We have considered formation of a multicomponent nonideal hot and dense gas of hadronic resonance... more We have considered formation of a multicomponent nonideal hot and dense gas of hadronic resonances in the ultrarelativistic heavy ion collisions. In the statistical thermal model approach, the equation of state (EoS) of the noninteracting ideal hadron resonance gas (IHRG) does not incorporate either the attractive part or the short-range repulsive part of the baryonic interaction. On the other hand, in the nonideal hadron resonance gas (NIHRG) model, we can incorporate these interactions using the van der Waals (VDW) type approach. Studies have been made to see its effect on the critical parameters of the quark-hadron phase transition. However, it can also lead to modifications in the calculated relative particle yields. In this paper, we have attempted to understand the effect of such van der Waals-type interactions on the relative particle yields and also studied their dependences on the system's thermal parameters, such as the temperature and baryon chemical potential ðμ B Þ. We have also taken into account the decay contributions of the heavier resonances. These results on particle ratios are compared with the corresponding results obtained from the point-like, i.e., noninteracting IHRG model. It is found that the particle ratios get modified by incorporating the van der Waals-type interactions, especially in a baryon-rich system which is expected to be formed at lower RHIC energies, SPS energies, and in the forthcoming CBM experiments due to high degree of nuclear stopping in these experiments.
The density functional theory calculation has been carried out for the analysis of 5-chlorouracil... more The density functional theory calculation has been carried out for the analysis of 5-chlorouracil using DFT/Gaussian 09 with GAR2PED. Recorded experimental spectra for Raman and IR of 5-chlorouracil have been analyzed all fundamental vibrational modes using the outcome results of DFT at 6-311++G** of Gaussian 09 calculations and the GaussView 5.09. To help the analysis of vibrational modes, GAR2PED program has been used in the calculation of PEDs. The charge transfer properties of 5-chlorouracil have been analyzed using HOMO and LUMO level energy analysis. HOMO and LUMO energy gap study supports the charge transfer possibility in molecule. These have been made to study for reactivity and stability of heterocyclic molecules for the analysis of antiviral drugs against the new corona virus: COVID-19. Here, the smaller energy gap of 5-chlorouracil is more responsible for charge transfer interaction in the heterocyclic drug molecules and a reason of more bioactivity. The electron density mapping within molecular electrostatic potential plot and electrostatic potential plotting within iso-surface plot have been evaluated the charge distribution concept in the molecule as the nucleophilic reactions and electrophilic sites. These computations have been used to produce the molecular charges, structure and thermodynamic functions of biomolecule. This study has been made to all internal modes of chloro group substituent at pyrimidine ring of C 5 atom. The splitting of frequencies has arisen in the two species for the normal distribution modes.
We study the identified particle ratios produced at mid-rapidity in heavy ion collisions, along w... more We study the identified particle ratios produced at mid-rapidity in heavy ion collisions, along with their correlations with the collision energy. We employ our earlier proposed Unified Statistical Thermal Freeze-out Model (USTFM), which incorporates the effects of both longitudinal as well as transverse hydrodynamic flow in the hot hadronic system. A fair agreement seen between the experimental data and our model results confirms that the particle production in these collisions is of statistical nature. The variation of the chemical freeze-out temperature and the baryon chemical potential with respect to collision energies is studied. The chemical freeze-out temperature is found to be almost constant beyond the RHIC energy and is found to be close to the QCD predicted phase transition temperature suggesting that the chemical freeze-out occurs soon after the hadronization takes place. The vanishing value of chemical potential at LHC indicates very high degree of nuclear transparency in the collision.
