arXiv subjects

Ekata Nandy

Publications and source records attributed to Ekata Nandy.

5 recordsLinked to original sources

arXiv2026

Intrinsic coupling between transverse spherocity and elliptic flow in heavy-ion collisions

Transverse spherocity ($S_{0}$) is an event-shape observable widely used to classify collision events according to their topology, particularly to distinguish jet-like from isotropic events. Low-spherocity events are generally interpreted as being associated with enhanced jet activity. This event classification has also been applied to heavy-ion collisions to investigate the influence of event topology on several observables, including elliptic flow and constituent-quark-number scaling. In this work, we demonstrate that such an interpretation requires careful reconsideration. Using toy Monte Carlo simulations, A Multiphase Transport (AMPT) model calculations, and an analytical formulation of the spherocity observable, we show that transverse spherocity is intrinsically related to the elliptic flow coefficient, $v_{2}$. This connection arises because the axis that minimizes the spherocity aligns with the event symmetry plane, causing events with larger elliptic anisotropy to naturally exhibit smaller spherocity values even in the absence of genuine jet-like topologies. We further show that this intrinsic relation gives rise to an inherent anti-correlation between transverse spherocity and $v_{2}$, implying that several characteristics previously attributed to the enhanced jet-like nature of low-spherocity events in heavy-ion collisions can instead be understood as consequences of collective anisotropic flow. Our results indicate that, in heavy-ion collisions, transverse spherocity should be interpreted primarily as a probe of the collective momentum-space anisotropy rather than as a direct measure of jetty event topology. Consequently, physics conclusions drawn from spherocity-selected events should explicitly account for its intrinsic correlation with elliptic flow.

nucl-th↗

arXiv2026

Impact of Baryon anti-Baryon annihilation on hyperon ($\Lambda$, $\bar\Lambda$) production and apparent strangeness enhancement in $\bar\Lambda/\bar{p}$ in heavy ion collisions at SPS energy

A deconfined medium of quarks and gluon, called the Quark-Gluon Plasma (QGP) is produced when heavy-nuclei are collided at relativistic energies. The QGP formation is often characterized by a phenomenon called strangeness enhancement where, the relative production of strange-to-non-strange particles are enhanced in central collisions compared to peripheral or proton-proton interactions. Besides the enhancement in K/$\pi$ ratios, a non-monotonic energy dependence was also reported for $\bar{\Lambda}$ to $\bar{p}$ ratios at CERN SPS, attributed to a signature for the strangeness enhancement as well. As anti-particles are produced directly from the reaction, the $\bar{\Lambda}$/$\bar{p}$ ratios are considered as a cleaner probe for the strangeness enhancement. However, at this energy range hadronic interactions have a dominant role to play and, importantly for $\bar{\Lambda}$ and $\bar{p}$, processes like baryon-anti-baryon ($\mathrm{B\bar{B}}$) annihilation can have a significant impact. In this work, we use a hadronic transport model UrQMD, to investigate the role of baryon-anti-baryon ($\mathrm{B\bar{B}}$) annihilation on $\Lambda$, $\bar{\Lambda}$ hyperon production and its effect on $\bar{\Lambda}$/$\bar{p}$ ratios. The UrQMD calculations that include $\mathrm{B\bar{B}}$ annihilation can produce the trend of average transverse mass spectra for $\Lambda$ and $\bar{\Lambda}$, as well as, the characteristic enhancement in $\bar{\Lambda}$/$\bar{p}$ ratios in data as a function of centrality and collision energy. Furthermore, $\bar{\Lambda}$/$\bar{p}$ ratios extracted from the feed-down corrected SPS data are seen to be in good agreement with UrQMD model calculations with $\mathrm{B\bar{B}}$ annihilation. This suggests that $\bar{\Lambda}$/$\bar{p}$ enhancement is not necessarily because of strangeness enhancement and $\mathrm{B\bar{B}}$ annihilation has a significant role to play.

nucl-th↗

arXiv2026

Searching for initial state fluctuations in heavy ion collisions at FAIR energy using Principal Component Analysis

