arXiv subjects

Georg Wolschin

Publications and source records attributed to Georg Wolschin.

At least 19 recordsLinked to original sources

arXiv2026

Particle production in $p$-O collisions at LHC energy

We compare our previous predictions for charged-hadron production in p-O collisions at an energy of sqrt(s_NN)=9.618 TeV as published in 2025 with preliminary Run 3 data from ALICE and adapt the model parameters to the data. Our three-source model comprises a gluon-gluon central source and two valence-quark soft-gluon fragmentation sources. We describe the initial conditions using color-glass-condensate states and calculate the time-dependent partial thermalization with a relativistic diffusion model. An inversion of the maximum production amplitude at larger pseudorapidities from backward to forward towards peripheral collisions is predicted.

hep-ph↗

arXiv2025

Time-dependent condensation of bosonic dysprosium

We investigate thermalization and time-dependent Bose-Einstein condensate formation in ultracold Dy-164 using a nonlinear boson diffusion equation. As compared to alkali atoms such as K-39 or Rb-87, the strong magnetic dipole interaction modifies the scattering-length dependence of the transport coefficients that govern thermalization and condensate formation. A prediction for the time-dependent condensate fraction in Dy-164 is made.

cond-mat.quant-gas↗

arXiv2025

Quark-model search for compact $c\bar c uds$ pentaquark states

A potential quark model is used to search for a $P_{c\bar{c}s}^0=(c\bar{c}uds)^0$, $J^P=1/2^-$ pentaquark state that has recently been observed experimentally by the LHCb collaboration at 4338.2 MeV, with a width of 7.0 MeV and high statistical significance $>15σ$. Our model Hamiltonian reproduces the masses of the low-lying charmed and strange hadrons. We use the Gaussian expansion method {to solve the} five-body Schrödinger equation. Employing the real scaling method {including} the relevant meson-baryon thresholds explicitly, sharp resonances are distinguished from the meson-baryon scattering states. We incorporate new color states of the color-octet meson and baryon configurations as well as the color-singlet configurations for the five-quark states. We find no $ J^P=1/2^-$ resonance close to the observed state, and also none in the $ J^P=3/2^-$ state. This increases the likelihood that $P^0_{c\bar{c}s}$ is a $Ξ_c\bar{D}$ hadronic molecule rather than a compact state.

hep-ph↗

arXiv2025

Predictions for charged-hadron production in $p$-O collisions at LHC energies

We present predictions for centrality-dependent charged-hadron production in p-O collisions at top LHC energies based on a nonequilibrium-statistical relativistic diffusion model. Colour-glass condensate initial conditions are used in a three-sources momentum-space model for gluon-gluon, quark-gluon and gluon-quark sources. Our results are to be compared with forthcoming Run3 pseudorapidity distributions for sqrt(s_NN)=9.618 TeV p-O collisions.

hep-ph↗

arXiv2024

Relativistic diffusion model for hadron production in p-Pb collisions at the LHC

We investigate charged-hadron production in relativistic heavy-ion collisions of asymmetric systems within a nonequilibrium-statistical framework. Calculated centrality-dependent pseudorapidity distributions for p-Pb collisions at sqrt(s_NN)=5.02 and 8.16 TeV are compared with data from the Large Hadron Collider (LHC). Our approach combines a relativistic diffusion model with formulations based on quantum chromodynamics while utilizing numerical solutions of a Fokker-Planck equation to account for the shift and broadening of the fragmentation sources for particle-production with respect to the stopping (net-baryon) rapidity distributions. To represent the centrality dependence of charged-hadron production in asymmetric systems over a broad region of pseudorapidities, the consideration and precise modelling of the fragmentation sources - along with the central gluon-gluon source - is found to be essential. Specifically, this results in an inversion of the particle-production amplitude from backward- to forward-dominance when transitioning from central to peripheral collisions, in agreement with recent ATLAS and ALICE p-Pb data at sqrt(s_NN)=5.02 TeV.

