Nuclear Theory

Bandeira, Yan B.; Goncalves, Victor P.; Schäfer, Wolfgang

doi: 10.48550/arxiv.2411.12675pmid: N/A

Abstract:The cross-section for the associated production of a jet with an electroweak gauge boson ($G = W^{\pm}, Z^0, \gamma$) at forward rapidities in $pp$ and $pA$ collisions is derived within the color - dipole $S$ - matrix framework. We present the full expressions for the differential cross-section of the $q p \rightarrow G q X$ process in the transverse momentum space, considering the longitudinal and transverse polarizations of the gauge boson. We demonstrate that the final formulae can be expressed in terms of the unintegrated gluon distribution and reproduce previous results for the associated jet + $\gamma$ and jet + $Z^0$ production, derived using other frameworks. Moreover, we derive the back - to - back correlation limit of the spectra and show that it can be expressed in terms of the unpolarized and linearly polarized transverse momentum gluon distributions. Our results improve the description of the inclusive jet plus color neutral particle production at forward rapidities, not far from the proton fragmentation region, in $pp$ or $pA$ collisions, and are the main ingredient to study the impact of nonlinear QCD effects in two - particle correlations.

Gavassino, Lorenzo

doi: 10.1103/physrevd.111.l081306pmid: N/A

Abstract:Radiation is a universal friction-increasing agent. When two fluid layers are in relative motion, the inevitable exchange of radiation between such layers gives rise to an effective force, which tries to prevent the layers from sliding. This friction is often modeled as a Navier-Stokes shear viscosity. However, non-Newtonian corrections are expected to appear at distances of about one optical depth from the layers' interface. Such corrections prevent the viscous stress from becoming too large. Here, we set the foundations of a rigorous theory for these corrections, valid along incompressible flows. We show that, in the linear regime, the infinite Chapman-Enskog series can be computed analytically, leading to universal formulas for all transport coefficients, which apply to any fluid, with any composition, with radiation of any type (also neutrinos), and with nearly any type of radiative process. We then show that, with an appropriate shear-heat coupling coefficient, Israel-Stewart theory can correctly describe most non-Newtonian features of radiative shear stresses.

Qian, Wenyang; Li, Meijian; Salgado, Carlos A.; Kreshchuk, Michael

doi: 10.1103/physrevd.111.096001pmid: N/A

Abstract:Quark and gluon jets provide one of the best ways to probe the matter produced in ultrarelativistic high-energy collisions, from cold nuclear matter to hot quark-gluon plasma. In this work, we propose a unified framework for efficient quantum simulation of many-body dynamics using the (3+1)-dimensional QCD Hamiltonian on the light front, particularly suited for studying the scattering of quark and gluon jets on nuclear matter in heavy-ion collisions. We describe scalable methods for mapping physical degrees of freedom onto qubits and for simulating in-medium jet evolution. We then validate our framework by implementing an algorithm that directly maps second-quantized Fock states onto qubits and uses Trotterized simulation for simulating time dynamics. Using a classical emulator, we investigate the evolution of quark and gluon jets with up to three particles in Fock states, extending prior studies. These calculations enable the study of key observables, including jet momentum broadening, particle production, and parton distribution functions.

Kobyakov, Dmitry; Viñas, Xavier

doi: 10.48550/arxiv.2411.17303pmid: N/A

Abstract:Within the liquid drop model built up with the nuclear interaction parametrization Sk$\chi$450, which is based on the chiral effective field theory, we calculate numerically the internal energy density for each of nuclear pasta phases and for the uniform nuclear matter. We provide quantitative arguments in favor of coexistence of various nuclear matter phases at a significant range of total pressure within the inner crust of neutron stars, a concept known as crystal polymorphism. Specifically, we find that differences of the internal energy per baryon for various phases are typically less than the thermal energy per a freedom degree at temperature about $10^8$--$10^9$ K, which sets the energetic scale for thermal fluctuations of state of Fermi liquid from the ground state. The nuclear energy contributions are described using the same parametrization Sk$\chi$450 for the bulk, plain surface and curvature terms. We find that the introduction of the curvature correction changes the ground state in a relevant way. This may be understood as a consequence of the corresponding change in size of the nucleus, which significantly modifies the phase transition densities. Using the calculated structural parameters from liquid drop model, we explore the physical consequences of the expected Cooper pairing of protons in lasagna phase. In this case, we find a crossover between the discreet layered and the three-dimensional anisotropic regimes of superconductivity. Additionally, we study the magnetic stress in lasagna accounting for a rotational lag between superfluid neutrons and the crystal lattice, which is believed to develop naturally in pulsars and magnetars. Our results offer a preliminary insight into rich magnetic properties of the inner crust of neutron stars.

