Nuclear Theory·nucl-th

Wednesday·October 30, 2024

15 papers—6 primary·9 cross-listed

07
Determination of the strong coupling constant and the Collins-Soper kernel from the energy-energy correlator in $e^{+} e^{-}$ collisions
Zhong-Bo Kang🇺🇸 · Jani Penttala🇺🇸 · Congyue Zhang🇺🇸
We have conducted the first simultaneous global fit of the strong coupling constant $α_{s}$ and the Collins-Soper (CS) kernel using the energy-energy correlators (EEC) of $e^{+} e^{-}$ collisions in the back-to-back limit. This analysis, based on the transverse-momentum-dependent (TMD) factorization of EEC at next-to-next-to-next-to-leading logarithmic ( $N^{3} LL$ ) accuracy, yields $α_{s}$ consistent with the world average. We have tested two different parametrizations for the non-perturbative CS kernel and found both to align with results obtained from lattice QCD and fits on semi-inclusive deep inelastic scattering and Drell-Yan process.
↳ hep-phhep-exnucl-exnucl-th37 citations
08
Pi in the Sky: Neutron Stars with Exceptionally Light QCD Axions
Mia Kumamoto🇺🇸 · Junwu Huang🇨🇦 · Christian Drischler🇺🇸 · Masha Baryakhtar🇺🇸 · Sanjay Reddy🇺🇸
We present a comprehensive study of axion condensed neutron stars that arise in models of an exceptionally light axion that couples to quantum chromodynamics (QCD). These axions solve the strong-charge-parity (CP) problem, but have a mass-squared lighter than that due to QCD by a factor of $ε < 1$ . Inside dense matter, the axion potential is altered, and much of the matter in neutron stars resides in the axion condensed phase where the strong-CP parameter $θ = π$ and CP remains a good symmetry. In these regions, masses and interactions of nuclei are modified, in turn changing the equation of state (EOS), structure and phenomenology of the neutron stars. We take first steps toward the study of the EOS of neutron star matter at $θ = π$ within chiral effective field theory and use relativistic mean field theory to deduce the resulting changes to nuclear matter and the neutron star low-density EOS. We derive constraints on the exceptionally light axion parameter space based on observations of the thermal relaxation of accreting neutron stars, isolated neutron star cooling, and pulsar glitches, excluding the region up to $5 \times 1 0^{- 7} ≲ ε ≲ 0.2$ for $m_{a} ≳ 2 \times 1 0^{- 9} eV$ . We comment on potential changes to the neutron star mass-radius relationship, and discuss the possibility of novel, nuclear-density compact objects with $θ = π$ that are stabilized not by gravity but by the axion potential.
↳ hep-phastro-ph.HEnucl-thPRD(2025)·34 citations
09
Transverse Orbital Angular Momentum in the Proton
Osamah Alkasassbeh🇯🇴 · Abha Rajan🇺🇸 · Michael Engelhardt🇺🇸 · Simonetta Liuti🇺🇸
Using the equations of motion of QCD and Lorentz invariance relations, we show a new, more direct way of obtaining the decomposition of the proton's quark transverse angular momentum into its spin and orbital components. The new decomposition can be understood as a twist-three relation, with the quark transverse spin described by the parton distribution $g_{T}$ . We find that the orbital component can be expressed in terms of a moment in the quark transverse momentum, $k_{T}$ , of the generalized transverse momentum-dependent distribution $F_{12}$ , or alternatively in terms of the twist-three generalized parton distributions $H_{2 T}$ and $E_{2 T}$ .
↳ hep-phnucl-thPLB(2026)·1 citation
10
Probing the mass effect of heavy quark jets in high-energy nuclear collisions
Sa Wang🇨🇳 · Shuang Li🇨🇳 · Yao Li🇨🇳 · Ben-Wei Zhang🇨🇳 · Enke Wang🇨🇳
