Nuclear Theory·nucl-th

Tuesday·July 9, 2019

14 papers—8 primary·6 cross-listed

01
Shell Model Calculations for Proton-rich Zn Isotopes via New Generated Effective Interaction by Artificial Neural Networks
Serkan Akkoyun
In this study, the artificial neural network method has been employed for the generation of the new two-body matrix elements which is used for pfg shell nuclei. For this purpose, jj44b interaction Hamiltonian has been considered as a source. After the generation of the new Hamiltonian, both, original and new generated, are tested on proton-rich Zn isotopes. According to the results, the calculated values are close to the each other. As well the results from new interaction (jj44b_nn) are closer to the available experimental values in some cases.
nucl-th0 citations
02
The role of the local conservation laws in fluctuations of conserved charges
Peter Braun-Munzinger🇩🇪 · Anar Rustamov🇩🇪 · Johanna Stachel🇩🇪
In this report we present the first quantitative determination of the correlations between baryons and anti-baryons induced by local baryon number conservation. This is important in view of the many experimental studies aiming at probing the phase structure of strongly interacting matter. We confront our results with the recent measurements of net-proton fluctuations reported by the CERN ALICE experiment. The role of local baryon number conservation is found to be small on the level of second cumulants.
nucl-th36 citations
03
Projection of Good Quantum Numbers for Reaction Fragments
Aurel Bulgac
In reactions the wave packets of the emerging products typically are not eigenstates of particle number operators or any other conserved quantities and their properties are entangled. I describe a particle projection technique in parts of space, which eschews the need to evaluate Pfaffians in the case of overlap of generalized Slater determinants or Hartree-Fock-Bogoliubov type of vacua. The extension of these formulas for calculating either angular momentum or particle projected energy distributions of the reaction fragments are presented as well. The generalization to simultaneous particle and angular momentum projection of various reaction fragment observables is straightforward.
nucl-thPRC(2019)·22 citations
04
Hot neutron stars with microscopic equations of state
Jia-Jing Lu · Zeng-Hua Li · G. F. Burgio · H.-J Schulze
We study the properties of hot beta-stable nuclear matter using equations of state derived within the Brueckner-Hartree-Fock approach at finite temperature including consistent three-body forces. Simple and accurate parametrizations of the finite-temperature equations of state are provided. The properties of hot neutron stars are then investigated within this framework, in particular the temperature dependence of the maximum mass. We find very small temperature effects and analyze the interplay of the different contributions.
nucl-thastro-ph.HEastro-ph.SRPRC(2019)·50 citations
05
Constraints from the GW170817 merger event on the nuclear matter equation of state
G. F. Burgio🇮🇹 · A. Figura🇮🇹 · H.-J. Schulze🇮🇹 · J.-B. Wei (Dipartimento di Fisica e Astronomia, Universita' di Catania, and INFN Sezione di Catania)🇮🇹
The detection of the GW170817 neutron star merger event has incited an intense research activity towards the understanding of the nuclear matter equation of state. In this paper we compare in particular the pressure-density relation obtained from heavy-ion collisions with the analysis of the NS merger event. Moreover, we present recent calculations of neutron star's moment of inertia and tidal deformability using various microscopic equations of state for nuclear and hybrid star configurations, and confirm several universal relations. We also discuss the recent constraints for the NS radii determined by GW170817, and find compatible radii between 12 and 13 kilometers, thus identifying the suitable equations of state.
nucl-thastro-ph.HEastro-ph.SRPoS(2018)·3 citations
06
System size scan of D meson $R_{AA}$ and $v_{n}$ using PbPb, XeXe, ArAr, and OO collisions at LHC
Roland Katz🇫🇷 · Caio A. G. Prado🇨🇳 · Jacquelyn Noronha-Hostler🇺🇸 · Alexandre A. P. Suaide🇧🇷
Experimental measurements indicate no suppression (e.g. $R_{pPb} \sim 1$ ) but a surprisingly large D meson $v_{2}$ was measured in pPb collisions. In order to understand these results we use Trento+v-USPhydro+DAB-MOD to make predictions and propose a system size scan at the LHC involving $^{208}$ PbPb, $^{129}$ XeXe, $^{40}$ ArAr, and $^{16}$ OO collisions. We find that the nuclear modification factor approaches unity as the system size is decreased, but nonetheless, in the 0-10% most central collisions $v_{2} {2}$ is roughly equivalent regardless of system size. These results arise from a rather non-trivial interplay between the shrinking path length and the enhancement of eccentricities in small systems at high multiplicity. Finally, we also find a surprising sensitivity of D mesons $v_{2} {2}$ in 0-10% at $p_{T} = 2 - 10$ GeV to the slight deformation of $^{129}$ Xe recently found at LHC.