We study the effect of finite size of hadrons on the quark hadron phase transition and in particu... more We study the effect of finite size of hadrons on the quark hadron phase transition and in particular on the location of the critical end point of such a phase transition. The corrections to the hadronic equation of state are incorporated in a thermodynamic consistent manner for a vander Walls like interaction. For quark gluon plasma phase we take a bag model like equation of state which takes into account the perturbative interactions among the plasma constituents. We find that for finite sized baryons the first order quark hadron phase transition is not possible for the entire QCD phase diagram. The end point of first order phase coexistence line arises towards the higher chemical potential values in comparison to the point sized baryons, beyond which the transition from hadronic phase to the quark gluon plasma phase might be either crossover or second order phase transition. Our findings are consistent with the finite size scaling (FSS) analysis of RHIC data which negates the critical end point with baryon chemical potential values of less than 400 MeV
We study the non-equilibrium properties of a dynamical fluid composed of quasi-particles whose ma... more We study the non-equilibrium properties of a dynamical fluid composed of quasi-particles whose mass is temperature and charge chemical potential dependent, in kinetic theory under the relaxation time approximation. In particular we calculate the scaling behaviour of bulk viscosity 'ζ' near the QCD chiral phase transition in the 3d O (2) universality class. It is found that the bulk viscosity 'ζ' does not show a divergent behaviour near the QCD chiral phase transition. This scaling behaviour of 'ζ' prevails in the presence of Gold-stone modes that arise due to the explicit breaking of continuous O (4) symmetry. On contrary these modes have a significant effect on the scaling behaviour of specific heat C V which diverges at the critical temperature T C .
Transverse momentum spectra of identified pions (π-+ π +), Kaons ((K-+ K +), K 0 s), protons (p +... more Transverse momentum spectra of identified pions (π-+ π +), Kaons ((K-+ K +), K 0 s), protons (p +) and Lambdas ( + ) produced at mid-rapidity (0 < y cm < 0.5) in p-Pb collisions at s NN = 5.02 TeV is studied for different collision centralities by using a Unified Statistical Thermal Freeze-out Model (USTFM). A fairly good agreement is seen between the calculated results and the experimental data points taken from the ALICE experiment. Kinetic freeze-out conditions are extracted from the fits of the transverse momentum spectra of these hadrons for each centrality class. A comparison of the obtained freezeout parameters with those of heavy-ion collisions (Pb + Pb) is made and discussed.
We have considered formation of a multi component non-ideal hot and dense gas of hadronic resonan... more We have considered formation of a multi component non-ideal hot and dense gas of hadronic resonances in the ultra-relativistic heavy-ion collisions. In the statistical thermal model approach the equation of state (EoS) of the non interacting ideal hadron resonance gas (IHRG) does not incorporate either the attractive part or the short range repulsive part of the baryonic interaction. On the other hand in the non-ideal hadron resonance gas (NIHRG) model we can incorporate these interactions using the Van der Waals (VDW) type approach. Studies have been made to see its effect on the critical parameters of the quark-hadron phase transition. However, it can also lead to modifications in the calculated relative particle yields. In this paper we have attempted to understand the effect of such Van der Waals type interactions on the relative particle yields and also studied their dependences on the system's thermal parameters, such as the temperature and baryon chemical potential (). We have also taken into account the decay contributions of the heavier resonances. These results on particle ratios are compared with the corresponding results obtained from the pointlike i.e. non interacting IHRG model. It is found that the particle ratios get modified by incorporating the Van der Waals type interactions, especially in a baryon rich system which is expected to be formed at lower RHIC energies, SPS energies and in the forthcoming CBM experiments due to high degree of nuclear stopping in these experiments.
We have considered formation of a multi component non-ideal hot and dense gas of hadronic resonan... more We have considered formation of a multi component non-ideal hot and dense gas of hadronic resonances in the ultra-relativistic heavy-ion collisions. In the statistical thermal model approach the equation of state (EoS) of the non interacting ideal hadron resonance gas (IHRG) does not incorporate either the attractive part or the short range repulsive part of the baryonic interaction. On the other hand in the non-ideal hadron resonance gas (NIHRG) model we can incorporate these interactions using the Van der Waals (VDW) type approach. Studies have been made to see its effect on the critical parameters of the quark-hadron phase transition. However, it can also lead to modifications in the calculated relative particle yields. In this paper we have attempted to understand the effect of such Van der Waals type interactions on the relative particle yields and also studied their dependences on the system's thermal parameters, such as the temperature and baryon chemical potential (). We have also taken into account the decay contributions of the heavier resonances. These results on particle ratios are compared with the corresponding results obtained from the pointlike i.e. non interacting IHRG model. It is found that the particle ratios get modified by incorporating the Van der Waals type interactions, especially in a baryon rich system which is expected to be formed at lower RHIC energies, SPS energies and in the forthcoming CBM experiments due to high degree of nuclear stopping in these experiments.
