Nuclear Theory·nucl-th

Thursday·February 23, 2023

12 papers—7 primary·5 cross-listed

01
Anchor-based optimization of energy density functionals
A. Taninah · A. V. Afanasjev
A new anchor-based optimization method of defining the energy density functionals (EDFs) is proposed. In this approach, the optimization of the parameters of EDF is carried out for the selected set of spherical anchor nuclei the physical observables of which are modified by the correction function which takes into account the global performance of EDF. It is shown that the use of this approach leads to a substantial improvement in global description of binding energies for several classes of covariant EDFs. The computational cost of defining a new functional within this approach is drastically lower as compared with the one for the optimization which includes the global experimental data on spherical, transitional and deformed nuclei into the fitting protocol.
nucl-thPRC(2023)·11 citations
02
Probing the incompressibility of dense hadronic matter near QCD phase transition in relativistic heavy-ion collisions
Zhi-Min Wu🇨🇳 · Gao-Chan Yong🇨🇳
Based on the extended hadronic transport model of relativistic heavy-ion collisions, the incompressibility of dense hadronic matter created in relativistic Au+Au heavy-ion collisions at $s_{N N} = 3$ GeV is studied. By comparing experimental proton directed flow, productions of strange hadrons $ϕ$ , $K^{-}$ as well as their ratio $ϕ / K^{-}$ , proton high-order cumulants to the model calculations, a large incompressibility of dense hadronic matter is obtained from nucleon observabels while a rather small incompressibility is needed to fit the data of strange hadrons. This may indicate hadronic matter possesses different incompressibilities in different density regions, i.e., the incompressibility may become stiffer from saturation density to a certain baryon density and then turn to soft before reaching hadron-quark phase transition. The study also shows that the incompressibility significantly affects the critical baryon density of hadron-quark phase transition.
nucl-thnucl-exPRC(2023)·10 citations
03
Manifestation of pairing modes in nuclear collisions
A. Makowski · M. C. Barton · P. Magierski · K. Sekizawa · G. Wlazłowski
We discuss the possible manifestation of pairing dynamics in nuclear collisions beyond the standard quasi-static treatment of pairing correlations. These involve solitonic excitations induced by pairing phase difference of colliding nuclei and pairing dynamic enhancement in the di-nuclear system formed by merging nuclei.
nucl-thActa Phys.Polon.Supp.(2023)·2 citations
04
Hartree-Fock-Bogoliubov study of quantum shell effects on the path to fission in $^{180}$ Hg, $^{236}$ U and $^{256}$ Fm
Rémi Bernard🇦🇺 · Cédric Simenel🇦🇺 · Guillaume Blanchon🇫🇷
Quantum shell effects stabilising fission fragments with various shapes have been invoked as a factor determining the distribution of nucleons between the fragments at scission. Shell effects also induce asymmetric shapes in the nucleus on its way to fission well before the final fragments are (pre)formed. These shell effects are studied in fission of $^{180}$ Hg, $^{236}$ U and $^{256}$ Fm with constrained Hartree-Fock-Bogoliubov calculations using the D1S parametrisation of the Gogny interaction. Strutinsky shell energy correction and single-particle energy level density near the Fermi surface are computed. Several neutron and proton shell effects are identified as drivers towards asymmetric fission. Shell effects are also used to identify the preformation of the fragments in the later stage of fission.
nucl-thEPJA(2023)·18 citations
05
Signatures of deuteron synthesis on the modified combinants in nuclear collisions
Rahul R. Nair🇵🇱 · Grzegorz Wilk🇵🇱 · Zbigniew Włodarczyk🇵🇱
The mechanism of deuteron production in heavy-ion collisions is shown to have a significant impact on the shape of the modified combinants of their multiplicity distribution. In light of this observation, an experimental study is proposed to tackle the long-standing problem of nuclei synthesis in hadronic and nuclear collisions. The proposed approach has the potential to provide stringent constraints on the models of deuteron synthesis.
