Nuclear Theory·nucl-th

Friday·January 26, 2024

12 papers—4 primary·8 cross-listed

01
The earliest phase of relativistic heavy-ion collisions
Margaret E. Carrington🇨🇦 · Stanislaw Mrowczynski🇵🇱
According to the Color Glass Condensate approach to relativistic heavy-ion collisions, the earliest phase of the collision is a glasma which is made of highly populated gluon fields that can be treated classically. Using a proper time expansion we study analytically various properties of the glasma. In particular, we compute the glasma energy-momentum tensor which allows us to obtain the energy density, longitudinal and transverse pressure, collective flow, and angular momentum. We also study the role of the glasma in jet quenching by computing collisional energy loss and transverse momentum broadening.
nucl-thhep-phActa Phys.Polon.B(2024)·4 citations
02
First-order relativistic hydrodynamics with an information current
Lorenzo Gavassino🇺🇸 · Nick Abboud🇺🇸 · Enrico Speranza🇨🇭 · Jorge Noronha🇺🇸
We show that it is possible to define a timelike future-directed information current within relativistic first-order hydrodynamics. This constitutes the first step toward a covariantly stable and causal formulation of first-order fluctuating hydrodynamics based on thermodynamic principles. We provide several explicit examples of first-order theories with an information current, covering many physical phenomena, ranging from electric conduction to viscosity and elasticity. We use these information currents to compute the corresponding equal-time correlation functions, and we find that the physically relevant (equal-time) correlators do not depend on the choice of the hydrodynamic frame as long as the frame leads to causal and stable dynamics. In the example of chiral hydrodynamics, we find that circularly polarized shear waves have different probabilities of being excited depending on their handedness, generating net helicity in chiral fluids.
nucl-thgr-qchep-thPRD(2024)·8 citations
03
Contribution of $π^{0}$ Exchange in Elastic Muon-Proton Scattering
Atharva Naik🇺🇸 · Andrei Afanasev🇺🇸
The effect of the lepton's mass is significantly enhanced when the beam's energy is on the order of the lepton's mass. In the case of electrons, this corresponds to beam momenta on the order of a few MeV and is negligible in higher energy experiments. In this study, we calculate the differential cross section $d σ / d Ω$ for the helicity-flip meson exchange interference in elastic muon-proton $(μ p)$ scattering $μ^{-} p \to μ^{-} p$ . In particular, we examine the $π^{0}$ meson exchange in the $t$ -channel for a longitudinally polarized beam and a transversely polarized target. We demonstrate the contribution to be larger for muons due to the lepton mass difference. Then we construct the corresponding beam-target double-spin asymmetries for the target polarized normal and parallel to the momentum transfer in the Breit frame, and then consider the model dependence of the calculation from the estimation of the $π^{0} μμ$ vertex. The contribution was found to be on the order of $\sim .15%$ for muons in the kinematic region of the MUSE experiment.
nucl-thhep-phPRC(2024)·1 citation
04
Estimation of the slope of nuclear symmetry energy via charge radii of mirror nuclei
Sakshi Gautam · Anagh Venneti · Sarmistha Banik · Bijay Agrawal
Charge radii of mirror nuclei are calculated by implementing pairing effects with the Hartree-Fock Bogoliubov approximation. Correlations between the difference of charge radii ( $Δ R_{c h}$ ) and slope of nuclear symmetry energy (L) are examined for different mirror nuclei pairs of varying masses using 40 different Skyrme energy density functionals. $Δ R_{c h} - L$ correlations are found to be robust for the binding constraints imposed on density functionals. We observe that $Δ R_{c h}$ and $L$ show better correlations in relatively heavier pairs than those obtained in the lighter pairs. Our calculations impose a constraint on the slope of nuclear symmetry energy as -20 MeV $\leq L \leq$ 55 MeV with 68\% confidence band using available measurements on charge radii. This is a moderately soft symmetry energy, in contrast to stiff and soft symmetry energy indicated by PREX-II and CREX measurements of neutron skin thickness in $^{208} P b$ and $^{48} C a$ , respectively. Our result is also in agreement with celestial constraints obtained from observational data for neutron stars.
nucl-thNPA(2024)·12 citations
05
Note on "Vacuum stability of a general scalar potential of a few fields"
Yisheng Song🇨🇳
The purpose of this letter is to point out that some conclusions in the paper (Eur. Phys. J. C {\bf 76}, 324(2016)) are incomplete, and to give complete and improved conclusions. The analytic necessary and sufficient conditions are given for the boundedness-from-below conditions of general scalar potentials of two real scalar fields $ϕ_{1}$ and $ϕ_{2}$ and the Higgs bonson $H$ .