In high energy heavy ion collisions, the initial configurations of the colliding nuclei play an important role in determining the reaction type and the products of the reaction. The initial arrangement of nucleons within the overlap region of two colliding nuclei is generally asymmetric and such asymmetries reflect themselves in the measurement final state momentum anisotropy. Also initial distribution of the nucleons are subjected to large quantum fluctuation causing large energy deposition in a small region. The final state observables related momentum anisotropies although sensitive to such localized fluctuations but their true effect gets diluted because these observables are calculated by averaging over a set of events. Also, such fluctuations in the initial states are random and uncontrolled. Thus, identifying their effect from event-averaged final state observable is difficult. However, it would be interesting to know the origin of such fluctuations and how these fluctuation are eventually translated to the final state. In this work, we at first introduce such localized fluctuations in the initial configurations, also called hot spots, by implementing spatial rearrangements of nucleon position in the colliding nuclei in the central Pb+Pb collisions at E$_{lab}$=20 AGeV ($\sqrt{s}$=6.27 GeV) using the UrQMD event generator. Then the final state distributions of one or two dimensional variables e.g., ($\eta$, $\phi$, $p_T$) and ($\eta-p_T$, $\phi-p_T$, $\eta-\phi$) of the produced pions are analysed using the principal component analysis (PCA) technique. The eigenvalues of the principal components have been studied for various initial configurations, event fractions containing hot spots in the initial condition and for event centralities with an aim to find it's sensitivity to the initial hot spot configurations.

nucl-th↗

arXiv2026

Analysis of quarkonium polarization in proton-proton (p-p) collisions at LHC using PYTHIA model

The measurement of polarization serves as an important probe to investigate the production mechanism of quarkonia, the bound state of heavy quark anti-quark (charm or bottom) pairs, in hadronic collisions. In experimental invesigations, the polarization is usually measured by analyzing the anisotropies in the angular distribution of the muons originating from the decay of the quarkonium state. In the present article, we study the charmonia ($J/\psi$) and bottomonia ($\Upsilon(1S)$) polarization at $\sqrt{s} =7 $ and 13 TeV in proton-proton(p-p) collisions at LHC using Monte Carlo (MC) event generator model PYTHIA8, which is based on perturbative QCD. The transverse momentum ($p_{T}$) differential distribution has been calculated at forward rapidity ($2.5 < y_{\mu\mu} < 4.0$) and the polarization parameters are estimated in Helicity and Collins-Sooper reference frames. In addition, to mimic realistic experimental conditions, we have incorporated, in PYTHIA simulations, effects like detector inefficiencies and muon momentum smearing. These contributions alter the polarization parameters, introducing an artificial degree of polarization, if not properly corrected for. The simulation results have been compared with the recent ALICE measurements for quarkonia polarization in p-p collisions at LHC energy regime.

hep-ph↗

arXiv2025

Testing a large size triple GEM detector for the first station of the CBM-Muon Chambers with a high-intensity gamma source at GIF++ under large-area illumination

The physics studies at heavy-ion nucleus-nucleus collision experiments demand reliable detectors at high particle flux. Therefore, Gas Electron Multipliers (GEM) detectors, which show resilience to extreme radiation, are one of the prime choices for the upcoming Compressed Baryonic Matter (CBM) experiment at the Facility of Antiproton and Ion Research, Germany. However, operating them under these demanding conditions requires a systemic study at the highest incident particle flux. To this end, we have conducted extensive tests on a real-size triple GEM detector module with the high-intensity gamma flux using the Cs-137 source at the upgraded Gamma Irradiation Facility (GIF++) at Conseil Europ\'een pour la Recherche Nucl\'eaire (CERN). The detector response, particularly regarding the gain and efficiency of muon detection, was studied extensively with and without a gamma source in a free-streaming mode using self-triggered electronics. This configuration will be necessary for the CBM experiment since it will observe unprecedented event rates of about 10 MHz for Au-Au collisions. The analysis reveals an alignment between the expected and observed value of gain and efficiency with an increasing intensity of gamma flux at the operating voltage. The test results demonstrate that the large-size GEM detector prototype can handle elevated gamma rates of approximately 17.25 MHz/cm2 without significantly impacting its performance or suffering irreversible damage.

hep-ex↗