Nuclear Theory·nucl-th

Friday·September 8, 2023

10 papers—2 primary·8 cross-listed

03
Tetraquark mass relations in quark and diquark models
Muhammad Naeem Anwar🇬🇧 · Timothy J. Burns🇬🇧
We present new linear relations among the masses of S-wave tetraquarks with either one flavour ( $QQ Q ˉ Q ˉ$ ) or two ( $QQ q ˉ q ˉ$ ). Because the relations are sensitive to the hidden-colour, spin, and spatial degrees of freedom, comparison to experimental data can help to reveal the internal structure of tetraquarks, and discriminate among different theoretical models. Depending on the model, the relations are either exact, or valid in perturbation theory, and a thorough comparison with existing literature confirms their validity at the MeV level. Additionally, we explore the connections among tetraquark models, and show how those with effective (quark or diquark) masses are related to dynamical potential models. We also show how the spectrum of diquark models is effectively a limiting case of (more general) quark models, and in particular, that the diquark concept is most relevant in the particular combination $QQ q ˉ q ˉ$ , where $Q$ is much heavier than $q ˉ$ .
↳ hep-phhep-exhep-latnucl-thPLB(2023)·10 citations
04
Diffusion in superfluid Fermi mixtures: General formalism
Oleg A. Goglichidze · Mikhail E. Gusakov
With neutron star applications in mind, we developed a theory of diffusion in mixtures of superfluid, strongly interacting Fermi liquids. By employing the Landau theory of Fermi liquids, we determined matrices that relate the currents of different particle species, their momentum densities, and the partial entropy currents to each other. Using these results, and applying the quasiclassical kinetic equation for the Bogoliubov excitations, we derived general expressions for the diffusion coefficients, which properly incorporate all the Fermi liquid effects and depend on the momentum transfer rates between different particle species. The developed framework can be used as a starting point for systematic calculations of the diffusion coefficients (as well as other kinetic coefficients) in superfluid Fermi mixtures, particularly, in superfluid neutron stars.
↳ astro-ph.HEcond-mat.quant-gasnucl-thPRC(2023)·5 citations
05
On the definition of fragmentation functions and the violation of sum rules
John Collins🇺🇸 · Ted Rogers🇺🇸
We point out a problem with the formulation and derivations of sum rules for quark fragmentation functions that impacts their validity in QCD, but which potentially points toward an improved understanding of final states in inclusive hard processes. Fragmentation functions give the distribution of final-state hadrons arising from a parton exiting a hard scattering, and the sum rules for momentum, electric charge, etc express conservation of these quantities. The problem arises from a mismatch between the quark quantum numbers of the initial quark and the fact that all observed final-state hadrons are confined bound states with color zero. We point that, in a confining theory like QCD, the Wilson line in the operator definition of a fragmentation function entails that the final state in a fragmentation function includes a bound state in the external field generated by the Wilson line. We justify this with the aid of general features of string hadronization. The anomalous bound states are restricted to fractional momentum $z = 0$ . They tend to invalidate sum rules like the one for charge conservation when applied to the fragmentation functions inferred from experimental data, but not the momentum sum rule. We propose to exploit our ideas in future studies as a way to relate the ffs extracted from inclusive cross sections to more detailed non-perturbative descriptions of final state hadronization. We also describe scenarios wherein the traditional sum rules might remain approximately valid with a reasonably high degree of accuracy.
↳ hep-phhep-thnucl-thPRD(2024)·22 citations
06
Charmonium production in hot magnetized hyperonic matter -- effects of baryonic Dirac sea and pseudoscalar-vector meson mixing
Amruta Mishra🇮🇳 · Arvind Kumar🇮🇳 · S. P. Misra🇮🇳
We investigate the medium modifications of the masses of pseudoscalar open charm ( $D$ and $D ˉ$ ) mesons and the charmonium state ( $ψ (3770)$ ) in hot isospin asymmetric strange hadronic medium in the presence of an external magnetic field within a chiral effective model. The in-medium partial decay widths of $ψ (3770)$ to $D D ˉ$ mesons are computed from the in-medium masses of the initial and final state mesons. These are computed using two light quark pair creation models - (I) the $^{3} P_{0}$ model and (II) a field theoretical (FT) model of composite hadrons with quark (and antiquark) constituents. The production cross-sections of $ψ (3770)$ , arising from scattering of the $D$ and $D ˉ$ mesons, are computed from the relativistic Breit-Wigner spectral function expressed in terms of the in-medium masses and the decay widths of the charmonium state. The effects of the magnetic field are considered due to the Dirac sea (DS) of the baryons, the mixing of the pseudoscalar and vector meson (PV mixing) and the Landau level contributions for the charged hadrons. The production cross-sections of $ψ (3770)$ arising due to scattering of $D^{+} D^{-} (D^{0} D ˉ^{0})$ mesons in the hot magnetized strange hadronic matter are observed to have distinct peak positions, when the magnetic field is large, due to the mass difference of the transverse and longitudinal components of $ψ (3770)$ , arising from PV mixing. These can have observable consequences on the dilepton spectra and the production of the charm mesons in ultra-relativistic peripheral heavy ion collision experiments, where the produced magnetic field is huge.
