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Khusniddin K. Olimov

Publications and source records attributed to Khusniddin K. Olimov.

At least 19 recordsLinked to original sources
arXiv2026

Kinetic freeze-out and diffusion dynamics in small-system asymmetric collisions at sqrt(sNN)=200 GeV in light of a generalized Fokker-Planck distribution

A generalized Fokker-Planck solution is used to examine the transverse momentum ($p_{T}$) spectra of neutral pions generated in small-system asymmetric collisions, $p$-Al, $p$-Au, $d$-Au, and $^3$He-Au, at $\sqrt{s_{NN}}=200$ GeV. This framework provides a cohesive explanation of particle production over a broad range of transverse momenta. We extract the energy scale governing the transition between a thermal and a hard regime, the effective temperature ($T$), and the exponents determining the high-momentum falloff from fits to PHENIX data. $T$ increases systematically with the collision centrality and colliding system size, ranging from about 0.33 GeV in peripheral $p$-Al collisions to 0.45 GeV in central $^3$He-Au collisions. This increase is correlated with the average number of participant nucleons, $ $, and the charged-particle pseudorapidity density, $ $, indicating that larger and more central collisions create a denser, more strongly interacting medium that freezes out at a higher temperature. The acquired transition scale and power-law exponents follow consistent patterns across systems and centralities, revealing details about the sharpness of the transition from thermal to hard processes, and the relative strength of momentum-space diffusion versus drag. Interestingly, when the gold target dominates the collision geometry in the largest system ($^3$He-Au), the transition scale becomes nearly independent of centrality, signifying saturation of the diffusion process. Our findings demonstrate that the generalized Fokker-Planck solution is a sensitive probe of transport properties and non-extensive dynamics in the quark-gluon plasma produced even in small-system relativistic collisions, and it consistently describes pion spectra in this set of collisions.

hep-ph↗
arXiv2026

Valence quark-stopping and gluon junction-stopping scenarios in electron-nucleus collisions at the forthcoming Electron-Ion Collider: Which one is correct?

In the current literature, two stopping scenarios are being discussed in the context of high-energy collisions: the valence quark scenario and the gluon or baryon junction scenario. In the valence quark-stopping scenario, three valence quarks each contribute one-third of the baryon number within a baryon. Conversely, in the gluon junction-stopping scenario, the gluon junction is responsible for carrying the entire baryon number. At present, there is no consensus regarding which type of stopping scenario is correct. Based on a multi-source thermal model, our investigation indicates that the experimental data analyzed in both previous and present studies suggest that the valence quark-stopping scenario is more suitable for semi-quantitative discussions in high-energy collisions. It is anticipated that this scenario can be further validated through electron-nucleus ($eA$) collisions at the forthcoming Electron-Ion Collider (EIC).

hep-ph↗
arXiv2026

Fragmentation of Nuclear Remnants in Electron-Nucleus Collisions at High Energy as a Nonextensive Process

Utilizing a partitioning method based on equal (or unequal) probabilities -- without incorporating the alpha-cluster ($α$-cluster) model -- allows for the derivation of diverse topological configurations of nuclear fragments resulting from fragmentation. Subsequently, we predict the multiplicity distribution of nuclear fragments for specific excited nuclei, such as $^9$Be$^*$, $^{12}$C$^*$, and $^{16}$O$^*$, which can be formed as nuclear remnants in electron-nucleus ($eA$) collisions at high energy. Based on the $α$-cluster model, an $α$-cluster structure may result in deviations in the multiplicity distributions of nuclear fragments with charge $Z=2$, compared to those predicted by the partitioning methods. Furthermore, in the framework of Tsallis statistics, the nonextensive generalized temperature, entropy index, and $q$-entropy are obtained from the multiplicity distribution of nuclear fragments with given charge number. Our work shows that fragmentation of nuclear remnants in electron-nucleus collisions at high energy is a nonextensive process.

nucl-th↗
arXiv2026

Extraction of Effective Parameters from Transverse Momentum Spectra of Heavy Quarkonia in Proton-Proton Collisions at the LHC

