Nuclear Theory·nucl-th

Thursday·November 13, 2025

9 papers—4 primary·5 cross-listed

05
Analytical solution and Lie algebra of the relativistic Boltzmann equation
Yi Wang · Xuan Zhao · Zhe Xu · Jin Hu
In this work, we present a novel and more efficient approach to constructing the relativistic Bobylev, Krook, and Wu (BKW) solution [A. V. Bobylev, Sov. Phys. Dokl. 20, 820 (1976); M. Krook and T. T. Wu, Phys. Fluids 20, 1589 (1977)] of the relativistic Boltzmann equation. Introducing a new ansatz for the distribution function, we demonstrate that within this specific ansatz space, only the equilibrium and BKW-type forms yield exact solutions to the nonlinear Boltzmann equation. Furthermore, we also derive the Lie algebra of invariant transformations admitted by the relativistic Boltzmann equation and show that the corresponding symmetry group transformations can be systematically constructed from this algebra.
↳ nucl-thcond-mat.stat-mechhep-phhep-thPRD(2026)·2 citations
06
Isospin-breaking in the $π π$ scattering amplitude I: Effects due to the pion mass difference
Gilberto Colangelo🇨🇭 · Martina Cottini🇨🇭 · Jacobo Ruiz de Elvira🇪🇸
This is the first of a series of papers devoted to a detailed analysis of isospin-breaking effects in the $π π$ scattering amplitude and the vector form factor of the pion. Isospin breaking originates from the mass difference between up and down quarks and from electromagnetic effects. The latter can be further split into effects due to the pion-mass difference and the remaining virtual and real photonic effects. In this paper, we derive the modifications to the Roy equations for $π π$ scattering due to the mass difference between the charged and the neutral pion. We solve the equations numerically after matching them to the chiral representation of the $π π$ scattering amplitude evaluated in the same approximation, which is also provided. Numerical results are presented and discussed in detail.
↳ hep-phhep-exhep-latnucl-thJHEP(2026)·7 citations
07
Correlations between heavy mesons and the creation of the charmonia, bottomonia, and $B_{c}$ mesons in high energy $pp$ collisions
Jiaxing Zhao🇫🇷 · Joerg Aichelin🇫🇷 · Pol Bernard Gossiaux🇫🇷 · Klaus Werner🇫🇷
The different QCD processes, which can produce a heavy quark-antiquark ( $Q Q ˉ$ ) pair, induce different correlations between the heavy quarks. Employing the EPOS4HQ event generator we study the consequences of these correlations and compare the calculation with experimental results on open and hidden heavy flavour mesons, measured in proton-proton (pp) collisions at RHIC and LHC energies. We find that the measured correlations between heavy mesons are a direct image of the different production mechanisms, which contribute also in a different way to the transverse momentum distribution of open and hidden heavy flavour mesons. The latter are calculated in a Wigner density approach which also enables to reproduce quantitatively the measured $B_{c}$ spectra. This agreement allows conclusions on the spatial distribution of the heavy quark creation processes.
↳ hep-phnucl-thPRD(2026)·8 citations
08
The color force acting on a quark in the pion and nucleon
Wei-Yang Liu🇺🇸 · Edward Shuryak🇺🇸 · Ismail Zahed🇺🇸
In the Operator Product Expansion (OPE) of hard scattering amplitudes, the twist-3 operators describe local colored Lorentz forces acting on a quark, thereby providing a measure of the strength of the gluon fields. Its value is directly accessible from the nucleon twist-3 polarized $g_{2}$ -parton distribution function. In the semiclassical (instanton-based) QCD vacuum models, the leading non-perturbative contribution stems from correlated instanton-anti-instanton pairs, or molecules. We analyze the magnitude of the color force on a struck quark in light hadrons (pion and nucleon), in the context of the instanton liquid model (ILM). We derive explicitly the pertinent form factors associated with the color Lorentz force and show that they are intimately related to the pertinent hadronic gravitational and transversity form factors. Using the ILM enhanced by molecules, we detail the ensuing colored force distribution in the transverse plane for the luminal pions and nucleons. The results for the nucleons are in good agreement with those recently reported from a lattice collaboration.
↳ hep-phhep-lathep-thnucl-thPRD(2026)·4 citations
09
Strongly intensive quantities for rapidity correlations of multiplicities
Evgeny Andronov🇷🇺
Studies of the phase diagram of strongly interacting matter created in nuclear collisions are typically carried out using event-by-event fluctuations. Well-known way to disentangle statistical and dynamical fluctuations is to construct special observables named strongly intensive which are free from trivial volume fluctuations. Within the color string model behavior of the second-order strongly intensive quantity $Σ$ is completely determined by the two-particle correlation function from a single string and the string fusion mechanism. In this paper, we analyze third-order strongly intensive observable for forward-backward rapidity correlations and test its behavior within the PYTHIA8 model.
↳ hep-phnucl-th0 citations

Affiliations

first authorsco-authorsvia INSPIRE

Analytical solution and Lie algebra of the relativistic Boltzmann equation

Isospin-breaking in the ππ scattering amplitude I: Effects due to the pion mass difference

Correlations between heavy mesons and the creation of the charmonia, bottomonia, and Bc​ mesons in high energy pp collisions

The color force acting on a quark in the pion and nucleon

Strongly intensive quantities for rapidity correlations of multiplicities

Affiliations

Isospin-breaking in the $π π$ scattering amplitude I: Effects due to the pion mass difference

Correlations between heavy mesons and the creation of the charmonia, bottomonia, and $B_{c}$ mesons in high energy $pp$ collisions