Faraday, Coleridge; Horowitz, W. A.

doi: 10.1016/j.physletb.2025.139437pmid: N/A

Abstract:We present quantitative predictions for the nuclear modification factor in both small and peripheral systems from a pQCD-based energy loss model that is constrained by light- and heavy-flavor suppression data from central heavy-ion collisions. We find nearly identical suppression for central $p / d + A$ collisions as for peripheral $A + A$ collisions, quantitatively consistent with the measured 20% suppression of neutral pions produced in $d + \mathrm{Au}$ collisions by PHENIX, but dramatically inconsistent with the measured 20% enhancement of charged hadrons produced in $p + \mathrm{Pb}$ collisions by ATLAS. We demonstrate that this equivalence of central small system suppression and peripheral large system suppression is insensitive to the underlying energy loss model.

Ambrus, Victor E.; Schlichting, Sören; Werthmann, Clemens

doi: 10.48550/arxiv.2411.19709pmid: N/A

Abstract:Exploiting the first measurements of the same ion species in OO collisons at RHIC and LHC, we propose an observable to distinguish whether collective behavior builds up through a hydrodynamic expansion of a strongly interacting QGP or few final state re-scatterings. Our procedure allows to disentangle the effects of the initial state geometry and the dynamical response mechanism on anisotropic flow. We validate its ability to discriminate between systems with different interaction rates using results from event-by-event simulations in kinetic theory.

Mäntysaari, Heikki; Penttala, Jani; Salazar, Farid; Schenke, Björn

doi: 10.1103/physrevd.111.054033pmid: N/A

Abstract:Within the Color Glass Condensate effective field theory, we assess the importance of including a finite size for the target on observables sensitive to small-$x$ evolution. To this end, we study the Balitsky-Kovchegov (BK) equation with impact-parameter dependence in the initial condition. We demonstrate that neglecting the dependence on the impact parameter can result in overestimated saturation effects for protons, while it has little effect for heavy nuclei at the energies available at current experiments. When fixing the nonperturbative parameters to the energy dependence of the exclusive $J/\psi$ photoproduction cross section with proton targets, predictions for lead targets are not sensitive to the applied running-coupling prescription, the scheme chosen to resum large transverse logarithms in the BK equation, or the infrared regulator in the evolution.

Song, Taesoo; Zhao, Jiaxing; Grishmanovskii, Ilia

doi: 10.48550/arxiv.2411.07383pmid: N/A

Abstract:Heavy quark mass in QGP is related to the heavy quark potential at a large distance. In this study we test three different heavy quark potentials, namely, the free energy, the internal energy of the heavy quark pair in QGP, and the unscreened potential, which was recently proposed by the HotQCD Collaboration, through the thermal production of charm quarks in heavy-ion collisions at the LHC. We find that the free energy potential overestimates charm production in heavy-ion collisions at the LHC, while the unscreened potential produces results closest to the experimental data from the ALICE Collaboration among the three potentials.

Sogabe, Noriyuki; Yin, Yi

doi: 10.1103/physrevlett.134.171903pmid: 40408732

Abstract:We explore the interplay between Berry curvature and topological properties in single-flavor color superconductors, where quarks form spin-one Cooper pairs. By deriving a new relation, we connect the topological nodal structure of the gap function in momentum space to the (nonabelian) Berry flux associated with paired quarks. This generalizes the early work by Li and Haldane [Phys. Rev. Lett. 120, 067003 (2018)] to systems with additional internal quantum numbers, such as color. In the ultrarelativistic limit, we uncover rich topological structures driven by the interplay of spin, chirality, and color. Specifically, we identify chirality-induced topological nodes in the transverse (opposite chirality pairing) polar and A phases. In contrast, the color-spin-locking phase lacks these nodes due to a nontrivial color Berry flux, which in turn induces gapless excitations with total Berry monopole charges of $\pm 3/2-$differing from conventional Weyl fermions. Our findings can be potentially extended to other fermionic systems carrying additional internal degrees of freedom.

Shvedov, Leonid; Burrello, Stefano; Colonna, Maria; Zheng, Hua

doi: 10.48550/arxiv.2411.07159pmid: N/A

Abstract:We investigate the pre-equilibrium dipole response in the charge-asymmetric reaction $^{40}$Ca+$^{152}$Sm, of recent experimental interest, at several beam energies within the range $[5, 11]$ AMeV and different collision centralities. By employing Skyrme-like effective interactions for the nuclear mean field, we probe the role of the different ingredients performing theoretical calculations based on the time-dependent Hartree-Fock approach or a semi-classical transport model that also includes two-body correlations. A comparative analysis between these approaches allowed us to disentangle the role of deformation effects in the entrance channel from the ones associated with structure details of genuine quantal nature on the dipole emission. Moreover, we also investigate the impact of the occurrence of residual two-body collisions on the reaction dynamics. This study contributes to the understanding of the microscopic processes that determine the complex dynamics of low-energy heavy-ion collisions along the fusion-fission path, which is relevant to super-heavy element synthesis, unraveling interesting connections with the characteristics of the nuclear effective interaction and the associated equation of state.