nucl-thhep-ph0 citations
06
Frequencies of $f$ - and $p$ -oscillation modes in cold and hot compact stars
Vivek Baruah Thapa · Mikhail V. Beznogov · Adriana R. Raduta · Pratik Thakur
A large collection of equations of state (EOSs) built within the covariant density functional (CDF) theory of hadronic matter and allowing for density dependent (DD) couplings is employed to study polar $f$ - and $p$ - oscillations of cold and hot compact stars. Correlations between oscillation frequencies of cold purely nucleonic neutron stars (NSs), their global parameters as well as properties of nuclear matter (NM) are investigated by considering a set of models from Beznogov and Raduta, [Phys.~Rev.~C 107, 045803 (2023)], where a number of constraints on the saturation properties of NM, pure neutron matter (PNM) and the lower bound of the maximal NS mass were imposed within a Bayesian framework. The roles of finite temperature and exotic particle degrees of freedom, e.g., hyperons, $Δ$ -resonances, anti-kaon condensates or a hadron to quark phase transition, are addressed by employing a family of models publicly available on \textsc{CompOSE} and assuming idealized profiles of temperature or entropy per baryon and charge fraction. We find that finite temperature effects reduce the oscillation frequencies of nucleonic stars while the opposite effect is obtained for stars with exotic particle degrees of freedom. When the $Γ$ -law is employed to build finite temperature EOSs, errors in estimating oscillation modes frequencies are of the order of 10\% to 30\%, depending on the mass. Throughout this work the Cowling approximation is used.
nucl-thastro-ph.HEPRD(2023)·18 citations
07
Recombination of $B_{c}$ mesons in ultra-relativistic heavy-ion collisions
Biaogang Wu🇺🇸 · Zhanduo Tang🇺🇸 · Min He🇨🇳 · Ralf Rapp🇺🇸
High-energy heavy-ion collisions have been suggested as a favorable environment for the production of $B_{c}$ mesons, due to a much larger abundance of charm and bottom quarks compared to elementary reactions. Motivated by recent CMS data for $B_{c}^{+}$ production in Pb-Pb( $5.02$ TeV) collisions at the LHC, we deploy a previously developed transport approach for charmonia and bottomonia to evaluate the kinetics of $B_{c}$ mesons throughout the fireball formed in these reactions. The main inputs to our approach are two transport parameters: the $B_{c}$ 's reaction rate and equilibrium limit. Both quantities are determined by previous calculations via a combination of charm and bottom sectors. In-medium binding energies of $B_{c}$ mesons are calculated from a thermodynamic $T$ -matrix with a lattice-QCD constrained potential, and figure in their inelastic reaction rates. Temperature-dependent equilibrium limits include charm- and bottom-quark fugacities based on their initial production. We compute the centrality dependence of inclusive $B_{c}$ production and transverse-momentum ( $p_{T}$ ) spectra using two different recombination models, instantaneous coalescence and resonance recombination. The main uncertainty in the resulting nuclear modification factors, $R_{AA}$ , is currently associated with the $B_{c}$ cross section in elementary $pp$ collisions, caused by the uncertainty in the branching ratio for the $B_{c}^{-} \to J / ψ μ^{-} ν ˉ$ decay. Our results indicate a large enhancement of the $R_{AA}$ at low $p_{T}$ , with significant regeneration contributions up to $p_{T} ≃ 20$ GeV. Comparisons to CMS data are carried out but firm conclusions will require a more accurate value of the branching ratio, or alternative channels to measure the $B_{c}$ production in $pp$ collisions.
nucl-thPRC(2024)·22 citations
08
The LPM effect in sequential bremsstrahlung: gluon shower development
Peter Arnold🇺🇸 · Omar Elgedawy🇺🇸 · Shahin Iqbal🇵🇰
We give details of our study of whether high-energy gluon showers inside a QCD medium can be treated as a sequence of individual splitting processes $g \to g g$ , or whether there is significant quantum overlap between where one splitting ends and the next begins (neglecting effects that can be absorbed into an effective value of the jet quenching parameter $q^$ that characterizes the medium). The study is carried out by imagining in-medium gluon shower development in the simplest theoretical situation, which includes imagining a very large, static, homogeneous medium and taking the large $N_{c}$ limit. Along the way, we also show how in-medium shower evolution can be written in terms of a "net" splitting rate $[d Γ/ d x]_{net}$ , and we provide a moderately simple analytic fit to our numerical results for the overlap effects included in that rate, which we hope may be of use to others wishing to study possible consequences of overlapping splittings.
↳ hep-phnucl-thPRD(2023)·28 citations
09
Measuring the vortex-nucleus pinning force from pulsar glitch rates
A. Melatos · M. Millhouse
Superfluid vortex avalanches are one plausible cause of pulsar glitch activity. If they occur according to a state-dependent Poisson process, the measured long-term glitch rate is determined by the spin-down rate of the stellar crust, $Ω ˙_{c}$ , and two phenomenological parameters quantifying the vortex-nucleus pinning force: a crust-superfluid angular velocity lag threshold, $X_{cr}$ , and a reference unpinning rate, $λ_{0}$ . A Bayesian analysis of 541 glitches in 177 pulsars, with $N_{g} \geq 1$ events per pulsar, yields $X_{cr} = 0.1 5_{- 0.04}^{+ 0.09} rad s^{- 1}$ , $λ_{ref} = 7. 6_{- 2.6}^{+ 3.7} \times 1 0^{- 8} s^{- 1}$ , and $a = - 0.2 7_{- 0.03}^{+ 0.04}$ assuming the phenomenological rate law $λ_{0} = λ_{ref} [τ / (1 yr)]^{a}$ , where $τ$ denotes the characteristic spin-down age. The results are broadly similar, whether one includes or excludes quasiperiodic glitch activity, giant glitches, or pulsars with $N_{g} = 0$ , up to uncertainties about the completeness of the sample and the total observation time per pulsar. The $X_{cr}$ and $λ_{0}$ estimates are consistent with first-principles calculations based on nuclear theory, e.g. in the semiclassical local density approximation.