↳ hep-phnucl-th0 citations
06
Spinning protons and gluons in the $η^{'}$
Steven D. Bass🇵🇱
The proton spin puzzle has inspired a vast programme of experiments and theoretical work challenging our understanding of QCD and its role in the structure of hadrons.The proton's internal spin structure is connected to chiral symmetry and, through gluon degrees of freedom in the flavour singlet channel, to the physics of the $η^{'}$ meson. Why do quarks contribute just about one third of the proton's spin? Why are $η^{'}$ mesons and their interactions so sensitive to gluonic degrees of freedom? We review the status of these topics and some key observables for forthcoming experiments.
↳ hep-phnucl-thInt.J.Mod.Phys.A(2024)·4 citations
07
Pseudoscalar mesons from a PNJL model at zero temperature
R. M. Aguirre🇦🇷 · O. Lourenço🇧🇷
We study pseudoscalar $π$ , $K$ and $η$ meson properties, such as masses and couplings, in dense matter at zero temperature. We use a recently proposed phenomenological quark model, known as the PNJL0, which takes into account the confinement/deconfinement phase transition by means of the traced Polyakov loop ( $Φ$ ) which serves as an order parameter at zero temperature. We consider two different scenarios, namely, symmetric quark matter with equal chemical potentials for all the flavors, and the beta equilibrated matter. In the latter case the hadron-quark phase transition is implemented by a two model approach. For the hadron side we use a relativistic mean-field model with density dependent couplings. We show that $Φ$ induces abrupt changes in the mesons properties with gap sizes regulated by the phenomenological gluonic sector of the model.
↳ hep-phnucl-thEPJC(2024)·1 citation
08
Interactions of the Pseudoscalar Meson Octet and the Baryon Decuplet in the Continuum and a Finite Volume
Teng Ji🇩🇪 · Xiang-Kun Dong🇩🇪 · Ulf-G. Meißner🇩🇪
This study focuses on the interaction of the pseudoscalar meson octet and the baryon decuplet. In the continuum, it is observed that several $J^{P} = \frac{3}{2}^{-}$ baryon resonances can be produced by the Weinberg-Tomozawa interaction in unitarized chiral perturbation theory, including the $N (1875)$ , $Σ (1670)$ , $Σ (1910)$ , $Ξ (1820)$ and $Ω (2012)$ . Among them, the $Ξ (1820)$ and $Σ (1670)$ may exhibit a potential two-pole structures. The unitarized chiral perturbation approach is then applied as the underlying theory to predict the energy levels of these systems in a finite volume. These energy levels are well described by the $K$ -matrix parameterization constrained by flavor SU(3) symmetry. With the parameters from the best fits, the poles extracted from the $K$ -matrix parameterization closely correspond to those derived from the underlying chiral effective field theory, as long as they are close to physical region and not significantly higher than the lowest relevant threshold.
↳ hep-phhep-exhep-latnucl-thEPJC(2024)·1 citation
09
Phenomenology of TMD parton distributions in Drell-Yan and $Z^{0}$ boson production in a hadron structure oriented approach
F. Aslan🇺🇸 · M. Boglione🇮🇹 · J. O. Gonzalez-Hernandez🇮🇹 · T. Rainaldi🇺🇸 · T. C. Rogers🇺🇸 · A. Simonelli🇺🇸
We present a first practical implementation of a recently proposed hadron structure oriented (HSO) approach to TMD phenomenology applied to Drell-Yan like processes, including lepton pair production at moderate $Q^{2}$ and $Z^{0}$ boson production. We compare and contrast general features of our methodology with other common practices and emphasize the improvements derived from our approach that we view as essential for applications where extracting details of nonperturbative transverse hadron structure is a major goal. These include the HSO's preservation of a basic TMD parton-model-like framework even while accounting for full TMD factorization and evolution, explicit preservation of the integral relationship between TMD and collinear pdfs, and the ability to meaningfully compare different theoretical models of nonperturbative TMD parton distributions. In our examples, we show that there is significant sensitivity at moderate $Q^{2}$ to both the form of the nonperturbative transverse momentum dependence and the parametrization of collinear parton densities. However, we also find that evolving to $Q^{2} = M_{Z}^{2}$ , without fitting, results in a satisfactory postdiction of existing data for $Z^{0}$ production, nearly independently of the modeling of nonperturbative transverse momentum behavior. We argue that this demonstrates that moderate $Q$ measurements should be given greater weight than high $Q$ measurements in extractions of nonperturbative transverse momentum dependence. We also obtain new extractions of the nonperturbative Collins-Soper kernel within the HSO approach. We discuss its features and compare with some earlier extractions.
