Nuclear Theory·nucl-th

Monday·May 8, 2023

8 papers—3 primary·5 cross-listed

01
Nonparametric model for the equations of state of neutron star from deep neural network
Wenjie Zhou · Jinniu Hu · Ying Zhang · Hong Shen
It is of great interest to understand the equation of state (EOS) of the neutron star (NS), whose core includes highly dense matter. However, there are large uncertainties in the theoretical predictions for the EOS of NS. It is useful to develop a new framework, which is flexible enough to consider the systematic error in theoretical predictions and to use them as a best guess at the same time. We employ a deep neural network to perform a non-parametric fit of the EOS of NS using currently available data. In this framework, the Gaussian process is applied to represent the EOSs and the training set data required to close physical solutions. Our model is constructed under the assumption that the true EOS of NS is a perturbation of the relativistic mean-field model prediction. We fit the EOSs of NS using two different example datasets, which can satisfy the latest constraints from the massive neutron stars, NICER, and the gravitational wave of the binary neutron stars. Given our assumptions, we find that a maximum neutron star mass is $2.3 8_{- 0.13}^{+ 0.15} M_{⊙}$ or $2.4 1_{- 0.14}^{+ 0.15}$ at $95%$ confidence level from two different example datasets. It implies that the $1.4 M_{⊙}$ radius is $12.3 1_{- 0.31}^{+ 0.29}$ km or $12.3 0_{- 0.37}^{+ 0.35}$ km. These results are consistent with results from previous studies using similar priors. It has demonstrated the recovery of the EOS of NS using a nonparametric model.
nucl-thastro-ph.HEastro-ph.SRApJ(2023)·23 citations
02
Impact of level densities and $γ$ -strength functions on $r$ -process simulations
Francesco Pogliano · Ann-Cecilie Larsen
Studies attempting to quantify the sensitivity of the $r$ -process abundances to nuclear input have to cope with the fact that the theoretical models they rely on, rarely come with confidence intervals. This problem has been dealt with by either estimating these intervals and propagating them statistically to the final abundances using reaction networks within simplified astrophysical models, or by running more realistic astrophysical simulations using different nuclear-physics models consistently for all the involved nuclei. Both of these approaches have their strengths and weaknesses. In this work, we run $r$ -process calculations for five trajectories using 49 different neutron-capture rate models. Our results shed light on the importance of taking into account shell effects and pairing correlations in the network calculations.
nucl-thPRC(2023)·9 citations
03
Impact of the pre-equilibrium phase for the determination of nuclear geometry in high-energy isobar collisions
Fernando G. Gardim🇧🇷 · André V. Giannini🇧🇷 · Frédérique Grassi🇧🇷 · Kevin P. Pala🇧🇷 · Willian M. Serenone🇧🇷
Ultrarelativistic isobar collisions have been proposed as a useful tool to investigate nuclear structure. These systems are not created in equilibrium, rather undergo a pre-thermalization stage. In this stage, some of the initial structure information may be lost and additional effects introduced. The objective of this paper is to study this possibility in the extreme case of a "free-streaming" pre-equilibrium stage. We do this by computing estimators for ratios of various measured (or measurable) quantities (elliptic and triangular flows, mean transverse momentum and associated cumulants, correlators between elliptic or triangular flows and mean transverse momentum, symmetric cumulant and two-plane correlator) and study their sensitivity to the duration of the free-streaming stage. We find that the correlators between elliptic or triangular flows and mean transverse momentum, the so-called $ρ_{2}$ and $ρ_{3}$ , are indeed sensitive to the duration of the free-streaming stage and that the normalized symmetric cumulant, $εN S C (2, 3)$ might also depend on this duration.
nucl-thhep-phPRC(2024)·3 citations
04
The maximum mass and deformation of rotating strange quark stars with strong magnetic fields
Fatemeh Kayanikhoo🇵🇱 · Mateusz Kapusta🇵🇱 · Miljenko Čemeljić🇨🇿
We study the structure and total energy of a strange quark star (SQS) endowed with a strong magnetic field with different rotational frequencies. The MIT bag model is used, with the density-dependent bag constant for the equation of state (EOS). The EOS is computed considering the Landau quantization effect regarding the strong magnetic fields (up to $5 \times 1 0^{17}$ G) in the interior of the strange quark star. Using the LORENE library, we calculate the structural parameters of SQS for different setups of magnetic field strengths and rotational frequencies. In each setup, we perform calculations for $51$ stellar configurations, with specified central enthalpy values. We investigate the configurations with the maximum gravitational mass of SQS in each setup. Our models of SQSs are compared in the maximum gravitational mass, binding energy, compactness, and deformation of the star. We show that the gravitational mass might exceed $2.3 M_{⊙}$ in some models, which is comparable with the mass of the recently detected ``black widow'' pulsar \emph{PSR J0952-0607} and the mass of \emph{GW190814} detected by the LIGO/Virgo collaboration. The deformation and maximum gravitational mass of SQS can be characterized by simple functions that have been fitted to account for variations in both magnetic field strength and frequency. Rapidly rotating strange stars have a minimum gravitational mass given by the equatorial mass-shedding limit.
↳ astro-ph.HEnucl-th1 citation
05
Probing the onset of maximal entanglement inside the proton in diffractive DIS