hep-ph↗

arXiv2024

Partial Ly$α$ thermalization in an analytic nonlinear diffusion model

During recombination, the cosmic background radiation is disturbed, in particular, by Lyman-alpha emissions from neutral hydrogen. It is proposed to account for the subsequent time-dependent partial thermalization of the Lyman-alpha energy content in an analytically solvable nonlinear diffusion model. The amplitude of the partially thermalized and redshifted Ly-$α$ line is found to be too low to be visible in the cosmic microwave spectrum, in accordance with previous numerical models and Planck observations.

astro-ph.CO↗

arXiv2024

Cylindrically symmetric diffusion model for relativistic heavy-ion collisions

A relativistic diffusion model with cylindrical symmetry, which propagates an initial state based on quantum chromodynamics in time towards a thermal equilibrium limit, is derived from nonequilibrium-statistical considerations: Adapting an existing framework for Markovian stochastic processes representing relativistic phase-space trajectories, a Fokker-Planck equation is obtained for the time evolution of particle-number distribution functions with respect to transverse and longitudinal rapidity. The resulting partially-evolved distribution functions are transformed to transverse-momentum and pseudorapidity space, and compared with charged-hadron data from the CERN Large Hadron Collider (LHC).

hep-ph↗

arXiv2023

Limiting fragmentation in heavy-ion stopping?

Based on a nonequilibrium-statistical relativistic diffusion model that is consistent with quantum chromodynamics (QCD), we investigate baryon stopping in relativistic heavy-ion collisions at SPS, RHIC, and LHC energies. The net-proton rapidity distributions of the individual fragments exhibit a scaling behaviour similar to limiting fragmentation (LF) that is related to geometric scaling in the colour-glass condensate (CGC) and depends upon the gluon saturation scale. Forward-angle net-proton data at energies reached at the LHC are required to verify the prediction.

hep-ph↗

arXiv2022

Time-dependent condensation of bosonic potassium

We calculate the time-dependent formation of Bose--Einstein condensates (BECs) in potassium vapours based on a previously derived exactly solvable nonlinear boson diffusion equation (NBDE). Thermalization following a sudden energy quench from an initial temperature $T_\mathrm{i}$ to a final temperature $T_\mathrm{f}$ below the critical value and BEC formation are accounted for using closed-form analytical solutions of the NBDE. The time-dependent condensate fraction is compared with available $^{39}$K data for various scattering lengths.

cond-mat.quant-gas↗

arXiv2022

Nonlinear diffusion of fermions and bosons

A nonlinear diffusion equation is proposed to account for thermalization in fermionic and bosonic systems through analytical solutions. For constant transport coefficients, exact time-dependent solutions are derived through nonlinear transformations, and the corresponding local equilibration times are deduced. Fermi-Dirac and Bose-Einstein distributions emerge as stationary solutions of the nonlinear equation. As examples, local thermalization of quarks and gluons in relativistic heavy-ion collisions, and of ultracold atoms including time-dependent Bose-Einstein condensate formation are discussed.

hep-ph↗

arXiv2022

Nonlinear diffusion of gluons

It is proposed to consider the fast thermalization of gluons in relativistic heavy-ion collisions as a diffusion process in momentum space. Closed-form analytical solutions of a nonlinear boson diffusion equation (NBDE) with constant drift and diffusion coefficients v, D and boundary conditions at the singularity are derived. The time evolution towards local central temperatures T< 600 MeV through inelastic gluon scatterings in heavy-ion collisions is calculated for under- and overoccupied systems in the full momentum range. The results are consistent with QCD-based numerical calculations for gluon thermalization via inelastic gluon collisions.

hep-ph↗

arXiv2020

Bottomonium spectroscopy in the quark-gluon plasma

The spectroscopic properties of heavy quarkonia are substantially different in the quark-gluon plasma (QGP) that is created in relativistic heavy-ion collisions as compared to the vacuum situation that can be tested in pp collisions at the same center-of-mass energy. In this article, a series of recent works about the dissociation of the Y(nS) and chi_b(nP) states in the hot QGP is summarized. Quarkonia dissociation occurs due to (1) screening of the real quark-antiquark potential, (2) collisional damping through the imaginary part of the potential, and (3) gluon-induced dissociation. In addition, reduced feed-down plays a decisive role for the spin-triplet ground state. Transverse-momentum and centrality-dependent data are well reproduced in Pb-Pb collisions at LHC energies. In the asymmetric p-Pb system, alterations of the parton density functions in the lead nucleus account for the leading fraction of the modifications in cold nuclear matter (CNM), but the hot-medium effects turn out to be relevant in spite of the small initial spatial extent of the fireball, providing additional evidence for the generation of a quark-gluon droplet.