The effective string tension ($κ$) in the Schwinger mechanism and the effective temperature ($T$) in Bose-Einstein statistics are extracted from the transverse momentum ($p_T$) spectra of heavy quarkonia produced in proton-proton (p+p) collisions at the Large Hadron Collider (LHC). Here, $T$ derived from the heavy quarkonium $p_T$ spectra also serves as the initial effective temperature (effective temperature at the initial stage) of small collision systems. This is because, despite the absence of quark-gluon plasma (QGP) formation during the collisions, which leaves $T$ largely unaffected by QGP-related effects, the initial geometric asymmetry and local partonic thermalization still induce radial and transverse flows, thereby contributing to an increase in $T$. The effective parameters ($κ$ and $T$) are obtained by fitting the experimental $p_T$ spectra of $J/ψ$ and $Υ(nS)$ ($n=1$, 2, and 3) within various rapidity intervals, produced in p+p collisions at center-of-mass energies of $\sqrt{s}=13$ and 8 TeV, as measured by the LHCb Collaboration. It is found that the multi-component distribution structured within the framework of the Schwinger mechanism or Bose-Einstein statistics can effectively describe the heavy quarkonium $p_T$ spectra in small collision systems. With decreasing rapidity in the forward region, both $κ$ and $T$ increase, indicating a directly proportional relationship between them. Based on $κ$, the average minimum strong force radius of participant quarks is determined.

hep-ph↗
arXiv2025

Comparing effective temperatures in standard and Tsallis distributions from transverse momentum spectra in small collision systems

The transverse momentum ($p_T$) spectra of identified light charged hadrons, specifically bosons ($π^{\pm}$ and $K^{\pm}$) as well as fermions [$p(\bar p)$], produced in small collision systems, namely deuteron-gold (d+Au) and proton-proton (p+p) collisions at the top energy of the Relativistic Heavy Ion Collider (RHIC) with a center-of-mass energy of $\sqrt{s_{NN}}=200$ GeV, are investigated in this paper. In present study, d+Au collisions are categorized into three centrality classes: central (0--20\%), semi-central (20--40\%), and peripheral (40--100\%) collisions. Various types of distributions, including standard [Bose-Einstein (Fermi-Dirac) and Boltzmann] and Tsallis distributions, are employed to fit the same $p_T$ spectra to derive different effective temperatures denoted as $T_{eff}$. The results indicate that $T_{eff}$ values obtained from Bose-Einstein, Boltzmann, Fermi-Dirac, and Tsallis distributions exhibit systematically a decreasing trend. Meanwhile, these $T_{eff}$ values also show a decreasing trend with a decrease in collision centrality. Furthermore, based on the spectra of given particles, a perfect linear relationship is observed between different pairwise combinations of $T_{eff}$ derived from both Boltzmann and Bose-Einstein (Fermi-Dirac) distributions as well as between Tsallis and Bose-Einstein (Fermi-Dirac) distributions.

hep-ph↗
arXiv2025

A hybrid model for multi-particle production and multi-fragment emission in electron-nucleus collisions at the forthcoming Electron-Ion Collider

To present a prediction of the multi-particle production and multi-fragment emission in electron-nucleus ($eA$) collisions at the forthcoming Electron-Ion Collider (EIC), a simple hybrid model which is based on the multi-source thermal model and the ideal gas model is proposed in this article. According to the hybrid model, some statistical laws such as the two-component Erlang distribution and others are presented, which means a two-source production. These statistical laws are hopeful to describe the bulk properties of multiple particles produced in the scattering of electron-nucleon ($eN$) and multiple fragments emitted in the fragmentation of excited residual nucleus. Although both the scattering and fragmentation can occur in $eA$ collisions at the EIC, their two-sources are different. In $eN$ scattering, the multiple particles come from the soft excitation and hard scattering processes respectively, which are classified as two different types of events. In nuclear fragmentation, the multiple fragments come from the cold and hot sources which exist in the same excited nucleus.

hep-ph↗
arXiv2025

On the Square Speed of Sound in High-Energy Collisions: Range of Values and How to Understand It

After reviewing the sound speeds in various forms and conditions of matter, we investigate the sound speed of hadronic matter that has decoupled from the hot and dense system formed during high-energy collisions. We comprehensively consider factors such as energy loss of the incident beam, rapidity shift of leading nucleons, and the Landau hydrodynamic model for hadron production. The sound speed is related to the width or standard deviation of the Gaussian rapidity distribution of hadrons. The extracted square speed of sound lies within a range from 0 to 1/3 in most cases. For scenarios exceeding this limit, we also provide an explanation.

hep-ph↗
arXiv2025

On Extracting Thermal Parameters and Scenario in High-Energy Collisions

In this minireview article, we examine the inconsistent results of thermal parameters derived from various models in high-energy collisions. Through a comprehensive literature review and based on the average transverse momentum or the root-mean-square transverse momentum, we propose model-independent parameters to address these inconsistencies. The relevant parameters include: the initial temperature, the effective temperature, the kinetic freeze-out temperature, and the average transverse velocity. Our findings indicate that these four parameters are larger in central collisions, within central rapidity regions, at higher energies, and in larger collision systems. As collision energy increases, excitation functions for all four parameters rise rapidly (slowly) within ranges below (above) approximately 7.7 GeV. At higher energies (>39) GeV, fluctuations occur in trends for these excitation functions, with only slight changes observed in their growth rates. Additionally, this work reveals a mass-dependent multi-temperature scenario pertaining to both initial states and kinetic freeze-out processes.

hep-ph↗
arXiv2024

Comparing effective temperatures in standard, Tsallis, and q-dual statistics from transverse momentum spectra of identified light charged hadrons produced in gold--gold collisions at RHIC energies

This study investigates the transverse momentum ($p_T$) spectra of identified light charged hadrons produced in gold--gold (Au+Au) collisions across various centrality classes at center-of-mass energies per nucleon pair, $\sqrt{s_{NN}}$, ranging from 7.7 to 200 GeV, as measured by the STAR Collaboration at the Relativistic Heavy Ion Collider (RHIC). The analysis employs standard (Bose-Einstein/Fermi-Dirac), Tsallis, and q-dual statistics to fit the same $p_T$ spectra and derive distinct effective temperatures: $T_{\text{Standard}}$, $T_{\text{Tsallis}}$, and $T_{\text{q-dual}}$. In most instances, there exists an approximately linear relationship or positive correlation between $T_{\text{Tsallis}}$ and $T_{\text{Standard}}$, as well as between $T_{\text{q-dual}}$ and $T_{\text{Standard}}$, when considering $T_{\text{Standard}}$ as a baseline. However, while both $T_{\text{Tsallis}}$ and $T_{\text{q-dual}}$ increase from semi-central to central Au+Au collisions at 62.4 GeV and 200 GeV, where QGP is expected, changes in $T_{\text{Standard}}$ occur more gradually. This work suggests that $T_{\text{Standard}}$ is better suited for characterizing phase transitions between hadronic matter and QGP compared to $T_{\text{Tsallis}}$ or $T_{\text{q-dual}}$, primarily due to the considerations related to entropy index in the Tsallis and q-dual statistics.

nucl-ex↗
arXiv2024

Extracting Kinetic Freeze-out Properties in High Energy Collisions Using a Multi-source Thermal Model

We study the transverse momentum ($p_T$) spectra of neutral pions and identified charged hadrons produced in proton--proton ($pp$), deuteron--gold ($d$--Au), and gold--gold (Au--Au) collisions at the center of mass energy $\sqrt{s_{NN}}=200$ GeV. The study is made in the framework of a multi-source thermal model used in the partonic level. It is assumed that the contribution to the $p_T$-value of any hadron comes from two or three partons with an isotropic distribution of the azimuthal angle. The contribution of each parton to the $p_T$-value of a given hadron is assumed to obey any one of the standard (Maxwell-Boltzmann, Fermi-Dirac, and Bose-Einstein) distributions with the kinetic freeze-out temperature and average transverse flow velocity. The $p_T$-spectra of the final-state hadrons can be fitted by the superposition of two or three components. The results obtained from our Monte Carlo method are used to fit the experimental results of the PHENIX and STAR Collaborations. The results of present work serve as a suitable reference baseline for other experiments and simulation studies.

hep-ph↗
arXiv2023

Thermodynamic and hydrodynamic characteristics of interacting system formed in relativistic heavy ion collisions

To study the energy-dependent characteristics of thermodynamic and hydrodynamic parameters, based on the framework of a multi-source thermal model, we analyze the soft transverse momentum ($p_{T}$) spectra of the charged particles ($π^{-}$, $π^{+}$, $K^{-}$, $K^{+}$, $\bar{p}$, and $p$) produced in gold-gold (Au-Au) collisions at the center-of-mass energies $\sqrt{s_{NN}}=7.7$, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV from the STAR Collaboration and in lead-lead (Pb-Pb) collisions at $\sqrt{s_{NN}}=2.76$ and 5.02 TeV from the ALICE Collaboration. In the rest framework of emission source, the probability density function obeyed by meson momenta satisfies the Bose-Einstein distribution, and that obeyed by baryon momenta satisfies the Fermi-Dirac distribution. To simulate the $p_{T}$ of the charged particles, the kinetic freeze-out temperature $T$ and transverse expansion velocity $β_{T}$ of emission source are introduced into the relativistic ideal gas model. Our results, based on the Monte Carlo method for numerical calculation, show a good agreement with the experimental data. The excitation functions of thermodynamic parameter $T$ and hydrodynamic parameter $β_{T}$ are then obtained from the analyses, which shows an increase tendency from 7.7 GeV to 5.02 TeV in collisions with different centralities.

hep-ph↗
arXiv2023

Rapidity and Energy Dependences of Temperatures and Volume Extracted from Identified Charged Hadron Spectra in Proton-Proton Collisions at a Super Proton Synchrotron (SPS)

The standard (Bose-Einstein/Fermi-Dirac or Maxwell-Boltzmann) distribution from the relativistic ideal gas model is used to study the transverse momentum ($p_{T}$) spectra of identified charged hadrons ($π^-$, $π^+$, $K^-$, $K^+$, $\bar p$, and $p$) with different rapidities produced in inelastic proton-proton ($pp$) collisions at the Super Proton Synchrotron (SPS). The experimental data measured by the NA61/SHINE Collaboration at the center-of-mass (c.m.) energies $\sqrt{s}=6.3$, 7.7, 8.8, 12.3, and 17.3 GeV are fitted well by the distribution. It is shown that the effective temperature ($T_{eff}$ or $T$), kinetic freeze-out temperature ($T_{0}$), and initial temperature ($T_{i}$) decrease with the increase in rapidity and increase with the increase in c.m. energy. The kinetic freeze-out volume ($V$) extracted from the $π^-$, $π^+$, $K^-$, $K^+$, and $\bar p$ spectra decreases with the rapidity and increase with the c.m. energy. The opposite tendency of $V$, extracted from the $p$ spectra, is observed to be increasing with the rapidity and decreasing with the c.m. energy due to the effect of leading protons.

hep-ph↗
arXiv2023

Multi-source thermal model describing multi-region structure of transverse momentum spectra of identified particles and parameter dynamics of system evolution in relativistic collisions

In this article, the multi-region structure of transverse momentum ($p_T$) spectra of identified particles produced in relativistic collisions is studied by the multi-component standard distribution (the Boltzmann, Fermi-Dirac, or Bose-Einstein distribution) in the framework of a multi-source thermal model. Results are interpreted in the framework of string model phenomenology in which the multi-region of $p_T$ spectra corresponds to the string hadronization in the cascade process of string breaking. The contributions of the string hadronizations from the first-, second-, and third-, i.e., last-generations of string breakings mainly form high-, intermediate-, and low-$p_T$ regions, respectively. From the high- to low-$p_T$ regions, the extracted volume parameter increases rapidly, and temperature and flow velocity parameters decrease gradually. The multi-region of $p_T$ spectra reflects the volume, temperature, and flow velocity dynamics of the system evolution. Due to the successful application of the multi-component standard distribution, this work reflects that the simple classical theory can still play a great role in the field of complex relativistic collisions.

hep-ph↗
arXiv2023

Excitation functions of related temperatures of η and η0 emission sources from squared momentum transfer spectra in high-energy collisions

The squared momentum transfer spectra of $η$ and $η^0$, produced in high-energy photon-proton ($γp$) $\rightarrow η(η^0)+p$ processes in electron-proton ($ep$) collisions performed at CEBAF, NINA, CEA, SLAC, DESY, and WLS are analyzed. The Monte Carlo calculations are used in the analysis of the squared momentum transfer spectra, where the transfer undergoes from the incident $γ$ to emitted $η(η^0)$ or equivalently from the target proton to emitted proton. In the calculations, the Erlang distribution and Tsallis-Levy function are used to describe the transverse momentum ($p_T$) spectra of emitted particles. Our results show that the average transverse momentum ($\langle p_T\rangle$), the initial-state temperature ($T_i$), and the final-state temperature ($T_0$) roughly decrease from the lower center-of-mass energy ($W$) to the higher one in the concerned energy range of a few GeV, which is different from the excitation function from heavy-ion collisions in the similar energy range.

hep-ph↗
arXiv2022

Random statistical analysis of transverse momentum spectra of strange particles and dependence of related parameters on centrality in high energy collisions at the LHC

We have studied the transverse momentum ($p_T$) spectra of the final-state strange particles, including $K^{\pm}$, $ϕ$, $\itΞ$, and $\itΩ$, produced in high energy lead-lead (Pb-Pb), proton-lead ($p$-Pb), xenon-xenon (Xe-Xe) collisions at the Large Hadron Collider (LHC). Taking into account the contribution of multi-quark composition, whose probability density distribution is described by the modified Tsallis-Pareto-type function, we simulate the $p_T$ spectra of the final-state strange particles by a Monte Carlo method, which is shown to be in good agreement with the experimental data in most the cases. The kinetic freeze-out parameters are obtained. The present method provides a new tool for studying the spectra of various particles produced in high energy collisions, reflecting more realistically the collision process, which is of great significance to study the formation and properties of the produced particles.

hep-ph↗
arXiv2022

Particle species and energy dependencies of freeze-out parameters in high-energy proton-proton collisions

We used blast wave model with Tsallis statistics to analyze the experimental data measured by ALICE Collaboration in proton-proton collisions at Large Hadron Collider and extracted the related parameters (kinetic freeze-out temperature, transverse flow velocity and kinetic freeze-out volume of emission source) from transverse momentum spectra of the particles. We found that the kinetic freeze-out temperature and kinetic freeze-out volume are mass dependent. The former increase while the latter decrease with the particle mass which is the evidence of a mass as well as volume differential kinetic freeze-out scenario. Furthermore we extracted the mean transverse momentum and initial temperature by an indirect method and observed that they increase with mass of the particles. All the above discussed parameters are observed to increase with energy. Triton ($t$), hyper-triton (${^3_{\barΛ} H}$) and helion (${^3 He}$) and their anti-matter are observed to freeze-out at the same time due to isospin symmetry.

hep-ph↗
arXiv2022

Thermal freeze-out parameters and pseudo-entropy from charged hadron spectra in high energy collisions

We collected the transverse momentum (mass) spectra of charged hadrons ($π^{-}$, $π^{+}$, $K^{-}$, $K^{+}$, $\overline{p}$, and $p$) produced in collisions over a center-of-mass energy range from 2.70 to 200 GeV (per nucleon pair). The modified Tsallis--Pareto-type function (the TP-like function) with average transverse flow velocity is used to describe the contribution of participant or constituent quarks to transverse momentum of considered hadron. The experimental spectra of $π^{\mp}$ and $K^{\mp}$ (or $\overline{p}$ and $p$) are fitted by the convolution of two (or three) TP-like functions due to the fact that two (or three) constituent quarks are regarded as two (or three) energy resources in the formation of considered hadron. From the reasonable fits to the spectra, the thermal freeze-out parameters are extracted, and the pseudo-entropy is newly defined and extracted. Some parameters quickly change in the energy range of less than 7.7 GeV, and slowly change in the energy range of greater than 7.7 GeV, indicating the variation of collision mechanism at around 7.7 GeV.

hep-ph↗
arXiv2022

An energy independent scaling of transverse momentum spectra of direct (prompt) photons from two-body processes in high-energy proton-proton collisions

Transverse momentum spectra of direct (prompt) photons from two-body processes in high-energy proton-proton (p+p) collisions are analyzed in this paper. We collected the experimental invariant cross-sections at mid-rapidity in p+p collisions measured by the UA6, CCOR, R806, R110, PHENIX, NA24, CMS, ALICE, and ATLAS Collaborations over a center-of-mass energy range from 24.3 GeV to 13 TeV. In fitting the data, we used different kinds of functions which include the revised Tsallis--Pareto-type function (the TP-like function) at the particle level, the convolution of two TP-like functions at the quark level, and the root-sum-of-squares of two revised Tsallis-like functions in which the quark chemical potentials $μ_i=μ_B/3$ or $μ_i=0$, where $μ_B$ is the baryon chemical potential. We have extracted the values of three main free parameters: the effective temperature $T$, power index $n_0$ (or entropy index $q$), and correction index $a_0$. After analyzing the changing trends of the parameters, we found that $T$, $q$, and $a_0$ increase and $n_0$ decreases with the increase of collision energy. Based on the analyses of transverse momentum spectra, an energy independent scaling, i.e. the $x_T$ scaling, is obtained.

hep-ph↗