Martin Hentschinski🇲🇽 · Dmitri E. Kharzeev🇺🇸 · Krzysztof Kutak🇵🇱 · Zhoudunming Tu🇺🇸
It has been proposed that at small Bjorken $x$ , or equivalently at high energy, hadrons represent maximally entangled states of quarks and gluons. This conjecture is in accord with experimental data from the electron-proton collider HERA at the smallest accessible $x$ . In this Letter, we propose to study the onset of the maximal entanglement inside the proton using Diffractive Deep Inelastic Scattering. It is shown that the data collected by the H1 Collaboration at HERA allows to probe the transition to the maximal entanglement regime. By relating the entanglement entropy to the entropy of final state hadrons, we find a good agreement with the H1 data using both the exact entropy formula as well as its asymptotic expansion which indicates the presence of a nearly maximally-entangled state. Finally, future opportunities at the Electron Ion Collider are discussed.
↳ hep-phhep-exnucl-exnucl-th+1PRL(2023)·52 citations
06
Minimal model for the $W$ -boson mass, $(g - 2)_{μ}$ , $h \to μ^{+} μ^{-}$ and quark-mixing-matrix unitarity
Andreas Crivellin🇨🇭 · Matthew Kirk🇪🇸 · Anil Thapa🇺🇸
The $S U (2)_{L}$ triplet scalar with hypercharge $Y = 0$ predicts a positive definite shift in the $W$ mass, w.r.t.~the Standard Model prediction, if it acquires a vacuum expectation value. As this new field cannot couple directly to SM fermions (on its own), it has no significant impact on other low-energy precision observables and is weakly constrained by collider searches. In fact, the multi-lepton anomalies at the LHC even point towards new scalars that decay dominantly to $W$ bosons, as the neutral component of the triplet naturally does. In this article, we show that with a minimal extension of the scalar triplet model by a heavy vector-like lepton, being either I) an $S U (2)_{L}$ doublet with $Y = - 1/2$ or II) an $S U (2)_{L}$ triplet with $Y = - 1$ , couplings of the triplet to Standard Model leptons are possible. This minimal extension can then provide, in addition to the desired positive shift in the $W$ mass, a chirally enhanced contribution to $(g - 2)_{μ}$ . In addition version I) and II) can improve on $Z \to μ^{+} μ^{-}$ and alleviate the tension in first-row CKM unitarity (known as the Cabibbo angle anomaly), respectively. Finally, both options, in general, predict sizable changes of $h \to μ^{+} μ^{-}$ , i.e.,~much larger than most other $(g - 2)_{μ}$ explanations where only $O (%)$ effects are expected, making this channel a smoking gun signature of our model.
↳ hep-phhep-exhep-latnucl-ex+1PRD(2023)·17 citations
07
Elasticity of neutron star mantle: improved compressible liquid drop model for cylindrical phases
Nikita A. Zemlyakov · Andrey I. Chugunov (Ioffe Institute)
Neutron stars are the densest objects in the Universe. They have microscopically homogeneous core and heterogeneous crust. In particular, there may be a specific layer inside neutron stars, the mantle, which consists of substantially non-spherical nuclei immersed in a background of relativistic degenerate electrons and quasi-free neutrons. In this paper we reconsider transverse shear modulus for cylindrical phases of the mantle within the framework of compressible liquid drop model. We demonstrate that transverse shear affects the shape of nuclear clusters: their cross-section becomes elliptical. This effect reduces respective elastic constant. Using a simple model we perform all derivations analytically and obtain the expression for the transverse shear modulus, which can be useful for astrophysical applications.
↳ astro-ph.HEastro-ph.SRnucl-thUniverse(2023)·4 citations
08
Multi-charmed and singled charmed hadrons from coalescence: yields and ratios in different collision systems at LHC
Vincenzo Minissale (1 and 2)🇮🇹 · Salvatore Plumari (1 and 2)🇮🇹 · Yifeng Sun (3)🇨🇳 · Vincenzo Greco (1 and 2) ((1) Department of Physics and Astronomy "E.Majorana", University of Catania, Catania, Italy, (2) Laboratori Nazionali del Sud, INFN-LNS, Catania, Italy, (3) School of Physics and Astronomy, Shanghai Key Laboratory for Particle Physics and Cosmology, and Key Laboratory for Particle Astrophysics and Cosmology (MOE), Shanghai Jiao Tong University, Shanghai, China)🇮🇹
We study the production of charmed and multi-charmed hadrons in ultra-relativistic Heavy Ion Collisions coupling the transport approach for charm dynamics in the medium to an hybrid hadronization model of coalescence plus fragmentation. In this paper, we mainly discuss the particle yields for single charmed and multi-charmed baryons focusing mainly on the production of $Ξ_{cc}$ and $Ω_{ccc}$ . We provide first predictions for PbPb collision in 0-10% centrality class and then we explore the system size dependence through KrKr, to ArAr and OO collisions, planned within the ALICE3 experiment. In these cases, a monotonic behavior for the yields emerges which can be tested in future experimental data. We found about three order of magnitude increase in the production of $Ω_{ccc}$ in PbPb collisions compared with the yield in small collision systems like OO collisions. Furthermore, we investigate the effects on the $Ω_{ccc}$ particle production and spectra coming from the modification of the charm quark distribution due to the different size of the collision systems comparing also to the case of thermalized charm distributions. These results suggest that observation on the $Ω_{ccc}$ spectra and their evolution across system size can give information about the partial thermalization of the charm quark distribution as well as to its wave function width.
↳ hep-phnucl-thEPJC(2024)·29 citations

Affiliations

first authorsco-authorsvia INSPIRE