↳ astro-ph.HEnucl-exnucl-thApJ(2023)·7 citations
10
Global QCD Analysis and Dark Photons
N. T. Hunt-Smith🇦🇺 · W. Melnitchouk🇦🇺 · N. Sato🇺🇸 · A. W. Thomas🇦🇺 · X. G. Wang🇦🇺 · M. J. White🇦🇺
We perform a global QCD analysis of high energy scattering data within the JAM Monte Carlo framework, including a coupling to a dark photon that augments the standard model electroweak coupling via kinetic mixing with the hypercharge $B$ boson. Including the most recent measurement of the anomalous magnetic moment of the muon as a constraint, we find a significant reduction in the combined $χ^{2}$ , favoring the inclusion of a dark photon, with a statistical significance in excess of 8 $σ$ . With respect to the experimental data, the improvements in the theoretical predictions are spread across a wide range of $x$ and $Q^{2}$ , with the largest improvement corresponding to neutral current data from HERA, while the best fit yields a value of $g - 2$ which significantly reduces the disagreement with the latest experimental determination. The best fit yields a dark photon mass in the range 4.2--6.2 GeV and a mixing parameter of order 0.1.
↳ hep-phhep-exnucl-thJHEP(2023)·16 citations
11
Fluctuations of atomic energy levels due to axion dark matter
V. V. Flambaum🇦🇺 · I.B. Samsonov🇦🇺
The amplitude of the pseudoscalar (axion) or scalar field fluctuates on a time scale of order of million field oscillation periods which is a typical coherence time in the virialized axion galactic dark matter halo model. This causes fluctuations of frequencies of atomic clocks on the same time scale. We show that this effect may be employed to search for the axion and scalar field dark matter with atomic and nuclear clocks. We re-purpose the results of the atomic clocks experiments comparing the variations of frequencies of hyperfine transitions in Rb and Cs atoms as well as in hydrogen atom vs cavity frequency fluctuations, and extract new limits on the axion coupling constant $f_{a}$ for masses in the range $2.4 \times 1 0^{- 17} eV ≲ m ≲ 1 0^{- 13} eV$ . We also show that similar energy shifts arise in the second-order perturbation theory with linear in the pseudoscalar field interaction. These shifts may be potentially measured with nuclear clocks based on the low-energy transition in $^{229}$ Th nucleus. We propose a procedure which could, in principle, help determine the axion mass if the axion dark matter signal is present in experimental data sets.
↳ hep-phastro-ph.COnucl-thphysics.atom-phPRD(2023)·22 citations
12
Unified tetraquark equations
A. N. Kvinikhidze🇬🇪 · B. Blankleider🇦🇺
We derive covariant equations describing the tetraquark in terms of an admixture of two-body states $D D ˉ$ (diquark-antidiquark), $M M$ (meson-meson), and three-body-like states $q q ˉ (T_{q q ˉ})$ , $q q (T_{q ˉ q ˉ})$ , and $q ˉ q ˉ (T_{q q})$ where two of the quarks are spectators while the other two are interacting (their t matrices denoted correspondingly as $T_{q q ˉ}$ , $T_{q ˉ q ˉ}$ , and $T_{q q}$ ). This has been achieved by describing the $q q q ˉ q ˉ$ system using the Faddeev-like four-body equations of Khvedelidze and Kvinikhidze [Theor. Math. Phys. 90, 62 (1992)] while retaining all two-body interactions (in contrast to previous works where terms involving isolated two-quark scattering were neglected). As such, our formulation, is able to unify seemingly unrelated models of the tetraquark, like, for example, the $D D ˉ$ model of the Moscow group [Faustov et al., Universe 7, 94 (2021)] and the coupled channel $D D ˉ - M M$ model of the Giessen group [Heupel et al., Phys. Lett. B718, 545 (2012)].
↳ hep-phnucl-thPRD(2023)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE