arXiv subjects

G. Wolschin

Publications and source records attributed to G. Wolschin.

At least 19 recordsLinked to original sources

arXiv2026

In-medium Y(1S,2S,3S) suppression in Pb-Pb collisions at sqrt(s_NN)=5.02 TeV

We present model calculations for the in-medium suppression of the Y(1S,2S,3S) states in sqrt(s_NN)=5.02 TeV Pb-Pb collisions at the Large Hadron Collider in comparison with recent CMS data for all three spin-triplet s-wave states. The model parameters initial central temperature, and formation times for the Y(nS) states are determined in simultaneous chi^2 minimizations with respect to the data, such that the sequential centrality- and transverse-momentum-dependent suppression of the observed states is reproduced.

hep-ph↗

arXiv2025

Numerical solution of the nonlinear boson diffusion equation for gluons

The nonlinear boson diffusion equation is taken as a basis to account for the fast thermalization of gluons in the initial stages of relativistic heavy-ion collisions. For constant drift and diffusion coefficients with schematic initial conditions, this equation has previously been solved exactly. In order to achieve a more realistic time evolution towards thermalization, energy-dependent transport coefficients are introduced, requiring numerical solutions of the nonlinear equation. Their accuracy is tested against the exact analytical results in the limit of constant coefficients. The consequences for transient gluon-condensate formation through elastic scatterings in overoccupied systems are discussed.

hep-ph↗

arXiv2024

Spectral eigenfunction decomposition of a Fokker-Planck operator for relativistic heavy-ion collisions

A spectral solution method is proposed to solve a previuously developed non-equilibrium statistical model describing partial thermalization of produced charged hadrons in relativistic heavy-ion collisions, thus improving the accuracy of the numerical solution. The particle's phase-space trajectories are treated as drift-diffusion stochastic process, leading to a Fokker-Planck equation (FPE) for the single-particle probability distribution function. The drift and diffusion coefficients are derived from the expected asymptotic states via appropriate fluctuation-dissipation relations, and the resulting FPE is then solved numerically using a spectral eigenfunction decomposition. The calculated time-dependent particle distributions are compared to Pb-Pb data from the ATLAS and ALICE collaborations at the Large Hadron Collider.

hep-ph↗

arXiv2024

Time-dependent condensate formation in ultracold atoms with energy-dependent transport coefficients

Time-dependent Bose-Einstein condensate (BEC) formation in ultracold atoms is investigated in a nonlinear diffusion model. For constant transport coefficients, the model has been solved analytically. Here, we extend it to include energy-dependent transport coeffcients and numerically solve the nonlinear equation. Our results are compared with the earlier analytical model for constant transport coeffcients, and with recent deep-quench data for K-39 at various scattering lengths. Some non-physical predictions from the constant-coefficient model are resolved using energy-dependent drift and diffusion.

cond-mat.quant-gas↗

arXiv2024

Exact solution of the nonlinear boson diffusion equation for gluon scattering

An exact analytical solution of the nonlinear boson diffusion equation (NBDE) is presented. It accounts for the time evolution towards the Bose-Einstein equilibrium distribution through inelastic and elastic collisions in case of constant transport coefficients. As a currently interesting application, gluon scattering in relativistic heavy-ion collisions is investigated. An estimate of time-dependent gluon-condensate formation in overoccupied systems through number-conserving elastic scatterings in Pb-Pb collisions at relativistic energies is given.

nucl-th↗

arXiv2021

Time-dependent condensate fraction in an analytical model

We apply analytical solutions of a nonlinear boson diffusion equation (NBDE) that include boundary conditions at the singularity to calculate the time evolution of the entropy during evaporative cooling of ultracold atoms, and the time-dependent condensate fraction. For suitable initial conditions it is found to agree with available data on Na-23.