The production of heavy quark (HQ) jets provides a new arena to address the mass effect of jet quenching in heavy-ion physics. This paper presents a theoretical study of HQ jet yield suppression in Pb+Pb collisions at the LHC and focuses on the energy loss of HQ jets produced by different mechanisms. The p+p baseline is carried out by the SHERPA generator, and the jet-medium interactions are described by the SHELL transport model, which considers the elastic and inelastic partonic energy loss in the quark-gluon plasma (QGP). In p+p collisions, our numerical results indicate that the HQ jets from gluon splitting ( $g \to Q$ -jet) give the dominant contribution at high $p_{T}$ , and it shows more dispersive structures than the HQ-initiated one ( $Q \to Q$ -jet). In nucleus-nucleus collisions, our calculations are consistent with the inclusive and b-jet $R_{AA}$ recently measured by the ATLAS collaboration, which suggests a remarkable manifestation of the mass effect of jet energy loss. As a result of the dispersive substructure, the $g \to Q$ -jet will lose more energy than the $Q \to Q$ -jet in the QGP. Due to the significant contribution of $g \to c$ -jet, the $R_{AA}$ of c-jet will be comparable or even smaller than that of inclusive jet. To experimentally distinguish the $g \to Q$ -jet and $Q \to Q$ -jet, we propose the event selection strategies based on their topological features and test the performances. By isolating the $c \to c$ -jet and $b \to b$ -jet, the jets initiated by heavy quarks, we predict that the order of their $R_{AA}$ are in line with the mass hierarchy of energy loss. Future measurements on the $R_{AA}$ of $Q \to Q$ -jet and $g \to Q$ -jet will provide a unique chance to test the flavor/mass dependence of energy loss at the jet level.
↳ hep-phnucl-thCPC(2025)·5 citations
11
On the scalar $π K$ form factor beyond the elastic region
Frederic Noël🇨🇭 · Leon von Detten🇩🇪 · Christoph Hanhart🇩🇪 · Martin Hoferichter🇨🇭 · Bastian Kubis🇩🇪
Pion-kaon ( $π K$ ) final states, often appearing in heavy-particle decays at the precision frontier, are important for Standard-Model tests, to describe crossed channels with exotic states, and for spectroscopy of excited kaon resonances. We construct a representation of the $π K$ $S$ -wave form factor using the elastic $π K$ scattering phase shift via dispersion relations in the elastic region and extend this model into the inelastic region using resonance exchange, while maintaining unitarity and the correct analytic structure. As a first application, we successfully described the $τ \to K_{S} π ν_{τ}$ spectrum to not only achieve a better distinction between $S$ - and $P$ -wave contributions, but also to provide an improved estimate of the $C P$ asymmetry produced by a tensor operator as well as the forward-backward asymmetry, both of which can be confronted with future data at Belle II.
↳ hep-phhep-exnucl-thSciPost Phys.Proc.(2025)·0 citations
12
Constraining the hidden-charm pentaquark predictions and discriminating the $P_{c} (4440)$ and $P_{c} (4457)$ spins through the effective range expansion
Fang-Zheng Peng🇨🇳 · Li-Sheng Geng🇨🇳 · Ju-Jun Xie🇨🇳
The Weinberg compositeness criterion dictates that a pure shallow bound state is characterized by a large scattering length $a_{0} ≫ O (1/ β)$ and a positive effective range $r_{0}$ that naturally scales to the size of $O (1/ β)$ , where $1/ β$ signifies the interaction range. In constructing the contact-range effective field theory (EFT) up to the next-to-leading order to describe the pentaquarks $P_{c} (4312)$ , $P_{c} (4440)$ , and $P_{c} (4457)$ observed by the LHCb collaboration in 2019, we match the effective range $r_{0}$ at single-channel situation for these pentaquarks with the low-energy couplings within the EFT framework. Three different schemes are used to connect the couplings with the effective range. We find positive effective ranges $r_{0}$ of the natural size of $O (1/ β)$ for the spin configurations $J^{P} = \frac{3}{2}^{-}$ for $P_{c} (4440)$ and $J^{P} = \frac{1}{2}^{-}$ for $P_{c} (4457)$ within the molecular $D ˉ^{*} Σ_{c}$ description. Additionally, predictions from the power counting for low-energy couplings or Wilsonian coefficients suggest that, under heavy quark spin symmetry, the broad $P_{c} (4380)$ resonance, discovered by the LHCb collaboration in 2015, when considered as part of the single-channel $D ˉ^{(*)} Σ_{c}^{(*)}$ molecular system alongside $P_{c} (4312)$ , $P_{c} (4440)$ , and $P_{c} (4457)$ , has a mass of approximately $4376$ $MeV$ .