We incorporate the Van der Waals interaction in the hadron resonance gas model to obtain the part... more We incorporate the Van der Waals interaction in the hadron resonance gas model to obtain the particle ratios $\bar N/N$, $\bar\Lambda/\Lambda$, $\bar\Xi/\Xi$, $\bar \Omega/\Omega$ and $K^-/K^+$ and study their dependence on temperature and baryon chemical potential . These results on particle ratios are compared with the point-like hadron case. It is found that the particle ratios get significantly modified in the case of van der Waals interactions. In the van der Waals type equation of state (EoS) both the attractive and repulsive parts of interactions are taken into account. In some previous works the attractive and repulsive parameters were fixed as (a=329-1250 MeV$fm^3$) and (b= 3.42- 5.75 $fm^3$), respectively. These parameters were fixed from the ground state properties of nuclear matter. However, by using a fixed value of the parameter a we don't get baryon antibaryon symmetry for $\mu_B=0$. This results in a situation where antibaryon/baryon ratio becomes greater than unity, which is unphysical. In order to solve this discrepancy, we make the attractive parameter function of temperature such that it gives physically acceptable results.
The mid-rapidity transverse momentum spectra of various hadrons and the available rapidity distri... more The mid-rapidity transverse momentum spectra of various hadrons and the available rapidity distributions of some strange hadrons produced in p-p collisions at LHC energy √s NN = 7.0 TeV have been studied using a Unified Statistical Thermal Freeze-out Model (USTFM). The calculated results are found to be in good agreement with the experimental data. The theoretical fits of the transverse momentum spectra using the model calculations provide the thermal freeze-out conditions in terms of the temperature and collective flow parameters for different hadronic species. The study reveal the presence of significant collective flow and a well defined temperature in the system thus indicating the formation of a thermally equilibrated hydrodynamic system in p-p collisions at LHC. Moreover, the fits to the available experimental rapidity distributions data of strange hadrons show the effect of almost complete transparency in p-p collisions at LHC. The transverse momentum distributions of protons and kaons produced in p-p collisions at √s NN = 200 GeV and √s NN = 2.76 TeV have also been reproduced successfully. The model incorporates longitudinal as well as a transverse hydrodynamic flow. The contributions from heavier decay resonances have also been taken into account. We have also imposed the criteria of exact strangeness conservation in the system.
The transverse momentum spectra of Identified particles such as p, pbar, K+, K-, K_s0, lambda, om... more The transverse momentum spectra of Identified particles such as p, pbar, K+, K-, K_s0, lambda, omega, omegabar, cascade and cascade-bar at midrapidity (|y| < 0.5) in Pb - Pb collisions at root (sNN) = 2.76 TeV have been studied as a function of collision centrality by using a unified statistical thermal freeze-out model. The calculated results are found to be in good agreement with the experimental data measured by the ALICE experiment at LHC. The model calculation fits provide the thermal freeze-out conditions in terms of the temperature and collective flow parameters for different particle species. Interestingly, the model parameter fits to the experimental data reveal a rise in the thermal freeze-out temperature but a mild decrease in the collective flow velocity parameter from central to peripheral collisions. The model used incorporates the simultaneous effect of the longitudinal as well as transverse hydrodynamic flows. The baryon chemical potential is assumed to be nearly zero for the bulk of the matter ({\mu}B ~ 0), a situation expected in the heavy ion collisions at LHC energies in the Bjorken approach. The contributions from heavier decay resonances are also taken into account in our calculations.
We study the transverse momentum spectra of identified pions (π-+ π +), Kaons ((K-+ K +), K 0 s),... more We study the transverse momentum spectra of identified pions (π-+ π +), Kaons ((K-+ K +), K 0 s), protons (p + ̅) and Lambdas (Ʌ + Ʌ) produced at mid-rapidity (0 < y < 0.5) in most central p-Pb collisions at √s NN = 5.02 TeV in comparison with a Unified Statistical Thermal Freeze-out Model (USTFM). The measurements of pions are reported upto p T = 3 GeV, the kaons (K-+ K +) are reported upto p T = 2.5 GeV, K 0 s is reported upto p T = 7 GeV and the baryons (protons and Lambdas) are reported upto p T = 3.5 GeV. A good agreement is seen between the calculated results and the experimental data points taken from the ALICE experiment. The transverse momentum spectra are found to be flatter for heavy particles than for light particles. Bulk freeze-out properties in terms of kinetic freeze-out temperature and the transverse collective flow velocity are extracted from the fits of the transverse momentum spectra of these hadrons. The effect of resonance decay contributions has also been taken care of.