cond-mat.quant-gas↗

arXiv2021

Centrality dependence of limiting fragmentation

We investigate the centrality-dependent validity of the limiting-fragmentation hypothesis in relativistic heavy-ion collisions at energies reached at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). A phenomenological analysis of Au-Au and Pb-Pb collisions within a three-source relativistic diffusion model (RDM) is performed at sqrt(s_NN) = 19.6, 62.4, 130, 200, 2760 and 5023 GeV using four centrality cuts at each energy. Linear and nonlinear expressions for the rapidity drift function are tested and their physical relevance is discussed. Our results are compatible with the limiting-fragmentation conjecture for the investigated centralities in the full energy range. The number of particles in the fragmentation and fireball sources are found to depend on sqrt(s_NN) logarithmically and cubic-logarithmically, respectively.

hep-ph↗

arXiv2019

Solving a nonlinear analytical model for bosonic equilibration

An integrable nonlinear model for the time-dependent equilibration of a bosonic system that has been devised earlier is solved exactly with boundary conditions that are appropriate for a truncated Bose-Einstein distribution, and include the singularity at $ε= μ$. The buildup of a thermal tail during evaporative cooling, as well as the transition to the condensed state are accounted for. To enforce particle-number conservation during the cooling process with an energy-dependent density of states for a three-dimensional thermal cloud, a time-dependent chemical potential is introduced.

cond-mat.stat-mech↗

arXiv2019

Hot-medium effects on $Υ$ yields in pPb collisions at $\sqrt{s_\text{NN}}=8.16$ TeV

The respective contributions of cold-matter and hot-medium effects to the suppression of $Υ(1S)$ and $Υ(2S)$ mesons in pPb collisions at energies reached at the Large Hadron Collider (LHC) are investigated. Whereas known alterations of the parton density functions in the lead nucleus and coherent parton energy loss account for the leading fraction of the modifications in cold nuclear matter (CNM), the hot-medium (quark-gluon plasma, QGP) effects turn out to be relevant in spite of the small initial spatial extent of the fireball. We compare our transverse-momentum-, rapidity-, and centrality-dependent theoretical results for the $Υ$ suppression in pPb collisions at a center-of-mass energy of $\sqrt{s_\text{NN}} = 8.16$ TeV with recent LHCb and preliminary ALICE data from the Large Hadron Collider (LHC). Both cold-matter and hot-medium effects are needed to account for the data. The initial central temperature of the fireball is found to be $T_0 \simeq 460$ MeV.

hep-ph↗

arXiv2019

Limiting fragmentation at LHC energies

We investigate the validity of the limiting-fragmentation hypothesis in relativistic heavy-ion collisions at energies reached at the Large Hadron Collider (LHC). A phenomenological analysis of central AuAu and PbPb collisions based on a three-source relativistic diffusion model (RDM) is used to extrapolate pseudorapidity distributions of produced charged hadrons from RHIC to LHC energies into the fragmentation region. Data in this region are not yet available at LHC energies, but our results are compatible with the limiting-fragmentation conjecture in the full energy range sqrt(s_NN) = 19.6 GeV to 5.02 TeV.

hep-ph↗

arXiv2018

Equilibration in fermionic systems

The time evolution of a finite fermion system towards statistical equilibrium is investigated using analytical solutions of a nonlinear partial differential equation that had been derived earlier from the Boltzmann collision term. The solutions of this fermionic diffusion equation are rederived in closed form, evaluated exactly for simplified initial conditions, and applied to hadron systems at low energies in the MeV-range, as well as to quark systems at relativistic energies in the TeV-range where antiparticle production is abundant. Conservation laws for particle number including created antiparticles, and for the energy are discussed.

cond-mat.stat-mech↗

arXiv2018

Diffusion-model analysis of pPb and PbPb collisions at LHC energies

We present an analysis of centrality-dependent pseudorapidity distributions of produced charged hadrons in pPb and PbPb collisions at the LHC energy of sqrt{s_NN}=5.02 TeV, and of minimum-bias pPb collisions at 8.16 TeV within the nonequilibrium-statistical relativistic diffusion model (RDM). In a three-source approach, the role of the fragmentation sources is emphasized. Together with the Jacobian transformation from rapidity to pseudorapidity and the limiting fragmentation conjecture, these are essential for modeling the centrality dependence. For central PbPb collisions, a prediction at the projected FCC energy of sqrt{s_NN}=39 TeV is made.

