Cumulants of net-strangeness multiplicity distributions at energies available at the BNL Relativistic Heavy Ion Collider

The higher-order cumulants of net-proton number, net-charge, and net-strangeness multiplicity distributions are widely studied to search for the quantum-chromodynamics critical point and extract the chemical freeze-out parameters in heavy-ion collisions. In this context, the event-by-event fluctuations of the net-strangeness multiplicity distributions play important roles in extracting the chemical freeze-out parameter in the strangeness sector. Due to having difficulties in detecting all strange hadrons event by event, the kaon ($K$) and lambda ($\Lambda$) particles serve as a proxy for the strangeness-related observables in heavy-ion collisions. We have studied the net-$K$, net-$\Lambda$, and net-($K$ + $\Lambda$) multiplicity distributions and calculated their different order of cumulants using the ultrarelativistic quantum molecular dynamics model and hadron resonance gas calculation. To adequately account for the net-strangeness cumulants, it has been found that the inclusion of resonance decay contributions in $K$ and $\Lambda$ is necessary.Comment: The title has been modified. Updated following the published versio

An experimental study of the swelling properties of spherical hydro-gel immersed in water and the formulation of a simple theoretical model for its explanation

The mechanism of variation of mass and volume, through the absorption of water, by the most commonly used and abundantly available spherical hydro-gel beads of various colors has been studied. Immersing the beads in distilled water, both mass and volume were measured at regular intervals. By an analysis of mass-versus-time data, using standard theoretical methods, the mechanism of diffusion of water has been studied. Relaxation controlled transport was found to be the predominant process of diffusion of water into the materials under study. The diffusion coefficient has been determined for hydro-gels of different colors. Various swelling related parameters such as equilibrium water content, equilibrium swelling ratio, characteristic time, initial rate of water absorption etc. were determined for these hydro-gels. The maximum attainable mass and the maximum number of water molecules that can be attached to active polymer sites in a single bead have been calculated. In this regard, the number of such active sites per unit volume and mass of dry hydro-gel was determined. A theoretical model has been developed, based on the consideration of water absorption through the occupation of vacant polymer sites in a highly porous hydro-gel. Considerations of cylindrical and spherical pores in this model predicted almost the same swelling behavior. Expressions relating mass and volume with time have been formulated and they agreed well with experimental observations. The dependence of characteristic time () upon structural parameters have been established. Values of swelling related parameters have been determined by a numerical fitting of theoretical model to experimental data. The agreement of experimental findings with theoretical predictions has been depicted graphically

Aspects of chiral transition in a Hadron Resonance Gas model

We study the chiral condensate for 2 + 1 flavor QCD with physical quarks within a non-interacting Hadron Resonance Gas (HRG) model. By including the latest information on the mass variation of the hadrons concerning the light quark mass, from lattice QCD and chiral perturbation theory, we show that it is possible to quite accurately account for the chiral crossover transition even within a conventional HRG model. We have calculated a pseudocritical temperature Tc=161.2±1.6 MeV and the curvature of crossover curve κ2=0.0203(7). These are in very good agreement with the latest continuum extrapolated results obtained from lattice QCD studies. We also discuss the limitations of extending such calculations toward the chiral limit. Furthermore, we study the effects of non-resonant hadron interactions within the HRG model and its consequences for the chiral transition in the regime of dense baryonic matter where lattice QCD results are not currently available

An experimental study of the swelling properties of spherical hydro-gel immersed in water and the formulation of a simple theoretical model for its explanation

The mechanism of variation of mass and volume, through the absorption of water, by the most commonly used and abundantly available spherical hydro-gel beads of various colors has been studied. Immersing the beads in distilled water, both mass and volume were measured at regular intervals. By an analysis of mass-versus-time data, using standard theoretical methods, the mechanism of diffusion of water has been studied. Relaxation controlled transport was found to be the predominant process of diffusion of water into the materials under study. The diffusion coefficient has been determined for hydro-gels of different colors. Various swelling related parameters such as equilibrium water content, equilibrium swelling ratio, characteristic time, initial rate of water absorption etc. were determined for these hydro-gels. The maximum attainable mass and the maximum number of water molecules that can be attached to active polymer sites in a single bead have been calculated. In this regard, the number of such active sites per unit volume and mass of dry hydro-gel was determined. A theoretical model has been developed, based on the consideration of water absorption through the occupation of vacant polymer sites in a highly porous hydro-gel. Considerations of cylindrical and spherical pores in this model predicted almost the same swelling behavior. Expressions relating mass and volume with time have been formulated and they agreed well with experimental observations. The dependence of characteristic time () upon structural parameters have been established. Values of swelling related parameters have been determined by a numerical fitting of theoretical model to experimental data. The agreement of experimental findings with theoretical predictions has been depicted graphically