↳ hep-phnucl-thPRD(2025)·8 citations
13
Chiral perturbation theory
Ulf-G. Meißner🇩🇪
In the limit of vanishing up, down and strange quark masses, QCD exhibits a chiral symmetry. This symmetry is broken spontaneously to its vector subgroup, giving rise to Goldstone bosons. These acquire a small mass through the explicit chiral symmetry breaking for non-vanishing quark masses. The consequences of these broken symmetries can be investigated in a suitably tailored effective field theory called chiral pertubation theory. It admits a perturbative expansion in the external momenta and the Goldstone boson masses and can be systematically analyzed in terms of a loop expansion. The appearing ultraviolet divergences in loop diagrams can be dealt with order-by-order through the Goldstone boson contact interactions. Matter fields like the lowest-lying baryons can also included, leading to a rich and testable phenomenology of low-energy QCD.
↳ hep-phhep-exhep-thnucl-ex+1Encyclopedia of Particle Physics(2026)·10 citations
14
Rapid cooling of the Cassiopeia A neutron star due to superfluid quantum criticality
Hao-Fu Zhu🇨🇳 · Guo-Zhu Liu🇨🇳 · Xufen Wu🇨🇳
The rapid cooling of the neutron star in Cassiopeia A is speculated to arise from an enhanced neutrino emission caused by the onset of $^{3} P_{2}$ -wave neutron superfluidity in the core. However, the neutrino emissivity due to Cooper-pair breaking and formation is in tension with the requirements for explaining the observed cooling rate. Here, we show that such a rapid cooling can be explained once the non-Fermi liquid behavior of the non-superfluid neutron liquid induced by superfluid quantum criticality is included into the theoretical description of neutron star cooling, without assuming the existence of additional energy loss processes. Our results indicate that the neutron star in Cassiopeia A remains in the thermal relaxation stage, which is greatly prolonged by the non-Fermi liquid behavior. The good agreement between our theoretical results and recent observational cooling data points to the pivotal role played by superfluid quantum criticality in neutron stars.
↳ astro-ph.HEcond-mat.supr-connucl-thPLB(2026)·4 citations
15
Entanglement as a probe of hadronization
Jaydeep Datta🇺🇸 · Abhay Deshpande🇺🇸 · Dmitri E. Kharzeev🇺🇸 · Charles Joseph Naïm🇺🇸 · Zhoudunming Tu🇺🇸
Recently, it was discovered that the proton structure at high energies exhibits maximal entanglement. This leads to a simple relation between the proton's parton distributions and the entropy of hadrons produced in high-energy inelastic interactions that has been experimentally confirmed. In this letter, we extend this approach to the production of jets. Here, the maximal entanglement predicts a relation between the jet fragmentation function and the entropy of hadrons produced in jet fragmentation. We test this relation using the ATLAS Collaboration data on jet production at the Large Hadron Collider and find good agreement between the prediction based on maximal entanglement within the jet and the data. This study represents the first use of the quantum entanglement framework in the experimental study of the hadronization process, offering a new perspective on the transition from perturbative to non-perturbative QCD. Our results open the door to a more comprehensive understanding of the quantum nature of hadronization.
↳ hep-phhep-exnucl-exnucl-thPRL(2025)·28 citations

Affiliations

first authorsco-authorsvia INSPIRE