Nuclear Theory·nucl-th

Thursday·March 23, 2023

14 papers—2 primary·12 cross-listed

03
Strongly interacting matter exhibits deconfined behavior in massive neutron stars
Eemeli Annala🇫🇮 · Tyler Gorda🇩🇪 · Joonas Hirvonen🇫🇮 · Oleg Komoltsev🇳🇴 · Aleksi Kurkela🇳🇴 · Joonas Nättilä🇺🇸 · Aleksi Vuorinen🇫🇮
Neutron-star cores contain matter at the highest densities in our Universe. This highly compressed matter may undergo a phase transition where nuclear matter melts into deconfined quark matter, liberating its constituent quarks and gluons. Quark matter exhibits an approximate conformal symmetry, predicting a specific form for its equation of state (EoS), but it is currently unknown whether the transition takes place inside at least some physical neutron stars. Here, we quantify this likelihood by combining information from astrophysical observations and theoretical calculations. Using Bayesian inference, we demonstrate that in the cores of maximally massive stars, the EoS is consistent with quark matter. We do this by establishing approximate conformal symmetry restoration with high credence at the highest densities probed and demonstrating that the number of active degrees of freedom is consistent with deconfined matter. The remaining likelihood is observed to correspond to EoSs exhibiting phase-transition-like behavior, treated as arbitrarily rapid crossovers in our framework.
↳ astro-ph.HEhep-phnucl-thNature Commun.(2023)·210 citations
04
Structure of Nucleons and Their Interaction in the Concept of Nonperturbative QCD as a Pressing Issue of 21st-Century Physics
Vladimir I. Komarov🇷🇺
The problem of the structure of nucleons and their interaction in the concept of nonperturbative QCD is discussed as an approach to studying the transformation of current quarks into constituent ones and the search for the mechanism of such a transformation, creating the bulk of the nucleon mass. Attention is drawn to the possibilities offered by studying central nucleon-nucleon collisions in this aspect.
↳ hep-phnucl-exnucl-thPhys.Part.Nucl.Lett.(2022)·1 citation
05
Light quark and antiquark constraints from new electroweak data
Alberto Accardi🇺🇸 · Xiaoxian Jing🇺🇸 · Joseph Francis Owens🇺🇸 · Sanghwa Park🇺🇸
We present a new parton distribution function analysis which includes new data for W boson production in proton-proton collisions and lepton pair production in proton-proton and proton-deuteron collisions. The new data provide strong constraints on the light antiquark parton distribution functions in the proton. We identify an interesting correlation between the $d / u$ ratio and the $d ˉ / u ˉ$ ratio which leads to a modification of our previous results for the $d / u$ ratio as the parton momentum fraction $x \to 1.$
↳ hep-phhep-exnucl-thPRD(2023)·24 citations
06
Gravitational transverse-momentum distributions
Cédric Lorcé🇫🇷 · Qin-Tao Song🇫🇷
We study the energy-momentum tensor of spin- $0$ and spin- $\frac{1}{2}$ hadrons in momentum space. We parametrize this object in terms of so-called gravitational transverse-momentum distributions, and we identify in the quark sector the relations between the latter and the usual transverse-momentum distributions. Focusing on particular components of the energy-momentum tensor, we study momentum densities, flux of inertia and stress distribution in momentum space, revealing part of the wealth of physical information that can be gained from higher-twist transverse-momentum distributions.
↳ hep-phhep-exhep-latnucl-thPLB(2023)·13 citations
07
A Comparative Analysis between Unbiased Exponential Resummation and Taylor Expansion in Finite-Density QCD with a new phasefactor for Isospin
Sabarnya Mitra🇮🇳
The recently introduced unbiased exponential resummation at finite chemical potential has become an important approach which promises to capture reliably the behaviour of higher order conserved charge cumulants appearing otherwise in the finite-density QCD Taylor series of thermodynamic observables. In this paper, we present a thorough analysis of the estimates of charge cumulants upto eighth order and have compared them using Taylor expansion method and unbiased exponential resummation approach for baryon and isospin chemical potentials. We also subsequently compare the different estimates of the radius of convergence obtained using these two methods and check if the zeros of phasefactor for baryochemical potential can indicate something about these estimated values. We propose a new method of finding a non-trivial phasefactor for isospin chemical potential and we attempt explaining the different estimates of radius of convergence from the zeroes of this newly constructed gauge-ensemble average phasefactor for isospin chemical potential. Lastly, we also illustrate kurtosis plots describing the behaviour of overlap problem in isospin chemical potential and check if it maintains consistency with the appearance of zeros of the newly proposed phasefactor.