nucl-thhep-exhep-phPRC(2020)·47 citations
07
Towards high-order calculations of three-nucleon scattering in chiral effective field theory
E. Epelbaum · J. Golak · K. Hebeler · H. Kamada · H. Krebs · U.-G. Meißner · A. Nogga · P. Reinert · R. Skibiński · K. Topolnicki · Y. Volkotrub · H. Witała
We discuss the current status of chiral effective field theory in the three-nucleon sector and present selected results for nucleon-deuteron scattering observables based on semilocal momentum-space-regularized chiral two-nucleon potentials together with consistently regularized three-nucleon forces up to third chiral order. Using a Bayesian model for estimating truncation errors, the obtained results are found to provide a good description of the experimental data. We confirm our earlier findings that a high-precision description of nucleon-deuteron scattering data below pion production threshold will require the theory to be pushed to fifth chiral order. This conclusion is substantiated by an exploratory study of selected short-range contributions to the three-nucleon force at that order, which, as expected, are found to have significant effects on polarization observables at intermediate and high energies. We also outline the challenges that will need to be addressed in order to push the chiral expansion of three-nucleon scattering observables to higher orders.
nucl-thnucl-exEPJA(2020)·96 citations
08
Scale and Scheme Independence and Position-Momentum Equivalence of Nuclear Short-Range Correlations
R. Cruz-Torres · D. Lonardoni · R. Weiss · N. Barnea · D. W. Higinbotham · E. Piasetzky · A. Schmidt · L. B. Weinstein · R. B. Wiringa · O. Hen
Ab-initio Quantum Monte Carlo (QMC) calculations of nuclei from deuterium to 40Ca, obtained using four different phenomenological and local chiral nuclear potentials, are analyzed using the Generalized Contact Formalism (GCF). We extract spin- and isospin-dependent "nuclear contact terms" for each interaction in both coordinate and momentum space. The extracted contact terms, that count the number of short-range correlated (SRC) pairs with different quantum numbers, are dependent on the nuclear interaction model used in the QMC calculation. However, the ratios of contact terms for a nucleus A to deuterium (for spin-1 pn pairs) or to 4He (for all NN pairs) are independent of the nuclear interaction model and are the same for both short-distance and high-momentum pairs. This implies that the relative abundance of short-range pairs in the nucleus is a long-range (mean-field) quantity that is insensitive to the short-distance nature of the nuclear force. Measurements of exclusive (e,e'NN) pair breakup processes are instead more sensitive to short-range dynamics
nucl-thnucl-exNat.Phys.(2021)·104 citations
09
Effective Coupling Constant of Plasmons
Margaret E. Carrington🇨🇦 · Stanislaw Mrowczynski🇵🇱
We study an ultrarelativistic QED plasma in thermal equilibrium. Plasmons - photon collective excitations - are postulated to correspond not to poles of the retarded photon propagator but to poles of the propagator multiplied by the fine structure constant. This product is an invariant of the renormalization group that is independent of an arbitrarily chosen renormalization scale. In addition, our proposal is physically motivated since one needs to scatter a charged particle off a plasma system to probe its spectrum of collective excitations. We present a detailed calculation of the QED running coupling constant at finite temperature using the Keldysh-Schwinger representation of the real-time formalism. We discuss the issue of how to choose the renormalization scale and show that the temperature is a natural choice which prevents the breakdown of perturbation theory through the generation of potentially large logarithmic terms. Our method could be applied to anisotropic systems where the choice of the renormalization scale is less clear, and could have important consequences for the study of collective modes.
↳ hep-phhep-thnucl-thPRD(2019)·4 citations
10
Cross sections for 2-to-3 meson-meson scattering
Wan-Xia Li🇨🇳 · Xiao-Ming Xu🇨🇳 · H. J. Weber🇺🇸
We study 2-to-3 meson-meson scattering based on the process that a gluon is created from a constituent quark or antiquark and subsequently the gluon creates a quark-antiquark pair. The transition potential for the process is derived in QCD. Eight Feynman diagrams at tree level are involved in the 2-to-3 meson-meson scattering. Starting from the $S$ -matrix element, we derive the unpolarized cross section from the eight transition amplitudes corresponding to the eight Feynman diagrams. The transition amplitudes contain color, spin, and flavor matrix elements. The 2-to-3 meson-meson scattering includes $π π \to π K K ˉ$ , $π K \to π π K$ , $π K \to K K K ˉ$ , $K K \to π K K$ , and $K K ˉ \to π K K ˉ$ . Cross sections for the reactions are calculated. The cross sections depend on temperature obviously, and the cross section for $π K \to π π K$ for total isospin $I = 3/2$ at zero temperature is compared to experimental data. By comparison with inelastic 2-to-2 meson-meson scattering, we find that 2-to-3 meson-meson scattering may be as important as inelastic 2-to-2 meson-meson scattering.