↳ hep-phnucl-thPRD(2024)·17 citations
07
Search for nonextensivity in electron-proton interactions at $s$ = 300 GeV
Soumya Sarkar🇮🇳 · R. Aggarwal🇮🇳 · M. Kaur🇮🇳
Study of canonical entropy in electron-proton interactions at $s$ = 300 GeV is presented. The precision data collected by the H1 experiment at the HERA in different ranges of invariant hadronic mass $W$ and the squared four-momentum exchange $Q^{2}$ in $e p$ interactions have been analyzed in the ensemble theory approach. The canonical partition function relates to the multiplicity distribution which is often studied in collider experiments. We use the canonical ensemble partition function to explore the dynamics of hadron production in $e p$ interactions by devising different methods to find the entropic parameter and the collision temperature. The inverse slope of the transverse momentum spectrum of produced hadrons also relates to the temperature. In the recent past, the CMS, ATLAS and ALICE experiments at the LHC have studied the charged hadron transverse momentum and particle distributions in proton-proton and proton-nucleus interactions by using the Tsallis function within this approach. A detailed investigation into the role of the system volume and relation amongst different dynamical parameters reveals interesting results.
↳ hep-phnucl-thPRD(2024)·1 citation
08
Anomalies in Particle Physics
Andreas Crivellin🇨🇭 · Bruce Mellado🇿🇦
The currently accepted mathematical description of the fundamental constituents and interactions of matter is the Standard Model of particle physics. Its last missing particle, the famous Higgs boson, was observed at the Large Hadron Collider at CERN in 2012. However, it is clear that the Standard Model cannot be the ultimate theory of Nature, and e.g. cannot account for Dark Matter or non-vanishing neutrino masses (and does not include gravity). In fact, searches for physics beyond the SM have been intensified since the Higgs boson discovery. In this article, we review the hints for new physics, called ``anomalies'', obtained in particle physics experiments within the last years. We consider both direct high-energy searches for new resonances at the LHC and indirect low-energy precision experiments. These anomalies range from the nuclear scale (approximately the mass of the proton) to the electroweak scale (i.e. the mass of the Higgs boson) to the TeV scale (the highest scale directly accessible at the LHC), therefore spanning over four orders of magnitude. After discussing the experimental and theoretical status of the anomalies, we summarize possible explanations in terms of new particles and new interactions. In particular, new Higgs bosons and leptoquarks are promising candidates. Discovery prospects and implications for future colliders are discussed.
↳ hep-phhep-exhep-lathep-th+1Nature Rev.Phys.(2024)·88 citations
09
A novel approach to the global analysis of proton form factors in elastic electron-proton scattering
Craig McRae🇨🇦 · P. G. Blunden🇨🇦
We present a novel method for the global analysis of elastic electron-proton scattering when combining data sets from experiments with different overall normalization uncertainties. The method is a modification of one employed by the NNPDF collaboration in the fitting of parton distribution data. This method is an alternative to the 'penalty trick' method traditionally employed in global fits to proton electric and magnetic form factors, while avoiding the biases inherent in that approach. We discuss issues that arise when extending the method to nonlinear models. For data with $Q^{2} > 1$ GeV $^{2}$ we find relatively minor differences to traditional model fits when the normalization uncertainties from different experiments are correctly accounted for. We discuss implications of this method for the well-known discrepancy between the form factor ratio $G_{E} / G_{M}$ extracted from the Rosenbluth and polarization transfer techniques.
↳ hep-phnucl-exnucl-thPRC(2024)·4 citations
10
Rapid neutron star cooling triggered by dark matter
Afonso Ávila🇵🇹 · Edoardo Giangrandi🇵🇹 · Violetta Sagun🇵🇹 · Oleksii Ivanytskyi🇵🇱 · Constança Providência🇵🇹
We study the effect of asymmetric fermionic dark matter (DM) on the thermal evolution of neutron stars (NSs). No interaction between DM and baryonic matter is assumed, except the gravitational one. Using the two-fluid formalism, we show that DM accumulated in the core of a star pulls inwards the outer baryonic layers of the star, increasing the baryonic density in the NS core. As a result, it significantly affects the star's thermal evolution by triggering an early onset of the direct Urca process and modifying the photon emission from the surface caused by the decrease of the radius. Thus, due to the gravitational pull of DM, the direct Urca process becomes kinematically allowed for stars with lower masses. Based on these results, we discuss the importance of NS observations at different distances from the Galactic center. Since the DM distribution peaks towards the Galactic center, NSs in this region are expected to contain higher DM fractions that could lead to a different cooling behavior.
↳ astro-ph.HEgr-qchep-phnucl-thMNRAS(2024)·29 citations

Affiliations

first authorsco-authorsvia INSPIRE