The transverse momentum spectra of various hadrons at different centralities at the RHIC energy o... more The transverse momentum spectra of various hadrons at different centralities at the RHIC energy of √ s N N = 200 GeV are studied. The study is based on a unified statistical thermal freeze-out model which incorporates the longitudinal as well as transverse boosts. The model also incorporates the dependence of the baryonic chemical potential on rapidity of the forward fireballs distributed along the longitudinal axis. The transverse momentum spectra have been found to be in close agreement with the available RHIC experimental data at all centralities. The kinetic freeze-out parameters are extracted by comparing our model results with the experimental data using the method of minimization of χ 2 /DOF. The extracted parameters indicate that the freeze-out temperature increases with decreasing centrality, while the collective flow velocity increases with the increase in centrality of the colliding system. The work is studied with the inclusion of all heavier resonance decay contributions.
We calculate the particle ratios + / + , − / − , and Λ/ − for a strongly interacting hadronic mat... more We calculate the particle ratios + / + , − / − , and Λ/ − for a strongly interacting hadronic matter using nonlinear Walecka model (NLWM) in relativistic mean field (RMF) approximation. It is found that interactions among hadrons modify + / + and Λ/ − particle ratios, while − / − is found to be insensitive to these interactions.
We study the centrality dependence of the mid-rapidity (|y|<0.5) yield (dN/dy) and transverse mom... more We study the centrality dependence of the mid-rapidity (|y|<0.5) yield (dN/dy) and transverse momentum distributions of K*(892)0 and {\phi}(1020) resonances produced in Pb+Pb collisions at root(sNN) = 2.76 TeV. The mid-rapidity density (dN/dy) and the shape of the transverse momentum spectra are well reproduced by our earlier proposed Unified Statistical Thermal Freeze-out Model (USTFM) which incorporates the effects of both longitudinal as well as transverse hydrodynamic flow. The freeze-out properties in terms of kinetic freeze-out temperature and transverse flow velocity parameter are extracted from the model fits to the ALICE data. The extracted kinetic freeze-out temperature is found to increase with decrease in centrality while as the transverse flow velocity parameter shows a mild decrease towards peripheral collisions. Moreover the centrality dependence of the mid-rapidity system size at freeze-out has also been studied in terms of transverse radius parameter.
Journal of Experimental and Theoretical Physics, Aug 1, 2019
The mid-rapidity (|y| < 0.5) transverse momentum distributions of identified charged pions produc... more The mid-rapidity (|y| < 0.5) transverse momentum distributions of identified charged pions produced in different collision systems at different centre-of-mass energies () ranging from RHIC to LHC have been studied using our early proposed unified statistical thermal freeze-out model (USTFM). We have also studied the effect of different collision centralities on the mid-rapidity (|y| < 0.5) production of pions. Our model results are found to be in good agreement with the experimental data. Different thermal freeze-out conditions which include transverse flow, thermal freeze-out temperature, and velocity profile have been extracted by providing the best fit to the experimental data points. We have incorporated the effects of transverse as well as longitudinal flow in this analysis. The effects of heavier decay resonances are also taken into account. Moreover, the strangeness conservation criteria have also been imposed in this analysis of pion distributions. The calculated freeze-out parameters indicates that the freeze-out temperature increases with decreasing centrality, while the transverse flow velocity increases by increase in the centrality of the colliding system.
We study the centrality and system size dependence of φ meson production by reproducing its trans... more We study the centrality and system size dependence of φ meson production by reproducing its transverse-momentum distributions and mid-rapidity distributions (dN /dy ) for various collision systems of Au+Au, Cu+Cu, d+Au and p+p at various RHIC energies of , 130 GeV and 200 GeV by using Unified Statistical Thermal Freeze-out Model (USTFM). The calculated results are found to be in good agreement with the experimental data points taken from the STAR experiment. Freeze-out conditions in terms of transverse flow velocity and thermal freeze-out temperature are extracted from the fits of transverse-momentum spectra of the particles at different centrality classes and for different collision systems. The transverse size of the system in terms of transverse-radius parameter is determined from the fits of rapidity distributions at various centrality classes and for various collision systems.
We have considered formation of a multicomponent nonideal hot and dense gas of hadronic resonance... more We have considered formation of a multicomponent nonideal hot and dense gas of hadronic resonances in the ultrarelativistic heavy ion collisions. In the statistical thermal model approach, the equation of state (EoS) of the noninteracting ideal hadron resonance gas (IHRG) does not incorporate either the attractive part or the short-range repulsive part of the baryonic interaction. On the other hand, in the nonideal hadron resonance gas (NIHRG) model, we can incorporate these interactions using the van der Waals (VDW) type approach. Studies have been made to see its effect on the critical parameters of the quark-hadron phase transition. However, it can also lead to modifications in the calculated relative particle yields. In this paper, we have attempted to understand the effect of such van der Waals-type interactions on the relative particle yields and also studied their dependences on the system's thermal parameters, such as the temperature and baryon chemical potential ðμ B Þ. We have also taken into account the decay contributions of the heavier resonances. These results on particle ratios are compared with the corresponding results obtained from the point-like, i.e., noninteracting IHRG model. It is found that the particle ratios get modified by incorporating the van der Waals-type interactions, especially in a baryon-rich system which is expected to be formed at lower RHIC energies, SPS energies, and in the forthcoming CBM experiments due to high degree of nuclear stopping in these experiments.
The density functional theory calculation has been carried out for the analysis of 5-chlorouracil... more The density functional theory calculation has been carried out for the analysis of 5-chlorouracil using DFT/Gaussian 09 with GAR2PED. Recorded experimental spectra for Raman and IR of 5-chlorouracil have been analyzed all fundamental vibrational modes using the outcome results of DFT at 6-311++G** of Gaussian 09 calculations and the GaussView 5.09. To help the analysis of vibrational modes, GAR2PED program has been used in the calculation of PEDs. The charge transfer properties of 5-chlorouracil have been analyzed using HOMO and LUMO level energy analysis. HOMO and LUMO energy gap study supports the charge transfer possibility in molecule. These have been made to study for reactivity and stability of heterocyclic molecules for the analysis of antiviral drugs against the new corona virus: COVID-19. Here, the smaller energy gap of 5-chlorouracil is more responsible for charge transfer interaction in the heterocyclic drug molecules and a reason of more bioactivity. The electron density mapping within molecular electrostatic potential plot and electrostatic potential plotting within iso-surface plot have been evaluated the charge distribution concept in the molecule as the nucleophilic reactions and electrophilic sites. These computations have been used to produce the molecular charges, structure and thermodynamic functions of biomolecule. This study has been made to all internal modes of chloro group substituent at pyrimidine ring of C 5 atom. The splitting of frequencies has arisen in the two species for the normal distribution modes.
We study the identified particle ratios produced at mid-rapidity in heavy ion collisions, along w... more We study the identified particle ratios produced at mid-rapidity in heavy ion collisions, along with their correlations with the collision energy. We employ our earlier proposed Unified Statistical Thermal Freeze-out Model (USTFM), which incorporates the effects of both longitudinal as well as transverse hydrodynamic flow in the hot hadronic system. A fair agreement seen between the experimental data and our model results confirms that the particle production in these collisions is of statistical nature. The variation of the chemical freeze-out temperature and the baryon chemical potential with respect to collision energies is studied. The chemical freeze-out temperature is found to be almost constant beyond the RHIC energy and is found to be close to the QCD predicted phase transition temperature suggesting that the chemical freeze-out occurs soon after the hadronization takes place. The vanishing value of chemical potential at LHC indicates very high degree of nuclear transparency in the collision.
We study the effect of finite size of hadrons on the quark hadron phase transition and in particu... more We study the effect of finite size of hadrons on the quark hadron phase transition and in particular on the location of the critical end point of such a phase transition. The corrections to the hadronic equation of state are incorporated in a thermodynamic consistent manner for a vander Walls like interaction. For quark gluon plasma phase we take a bag model like equation of state which takes into account the perturbative interactions among the plasma constituents. We find that for finite sized baryons the first order quark hadron phase transition is not possible for the entire QCD phase diagram. The end point of first order phase coexistence line arises towards the higher chemical potential values in comparison to the point sized baryons, beyond which the transition from hadronic phase to the quark gluon plasma phase might be either crossover or second order phase transition. Our findings are consistent with the finite size scaling (FSS) analysis of RHIC data which negates the critical end point with baryon chemical potential values of less than 400 MeV
We study the non-equilibrium properties of a dynamical fluid composed of quasi-particles whose ma... more We study the non-equilibrium properties of a dynamical fluid composed of quasi-particles whose mass is temperature and charge chemical potential dependent, in kinetic theory under the relaxation time approximation. In particular we calculate the scaling behaviour of bulk viscosity 'ζ' near the QCD chiral phase transition in the 3d O (2) universality class. It is found that the bulk viscosity 'ζ' does not show a divergent behaviour near the QCD chiral phase transition. This scaling behaviour of 'ζ' prevails in the presence of Gold-stone modes that arise due to the explicit breaking of continuous O (4) symmetry. On contrary these modes have a significant effect on the scaling behaviour of specific heat C V which diverges at the critical temperature T C .
Transverse momentum spectra of identified pions (π-+ π +), Kaons ((K-+ K +), K 0 s), protons (p +... more Transverse momentum spectra of identified pions (π-+ π +), Kaons ((K-+ K +), K 0 s), protons (p +) and Lambdas ( + ) produced at mid-rapidity (0 < y cm < 0.5) in p-Pb collisions at s NN = 5.02 TeV is studied for different collision centralities by using a Unified Statistical Thermal Freeze-out Model (USTFM). A fairly good agreement is seen between the calculated results and the experimental data points taken from the ALICE experiment. Kinetic freeze-out conditions are extracted from the fits of the transverse momentum spectra of these hadrons for each centrality class. A comparison of the obtained freezeout parameters with those of heavy-ion collisions (Pb + Pb) is made and discussed.
We have considered formation of a multi component non-ideal hot and dense gas of hadronic resonan... more We have considered formation of a multi component non-ideal hot and dense gas of hadronic resonances in the ultra-relativistic heavy-ion collisions. In the statistical thermal model approach the equation of state (EoS) of the non interacting ideal hadron resonance gas (IHRG) does not incorporate either the attractive part or the short range repulsive part of the baryonic interaction. On the other hand in the non-ideal hadron resonance gas (NIHRG) model we can incorporate these interactions using the Van der Waals (VDW) type approach. Studies have been made to see its effect on the critical parameters of the quark-hadron phase transition. However, it can also lead to modifications in the calculated relative particle yields. In this paper we have attempted to understand the effect of such Van der Waals type interactions on the relative particle yields and also studied their dependences on the system's thermal parameters, such as the temperature and baryon chemical potential (). We have also taken into account the decay contributions of the heavier resonances. These results on particle ratios are compared with the corresponding results obtained from the pointlike i.e. non interacting IHRG model. It is found that the particle ratios get modified by incorporating the Van der Waals type interactions, especially in a baryon rich system which is expected to be formed at lower RHIC energies, SPS energies and in the forthcoming CBM experiments due to high degree of nuclear stopping in these experiments.
We have considered formation of a multi component non-ideal hot and dense gas of hadronic resonan... more We have considered formation of a multi component non-ideal hot and dense gas of hadronic resonances in the ultra-relativistic heavy-ion collisions. In the statistical thermal model approach the equation of state (EoS) of the non interacting ideal hadron resonance gas (IHRG) does not incorporate either the attractive part or the short range repulsive part of the baryonic interaction. On the other hand in the non-ideal hadron resonance gas (NIHRG) model we can incorporate these interactions using the Van der Waals (VDW) type approach. Studies have been made to see its effect on the critical parameters of the quark-hadron phase transition. However, it can also lead to modifications in the calculated relative particle yields. In this paper we have attempted to understand the effect of such Van der Waals type interactions on the relative particle yields and also studied their dependences on the system's thermal parameters, such as the temperature and baryon chemical potential (). We have also taken into account the decay contributions of the heavier resonances. These results on particle ratios are compared with the corresponding results obtained from the pointlike i.e. non interacting IHRG model. It is found that the particle ratios get modified by incorporating the Van der Waals type interactions, especially in a baryon rich system which is expected to be formed at lower RHIC energies, SPS energies and in the forthcoming CBM experiments due to high degree of nuclear stopping in these experiments.
We incorporate the Van der Waals interaction in the hadron resonance gas model to obtain the part... more We incorporate the Van der Waals interaction in the hadron resonance gas model to obtain the particle ratios $\bar N/N$, $\bar\Lambda/\Lambda$, $\bar\Xi/\Xi$, $\bar \Omega/\Omega$ and $K^-/K^+$ and study their dependence on temperature and baryon chemical potential . These results on particle ratios are compared with the point-like hadron case. It is found that the particle ratios get significantly modified in the case of van der Waals interactions. In the van der Waals type equation of state (EoS) both the attractive and repulsive parts of interactions are taken into account. In some previous works the attractive and repulsive parameters were fixed as (a=329-1250 MeV$fm^3$) and (b= 3.42- 5.75 $fm^3$), respectively. These parameters were fixed from the ground state properties of nuclear matter. However, by using a fixed value of the parameter a we don't get baryon antibaryon symmetry for $\mu_B=0$. This results in a situation where antibaryon/baryon ratio becomes greater than unity, which is unphysical. In order to solve this discrepancy, we make the attractive parameter function of temperature such that it gives physically acceptable results.
The mid-rapidity transverse momentum spectra of various hadrons and the available rapidity distri... more The mid-rapidity transverse momentum spectra of various hadrons and the available rapidity distributions of some strange hadrons produced in p-p collisions at LHC energy √s NN = 7.0 TeV have been studied using a Unified Statistical Thermal Freeze-out Model (USTFM). The calculated results are found to be in good agreement with the experimental data. The theoretical fits of the transverse momentum spectra using the model calculations provide the thermal freeze-out conditions in terms of the temperature and collective flow parameters for different hadronic species. The study reveal the presence of significant collective flow and a well defined temperature in the system thus indicating the formation of a thermally equilibrated hydrodynamic system in p-p collisions at LHC. Moreover, the fits to the available experimental rapidity distributions data of strange hadrons show the effect of almost complete transparency in p-p collisions at LHC. The transverse momentum distributions of protons and kaons produced in p-p collisions at √s NN = 200 GeV and √s NN = 2.76 TeV have also been reproduced successfully. The model incorporates longitudinal as well as a transverse hydrodynamic flow. The contributions from heavier decay resonances have also been taken into account. We have also imposed the criteria of exact strangeness conservation in the system.
The transverse momentum spectra of Identified particles such as p, pbar, K+, K-, K_s0, lambda, om... more The transverse momentum spectra of Identified particles such as p, pbar, K+, K-, K_s0, lambda, omega, omegabar, cascade and cascade-bar at midrapidity (|y| < 0.5) in Pb - Pb collisions at root (sNN) = 2.76 TeV have been studied as a function of collision centrality by using a unified statistical thermal freeze-out model. The calculated results are found to be in good agreement with the experimental data measured by the ALICE experiment at LHC. The model calculation fits provide the thermal freeze-out conditions in terms of the temperature and collective flow parameters for different particle species. Interestingly, the model parameter fits to the experimental data reveal a rise in the thermal freeze-out temperature but a mild decrease in the collective flow velocity parameter from central to peripheral collisions. The model used incorporates the simultaneous effect of the longitudinal as well as transverse hydrodynamic flows. The baryon chemical potential is assumed to be nearly zero for the bulk of the matter ({\mu}B ~ 0), a situation expected in the heavy ion collisions at LHC energies in the Bjorken approach. The contributions from heavier decay resonances are also taken into account in our calculations.
We study the transverse momentum spectra of identified pions (π-+ π +), Kaons ((K-+ K +), K 0 s),... more We study the transverse momentum spectra of identified pions (π-+ π +), Kaons ((K-+ K +), K 0 s), protons (p + ̅) and Lambdas (Ʌ + Ʌ) produced at mid-rapidity (0 < y < 0.5) in most central p-Pb collisions at √s NN = 5.02 TeV in comparison with a Unified Statistical Thermal Freeze-out Model (USTFM). The measurements of pions are reported upto p T = 3 GeV, the kaons (K-+ K +) are reported upto p T = 2.5 GeV, K 0 s is reported upto p T = 7 GeV and the baryons (protons and Lambdas) are reported upto p T = 3.5 GeV. A good agreement is seen between the calculated results and the experimental data points taken from the ALICE experiment. The transverse momentum spectra are found to be flatter for heavy particles than for light particles. Bulk freeze-out properties in terms of kinetic freeze-out temperature and the transverse collective flow velocity are extracted from the fits of the transverse momentum spectra of these hadrons. The effect of resonance decay contributions has also been taken care of.
The transverse momentum spectra of various hadrons at different centralities at the RHIC energy o... more The transverse momentum spectra of various hadrons at different centralities at the RHIC energy of √ s N N = 200 GeV are studied. The study is based on a unified statistical thermal freeze-out model which incorporates the longitudinal as well as transverse boosts. The model also incorporates the dependence of the baryonic chemical potential on rapidity of the forward fireballs distributed along the longitudinal axis. The transverse momentum spectra have been found to be in close agreement with the available RHIC experimental data at all centralities. The kinetic freeze-out parameters are extracted by comparing our model results with the experimental data using the method of minimization of χ 2 /DOF. The extracted parameters indicate that the freeze-out temperature increases with decreasing centrality, while the collective flow velocity increases with the increase in centrality of the colliding system. The work is studied with the inclusion of all heavier resonance decay contributions.
We calculate the particle ratios + / + , − / − , and Λ/ − for a strongly interacting hadronic mat... more We calculate the particle ratios + / + , − / − , and Λ/ − for a strongly interacting hadronic matter using nonlinear Walecka model (NLWM) in relativistic mean field (RMF) approximation. It is found that interactions among hadrons modify + / + and Λ/ − particle ratios, while − / − is found to be insensitive to these interactions.
We study the centrality dependence of the mid-rapidity (|y|<0.5) yield (dN/dy) and transverse mom... more We study the centrality dependence of the mid-rapidity (|y|<0.5) yield (dN/dy) and transverse momentum distributions of K*(892)0 and {\phi}(1020) resonances produced in Pb+Pb collisions at root(sNN) = 2.76 TeV. The mid-rapidity density (dN/dy) and the shape of the transverse momentum spectra are well reproduced by our earlier proposed Unified Statistical Thermal Freeze-out Model (USTFM) which incorporates the effects of both longitudinal as well as transverse hydrodynamic flow. The freeze-out properties in terms of kinetic freeze-out temperature and transverse flow velocity parameter are extracted from the model fits to the ALICE data. The extracted kinetic freeze-out temperature is found to increase with decrease in centrality while as the transverse flow velocity parameter shows a mild decrease towards peripheral collisions. Moreover the centrality dependence of the mid-rapidity system size at freeze-out has also been studied in terms of transverse radius parameter.
Journal of Experimental and Theoretical Physics, Aug 1, 2019
The mid-rapidity (|y| < 0.5) transverse momentum distributions of identified charged pions produc... more The mid-rapidity (|y| < 0.5) transverse momentum distributions of identified charged pions produced in different collision systems at different centre-of-mass energies () ranging from RHIC to LHC have been studied using our early proposed unified statistical thermal freeze-out model (USTFM). We have also studied the effect of different collision centralities on the mid-rapidity (|y| < 0.5) production of pions. Our model results are found to be in good agreement with the experimental data. Different thermal freeze-out conditions which include transverse flow, thermal freeze-out temperature, and velocity profile have been extracted by providing the best fit to the experimental data points. We have incorporated the effects of transverse as well as longitudinal flow in this analysis. The effects of heavier decay resonances are also taken into account. Moreover, the strangeness conservation criteria have also been imposed in this analysis of pion distributions. The calculated freeze-out parameters indicates that the freeze-out temperature increases with decreasing centrality, while the transverse flow velocity increases by increase in the centrality of the colliding system.
We study the centrality and system size dependence of φ meson production by reproducing its trans... more We study the centrality and system size dependence of φ meson production by reproducing its transverse-momentum distributions and mid-rapidity distributions (dN /dy ) for various collision systems of Au+Au, Cu+Cu, d+Au and p+p at various RHIC energies of , 130 GeV and 200 GeV by using Unified Statistical Thermal Freeze-out Model (USTFM). The calculated results are found to be in good agreement with the experimental data points taken from the STAR experiment. Freeze-out conditions in terms of transverse flow velocity and thermal freeze-out temperature are extracted from the fits of transverse-momentum spectra of the particles at different centrality classes and for different collision systems. The transverse size of the system in terms of transverse-radius parameter is determined from the fits of rapidity distributions at various centrality classes and for various collision systems.
Uploads
Papers by Saeed Uddin