hep-ph↗

arXiv2018

Examining nonextensive statistics in relativistic heavy-ion collisions

We show in detailed numerical solutions of the nonlinear Fokker-Planck equation (FPE) which has been associated with nonextensive q-statistics that the available data on rapidity distributions for stopping in relativistic heavy-ion collisions cannot be reproduced with any permitted value of the nonextensivity parameter (1 < q < 1.5). This casts doubt on the nonextensivity concept that is widely used in relativistic heavy-ion physics.

nucl-th↗

arXiv2017

Electromagnetic field effects on $Υ$-meson dissociation in PbPb collisions at LHC energies

We investigate the effect of the electromagnetic field generated in relativistic heavy-ion collisions on the dissociation of $Υ$ mesons. The electromagnetic field is calculated using a simple model which characterizes the emerging quark-gluon plasma (QGP) by its conductivity only. A numerical estimate of the field strength experienced by $Υ$ mesons embedded in the expanding QGP and its consequences on the $Υ$ dissociation is made. The electromagnetic field effects prove to be negligible compared to the established strong-interaction suppression mechanisms.

hep-ph↗

arXiv2017

In-Medium Y-Suppression and Feed-down in UU and PbPb Collisions

The suppression of Y mesons in the hot quark-gluon medium (QGP) versus reduced feed-down is investigated in UU collisions at RHIC energies and PbPb collisions at LHC energies. Our centrality- and p_T-dependent model encompasses screening, collisional damping and gluodissociation in the QGP. For Y(1S) it is in agreement with both STAR and CMS data provided the relativistic Doppler effect and the reduced feed-down from the Y(nS) and chi_b(nP) states are properly considered. At both energies, most of the Y(1S) suppression is found to be due to reduced feed-down, whereas most of the Y(2S) suppression is caused by the hot-medium effects. The role of the latter increases with energy. The p_T-dependence is flat due to the relativistic Doppler effect and reduced feed-down. We predict the Y(1S)-suppression in PbPb at sqrt(s_NN) = 5.02 TeV.

hep-ph↗

arXiv2015

Analysis of pPb collisions at LHC energies in the relativistic diffusion model

Particle production sources in pPb collisions at LHC energies are investigated in pseudorapidity space as functions of centrality. The nonequilibrium-statistical relativistic diffusion model (RDM) with three sources is applied to the analysis of preliminary charged-hadron distributions measured by the ATLAS and ALICE collaborations in pPb collisions at 5.02 TeV. The size of the midrapidity source relative to the fragmentation sources in pPb collisions is considered as function of centrality, and incident energy. At LHC energies particle production from the mid-rapidity gluon-gluon source is larger than that from the fragmentation sources at all centralities. Conclusions regarding the statistical equilibration process are drawn.

hep-ph↗

arXiv2013

The influence of the Chi_b(3P) state on the decay cascade of bottomium in PbPb collisions at LHC energies

We investigate the decay cascade of the Upsilon(nS) meson including the newly found Chi_b(3P) state in pp and PbPb collisions at LHC energies. The main goal is to quantitatively determine the additional suppression of the Upsilon(nS) states in PbPb collisions relative to pp at LHC energies of sqrt(s_NN) = 2.76 TeV when the Chi_b(3P) state is included together with the Upsilon(nS) and Chi_b(1P,2P) states. It is found that the suppression of Upsilon(1S) in PbPb collisions relative to pp is increased by at most 7% through the inclusion of Chi_b(3P), whereas the suppression factors for the Upsilon(2S) and Upsilon(3S) states do not change significantly.

hep-ph↗

arXiv2005

Local thermalization in d + Au collisions

The extent of a locally equilibrated parton plasma in d + Au collisions at sqrt(s_NN) = 200 GeV is investigated as a function of centrality in a nonequilibrium-statistical framework. Based on a three-sources model, analytical solutions of a relativistic diffusion equation are in precise agreement with recent data for charged-particle pseudorapidity distributions. The moving midrapidity source indicates the size of the local thermal equilibrium region after hadronization. In central d + Au collisions it contains 19% of the produced particles.

hep-ph↗