↳ hep-lathep-phnucl-exnucl-th1 citation
08
Precise description of medium-induced emissions
Johannes Hamre Isaksen🇳🇴 · Konrad Tywoniuk🇳🇴
We study jet fragmentation via final-state parton splittings in the medium. These processes are usually calculated theoretically by invoking the large- $N_{c}$ limit. In this paper we perform the first computation of a $1 \to 2$ parton splitting in a thermal medium at finite numbers of colors $N_{c}$ , for arbitrary momentum-sharing fraction $z$ and with full transverse dynamics. We show how the problem can be transformed into a system of coupled Schrödinger equations, that we solve numerically. The novel numerical results are used to estimate the accuracy of several widely used approximations. We check the error introduced while going from finite $N_{c}$ (i.e. $N_{c} = 3$ ) to the large- $N_{c}$ limit, which we find to be small. For unbalanced splittings, e.g. when $z \to 0$ , only one of the partons is affected by transverse momentum exchanges with the medium. The emission process then separates into a term responsible for the $1 \to 2$ splitting and the subsequent independent broadening of the daughter partons. This is also referred to as the factorizable term. For finite $z$ , further contributions arise that are responsible for the coherent color dynamics of the two-parton system, and these are referred to as non-factorizable terms. These were argued to be small for soft (unbalanced) splittings and for large media. In this work we therefore determine the accuracy of keeping only the factorizable term of the large- $N_{c}$ solution. We find that the error is insignificant at a small splitting fraction $z \sim 0$ , but can be sizable in a more balanced splitting with $z \sim 0.5$ . Finally, we also examine the eikonal approximation, which amounts to approximating the partons' paths through the medium as straight lines. We find that it is associated with a substantial error for the parameter values we explored in this work.
↳ hep-phhep-thnucl-thJHEP(2023)·28 citations
09
Precise determination of quadrupole and hexadecapole deformation parameters of the $s d$ -shell nucleus, $^{28}$ Si
Y. K. Gupta · V. B. Katariy · G. K. Prajapati · K. Hagino · D. Patel · V. Ranga · L. S. Danu · A. Pal · B. N. Joshi · S. Dubey · V. V. Desai · S. Panwar and 8 other authors
Quasi-elastic (QEL) scattering measurements have been performed using $^{28}$ Si projectile off a $^{90}$ Zr target at energies around the Coulomb barrier. A Bayesian analysis within the framework of coupled channels (CC) calculations is performed in a large parameter space of quadrupole and hexadecapole deformations ( $β_{2}$ and $β_{4}$ ) of $^{28}$ Si. Our results clearly show that $^{28}$ Si is an oblate shaped nucleus with $β_{2}$ =- $0.38 \pm 0.01$ which is in excellent agreement with electromagnetic probes. A precise value of hexadecapole deformation for $^{28}$ Si, $β_{4}$ =+ $0.03 \pm 0.01$ , along with a consistent value of quadrupole deformation has now been determined for the first time using QEL scattering. A remarkable agreement between the experimental $β_{4}$ value of $^{28}$ Si and Skyrme-Hartree-Fock based calculations is obtained. The QEL results obtained previously for $^{24}$ Mg (prolate) and the present result for $^{28}$ Si (oblate) hereby affirm the strong sensitivity of the quasi-elastic scattering to ground state deformations, thus reinforcing its suitability as a potential probe for rare exotic nuclei.
↳ nucl-exnucl-thPLB(2023)·22 citations
10
Heavy quark diffusion coefficient in heavy-ion collisions via kinetic theory
Kirill Boguslavski🇦🇹 · Aleksi Kurkela🇳🇴 · Tuomas Lappi🇫🇮 · Florian Lindenbauer🇦🇹 · Jarkko Peuron🇫🇮
We compute the heavy quark momentum diffusion coefficient $κ$ using QCD kinetic theory for a system going through bottom-up isotropization in the initial stages of a heavy ion collision. We find that the values of $κ$ are within 30% from a thermal system at the same energy density. When matching for other quantities we observe considerably larger deviations. We also observe that the diffusion coefficient in the transverse direction is larger at high occupation numbers, whereas for an underoccupied system the longitudinal diffusion coefficient dominates. The behavior of the diffusion coefficient can be understood on a qualitative level based on the Debye mass $m_{D}$ and the effective temperature of soft modes $T_{*}$ . Our results for the kinetic evolution of $κ$ in different directions can be used in phenomenological descriptions of heavy quark diffusion and quarkonium dynamics to include the impact of pre-equilibrium stages.
