Pawan Kumar Netrakanti

Net-baryon, net-charge and net-strangeness number fluctuations in high energy heavy-ion collisions are discussed within the framework of a hadron resonance gas (HRG) model. Ratios of the conserved number susceptibilities calculated in HRG are being compared to the corresponding experimental measurements to extract information about the freeze-out condition and the phase structure of systems with strong interactions. We emphasize the importance of considering the actual experimental acceptances in terms of kinematics (pseudorapidity (η) and transverse momentum (pT)), the detected charge state, effect of collective motion of particles in the system and the resonance decay contributions before comparisons are made to the theoretical calculations. In this work, based on HRG model, we report that the net-baryon number fluctuations are least affected by experimental acceptances compared to the net-charge and net-strangeness number fluctuations.

We have compared the experimental data on charged-particle elliptic flow parameter (${v}_{2}$) in Au $+$ Au collisions at midrapidity for $\sqrt{{s}_{\mathrm{NN}}}=9.2$, $19.6$, $62.4$, and $200$ GeV with results from various models in heavy-ion collisions such as the ultrarelativistic quantum molecular dynamics (UrQMD) model, a multiphase transport model (AMPT), and heavy-ion jet interaction generator (HIJING). We observe that the average ${v}_{2}$ ($\ensuremath{\langle}{v}_{2}\ensuremath{\rangle}$) from the transport model UrQMD agrees well with the measurements at $\sqrt{{s}_{\mathrm{NN}}}=9.2$ GeV but increasingly falls short of the experimental $\ensuremath{\langle}{v}_{2}\ensuremath{\rangle}$ values as the beam energy increases. The difference in $\ensuremath{\langle}{v}_{2}\ensuremath{\rangle}$ is of the order of $60%$ at $\sqrt{{s}_{\mathrm{NN}}}=200$ GeV. The $\ensuremath{\langle}{v}_{2}\ensuremath{\rangle}$ results from HIJING are consistent with zero, while those from AMPT with default settings, a model based on HIJING with additional initial- and final-state rescattering effects included, give a $\ensuremath{\langle}{v}_{2}\ensuremath{\rangle}$ value of about $4%$ for all the beam energies studied. This is in contrast to an increase in $\ensuremath{\langle}{v}_{2}\ensuremath{\rangle}$ with beam energy for the experimental data. A different version of the AMPT model, which includes partonic effects and quark coalescence as a mechanism of hadronization, gives higher values of $\ensuremath{\langle}{v}_{2}\ensuremath{\rangle}$ among the models studied and is in agreement with the measured $\ensuremath{\langle}{v}_{2}\ensuremath{\rangle}$ values at $\sqrt{{s}_{\mathrm{NN}}}=200$ GeV. These studies show that the experimental $\ensuremath{\langle}{v}_{2}\ensuremath{\rangle}$ has substantial contribution from partonic interactions at $\sqrt{{s}_{\mathrm{NN}}}=200$ GeV, whose magnitude reduces with decrease in beam energy. We also compare the available data on the transverse momentum and pseudorapidity dependence of ${v}_{2}$ to those from these models.

Single crystals of Gd3Ga3Al2O12:Ce,B and CsI:Tl were grown by Czochralski and Bridgman techniques, respectively. While both the crystals exhibited similar emission at about 550 nm, their scintillation decay times showed significantly different characteristics. The average scintillation decay time of Gd3Ga3Al2O12:Ce,B crystal was found to be about 284 ns for alpha excitation compared to 108 ns measured for a gamma source. On the other hand in CsI:Tl crystals, the alpha excitation resulted in a lower average decay time of 600 ns compared to 1200 ns with gamma excitation. Their pulse shape discrimination (PSD) for gamma and alpha radiations were studied by coupling the scintillators with photomultiplier tube or SiPM and employing an advanced digitizer as well as a conventional zero-crossing setup. In spite of having a poor α/γ light yield ratio, the PSD figure of merit and the difference of zero-crossing time in Gd3Ga3Al2O12:Ce,B crystals were found to be superior in comparison to CsI:Tl crystals.

Indian Scintillator Matrix for Reactor Anti-Neutrinos (ISMRAN), a plastic scintillator array (10 × 10), is being constructed for the purpose of electron anti-neutrino (ν¯e) detection for reactor monitoring applications. A prototype detector called mini-ISMRAN, which consists of 16% of ISMRAN, has been setup for studying the detector response, background rates and event characterization in the reactor and non-reactor environment. The data acquisition system based on waveform digitizers is being used for pulse processing and event triggering. Monte-Carlo based simulations using GEANT4 are performed to optimize lead (Pb) and borated polyethylene (BP) shielding for background reduction and to study the positron, neutron and γ-ray response in the ISMRAN detector. Characterization of plastic scintillator detectors with known radioactive sources is performed for energy, timing and position measurements. Using the energy summation and bar multiplicity selection, coincident events from 60Co decay are reconstructed in non-reactor environment. Results from background measurements using various detectors are quantified in reactor ON and OFF condition. The shielding of 10 cm Pb and 10 cm BP along with the requirement of hits in multiple bars, reduces the uncorrelated background in reactor ON condition.

We study the effect of charged secondaries coming from resonance decay on the net-baryon, net-charge, and net-strangeness fluctuations in high-energy heavy-ion collisions within the hadron resonance gas (HRG) model. We emphasize the importance of including weak decays along with other resonance decays in the HRG, while comparing with the experimental observables. The effect of kinematic cuts on resonances and primordial particles on the conserved number fluctuations are also studied. The HRG model calculations with the inclusion of resonance decays and kinematical cuts are compared with the recent experimental data from STAR and PHENIX experiments. We find good agreement between our model calculations and the experimental measurements for both net-proton and net-charge distributions.

We derive a method to improve particle identification (PID) at high transverse momentum ($p_T$) using the relativistic rise of the ionization energy loss ($rdE/dx$) when charged particles traverse the Time Projection Chamber (TPC) at STAR. Electrons triggered and identified by the Barrel Electro-Magnetic Calorimeter (BEMC), pure protons and pions from $\Lambda\to p+\pi^{-}$ ($\bar{\Lambda}\to \bar{p}+\pi^{+}$), and $K^{0}_{S}\to\pi^{+}+\pi^{-}$ decays are used to obtain the $dE/dx$ value and its width at given $\beta\gamma=p/m$. We found that the deviation of the $dE/dx$ from the Bichsel function can be up to $0.4\sigma$ ($\sim3%$) in p+p collisions at $\sqrt{s_{NN}}=200$ GeV taken and subsequently calibrated in year 2005. The deviation is approximately a function of $\beta\gamma$ independent of particle species and can be described with a function of $f(x) = A+\frac{B}{C+x^{2}}$. The deviations obtained with this method are used to re-calibrate the data sample from p+p collision for physics analysis of identified hadron spectra and their correlations up to transverse momentum of 15 GeV/$c$. The ratio of $e^{-}/e^{+}$ (dominantly from $\gamma$-conversion) is also used to correct the residual asymmetry in the negative and positive charged hadrons due to momentun distortion in the STAR TPC.

We review a subset of experimental results from the heavy-ion collisions at the Large Hadron Collider (LHC) facility at CERN. Excellent consistency is observed across all the experiments at the LHC (at center of mass energy of 2.76 TeV) for the measurements such as charged particle multiplicity density, azimuthal anisotropy coefficients and nuclear modification factor of charged hadrons. Comparison to similar measurements from the Relativistic Heavy Ion Collider (RHIC) at lower energy (center of mass energy of 200 GeV) suggests that system formed at LHC has a higher energy density, larger system size, and lives for a longer time. These measurements are compared to model calculations to obtain physical insights on the properties of matter created at the RHIC and LHC.

Indian Scintillator Matrix for Reactor Anti-Neutrino (ISMRAN) experiment is the first indigenous effort in the country to measure the reactor based antineutrinos at very close distances (∼13 m) from the reactor core.The experiment is setup in DHRUVA research reactor and has been in the data taking mode since January 2022.The main goal of ISMRAN is to understand the Reactor Anti-neutrino Anamoly from a reactor core, which utilizes natural uranium as fuel.All previous measurements are performed using highly enriched 235 U fuel and observed a deficit of 4-6% in the antineutrino yield when compared with theory predictions.In this proceedings, we present first results from the complete ISMRAN setup at DHRUVA reactor hall.We will summarize the foreground activities that were carried out for the understanding of the ISMRAN detector response.A new generation of experiments for future, involving the measurement of reactor antineutrinos using coherent elastic scattering will also be discussed.

We show that the centrality dependence of charged particle and photon pseudorapidity density at midrapidity along with the transverse energy pseudorapidity density at SPS and RHIC energies scales with the number of participating constituent quarks. The number of charged particles and transverse energy per participant constituent quark is found to increase with increase in beam energy.

We report a systematic comparison of the recently measured cumulants of the net-proton distributions for 0–5% central Au + Au collisions in the first phase of the Beam Energy Scan (BES) Program at the Relativistic Heavy Collider facility to various kinds of possible baseline measures. These baseline measures correspond to an assumption that the proton and anti-proton distributions follow Poisson statistics, Binomial statistics, obtained from a transport model calculation and from a hadron resonance gas model. The higher order cumulant net-proton data for the center of mass energies (sNN) of 19.6 and 27 GeV are observed to deviate from most of the baseline measures studied. The deviations are predominantly due to the difference in shape of the proton distributions between data and those obtained in the baseline measures. We also present a detailed study on the relevance of the independent production approach as a baseline for comparison with the measurements at various beam energies. Our studies point to the need of either more detailed baseline models for the experimental measurements or a description via QCD calculations in order to extract the exact physics process that leads to deviation of the data from the baselines presented.

We discuss a method to obtain the true event-by-event net-charge multiplicity distributions from a corresponding measured distribution which is subjected to detector effects such as finite particle counting efficiency. The approach is based on the Bayes method for the unfolding of distributions. We are able to faithfully unfold back the measured distributions to match their corresponding true distributions obtained for a widely varying underlying particle production mechanism, beam energy and collision centrality. Particularly the mean, variance, skewness, kurtosis and their products and ratios of net-charge distributions from the event generators are shown to be successfully unfolded from the measured distributions constructed to mimic a real experimental distribution. We demonstrate the necessity to account for detector effects before associating the higher moments of net-charge distributions with physical quantities or phenomena. The advantage of this approach is that one need not construct new observables to cancel out detector effects which lose their ability to be connected to physical quantities calculable in standard theories.

We have studied the widths of the rapidity distributions of particles produced in nucleus-nucleus collisions at various center of mass energies and as a function of centrality at CERN Super Proton Synchrotron (SPS) energies. We show that the width of the rapidity distribution is sensitive to longitudinal flow, velocity of sound in the medium, and rescattering of particles. We explore the possibility of distinguishing the initial hard scattering regime from final state effects by studying the variation in the width of the rapidity distribution of the particles with centrality for various ${p}_{T}$ values.

We present the first results on 3-particle $Δη$-$Δη$ correlations in minimum bias $d$+Au, peripheral and central Au+Au collisions at $\sqrt{{\it s}_{NN}}$ = 200 GeV measured by the STAR experiment. The analysis technique is described in detail. The ridge particles, observed at large $Δη$ in dihadron correlations in central Au+Au collisions, appear to be uniformly distributed over the measured $Δη$-$Δη$ region in 3-particle correlation. The results, together with theoretical models, should help further our understanding of the underlying physics of the ridge.

Longitudinal scaling of pseudorapidity distribution of charged particles ($dN_{\mathrm {ch}}/d\eta$) is observed when presented as a function of pseudorapidity ($\eta$) shifted by the beam rapidity ($\eta$ - $y_{\mathrm {beam}}$) for a wide range of collision systems ($e^{+}+e^{-}$, p+p, $d$+A and A+A) and beam energies. Such a scaling is also observed for the elliptic flow ($v_{2}$) of charged hadrons in A+A collisions. This is a striking observation, as $v_{2}$ is expected to be sensitive to the initial conditions, the expansion dynamics and the degrees of freedom of the system, all of which potentially varies with collision system and colliding energies. We present a study of the longitudinal scalings of $dN_{\mathrm {ch}}/d\eta$, average transverse momentum ($< p_{\mathrm T}>$) and $v_{2}$ using transport models UrQMD and AMPT for Au+Au collisions at center of mass energies ($\sqrt{s_{\mathrm {NN}}}$) of 19.6, 62.4, 200 GeV and Pb+Pb collisions at 2760 GeV. Only the AMPT models which includes partonic effects and quark coalescence as a mechanism of hadronization, shows longitudinal scaling for $dN_{\mathrm {ch}}/d\eta$, $< p_{\mathrm T}>$ and $v_{2}$. Whereas the UrQMD and AMPT default versions show longitudinal scaling only for $dN_{\mathrm {ch}}/d\eta$ and $<p_{\mathrm T}>$. We also discuss the possibility of longitudinal scaling of $v_{2}$ within two extreme scenarios of models with hydrodynamic and collisionless limits. We find the longitudinal scaling of bulk observables to be an important test for the underlying physics mechanism in models of particle production.

We explore a hadron resonance gas model using Tsallis non-extensive distribution to study the energy dependence of the product of the moments, $S\sigma$ and $\kappa\sigma^2$ of net-proton multiplicity distributions of published STAR data in \auau collisions at relativistic heavy-ion collider (RHIC) energies. While excellent agreements are found between model predictions and measurements of $S\sigma$ and $\kappa \sigma^2$ of most peripheral collisions and $S\sigma$ of most central collisions, the $\kappa \sigma^2$ for most central collisions deviates significantly from the predictions particularly at \sqsn = 19.6 GeV and $27$ GeV. This could be an indication of the presence of dynamical fluctuations, which are not contained in the HRG-Tsallis model.

We report measurement of reactor based electron anti-neutrinos from a prototype array of plastic scintillator bars (mini-ISMRAN) located inside Dhruva research reactor hall, BARC. The detector setup took data for 128 days for reactor on (RON) and 51 days for reactor off (ROFF) condition. A detailed analysis procedure is developed to select the anti-neutrino candidate events based on the energy deposition, number of bars hit as well as topological event selection criteria in position and time. Each of these selection criteria are compared with Monte Carlo based simulations and further an embedding technique is used to estimate the efficiencies from a data driven background study. The obtained anti-neutrino like events in RON condition are 218 ± 50 (stat) ± 37 (sys) after background subtraction. The obtained results are compared with theoretical estimation which yields 214 ± 32 (sys) anti-neutrino events for the RON condition.

Abstract In this paper, we present a study to use thick plastic scintillators to reconstruct the cosmic muon tracks, that can be used for the applications like Muon Tomography. At Bhabha Atomic Research Centre (BARC), India, a plastic scintillator array — `ISMRAN (Indian Scintillator Matrix for Reactor Anti-Neutrinos),' with a total weight of 1.0 ton has been configured for neutrino physics study. Using the ISMRAN scintillators matrix, we present a technique of the position calibration of thick plastic scintillators using cosmic muons as a probe. The position resolution obtained from the cosmic muons based calibration method is compared with the one obtained from the traditional calibration method using the radioactive source. Finally, the accuracy of reconstructed cosmic muon tracks from the two position calibration techniques is compared using the χ 2 /ndf distribution of the fitted cosmic muon tracks.

Abstract We present new results from 3-particle pseudorapidity (Δ η ) correlation at mid-rapidity in Au + Au collisions at s N N = 200 GeV , measured by the STAR experiment. The charge ordering properties between associated and trigger particles are exploited to separate jet-like and ridge contributions in 3-particle Δ η – Δ η correlations. We found that like-sign triplets are dominated by ridge. The separated ridge, while narrow in Δ ϕ , is extremely broad in Δ η . The results indicate that the correlation of ridge particles are uniform not only with respect to the trigger particle but also between themselves event-by-event in our measured Δ η . In addition, the production of the ridge appears to be uncorrelated to the presence of the narrow jet-like component.

The Indian Scintillator Matrix for Reactor Anti-Neutrino detection—ISMRAN experiment aims to detect electron anti-neutrinos (e) emitted from a reactor via inverse beta decay reaction (IBD). The setup, consisting of 1 ton segmented Gadolinium foil wrapped plastic scintillator array, is planned for remote reactor monitoring and sterile neutrino search. The detection of prompt positron and delayed neutron from IBD will provide the signature of e event in ISMRAN. The number of segments with energy deposit (Nbars) and sum total of these deposited energies are used as discriminants for identifying prompt positron event and delayed neutron capture event. However, a simple cut based selection of above variables leads to a low e signal detection efficiency due to overlapping region of Nbars and sum energy for the prompt and delayed events. Multivariate analysis (MVA) tools, employing variables suitably tuned for discrimination, can be useful in such scenarios. In this work we report the results from an application of artificial neural network—the multilayer perceptron (MLP), particularly the Bayesian extension—MLPBNN, to the simulated signal and background events in ISMRAN. The results from application of MLP to classify prompt positron events from delayed neutron capture events on Hydrogen, Gadolinium nuclei and also from the typical reactor γ-ray and fast neutron backgrounds is reported. An enhanced efficiency of ∼ 91% with a background rejection of ∼ 73% for prompt selection and an efficiency of ∼ 89% with a background rejection of ∼ 71% for the delayed capture event, is achieved using the MLPBNN classifier for the ISMRAN experiment.

We study the effects of correlations on cumulants and their ratios of net-proton multiplicity distributions which have been measured for central (0\%-5\%) Au + Au collisions at the Relativistic Heavy Ion Collider (RHIC). This effect has been studied assuming individual proton and anti-proton distributions as a Poisson or Negative Binomial Distribution (NBD). In-spite of significantly correlated production due to baryon number, electric charge conservation and kinematical correlations of protons and anti-protons, the measured cumulants of the net-proton distribution follow the independent production model. In the present work we demonstrate how the introduction of the correlations will affect the cumulants and their ratios for the difference distributions. We have also demonstrated this study using the proton and anti-proton distributions obtained from the HIJING event generator.

We present a subset of experimental results on charge fluctuation from the heavy-ion collisions to search for phase transition and location of critical point in the QCD phase diagram. Measurements from the heavy-ion experiments at the SPS and RHIC energies observe that total charge fluctuations increase from central to peripheral collisions. The net-charge fluctuations in terms of dynamical fluctuation measure $\nu_{(+-,dyn)}$ are studied as a function of collision energy (\sqsn) and centrality of the collisions. The product of $\nu_{(+-,dyn)}$ and $\langle N_{ch} \rangle$ shows a monotonic decrease with collision energies, which indicates that at LHC energy the fluctuations have their origin in the QGP phase. The fluctuations in terms of higher moments of net-proton, net-electric charge and net-kaon have been measured for various \sqsn. Deviations are observed in both $S\sigma$ and $\kappa\sigma^2$ for net-proton multiplicity distributions from the Skellam and hadron resonance gas model for \sqsn $<$ 39 GeV. Higher moment results of the net-electric charge and net-kaon do not observe any significant non-monotonic behavior as a function of collision energy. We also discuss the extraction of the freeze-out parameters using particle ratios and experimentally measured higher moments of net-charge fluctuations. The extracted freeze-out parameters from experimentally measured moments and lattice calculations, are found to be in agreement with the results obtained from the fit of particle ratios to the thermal model calculations.

We report the higher-order cumulants and their ratios for baryon, charge and strangeness multiplicity in canonical and grand-canonical ensembles in ideal thermal model including all the resonances. When the number of conserved quanta is small, an explicit treatment of these conserved charges is required, which leads to a canonical description of the system and the fluctuations are significantly different from the grand-canonical ensemble. Cumulant ratios of total-charge and net-charge multiplicity as a function of collision energies are also compared in grand-canonical ensemble.

The ratios of off-diagonal and diagonal susceptibilities of conserved charges are studied using a hadron resonance gas (HRG) model with an emphasis towards providing a proper baseline for comparison to the corresponding future experimental measurements. We have studied the effect of kinematic acceptances, transverse momentum ($p_T$) and pseudorapidity ($\eta$), and different charged states on the ratios of the calculated susceptibilities. We find that the effect of $p_T$ and $\eta$ acceptance on the ratio of the susceptibilities are small relative to their dependence on the beam energy or the charged states of the used particles. We also present a HRG based calculation for various combinations of cumulant ratios of protons and pions, recently proposed as robust observables (with no theoretical uncertainties) for critical point search in the experiments. These results which increase as a function of collision energy will provide a better baseline for non-critical point physics compared to Poisson expectation.

We present new results on 2-particle azimuthal ($\Delta\phi$) correlation relative to event plane and 3-particle pseudorapidity ($\Delta\eta$) correlation at mid-rapidity in Au+Au collisions at $\sqrt{{\it s}_{NN}}$ = 200 GeV, measured by the STAR experiment. While jet-like correlation is symmetric, ridge is found to be asymmetric when trigger particle azimuth is between in- and out-of-plane. The charge ordering properties between associated and trigger particles are exploited to separate jet-like and ridge contributions in 3-particle $\Delta\eta$-$\Delta\eta$ correlations. We found that like-sign triplets are dominated by ridge. The separated ridge, while narrow in $\Delta\phi$, is extremely broad in $\Delta\eta$. The ridge particles are not only uncorrelated to the trigger particle in $\Delta\eta$, but also uncorrelated between themselves.

We study the net-charge fluctuation $D$-measure variable, in high-energy heavy-ion collisions in heavy-ion jet interaction generator (HIJING), ultrarelativistic quantum molecular dynamics (UrQMD), and hadron resonance gas (HRG) models for various center-of-mass energies ($\sqrt{{s}_{{}_{NN}}}$). The effects of kinematic acceptance and resonance decay, in the pseudorapidity acceptance interval ($\mathrm{\ensuremath{\Delta}}\ensuremath{\eta}$) and lower transverse momentum (${p}_{T}^{\text{min}}$) threshold, on fluctuation measures are discussed. A strong dependence of $D$ with the $\mathrm{\ensuremath{\Delta}}\ensuremath{\eta}$ in HIJING and UrQMD models is observed as opposed to results obtained from the HRG model. The dissipation of fluctuation signal is estimated by fitting the $D$ measure as a function of the $\mathrm{\ensuremath{\Delta}}\ensuremath{\eta}$. An extrapolated function for higher $\mathrm{\ensuremath{\Delta}}\ensuremath{\eta}$ values at lower $\sqrt{{s}_{{}_{NN}}}$ is different from the results obtained from models. Particle species dependence of $D$ and the effect of the ${p}_{T}^{\text{min}}$ selection threshold are discussed in HIJING and HRG models. The comparison of $D$, at midrapidity, of net-charge fluctuations at various $\sqrt{{s}_{{}_{NN}}}$ obtained from the models with the data from the A Large Ion Collider Experiment (ALICE) experiment is discussed. The results from the present paper as a function of $\mathrm{\ensuremath{\Delta}}\ensuremath{\eta}$ and $\sqrt{{s}_{{}_{NN}}}$ will provide a baseline for comparison to experimental measurements.

We report results of fast neutron response in plastic scintillator (PS) bars from deuterium-deuterium (D-D) and deuterium-tritium (D-T) reactions using Purnima Neutron Generator Facility, BARC, Mumbai. These measurements are useful in context of Indian Scintillator Matrix for Reactor Anti-Neutrino (ISMRAN) detection, an array of 10×10 PS bars, used to measure reactor anti-neutrinos through inverse beta decay (IBD) signal. ISMRAN detector, an above-ground experiment close to the reactor core (∼13m), deals with an active fast neutron background inside the reactor hall. A good understanding of fast neutron response in PS bars is an essential pre-requisite for suppression and discrimination of fast neutron background from IBD events. A monoenergetic neutron beam from the fusion reaction of D-D at 2.45 MeV and D-T at 14.1 MeV are used to characterize the energy response in these bars. The neutron energy response function has been simulated using the GEANT4 package and are compared with the measured data. A reasonable agreement of deposited energies by fast neutrons in PS bars between data and simulation are obtained for these reactions. The ratio of energy deposition in adjacent bars is used to discriminate between prompt IBD, fast neutron and neutron capture cascade gamma events.

We report the measurements of the fast neutron energy response in Indian Scintillator Matrix for Reactor Anti-Neutrinos (ISMRAN) detector consisting of an array of 9 $$\times $$ 10 Plastic Scintillator Bars (PSBs) at BARC, Mumbai. ISMRAN is an above ground detector setup at $${\sim }13\,\text {m}$$ from the Dhruva reactor core for the detection of reactor anti-neutrinos ( $${\overline{\nu }}_{e}$$ ) via the inverse beta decay (IBD) process. The dominant sources of reactor-related background in the vicinity of the detector are high energy $$\gamma $$ -rays and fast neutrons. Therefore, a good understanding of fast neutron response in PSB is an essential pre-requisite for suppression and discrimination of the fast neutron background from IBD events. Kinetic energies of the fast neutron were determined using the Time-of-Flight (TOF) technique, which is used to get the scintillation light yield due to recoiling proton in PSB. We also measured the fast neutron capture time distribution in ISMRAN array using a novel technique involving TOF of the measured fast neutrons. The observed characteristic neutron capture time ( $$\tau $$ ) of 68.29 ± 9.48 $$\upmu \text {s}$$ is in good agreement with GEANT4 based MC simulation. These experimentally measured results will be useful for discriminating correlated and uncorrelated (accidental) background events from the true IBD events in reactor ON and OFF conditions inside the reactor hall.

We present an analysis on the sensitivity to the active-sterile neutrino mixing with Germanium (Ge) and Silicon (Si) detectors in the context of the proposed coherent elastic neutrino-nucleus experiment in India. The study has been carried out with 3 (active) $+$ 1 (sterile) neutrino oscillation model. It is observed that the measurements that can be carried out with the Ge detector exhibit better sensitivity to the active-sterile neutrino mixing as compared to the Si detector. Both detectors are able to exclude most of the anomaly regions observed by the GALLIUM experiment. The Ge detector with mass 10 kg, can observe the active-sterile neutrino oscillation at 95$\%$ confidence level, provided that $\sin^{2}2\theta_{14}\geq 0.09$ at $\Delta m^{2}_{41}$ = 1.0 eV$^{2}$ for an exposure of 1-yr. At higher values of $\Delta m^{2}_{41}$, a better sensitivity is obtained at a short baseline. It is also found that the threshold as well as resolution of the detectors play a crucial role on the measurements of active-sterile neutrino mixing parameters.

The MACE (Major Atmospheric Cherenkov Experiment) telescope has started its regular gammaray observations at Hanle in India.Located at an altitude of ∼ 4.3 km above sea level and equipped with a 21 m diameter large quasi-parabolic reflector, it has the capability to explore the gamma-ray sky in the energy range above 20 GeV with very high sensitivity.In this work, we present the results from the feasibility studies for searching high-energy gamma-ray signals from dark matter interaction in potential astrophysical environments.We study the impact of MACE response function and other instrumental characteristics to probe the velocity average interaction cross-section (< >) of the weakly interacting massive particles (WIMPs), expected from the thermal dark matter freeze-out during the decoupling era.We consider the presence of dark matter in the form of pure WIMPs in the mass range 200 GeV -10 TeV to produce distinctive gamma-ray spectra through its self-annihilation into standard model particles using the Pythia simulation package.The convolution of gamma-ray spectra corresponding to different standard model channels with the MACE response function is used to estimate the upper limit on < > for 100 hours of expected MACE observation of Segue1 (a dwarf spheroidal galaxy) which is a potential site of dark matter.

The MACE (Major Atmospheric Cherenkov Experiment) telescope has started its regular gamma-ray observations at Hanle in India. Located at an altitude of $\sim$ 4.3 km above sea level and equipped with a 21 m diameter large quasi-parabolic reflector, it has the capability to explore the gamma-ray sky in the energy range above 20 GeV with very high sensitivity. In this work, we present the results from the feasibility studies for searching high-energy gamma-ray signals from dark matter interaction in potential astrophysical environments. We study the impact of MACE response function and other instrumental characteristics to probe the velocity average interaction cross-section ($<\sigma v>$) of the weakly interacting massive particles (WIMPs), expected from the thermal dark matter freeze-out during the decoupling era. We consider the presence of dark matter in the form of pure WIMPs in the mass range 200 GeV - 10 TeV to produce distinctive gamma-ray spectra through its self-annihilation into standard model particles using the Pythia simulation package. The convolution of gamma-ray spectra corresponding to different standard model channels with the MACE response function is used to estimate the upper limit on $<\sigma v>$ for 100 hours of expected MACE observation of Segue1 (a dwarf spheroidal galaxy) which is a potential site of dark matter.

We present an analysis on the sensitivity to the active-sterile neutrino mixing with Germanium (Ge) and Silicon (Si) detectors in the context of the proposed coherent elastic neutrino-nucleus experiment in India. The study has been carried out with 3 $(\mathrm{active})+1\text{ }(\mathrm{sterile})$ neutrino oscillation model. It is observed that the measurements that can be carried out with the Ge detector exhibit better sensitivity to the active-sterile neutrino mixing as compared to the Si detector. Both detectors are able to exclude most of the anomaly regions observed by the GALLIUM experiment. The Ge detector with mass 10 kg, can observe the active-sterile neutrino oscillation at 95% confidence level, provided that ${\mathrm{sin}}^{2}2{\ensuremath{\theta}}_{14}\ensuremath{\ge}0.09$ at $\mathrm{\ensuremath{\Delta}}{m}_{41}^{2}=1.0\text{ }\text{ }{\mathrm{eV}}^{2}$ for an exposure of 1-yr. At higher values of $\mathrm{\ensuremath{\Delta}}{m}_{41}^{2}$, a better sensitivity is obtained at a short baseline. It is also found that the threshold as well as resolution of the detectors play a crucial role on the measurements of active-sterile neutrino mixing parameters.

The cosmic rays data collected using a large area plastic scintillator array ISMRAN (Indian Scintillator Matrix for Reactor AntiNeutrino) are presented. The data collected serve as a useful benchmark of cosmogenic background in a non-reactor environment for the future measurements of electron–antineutrinos to be performed using the ISMRAN setup. The zenith angle distribution of the atmospheric muons has been measured and compared with Monte Carlo expectations. The detector setup was further used to measure the lifetime distribution of stopped muons and extract their rates inside the detector matrix. The measured spectra of decaying muons and associated electrons show a good agreement with the MC simulations performed through GEANT4 simulation.

We present a detailed study on detector response to different radioactive sources and the measurements of non-reactor environmental backgrounds with the Indian Scintillator Matrix for Reactor Anti-Neutrinos (ISMRAN) detector setup consisting of 9 × 10 Plastic Scintillator Bars (PSBs) array at BARC, Mumbai. These measurements are useful in the context of the ISMRAN detector setup, which will be used to detect the reactor anti-neutrinos (ν¯e) and measure its energy spectra through the inverse beta decay (IBD) process. A GEANT4 based Monte Carlo (MC) simulation is used to understand the optical transmission, energy resolution and energy non-linearity of the ISMRAN detector. A detailed analysis procedure has been developed to understand the natural radioactive, cosmogenic and cosmic muon-induced backgrounds with the ISMRAN detector setup in a non-reactor environment, based on their energy deposition, number of bars hit as well as topological event selection criteria in position and time for triggered events. Data and MC simulated distributions of reconstructed sum energy and number of bars hit has been compared for the radioactive γ + positron source such as 22Na placed at the center of the ISMRAN array. Fast neutron energy response and capture time distribution in ISMRAN array has been studied using a novel technique involving Time of Flight (TOF) of the measured fast neutrons. The observed characteristic neutron capture time (τ) of 68.29±9.48μs is in good agreement with ∼65μs obtained from MC simulation. These experimentally measured results will be useful for discriminating the correlated and uncorrelated background events from the true IBD events in reactor ON and OFF conditions inside the reactor hall.

An estimate of environmental background hit rate on triple-GEM chambers is performed using Monte Carlo (MC) simulation and compared to data taken by test chambers installed in the CMS experiment (GE1/1) during Run-2 at the Large Hadron Collider (LHC). The hit rate is measured using data collected with proton-proton collisions at 13 TeV and a luminosity of 1.5$\times10^{34}$ cm$^{-2}$ s$^{-1}$. The simulation framework uses a combination of the FLUKA and Geant4 packages to obtain the hit rate. FLUKA provides the radiation environment around the GE1/1 chambers, which is comprised of the particle flux with momentum direction and energy spectra ranging from $10^{-11}$ to $10^{4}$ MeV for neutrons, $10^{-3}$ to $10^{4}$ MeV for $\gamma$'s, $10^{-2}$ to $10^{4}$ MeV for $e^{\pm}$, and $10^{-1}$ to $10^{4}$ MeV for charged hadrons. Geant4 provides an estimate of detector response (sensitivity) based on an accurate description of detector geometry, material composition and interaction of particles with the various detector layers. The MC simulated hit rate is estimated as a function of the perpendicular distance from the beam line and agrees with data within the assigned uncertainties of 10-14.5%. This simulation framework can be used to obtain a reliable estimate of background rates expected at the High Luminosity LHC.

We report a systematic comparison of the recently measured cumulants of the net-proton distributions for 0-5\% central Au+Au collisions in the first phase of the Beam Energy Scan (BES) Program at the Relativistic Heavy Collider facility to various kinds of possible baseline measures. These baseline measures correspond to assuming that the proton and anti-proton distributions, follow Poisson statistics, Binomial statistics, obtained from a transport model calculation and from a hadron resonance gas model. The higher order cumulant net-proton data corresponding to the center of mass energies ($\sqrt{s_{NN}}$) of 19.6 and 27 GeV are observed to deviate from all the baseline measures studied. The deviations are predominantly due to the difference in shape of the proton distributions between data and those obtained in the baseline measures. We also present a detailed study on the relevance of the independent production approach as a baseline for comparison with the measurements at various beam energies. Our studies points to the need for a proper comparison of the experimental measurements to QCD calculations in order to extract the exact physics process that leads to deviation of the data from the baselines presented.

New results of the STAR collaboration show the energy dependence of the moments (mean M , variance σ, skewness S and kurtosis κ) and their products for net-proton multiplicity distribution at RHIC energies [1]. The product of the moments Sσ and κσ are related to the ratios of susceptibilities (χ) associated with the baryon number conservation. The recent STAR measurements of Sσ and κσ show significant deviations from the predictions of the Skellam distribution (where κσ should be unity) at all energies indicating presence of large non-statistical fluctuations. The particle production in heavy ion collisions at relativistic energies is well described in terms of the hadron resonance gas (HRG) model. The success of HRG model would mean that thermal system which might have gone through a possible phase transition has (nearly) equilibrated. It is believed that if the thermal system has retained some memory of the phase transition with finite correlation length at freeze out, it must be reflected in the higher moments of the conserved quantities. Therefore, the study of fluctuations in various conserved quantities like: netbaryon number through the higher moments using HRG model is expected to provide a baseline to observe the deviation in experimental observables, which may indicate the presence of non statistical fluctuations, if any. It has been realized that particle production in heavy ion and proton-proton collisions at RHIC and LHC energies can be described successfully using a power law type distribution rather than the exponential one. Therefore, the Tsallis distribution function is being used for particle production with nonextensive pa-

We explore a hadron resonance gas model using Tsallis non-extensive distribution to study the energy dependence of the product of the moments, $S\sigma$ and $\kappa\sigma^2$ of net-proton multiplicity distributions of published STAR data in \auau collisions at relativistic heavy-ion collider (RHIC) energies. While excellent agreements are found between model predictions and measurements of $S\sigma$ and $\kappa \sigma^2$ of most peripheral collisions and $S\sigma$ of most central collisions, the $\kappa \sigma^2$ for most central collisions deviates significantly from the predictions particularly at \sqsn = 19.6 GeV and $27$ GeV. This could be an indication of the presence of dynamical fluctuations, which are not contained in the HRG-Tsallis model.

Quantum chromodynamics (QCD), the theory of strong interaction, predicts that nuclear matter at high temperature and/or densities undergoes a phase transition from a state with hadrons as dominant degrees of freedom to a state where partonic degrees of freedom prevail. One of the major goal of recent theoretical and experimental study is to discover an important feature of the QCD phase diagram, namely the critical end point (CEP) at which a line of the first order phase transitions separating quark-gluon plasma from hadronic matter comes to an end [1]. The presence of CEP would result in large correlation lengths i.e. large fluctuations in various thermodynamic quantities. Higher moments of the conserved quantities like net-baryon (∆B), net-electric charge (∆Q) and net-strangeness (∆S), which can be related to the susceptibility of the system, are generally considered to be sensitive indicators to search for CEP in heavy-ion collisions.

One of the main reasons for studying high energy heavy ion collisions came from QCD prediction for possible manifestation of the phase transition in which a new phase of matter, quark gluon plasma (QGP), is produced. Although the exact nature of phase transition (whether first or second order) is still not known, the lattice results suggest that the phase transition at high temperature and low baryon density could be a simple cross over from QGP to hadron phase as contrast to a first order phase transition which is expected at low temperature and high baryon density. Consequently, it is natural to assume the existence of a critical end point (CEP) on the μ − T phase diagram that indicates a change from cross over to a first order transition. Recently, experiments are carried out at RHIC at various collision energies to search for the possible existence of CEP. While analyzing the data from PHENIX experiment at various energies for net-charge fluctuations, which could be a possible signature of phase transition, we developed a phenomenological model to interpret the results.

An unfolding method, based on Bayes theorem is presented to obtain true event-by-event netcharge multiplicity distribution from a corresponding measured distribution, which is subjected to detector artifacts.The unfolding is demonstrated to work for widely varying particle production mechanism, beam energy and collision centrality.Further the necessity of taking into account the detector effects is emphasized before comparing the experimental measurements to the theoretical calculations, particularly in case of higher moments.The advantage of this approach being that one need not construct new observable to cancel out detector effects which loose their ability to be connected to physical quantities calculable in standard theories.

We review a subset of experimental results from the heavy-ion collisions at the Large Hadron Collider (LHC) facility at CERN. Excellent consistency is observed across all the experiments at the LHC (at center of mass energy of 2.76 TeV) for the measurements such as charged particle multiplicity density, azimuthal anisotropy coefficients and nuclear modification factor of charged hadrons. Comparison to similar measurements from the Relativistic Heavy Ion Collider (RHIC) at lower energy (center of mass energy of 200 GeV) suggests that system formed at LHC has a higher energy density, larger system size, and lives for a longer time. These measurements are compared to model calculations to obtain physical insights on the properties of matter created at the RHIC and LHC.

An unfolding method, based on Bayes theorem is presented to obtain true event-by-event net-charge multiplicity distribution from a corresponding measured distribution, which is subjected to detector artifacts. The unfolding is demonstrated to work for widely varying particle production mechanism, beam energy and collision centrality. Further the necessity of taking into account the detector effects is emphasized before comparing the experimental measurements to the theoretical calculations, particularly in case of higher moments. The advantage of this approach being that one need not construct new observable to cancel out detector effects which loose their ability to be connected to physical quantities calculable in standard theories.

