arXiv subjects

Ashwini Kumar

Publications and source records attributed to Ashwini Kumar.

9 recordsLinked to original sources

arXiv2022

Pseudorapidity Window Size Dependence of Multiplicity Fluctuations in High-Energy Collisions with System Size and Beam Energies

An investigation of the critical behavior of strongly interacting QCD matter has been performed by analyzing fluctuation observables on event-by-event (ebe) basis measured in high-energy collision experiments. The fluctuation analysis is performed using nuclear interactions at different target sizes and at different colliding beam energies as a function of varying width of pseudorapidity interval. For the sake of comparison, event-by-event multiplicity fluctuations in hadronic and heavy-ion collisions (p-H, p-A and A-B) are studied within the framework of the Lund Monte Carlo based FRITIOF model. Charged particle multiplicity and the variance of the multiplicity distribution are estimated for the interactions involving different target sizes and beam momenta i.e., p-H, p-CNO, p-AgBr at 200A GeV/c and $^{16}$O-AgBr collisions at 14.6, 60 and 200A GeV/c. Further, multiplicity fluctuations are quantified in terms of intensive quantity, the scaled variances $\omega$ and the strongly intensive quantity $\Sigma_{FB}$ derived from the charged particle multiplicity and the width of the multiplicity distribution. Strongly intensive quantity $\Sigma_{FB}$ is a quantity of great significance to extract information about short and long-range multiplicity correlations. Furthermore, the collision centrality and centrality bin width dependent behavior of the multiplicity fluctuation have been examined in the framework of Lund Monte Carlo based FRITIOF model. Results based on the fluctuation analysis carried out in the present study are interpreted in terms of dynamics of collision process and the possibility of related QCD phase transition.

nucl-ex↗

arXiv2019

Multiple-Rate Channel Codes in $\texttt{GF}(p^{n^{2}})$

A code $\mathcal{C}(n, k, d)$ defined over $\texttt{GF}(q^{n})$ is conventionally designed to encode a $k$-symbol user data into a codeword of length $n$, resulting in a fixed-rate coding. This paper proposes a coding procedure to derive a multiple-rate code from existing channel codes defined over a composite field $\texttt{GF}(q^{n})$. Formally, by viewing a symbol of $\texttt{GF}(q^{n})$ as an $n$-tuple over the base field $\texttt{GF}(q)$, the proposed coding scheme employs children codes $\mathcal{C}_{1}(n, 1), \mathcal{C}_{2}(n, 2), \ldots, \mathcal{C}_{n}(n, n)$ defined over $\texttt{GF}(q)$ to encode user messages of arbitrary lengths and incorporates a variable-rate feature. In sequel, unlike the conventional block codes of length $n$, the derived multiple-rate code of fixed blocklength $n$ (over $\texttt{GF}(q^{n})$) can be used to encode and decode user messages ${\bf m}$ (over $\texttt{GF}(q)$) of arbitrary lengths $|{\bf m}| = k, k+1, \ldots, kn$, thereby supporting a range of information rates - inclusive of the code rates $1/n, 2/n, \ldots, (k-1)/n$, in addition to the existing code rate $k/n$. The proposed multiple-rate coding scheme is also equipped with a decoding strategy, wherein the identification of children encoded user messages of variable length are carried out through a simple procedure using {\it orthogonal projectors}.

cs.IT↗

arXiv2018

Correlations and Event-by-Event Fluctuations in High Multiplicity Events Produced in $^{208}$Pb-$^{208}$Pb Collisions

Analysis of high multiplicity events produced in 158A GeV/c $^{208}$Pb-$^{208}$Pb collisions is carried out to study the event-by-event fluctuations. The findings reveal that the method of scaled factorial moments can be used to identify the events having densely populated narrow phase space bins. A few events sorted out adopting this approach are individually analyzed. It is observed that these events do exhibit large fluctuations in their pseudorapidity, $\eta$ and azimuthal angle, $\phi$ distributions arising out due to some dynamical reasons. Two particle $\Delta\eta$-$\Delta\phi$ correlation study applied to these events too indicates that some complex two-dimensional structure of significantly high magnitude are present in these events which might have some dynamical origin. The findings reveal that the method of scaled factorial moments may be used as an effective triggering for events with large dynamical fluctuations.

hep-ex↗

arXiv2017

Study of charged particle production in $U$-$U$ collisions in a Wounded Quark Model

Recently, there has been a growing interest in the study of deformed uranium-uranium ($U$-$U$) collisions in its various geometrical configurations due to their usefulness in understanding the different aspects of quantum chromodynamics (QCD). In this paper we have studied the particle production in deformed $U$-$U$ collisions at $\sqrt{s_{NN}}$ = $193$ GeV using modified wounded quark model (WQM). At first, we have shown the variation of quark-nucleus inelastic scattering cross-section ($\sigma_{qA}^{in}$) with respect to centralities for various geometrical orientations of $U$-$U$ collisions in WQM. After that we have calculated the pseudorapidity density ($dn_{ch}/d\eta$) within WQM using two-component prescription. Further we have calculated the transverse energy density distribution ($dE_{T}/d\eta$) along with the ratio of transverse energy to charged hadron multiplicity ($E_{T}/N_{ch}$) for $U$-$U$ collisions and compared them with the corresponding experimental data. We have shown the scaling behavior of $dn_{ch}/d\eta$ and $dE_{T}/d\eta$ for different initial geometry of $U$-$U$ collision with respect to $p$-$p$ data at $\sqrt{s_{NN}}=200$ GeV. Furthermore we have shown the Bjorken energy density achieved in $U$-$U$ collisions for various configurations and compared them with experimental data of $Au$-$Au$ at 200 GeV. We observe that the present model suitably describes the experimental data for minimum bias geometrical configuration of $U$-$U$ collisions. An estimate for various observables in different initial geometries of $U$-$U$ collisions is also presented which will be tested in future by experimental data.

nucl-th↗

arXiv2016

Multiplicity and Pseudorapidity distributions of charged particles in asymmetric and deformed nuclear collisions in a Wounded Quark Model

The charged particle multiplicity ($n_{ch}$) and pseudorapidity density $(dn_{ch}/d\eta)$ are key observables to characterize the properties of matter created in heavy ion collisions. The dependence of these observables on collision energy and the collision geometry are a key tool to understand the underlying particle production mechanism. Recently a lot of focus has been made on asymmetric and deformed nuclei collisions since these collisions can provide a deeper understanding about the nature of quantum chromodynamics (QCD). On phenomenological perspective a unified model which describes the experimental data coming from various kind of collision experiments, is much needed to provide the physical insights about the production mechanism. In this paper, we have calculated the charged hadron multiplicities for nucleon-nucleus (such as proton-lead $(p-Pb)$ and asymmetric nuclei collisions like deutron-gold $(d-Au)$, and copper-gold $(Cu-Au)$ within a new version of wounded quark model (WQM) and shown their variation with respect to centrality. Further we have used a suitable density function within our WQM to calculate pseudorapidity density of charged hadrons at mid-rapidity in the collisions of deformed uranium nuclei. We found that our model with suitable density functions describes the experimental data for symmetric, asymmetric and deformed nuclei collisions simultaneously over a wide range of collision energy.

hep-ph↗

arXiv2015

Event by Event Analysis of High Multiplicity Events Produced in 158 A GeV/c 208 Pb- 208 Pb Collisions

An extensive analysis of individual high multiplicity events produced in 158 A GeV /c 208Pb- 208Pb collisions is carried by adopting different methods to examine the anomalous behavior of these rare events. A method of selecting the events with densely populated narrow regions or spikes out of a given sample of collision events is discussed.Employing this approach two events with large spikes in their eta- and phi- distributions are selected for further analysis. For the sake of comparison, another two events which do not exhibit such spikes are simultaneously analyzed. The findings suggest that the systematic studies of particle density fluctuations in one- and two-dimensional phase-spaces and comparison with those obtained from the studies of correlation free Monte Carlo events, would be useful for identifying the events with large dynamical fluctuations. Formation of clusters or jet like phenomena in multihadronic final states in individual events is also discussed and the experimental findings are compared with the independent particle emission hypothesis by carrying out Monte Carlo simulations.

nucl-ex↗

arXiv2013

Charged Hadron Multiplicity Distribution at Relativistic Heavy Ion Colliders

The present article reviews facts and problems concerning charge hadron production in high energy collisions. Main emphasis is laid on the qualitative and quantitative description of general characteristics and properties observed for charged hadrons produced in such high energy collisions. Various features of available experimental data e.g., the variations of charged hadron multiplicity and pseudo-rapidity density with the mass number of colliding nuclei, center-of-mass energies and the collision centrality obtained from heavy-ion collider experiments are interpreted in the context of various theoretical concepts and their implications. Finally, several important scaling features observed in the measurements mainly at RHIC and LHC experiments are highlighted in the view of these models to draw some insight regarding the particle production mechanism in heavy-ion collisions.

hep-ph↗

arXiv2013

Wounded Quarks and Multiplicity at Relativistic Ion Colliders

In this paper, we propose a parameterization which is based on a phenomenological model involving the wounded quarks interactions for explaining the average charged particle multiplicity $\ < n_{ch}\ >$, the central pseudo-rapidity density $\ < (dn/dη)_{η=0}\ >$ and complete rapidity dependence of $dn/dη$ in relativistic heavy-ion collider experiments. The model also interrelates nucleus-nucleus (A-A) collisions with p-A and p-p interactions. Our parameterization rests on simple assumptions regarding mean number of participating quarks and their average number of collisions. The results for $\ < n_{ch}\ >$ and their variations with the mass number of colliding nuclei, center-of-mass energy ($\sqrt{s_{NN}}$) and collision centrality are well supported by the available experimental data. Finally we give the predictions from our model for A-A collisions at the Large Hadron Collider (LHC) and Compressed Baryonic Matter (CBM) experiments. Our results indicate the existence of a possible universal production mechanism for p-p, p-A and A-A collisions.

hep-ph↗

arXiv2012

Prediction of Charged Hadron Multiplicity at LHC and CBM Experiments

A systematic study of charged hadron multiplicities ($n_{ch}$) at various collision energies is very much important in understanding the basic production mechanism of the hadrons in nucleus-nucleus collision experiments. Furthermore, the variations of $n_{ch}$ in nucleus-nucleus collisions with respect to the colliding energy and mass number can provide a potential probe for the formation of quark gluon plasma (QGP) in the laboratory. In this paper, we propose a phenomenological model based on the constituent quark-quark interactions to calculate the average multiplicity ($n_{ch}$) and pseudorapidity density at mid-rapidity ($(dn_{ch}/dη)_{η=0}$) of charged hadrons at various center-of-mass energies $(\sqrt{s_{NN}})$ for nucleus-nucleus ($A-A$) collisions. We first propose a new parametrization for $n_{ch}^{pp}$ and $(dn_{ch}/dη)^{pp}_{η=0}$ in $p-p$ interactions based on some initial inputs which fit the experimental data very well. We further extend this parametrization by using simple phenomenological assumptions regarding mean number of participating quarks and mean number of collisions to obtain the $n_{ch}$ and $(dn_{ch}/dη)_{η=0}$ for $A-A$ collisions and show their dependencies on the mass number of colliding nuclei as well as on $\sqrt{s_{NN}}$. We also compare the results obtained from our model with the results obtained from the modified Glauber model in order to demonstrate the difference between the two formalisms. Finally, we compare the charged hadron multiplicity and pseudorapidity density at mid-rapidity for $A-A$ collisions obtained from our model with the available experimetal data from various heavy-ion collision experiments and give our predictions for $A-A$ collisions at the Large Hadron Collider (LHC) and at Compressed Baryonic Matter (CBM) experiments.

hep-ph↗