↳ hep-phnucl-thPRD(2024)·49 citations
11
Cross sections for inelastic $K$ + $ϕ$ scattering
Yi-Hao Pan🇨🇳 · Xiao-Ming Xu🇨🇳
In the first Born approximation we study the reactions $K ϕ \to π K$ , $ρ K$ , $π K^{*}$ , and $ρ K^{*}$ with quark-antiquark annihilation and creation. Transition amplitudes are derived with the development in spherical harmonics of the relative-motion wave functions of the two initial mesons and of the two final mesons so that parity is conserved and the total angular momentum of the final mesons equals the one of the initial mesons. Unpolarized cross sections are calculated from the transition amplitudes that also contain mesonic quark-antiquark relative-motion wave functions and transition potentials for quark-antiquark annihilation and creation. Notable temperature dependence of the cross sections is shown. While the cross sections for $K ϕ \to ρ K$ , $K ϕ \to π K^{*}$ , and $K ϕ \to ρ K^{*}$ may be of the millibarn scale, the cross section for $K ϕ \to π K$ is very small.
↳ hep-phnucl-thCPC(2023)·0 citations
12
Jet momentum broadening during initial stages in heavy-ion collisions
Kirill Boguslavski🇦🇹 · Aleksi Kurkela🇳🇴 · Tuomas Lappi🇫🇮 · Florian Lindenbauer🇦🇹 · Jarkko Peuron🇫🇮
We study the jet quenching parameter $q^$ in the initial pre-equilibrium stages of heavy-ion collisions using the QCD kinetic theory description of the anisotropic quark-gluon plasma. This allows us to smoothly close the gap in the literature between the early glasma stage of the collision and the onset of hydrodynamics. We find that the pre-hydrodynamic evolution of $q^$ during the bottom-up kinetic scenario shows little sensitivity to the initial conditions, jet energies and models of the transverse momentum cutoff. We also observe that, similarly to the glasma case, the jet quenching parameter is enhanced along the beam axis as compared to the transverse direction during most of the kinetic evolution.
↳ hep-phnucl-thPLB(2024)·65 citations
13
Universality of isolated $N$ -body resonances at large scattering length
Ludovic Pricoupenko🇫🇷
Non Efimovian $N$ -body resonances are investigated in the regime of a large two-body s wave scattering length. In view of a universal description of low-energy bound and quasi-bound states, a contact model is introduced. The modeling requires two parameters in addition to the scattering length. Using a modified scalar product, the contact model provides a normalization of bound states, possibly not square-integrable, that coincides with that of the corresponding finite range model.
↳ cond-mat.quant-gasnucl-thPRA(2023)·5 citations
14
Target normal single-spin asymmetry in inclusive electron-nucleon scattering in the 1/Nc expansion
Jose L. Goity🇺🇸 · Christian Weiss🇺🇸 · Cintia Willemyns🇧🇪
The target normal single-spin asymmetry in inclusive electron-nucleon scattering is studied in the low-energy regime that includes the $Δ$ resonance. The particular interest in the asymmetry resides in that it is driven by two-photon exchange effects. It probes the spin-dependent absorptive part of the two-photon exchange amplitude, which is free of infrared and collinear singularities and represents the most pristine expression of two-photon exchange dynamics. The study presented here uses the 1/Nc expansion of QCD, which combines the $N$ and $Δ$ through the emergent SU(4) spin-flavor symmetry in the baryon sector and allows for a systematic construction of the transition EM currents. The analysis includes the first subleading corrections in the 1/Nc expansion and presents results for elastic and inelastic final states. The asymmetry is found to be in the range $1 0^{- 3} - 1 0^{- 2}$ . The $Δ$ resonance plays an important role as an intermediate state in the elastic asymmetry and as a final state in the inclusive asymmetry.
↳ hep-phnucl-thPRD(2023)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE