Search Results (42)

The blast-wave model with Boltzmann–Gibbs statistics is used to examine the transverse momentum spectra of ${K\ast }^0$ mesons generated at the Relativistic High-Energy Collider (RHIC) Beam Energies with mid-rapidity ($\left|y\right|<1$) in symmetric $Au-Au$ collisions. There is a clear correlation between the extracted kinetic freeze-out temperature ($T_0$) and transverse flow velocity (${\beta }_T$) in various collision centralities and center-of-mass energies ($\sqrt{s_{NN}}$). Since a larger initial energy density delays freeze-out and a shorter system lifetime limits cooling, $T_0$ is directly proportional to both $\sqrt{s_{NN}}$ and peripheral collisions. On the other hand, ${\beta }_T$ drops in peripheral symmetric collisions due to weaker collective expansion, while it rises with $\sqrt{s_{NN}}$ because of larger pressure gradients. The concurrence between the thermal and collective energy components in the expanding fireball is reflected in the obvious anti-correlation between $T_0$ and ${\beta }_T$. These findings support hydrodynamic predictions and offer important new information about QGP’s freeze-out behavior. Full article

In ultra-relativistic heavy-ion collisions, the study of muons from kaon (K) and pion ($\pi$) decays provides insights into hadron production and propagation in the Quark–Gluon Plasma (QGP). This paper investigates muon yields from K and $\pi$ decays in Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV using a fast simulation method. We employ a fast Monte Carlo procedure to estimate muon yields from charged kaons and pions. The simulation involves generating pions and kaons with uniform $p_{\mathrm{T}}$ and y distributions, simulating their decay kinematics via PYTHIA, and reweighting to match the physical spectra. Our results show the transverse momentum distributions of muons from K and $\pi$ decays at forward rapidity ($2.5<y<4.0$) for different centrality classes. The systematic uncertainties are primarily from the mid-rapidity charged K/$\pi$ spectra and rapidity-dependent $R_{\mathrm{AA}}$ uncertainties. The muon yields from pion and kaon decays exhibit consistency across centrality classes in the $p_{\mathrm{T}}$ range of 3–10 GeV/c. This study contributes to understanding hadronic interactions and decay kinematics in heavy-ion collisions, offering references for investigating pion and kaon decay channels and hot medium effects. Full article

This study presents the investigation of freezeout parameters, namely the kinetic freezeout temperature (T) and transverse flow velocity (${\beta }_T$), in different centrality intervals with fixed as well as with variable flow profile ($n_0$) in the blast-wave model (using Boltzmann Gibbs statistics). The model is used to fit the experimental data of transverse momentum spectra of ${\pi }^{+}$, $K^{+}$, and p in $Au$–$Au$ and $Pb$–$Pb$ collisions at 200 GeV and 2.76 TeV, respectively. In our observation, when the parameter $n_0$ is considered as a free parameter, the parameter T decreases from head-on to peripheral collisions, while it increases towards the periphery if $n_0$ is fixed. In addition, parameter ${\beta }_T$ decreases from central to peripheral collisions in both cases. These findings provide valuable insights into the dynamics of quark-gluon plasma formation and expansion in high-energy nuclear collisions. Moreover, the kinetic freezeout temperature T and the transverse flow velocity ${\beta }_T$ are mass-dependent; while the former becomes larger for massive particles, the latter becomes larger for light particles, showing the mass differential kinetic freezeout scenario. Full article

The strange baryon production in Bi + Bi collisions at $\sqrt{s_{NN}}=9.0$ GeV is studied using the PHSD transport model. Hyperon and anti-hyperon yields, transverse momentum spectra, and rapidity spectra are calculated, and their centrality dependence and the effect of rapidity and transverse momentum cuts are studied. The rapidity distributions for $\overline{\mathsf{\Lambda }}$, $\mathsf{\Xi }$, $\overline{\mathsf{\Xi }}$ baryons are found to be systematically narrower than for $\mathsf{\Lambda }$s. The $p_T$ slope parameters for anti-hyperons vary more with centrality than those for hyperons. Restricting the accepted rapidity range to $\left|y\right|<1$ increases the slope parameters by 13–30 MeV, depending on the centrality class and the hyperon mass. Hydrodynamic velocity and vorticity fields are calculated, and the formation of two oppositely rotating vortex rings moving in opposite directions along the collision axis is found. The hyperon spin polarization induced by the medium vorticity within the thermodynamic approach is calculated, and the dependence of the polarization on the transverse momentum and rapidity cuts and on the centrality selection is analyzed. The cuts have stronger effect on the polarization of $\mathsf{\Lambda }$ and $\mathsf{\Xi }$ hyperons than on the corresponding anti-hyperons. The polarization signal is maximal for the centrality class, 60–70%. We show that, for the considered hyperon polarization mechanism, the structure of the vorticity field makes an imprint on the polarization signal as a function of the azimuthal angle in the transverse momentum plane, ${\varphi }_H$, $cos{\varphi }_H=p_x/p_T$. For particles with positive longitudinal momentum, $p_z>0$, the polarization increases with $cos{\varphi }_H$, while for particles with $p_z<0$ it decreases. Full article

This study explores the inelastic doubly differential transverse momentum spectra of the primary charged particles, $({\pi }^{+}+{\pi }^{-})$, $(K^{+}+K^{-})$ and $\left(p\overline{p}\right)$, as a function of observables associated with underlying event (UE) at $\sqrt{s}=13TeV$. The particle production is measured on the basis of different angular regions like toward, transverse and away, elucidated with respect to the direction of leading particle of an event. To study the thermal freeze-out parameters, the non-extensive Tsallis distribution function is used to extract the temperature $T_{eff}$ and chemical potential $\mu$, which provide a basis to explain the QCD matter. The Tsallis distribution function describes transverse momentum spectra in pseudorapidity region of $\left|\eta \right|<0.8$. It is observed that effective temperature $T_{eff}$ changes from away to towards and forward region. Full article

In the first few microseconds after the Big Bang, the hot dense matter was in the form of quark–gluon plasma consisting of free quarks and gluons. By colliding heavy nuclei at RHIC and LHC at a velocity close to the speed of light, we were able to recreate primordial matter and observe that matter after expansion and cooling. In the present work, we have analyzed the transverse-momentum spectra of charged particles in high-multiplicity $\mathit{pp}$ collisions at LHC energies $\sqrt{s}=$ 5.02 and 13 TeV, published by the ALICE Collaboration, using the Color-String Percolation Model. For heavy ions, Pb–Pb at $\sqrt{s_{NN}}=$ 2.76 and 5.02 TeV along with Xe–Xe at $\sqrt{s_{NN}}=$ 5.44 TeV have been analyzed. The initial temperature was extracted both in low- and high-multiplicity events in $\mathit{pp}$ collisions. For $A-A$ collisions, the temperature was obtained as a function of centrality. A universal scaling in the temperature from $pp$ and $A-A$ collisions was obtained when multiplicity was scaled by the transverse interaction area. For the higher-multiplicity events in $\mathit{pp}$ collisions at $\sqrt{s}=$ 5.02 and 13 TeV, the initial temperature was above the universal hadronization temperature and was consistent with the creation of deconfined matter. From the measured energy density $\epsilon$ and the temperature, the dimensionless quantity $\epsilon /T^4$ was obtained, to obtain the degree of freedom of the deconfined matter. Full article

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 (${\pi }^{-}$, ${\pi }^{+}$, $K^{-}$, $K^{+}$, $\overline{p}$, and p) with different rapidities produced in inelastic proton–proton ($pp$) collisions at a Super Proton Synchrotron (SPS). The experimental data measured using 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 with 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 ${\pi }^{-}$, ${\pi }^{+}$, $K^{-}$, $K^{+}$, and $\overline{p}$ 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. Full article

Strange hadron transverse momentum spectra are analyzed in symmetric $pp$ and $PbPb$ and asymmetric $pPb$ collision systems for their dependence on rapidity and event charged-particle multiplicity. The thermodynamically consistent Tsallis models with and without flow velocity are used to reproduce the experimental data, extracting the freeze-out parameters to gain insights into the underlying physics of the collision processes by looking into the parameters change with different multiplicities, particle types, and collision geometries. We found that with an increase in the event multiplicity, the average transverse flow velocity, effective, and kinetic freezeout temperatures increase, with heavier strange particle species exhibiting a more significant increase. The value of the non-extensivity parameter decreases with an increase in the multiplicity of the particles. For heavier particles, larger $T_{eff}$ and $T_0$ and smaller q have been observed, confirming the quick thermalization and equilibrium for massive particles. Furthermore, the differences in parameter values for particle species are more significant in $pp$ and $pPb$ collisions than in $PbPb$ collisions. In addition, in symmetric $pp$ and $PbPb$ collisions, parameter values ($q,T_0,{\beta }_T$) show more significant shifts for heavier particles compared to the lighter ones. In contrast, in asymmetric $pPb$ collisions, both heavier and lighter particles display uniform linear progression. Full article

Although partition temperature derived using the Darwin–Fowler method is exact for simple scenarios, the derivation for complex systems might reside in specific approximations whose viability is not ensured if the thermodynamic limit is not attained. This work elaborates on a related problem relevant to relativistic high-energy collisions. On the one hand, it is simple enough that closed-form expressions can be obtained precisely for the one-particle distribution function. On the other hand, the resulting expression is not an exponential form, and therefore, it is not straightforward that the notion of partition function could be implied. Specifically, we derive the one-particle distribution function for massless particles where the phase-space integration is performed exactly for the underlying canonical ensemble consisting of a given number of particles. We discuss the viability of the partition temperature in this case. Possible implications of the obtained results regarding the observed Tsallis distribution in transverse momentum spectra in high-energy collisions are also addressed. Full article

We analyze the transverse momentum ($p_T$) spectra of ${\pi }^{+}$, ${\pi }^{-}$, $K^{+}$, $K^{-}$, p, $\overline{p}$, $\Lambda$, $\overline{\Lambda }$, $\Xi$, $\overline{\Xi }$, ${\Omega }^{-}$, ${\overline{\Omega }}^{+}$ or ${\Omega }^{-}+{\overline{\Omega }}^{+}$ in different centrality intervals in gold–gold (Au–Au) and lead–lead (Pb–Pb) symmetric collisions at 200 GeV and 2.76 TeV, respectively, by Tsallis–Pareto-type function. Proton–proton collisions at the same centre of mass energies are also analyzed for these particles to compare the results obtained from these systems. The present work extracts the effective temperature T, non-extensivity parameter $\left(q\right)$, the mean transverse momentum spectra ($⟨p_T⟩$), the multiplicity parameter ($N_0$), kinetic freeze-out temperature ($T_0$) and transverse flow velocity (${\beta }_T$). We reported a plateau structure of $p_T$, T, $T_0$, ${\beta }_T$, $p_T$ and q in central collisions. Beyond the plateau region, the excitation function of all the above parameters decreases towards the periphery, except q, which has a reverse trend. The multiplicity parameter is also extracted, which is found to be decreasing towards the periphery from the central collisions. In addition, we observed that the excitation function of pp collisions is nearly the same to that of the most peripheral symmetric nucleus–nucleus collisions at the same colliding energy. Throughout the analyses, the same multiplicity parameters for particles and their antiparticles have been reported, which show the symmetric production of particles and their antiparticles. Full article

The squared momentum transfer spectra of $\eta$ and ${\eta }^0$, produced in high-energy photon–proton ($\gamma p$) $\to \eta \left({\eta }^0\right)+p$ 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 $\gamma$ to emitted $\eta \left({\eta }^0\right)$ 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 ($⟨p_T⟩$), 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. Full article

In this work, we performed a comparative study between HIJING, Sibyll, and QGSJET model-based event generators. Such Monte Carlo (MC) models are used to simulate the interaction and propagation of high-energy cosmic radiation (e.g., coming from the sun) with the Earth’s atmosphere. The global event observables selected for the study were the transverse momentum ($p_{\mathrm{T}}$) spectra and rapidity density distributions of strange particles (${\mathrm{K}}_{\mathrm{S}}^0$, $\Lambda$, and ${\Xi }^{-}$). This study was performed in the STAR and CMS fiducial phase spaces by simulating the strange particles in $pp$ collisions at $\sqrt{\mathrm{s}}$ = 200 GeV, 900 GeV, and 7 TeV, and the simulations were then compared to the experimental measurements. It was observed that none of the discussed model-based event generators ultimately predicted the experimental results, except QGSJET, which generally agrees reasonably with the data. However, QGSJET does not produce $\Xi$ particles; therefore, it does not provide any predictions for $\Xi$. The other two models reproduced the data only in a limited rapidity or transverse momentum region while mainly underpredicting the data in the rest of the areas. These cosmic radiation simulation models are capable of covering the mid-rapidity regions of density distributions. Utilizing model-based observations, some fundamental parameters can be re-tuned and extrapolations to the highest energies can be investigated. Furthermore, these observations can provide valuable insights that could potentially constrain and improve perturbative- and non-perturbative-based QCD event generators, thereby facilitating a better understanding of the underlying physics. Full article

We present an analysis of the pseudorapidity $\eta$ and transverse momentum $p_T$ distributions of charged hadrons in $pp$ collisions for the kinematic range of $0<p_T<4$ GeV/c and $\left|\eta \right|<2.4$ at 0.9, 2.36, and 7 TeV. Charged particles are produced in $pp$ collision using several Monte Carlo event generators (Pythia Simple, Vincia, Dire showers, Sibyll2.3d, QGSJETII-04, EPOS-LHC) and compared with CMS data at LHC. It is observed that the Simple parton showers can explain the CMS data very well for $p_T>1$ GeV/c at 0.9 and 2.36 TeV within the experimental errors, while Dire overshoots and Vicia undershoots the data by 50% each. At 7 TeV, the Dire module presents a good prediction, whereas the Simple and Vincia modules underestimate the data within 30% and 50%. Comparing the Simple module of the Pythia model and the predictions of the CRMC models with the experimental data shows that at 0.9 TeV, EPOS-LHC has better results than the others. At 2.36 GeV, the cosmic rays Monte Carlo (CRMC) models have better prediction than the Simple module of Pythia at low $p_T$, while QGSJETII-04 predicts well at high $p_T$. QGSJETII-04 and EPOS-LHC have closer results than the Pythia-Simple and Sibyll2.3d at 7 TeV. In the case of the pseudorapidity distributions, only the Pythia-Simple reproduced the experimental measurements at all energies. The Dire module overestimates, while Vincia underestimates the data in decreasing order of discrepancy (20%, 12%, 5%) with energy. All CRMC models underestimate the data over the entire $\eta$ range at all energies by 20%. The angular ordering of partons and the parton fragmentation could be possible reasons for this deviation. Furthermore, we used the two-component standard distribution to fit the $p_T$ spectra to the experimental data and extracted the effective temperature ($T_{eff}$) and the multiplicity parameter ($N_0$). It is observed that $T_{eff}$ increases with the increase in the center of mass energy. The fit yielded $0.20368\pm 0.01$, $0.22348\pm 0.011$, and $0.24128\pm 0.012$ GeV for 0.9, 2.36, and 7 TeV, respectively. This shows that the system at higher energies freezes out earlier than lower ones because they quickly attain the equilibrium state. Full article

This manuscript presents a simulation study of a track-based analysis of the multiplicity distributions of the primary charged particle compared to experimental measurements in symmetric hadron–hadron collisions acquiring maximum energy for the new particle production. The data are compared to the simulations of EPOS, PYTHIA8, Sibyll, and QGSJET under the same conditions. The event generators in the current study are simple parton-based models that incorporate the Reggie–Gribov theory. The latter is a field theory based on the QCD that uses the mechanism of multiple parton interactions. It has been found that the PYTHIA8 model chases the data well in most of the distributions but depends on the momentum and the requirement of charged particles in a given track, due to its feature-like color reshuffling of quarks and gluons through the color re-connection modes and initial and final state radiations by incorporating the parton showers. The EPOS model could also reproduce some spectral regions and presents a good comparison after the PYTHIA8. All the other models could not produce most of the spectra except for the limited region, which also depends on the analysis’s cuts. Besides the model’s prediction, we used Tsallis–Pareto and Hagedorn functions to fit the aforementioned spectra of the charged particles. The fit is applied to the data and models, and their results are compared. We extract the temperature parameter T₀₁ (effective temperature (T_eff)) from the Tsallis–Pareto-kind function and T₀₂ (kinetic freezeout temperature) from the Hagedorn function. The temperatures are affected by p_T as well N_ch cuts. Full article

Analysis of transverse momentum distributions is a useful tool to understand the dynamics of relativistic particles produced in high-energy collisions. Finding a proper distribution function to approximate the spectra is a vastly developing area of research in particle physics. In this work, we have provided a detailed theoretical description of the unified statistical framework in high-energy physics. We have tested the applicability of this framework on experimental data by analyzing the transverse momentum spectra of pion produced in heavy-ion collision at RHIC and LHC. We have also attempted to explain the transverse momentum spectra of charged hadrons formed in pp collision at different energies using the unified statistical framework. This formalism has been proved to nicely explain the spectra of particles produced in soft processes as well as hard scattering processes in a consistent manner. Full article