hep-ph↗

arXiv2020

Baryon stopping as a relativistic Markov process in phase space

We reconsider baryon stopping in relativistic heavy-ion collisions in a nonequilibrium-statistical framework. The approach combines earlier formulations based on quantum chromodynamics with a relativistic diffusion model through a suitably derived fluctuation-dissipation relation, thus allowing for a fully time-dependent theory that is consistent with QCD. We use an existing framework for relativistic stochastic processes in spacetime that are Markovian in phase space, and adapt it to derive a Fokker-Planck equation in rapidity space, which is solved numerically. The time evolution of the net-proton distribution function in rapidity space agrees with stopping data from the CERN Super Proton Synchrotron and the BNL Relativistic Heavy Ion Collider.

nucl-th↗

arXiv2020

Aspects of relativistic heavy-ion collisions

The rapid thermalization of quarks and gluons in the initial stages of relativistic heavy-ion collisions is treated using analytic solutions of a nonlinear diffusion equation with schematic initial conditions, and for gluons with boundary conditions at the singularity. On a similarly short time scale of $t \le1$ fm/$c$, the stopping of baryons is accounted for through a QCD-inspired approach based on the parton distribution functions of valence quarks, and gluons. Charged-hadron production is considered phenomenologically using a linear relativistic diffusion model with two fragmentation sources, and a central gluonic source that rises with $\ln^3(s_{NN})$. The limiting-fragmentation conjecture that agrees with data at energies reached at the Relativistic Heavy Ion Collider (RHIC) is found to be consistent with Large Hadron Collider (LHC) data for Pb-Pb at $\sqrt{s_{NN}}= 2.76$ and $5.02$ TeV. Quarkonia are used as hard probes for the properties of the quark-gluon plasma (QGP) through a comparison of theoretical predictions with recent CMS, ALICE and LHCb data for Pb-Pb and p-Pb collisions.

hep-ph↗

arXiv2020

Time-dependent entropy of a cooling Bose gas

Exact analytic solutions of a nonlinear boson diffusion equation with suitable initial conditions that account for evaporative cooling of ultracold atoms, plus boundary conditions at the singularity $ε=μ<0$ are presented, and used to calculate the time-dependent entropy of a cold quantum gas.

cond-mat.quant-gas↗

arXiv2019

Local equilibration of fermions and bosons

Local kinetic equilibration is a prerequisite for hydrodynamics to be valid. Here it is described through a nonlinear diffusion equation for finite systems of fermions and bosons. The model is solved exactly for constant transport coefficients in both cases. It has the proper Fermi-Dirac and Bose-Einstein equilibrium limits and can replace the relaxation-time approximation (RTA). The microscopic transport coefficients are determined through the macroscopic variables temperature and local equilibration time. Applications to the transverse energy of quarks and gluons in the initial stages of central relativistic heavy-ion collisions, and to bosonic and fermionic atoms at low energies appropriate for cold quantum gases are discussed.

cond-mat.quant-gas↗

arXiv2018

Equilibration in finite Bose systems

The equilibration of a finite Bose system is modelled using a gradient expansion of the collision integral that leads to a nonlinear transport equation. For constant transport coefficients, it is solved in closed form through a nonlinear transformation. Using schematic initial conditions, the exact solution and the equilibration time are derived and compared to the corresponding case for fermions. Applications to the equilibration of the gluon system created initially in relativistic heavy-ion collisions, and to cold quantum gases are envisaged.

hep-ph↗

arXiv2016

Beyond the thermal model in relativistic heavy-ion collisions

Deviations from thermal distribution functions of produced particles in relativistic heavy-ion collisions are discussed as indicators for nonequilibrium processes. The focus is on rapidity distributions of produced charged hadrons as functions of collision energy and centrality which are used to infer the fraction of produced particles from a central fireball as compared to the one from the fragmentation sources that are out of equilibrium with the rest of the system. Overall thermal equilibrium would only be reached for large times t -> infinity.

hep-ph↗