We have compiled the experimentally measured pbar/p ratio at midrapidity in p+p collisions from \sqrt{s} = 23 to 7000 GeV and compared it to various mechanisms of baryon production as implemented in PYTHIA, PHOJET and HIJING/B-Bbar models. For the models studied with default settings, PHOJET has the best agreement with the measurements, PYTHIA gives a higher value for \sqrt{s} < 200 GeV and the ratios from HIJING/B-Bbar are consistently lower for all the \sqrt{s} studied. Comparison of the data to different mechanisms of baryon production as implemented in PYTHIA shows that through a suitable tuning of the suppression of diquark-antidiquark pair production in the color field relative to quark-antiquark production and allowing the diquarks to split according to the popcorn scheme gives a fairly reasonable description of the measured pbar/p ratio for \sqrt{s} < 200 GeV. Comparison of the beam energy dependence of the pbar/p ratio in p+p and nucleus-nucleus (A+A) collisions at midrapidity shows that the baryon production is significantly more for A+A collisions relative to p+p collisions for \sqrt{s} < 200 GeV. We also carry out a phenomenological fit to the y_beam dependence of the pbar/p ratio.

Protons (p) and anti-protons (p) are the most abundantly produced baryons in high energy collisions. These have been measured at various center of mass energies ( √ s) in hadron-hadron collisions at ISR, STAR and ALICE experiments as a function of rapidity (y) and transverse momentum (pT). In this paper, we compare the experimentally measured anti-proton to proton ratio at midrapidity in p+p collision at various center of mass energy ( √ s = 23 to 7000 GeV) with models PYTHIA [1], PHOJET [2] and HIJING/B-B [3] to understand the baryon production mechanism in these collisions. We also present the asymmetry for proton and anti-proton production at midrapidity for p+p collisions as a function of √ s.

Jet production in heavy-ion collisions at relativistic energies provide an excellent opportunity to study the in-medium modification and the energy loss mechanism of partons in strongly interacting quark-gluon plasma.A detailed overview of jet results from CMS experiment for PbPb, pp and pPb collisions are presented in this paper.The in-medium modification of the jets are quantified with the isolated photon-jet imbalance measurements in the PbPb collisions.Comparison of nuclear modification factor (R AA ) for different particles, inclusive jets and b-jets are presented for PbPb and pPb collisions at 2.76 TeV and 5.02 TeV, respectively.The differential jet shapes and jet fragmentation functions are presented for the charged particles in pp and PbPb collisions.The momentum flow of charged particles in unbalanced jet events is discussed in context of recovery of the lost energy by these energetic jets in the PbPb collisions.

We report the measurement of the non-reactor environmental backgrounds and the detector response with the Indian Scintillator Matrix for Reactor Anti-Neutrinos (ISMRAN), which is $\sim$1 ton detector setup by volume, consisting of 10$\times$9 (10 rows and 9 columns) Plastic Scintillator Bars (PSBs) array at BARC, Mumbai, India. ISMRAN is an above-ground anti-neutrino ($\mathrm{\overline\nu_{e}}$) experiment at very short baseline located at Dhruva research reactor facility. It is enclosed by a shielding made of 10 cm thick lead and 10 cm thick borated polyethylene to minimize the backgrounds and is mounted on a movable base structure, situated at $\sim$ 13 m away from the reactor core. These measurements are useful in the context of the ISMRAN detector setup that will be used to detect the reactor $\mathrm{\overline\nu_{e}}$ and measure its energy spectrum through the inverse beta decay (IBD) process. In this paper, we present the energy resolution model and energy non-linearity model of PSB and the cosmogenic muon-induced background, based on the sum of their energy depositions and number of hit bars. Reconstructed sum energy spectrum and number of hit bars distribution for $\mathrm{{}^{22}Na}$ radioactive source has been compared with Geant4 based Monte Carlo simulations. These experimentally measured results will be useful for discriminating the correlated and uncorrelated background events from the true IBD events in reactor ON and OFF conditions inside the reactor hall.

Indian Scintillator Matrix for Reactor Anti-Neutrino (ISMRAN), made of an array of plastic scintillator bars, has been proposed for the remote monitoring of the nuclear reactor by using anti-neutrinos . The proposed experiment will be housed in Dhruva reactor at Bhabha Atomic Research Centre, Mumbai, India. In this talk, we present the progress and status of the ISMRAN project and will discuss the results related to the gamma and neutron background measurements at the reactor hall. We will also present the preliminary estimates of the feasibility of this project at Dhruva reactor.

The transverse momentum ($p_{\mathrm T}$) spectra for identified charged pions, protons and anti-protons from $p$+$p$ and $d$+Au collisions are measured around midrapidity ($\mid$y$\mid$ $<$ 0.5) over the range of 0.3 $<$ $p_{\mathrm T}$ $<$ 10 GeV/$c$ at $\sqrt{s_{\mathrm {NN}}}$ = 200 GeV. The charged pion and proton+anti-proton spectra at high p_{T} in p+p collisions have been compared with the next-to-leading order perturbative quantum chromodynamic (NLO pQCD) calculations with a specific fragmentation scheme. The p/pi^{+} and pbar/pi^{-}has been studied at high p_{T}. The nuclear modification factor (R_{dAu}) shows that the identified particle Cronin effects around midrapidity are significantly non-zero for charged pions and to be even larger for protons at intermediate p_{T} (2 < p_{T} < 5 GeV/c).

The cosmic rays data collected using a large area plastic scintillator array ISMRAN (Indian Scintillator Matrix for Reactor AntiNeutrino) are presented. The data collected serve as a useful benchmark of cosmogenic background in a non-reactor environment for the future measurements of electron-antineutrinos to be performed using the ISMRAN setup. The zenith angle distribution of the atmospheric muons has been measured and compared with Monte Carlo expectations. The detector setup was further used to measure the lifetime distribution of stopped muons and extract their rates inside the detector matrix. The measured spectra of decaying muons and associated electrons show a good agreement with the MC simulations performed through GEANT4 simulation.