↳ hep-phnucl-thPRD(2024)·30 citations
10
How far can we see back in time in high-energy collisions using charm hadrons?
Laszlo Gyulai🇭🇺 · Gabor Biro🇭🇺 · Robert Vertesi🇭🇺 · Gergely Gabor Barnafoldi🇭🇺
We use open charm production to estimate how far we can see back in time in high-energy hadron-hadron collisions. We analyze the transverse momentum distributions of the identified D mesons from pp, p--Pb and A--A collisions at the ALICE and STAR experiments covering the energy range from $s_{NN} = 200$ ~GeV up to 7~TeV. Within a non-extensive statistical framework, the common Tsallis parameters for D mesons represent higher temperature and more degrees of freedom than that of light-flavour hadrons. Assuming Bjorken-expansion, the production of D mesons corresponds to a significantly earlier proper time, $τ_{D} = (0.18 \pm 0.06) τ_{LF}$ .
↳ hep-phnucl-thJ.Phys.G(2024)·3 citations
11
The three-pion $K$ -matrix at NLO in ChPT
Jorge Baeza-Ballesteros (IFIC, Valencia)🇪🇸 · Johan Bijnens (Lund U.)🇸🇪 · Tomáš Husek (Charles U. and Birmingham U.)🇨🇿 · Fernando Romero-López (MIT)🇺🇸 · Stephen R. Sharpe (Washington U.)🇺🇸 · Mattias Sjö (Lund U. and CPT, Marseille)🇫🇷
The three-particle $K$ -matrix, $K_{df, 3}$ , is a scheme-dependent quantity that parametrizes short-range three-particle interactions in the relativistic-field-theory three-particle finite-volume formalism. In this work, we compute its value for systems of three pions in all isospin channels through next-to-leading order in Chiral Perturbation Theory, generalizing previous work done at maximum isospin. We obtain analytic expressions through quadratic order (or cubic order, in the case of zero isospin) in the expansion about the three-pion threshold.
↳ hep-phhep-latnucl-thJHEP(2024)·13 citations
12
Estimates of Lee-Yang zeros and a possible critical point on the pion condensate boundary in the QCD isospin phase diagram using an unbiased exponential resummation on the lattice
Sabarnya Mitra🇮🇳
Without invoking any cumulant determination at the input level, we present here the first calculations of direct estimates of the Lee-Yang zeros of QCD partition function in (2+1)-flavor QCD. These zeros are obtained in complex isospin chemical potential $μ_{I}$ plane using the unbiased exponential resummation formalism on $N_{τ} = 8$ lattices and with physical quark masses. For different temperatures, we illustrate the stability of the zeros closest to the origin from which, we subsequently procure the radius of convergence estimates. From the temperature-dependence study of the real and imaginary parts of these zeros, we try estimating one of the possible critical points forming the second order pion condensate critical line in the isospin phase diagram. Further, we compare these resummed estimates with the corresponding Mercer-Roberts estimates of the subsequent Taylor series expansions of the first three partition function cumulants. We also outline comparisons between resummed and Taylor series results of these cumulants for real and imaginary values of $μ_{I}$ and highlight the behavior of different expansion orders within and beyond the obtained resummed estimates of radius of convergence. We also re-establish that this resummed radius of convergence can efficiently capture the onset of overlap problem for finite real $μ_{I}$ simulations.
↳ hep-lathep-phnucl-exnucl-thPRD(2025)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE