.01 to 10 T9. The parametrization of the total reaction rate with a simple form is performed, which allows to obtain xi2 equal to 0.06 with 5% errors of the calculated rate.
nucl-thIJMPE(2020)·4 citations
06
Coupled Self-Consistent RPA Equations for Even and Odd Particle Numbers. Tests with Solvable Models
M. Jemai🇹🇳 · P. Schuck🇫🇷
Coupled equations for even and odd particle number correlation functions are set up via the equation of motion method. For the even particle number case this leads to self-consistent RPA (SCRPA) equations already known from the literature. From the equations of the odd particle number case the single particle occupation probabilities are obtained in a self-consistent way. This is the essential new procedure of this work. Both, even and odd particle number cases are based on the same correlated vacuum and, thus, are coupled equations. Applications to the Lipkin model and the 1D Hubbard model give very good results.
nucl-thcond-mat.str-elPRC(2019)·3 citations
07
Some Features of Semiclassical Chiral Transport in Rotating Frames
O.F. Dayi🇹🇷 · E. Kilincarslan🇹🇷
Semiclassical chiral kinetic theories in the presence of electromagnetic fields as well as vorticity can be constructed by means of some different relativistic or nonrelativistic approaches. To cover the noninertial features of rotating frames one can start from the modified quantum kinetic equation of Wigner function in Minkowski spacetime. It provides a relativistic chiral transport equation whose nonrelativistic limit yields a consistent three-dimensional kinetic theory which does not depend explicitly on spatial coordinates. Recently a chiral transport equation in curved spacetime has been proposed and its nonrelativistic limit in rotating coordinates was considered in the absence of electromagnetic fields. We show that the modified theory can be extended to curved spacetime. The related particle current density and chiral transport equation for an inertial observer in the rotating frame are derived. A novel three-dimensional chiral kinetic transport equation is established by inspecting the nonrelativistic limit of the curved spacetime approach in the rotating frame for a comoving observer in the presence of electromagnetic fields. It explicitly depends on spatial coordinates. We prove that it is consistent with the chiral anomaly, chiral magnetic and vortical effects.
↳ hep-thhep-phnucl-thPRD(2019)·6 citations
08
Normalized symmetric cumulants as a measure of QCD phase transition: a viscous hydrodynamic study
Ashutosh Dash🇮🇳 · Victor Roy🇮🇳
Finding the existence and the location of the QCD critical point is one of the main goals of the RHIC beam energy scan program. To make theoretical predictions and corroborate with the experimental data requires modeling the space-time evolution of the matter created in heavy-ion collisions by dynamical models such as the relativistic hydrodynamics with an appropriate Equation of State (EoS). In the present exploratory study, we use a viscous 2+1 dimensional event-by-event (e-by-e) hydrodynamic code at finite baryon densities with two different EoSs (i) Lattice QCD + HRG with a crossover transition and (ii) EoS with a first-order phase transition to studying the normalized symmetric cumulants of charged pions $v_{n}$ $(n = 2 - 4)$ . We show that the normalized symmetric cumulants can differentiate the two EoSs while all other conditions remain the same. The conclusion does not change for various initial conditions and shear viscosity. This indicates that these observables can be used to gain information about the QCD EoS from experimental data and can be used as an EoS meter.
↳ hep-phnucl-th2 citations
09
Strong decays of the latest LHCb pentaquark candidates in hadronic molecule pictures
Yong-Hui Lin🇨🇳 · Bing-Song Zou🇨🇳
We investigate the observed pentaquark candidates $P_{c} (4312)$ , $P_{c} (4440)$ and $P_{c} (4457)$ from the latest LHCb measurement, as well as four possible spin partners in the $D ˉ^{(*)} Σ_{c}^{*}$ system predicted from the heavy quark spin symmetry with the hadronic molecule scenarios. Similar to the previous calculation on $P_{c} (4380)$ and $P_{c} (4450)$ , the partial widths of all the allowed decay channels for these $P_{c}$ states are estimated with the effective Lagrangian method. The cutoff dependence of our numerical results are also presented. Comparing with the experimental widths, our results show that $P_{c} (4312)$ , $P_{c} (4440)$ and $P_{c} (4457)$ can be described well with the spin-parity- $1/ 2^{-}$ - $D ˉ Σ_{c}$ , $1/ 2^{-}$ - $D ˉ^{*} Σ_{c}$ and $3/ 2^{-}$ - $D ˉ^{*} Σ_{c}$ molecule pictures, respectively.
↳ hep-phnucl-thPRD(2019)·108 citations

Affiliations

first authorsco-authorsvia INSPIRE