↳ hep-phnucl-thPRD(2020)·2 citations
11
$N π$ -excited state contamination in nucleon 3-point functions using ChPT
Oliver Bar🇩🇪
The $N π$ -state contribution to nucleon 3-pt functions involving the pseudoscalar density $P (x)$ and the time component $A_{4} (x)$ of the axial vector current are computed to LO in ChPT. In case of the latter the $N π$ contribution is O( $M_{N}$ ) enhanced compared to the single-nucleon ground state contribution. In addition, a relative sign in two terms of the $N π$ contribution leads an almost linear dependence on the operator insertion time, as it is observed in lattice data. In case of the pseudoscalar density the $N π$ contribution is strongly dependent on the momentum transfer, leading to a distortion of the pseudoscalar nucleon form factor. Finally, the $N π$ state contamination in the form factors result in a violation of the generalized Goldberger-Treiman relation as observed in various lattice calculations.
↳ hep-latnucl-thPoS(2019)·8 citations
12
Theory of elastic neutrino-electron scattering
Oleksandr Tomalak🇺🇸 · Richard J Hill🇺🇸
Theoretical predictions for elastic neutrino-electron scattering have no hadronic or nuclear uncertainties at leading order making this process an important tool for normalizing neutrino flux. However, the process is subject to large radiative corrections that differ according to experimental conditions. In this paper, we collect new and existing results for total and differential cross sections accompanied by radiation of one photon, $ν e \to ν e (γ)$ . We perform calculations within the Fermi effective theory and provide analytic expressions for the electron energy spectrum and for the total electromagnetic energy spectrum as well as for double- and triple-differential cross sections with respect to electron energy, electron angle, photon energy, and photon angle. We discuss illustrative applications to accelerator-based neutrino experiments and provide the most precise up-to-date values of neutrino-electron scattering cross sections. We present an analysis of theoretical error, which is dominated by the $\sim 0.2 - 0.4%$ uncertainty of the hadronic correction. We also discuss how searches for new physics can be affected by radiative corrections.
↳ hep-phhep-exnucl-exnucl-thPRD(2020)·78 citations
13
Mapping collinear in-medium parton splittings
Fabio Dominguez🇪🇸 · Jose Guilherme Milhano🇵🇹 · Carlos A. Salgado🇪🇸 · Konrad Tywoniuk🇳🇴 · Victor Vila🇪🇸
We map the spectrum of $1 \to 2$ parton splittings inside a medium characterized by a transport coefficient $q^$ onto the kinematical Lund plane, taking into account the finite formation time of the process. We discuss the distinct regimes arising in this map for in-medium splittings, pointing out the close correspondence to a semi-classical description in the limit of hard, collinear radiation with short formation times. Although we disregard any modifications of the original parton kinematics in course of the propagation through the medium, subtle modifications to the radiation pattern compared to the vacuum baseline can be traced back to the physics of color decoherence and accumulated interactions in the medium. We provide theoretical support to vacuum-like emissions inside the medium by delimiting the regions of phase space where it is dominant, identifying also the relevant time-scales involved. The observed modifications are shown to be quite general for any dipole created in the medium.
↳ hep-phnucl-thEPJC(2020)·57 citations
14
Effect of non-eikonal corrections on azimuthal asymmetries in the Color Glass Condensate
Pedro Agostini🇪🇸 · Tolga Altinoluk🇵🇱 · Néstor Armesto🇪🇸
We analyse the azimuthal structure of two gluon correlations in the Color Glass Condensate including those effects that result from relaxing the shockwave approximation for the target. Working in the Glasma graph approach suitable for collisions between dilute systems, we compute numerically the azimuthal distributions and show that both even and odd harmonics appear. We study their dependence on model parameters, energy of the collision, pseudorapidity and transverse momentum of the produced particles, and length of the target. While the contribution from non-eikonal corrections vanishes with increasing collision energy and becomes negligible at the energies of the Large Hadron Collider, it is found to be sizeable up to top energies at the Relativistic Heavy Ion Collider.
↳ hep-phnucl-thEPJC(2019)·44 citations

Affiliations

first authorsco-authorsvia INSPIRE