arXiv subjects

Biswarup Paul

Publications and source records attributed to Biswarup Paul.

18 recordsLinked to original sources

arXiv2026

Quarkonium $p_{\rm T}$ spectra in heavy--ion collisions at LHC energies within a hydrodynamic core--corona framework

We present a systematic study of the transverse momentum ($p_{\rm T}$) spectra of charmonium (J/$\psi$, $\psi(2S)$) and bottomonium ($\Upsilon(nS)$) states in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV within an analytical relativistic hydrodynamics framework. The medium evolution is described assuming cylindrical symmetry with boost-invariant longitudinal expansion and Hubble-like transverse flow. Quarkonium spectra are evaluated using the Cooper-Frye formalism on a constant-temperature freeze-out hypersurface, supplemented by a core--corona approach to include both thermal and non-thermal contributions. The model describes the measurements from ALICE and CMS over a broad $p_{\rm T}$ range. For charmonium, both the spectra and the $\psi(2S)$/J/$\psi$ ratio are well reproduced, while deviations at high $p_{\rm T}$ for J/$\psi$ indicate additional hard production mechanisms. In the bottomonium sector, the $\Upsilon(nS)$ spectra and their yield ratios are successfully described, consistent with the expected sequential suppression pattern. These results demonstrate that an analytical hydrodynamic approach combined with a core-corona framework provides a unified and transparent description of quarkonium production in heavy--ion collisions at LHC energies.

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↗

arXiv2026

Systematic study of bottomonium production in proton-proton collisions at LHC energies

We present a comprehensive study of $\Upsilon(nS)$ ($n=1,2,3$) production in proton-proton ($pp$) collisions at various LHC energies and rapidity ranges within the framework of leading-order non-relativistic quantum chromodynamics (NRQCD) factorization. The transverse momentum ($p_{\rm T}$)-dependent production cross sections are calculated, incorporating both direct and feed-down contributions. Specifically, the feed-down contributions to $\Upsilon(1S)$ include those from $\Upsilon(2S)$, $\Upsilon(3S)$, $\chi_{bJ}(1P)$, and $\chi_{bJ}(2P)$, while $\Upsilon(2S)$ receives feed-down from $\Upsilon(3S)$ and $\chi_{bJ}(2P)$. For $\Upsilon(3S)$, feed-down from the $\chi_{bJ}(3P)$ states is also taken into account. The computed cross sections and cross section ratios among different $\Upsilon$ states are compared with experimental measurements from ALICE, ATLAS, CMS, and LHCb. It is found that the experimental cross sections and cross section ratios are well described within the theoretical uncertainties arising from the choices of the factorization and renormalization scales for $p_{\rm T}>4$ GeV and $p_{\rm T}>0$ GeV, respectively. Furthermore, the cross section ratios exhibit a clear saturation behavior beyond $p_{\rm T}\approx 40$ GeV.

hep-ph↗

arXiv2026

Charmonium suppression in fixed target proton-nucleus collisions

In this article, we perform a systematic investigation of the cold nuclear matter (CNM) effects, operative on charmonium ($J/\psi$, $\psi(2S)$) production, in fixed target proton-nucleus (p+A) collisions. Influence on charmonium production cross section due to the interplay of three different plausible CNM effects namely the initial-state parton energy loss, nuclear shadowing, and final-state absorption of the resonant states, are evaluated in detail. The available data on charmonium production in fixed target p+A collision experiments from SPS, Fermilab and HERA-B are examined for this purpose. The beam energy dependence of the observed $J/\psi$ production patterns are utilized to anticipate level of "normal" absorption in the upcoming proton induced collisions by the NA60+ experiment at CERN SPS and the CBM experiment at FAIR SIS100 accelerator facilities.

nucl-th↗

arXiv2025

Wave-Breaking Phenomena in Quark-Gluon Plasma

We investigate the onset of wave-breaking in the quark-gluon plasma (QGP) formed in heavy-ion collisions at both RHIC and the LHC. A nonlinear longitudinal color field is coupled to a three-dimensional viscous hydrodynamic background constrained by experimental conditions: Pb-Pb at $\sqrt{s_{\rm NN}}=5.02$ TeV (LHC) and Au-Au at $\sqrt{s_{\rm NN}}=200$ GeV (RHIC). The instantaneous wave-breaking threshold is determined from the in-medium plasma frequency, while the field evolution follows a nonlinear Landau equation with Debye screening and expansion damping. At the LHC, the higher initial temperature and density drive the system above the threshold within $τ\lesssim $ 2.3 fm/$c$, whereas at RHIC the cooler and more dilute medium delays wave-breaking to $τ\simeq 2.8$~fm/$c$. Scans over initial temperature, density, thermalization time, QGP lifetime, and collision system (RHIC vs LHC) confirm the robustness of this instability against parameter variations. These results identify wave-breaking as a universal microscopic mechanism for the early loss of coherence and rapid onset of hydrodynamics in the QGP, providing a common explanation for the fast equilibration observed at both RHIC and the LHC.

nucl-th↗

arXiv2025

A systematic study of initial state quark energy loss in fixed target proton nucleus collision

In this article, we investigate parton energy loss in cold nuclear matter by studying the ratio of Drell-Yan production cross sections in fixed-target proton-nucleus (p + A) collisions. We analyze Drell-Yan production cross-section data from the Fermilab E866 and E906 experiments using two different quark energy loss parametrization models and various parton distribution functions for 800 GeV and 120 GeV proton beams incident on light and heavy nuclear targets. The sensitivity of the energy loss parameter on the employed parton distribution function has been thoroughly investigated. Our results have been used to predict the target mass dependence of Drell-Yan production in upcoming proton-induced collisions at SPS and FAIR.

nucl-th↗

arXiv2022

Charmonium production in pp collisions at energies available at the CERN Large Hadron Collider

We have performed a systematic study of J/$ψ$ and $ψ$(2S) production in p--p collisions at different Large Hadron Collider (LHC) energies and at different rapidities using the leading order non-relativistic quantum chromodynamics model of heavy quarkonium production. We have included the contributions from hiher excited states decaying to J$ψ$ . The calculated values have been compared with the available data from the four experiments at LHC, namely ALICE, ATLAS, CMS and LHCb. In the case of ALICE, inclusive J/$ψ$ and $ψ$(2S) cross-sections have been calculated by including the feed-down from B mesons using a fixed-order next-to-leading logarithm formalism. It is found that all the experimental cross-sections are well described for $p_{\rm T} >$ 3 GeV within the theoretical uncertainties arising due to the choices of the factorization and renormalization scales.

hep-ph↗

arXiv2022

Quarkonium production in p-Pb collisions with ALICE

ALICE has measured quarkonium production in p-Pb collisions at backward ($-$4.46 $<$ $y_{\rm cms}$ $<$ $-$2.96), mid ($-$1.37 $<$ $y_{\rm cms}$ $<$ 0.43) and forward (2.03 $<$ $y_{\rm cms}$ $<$ 3.53) rapidity ($y$) regions down to zero transverse momentum ($p_{\rm T}$). The inclusive J/$ψ$ production has been studied at mid-$y$ in p-Pb interactions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV and at forward and backward $y$ in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV and 8.16 TeV. The comparison of the J/$ψ$ production to the one of the loosely bound $ψ$(2S) state is discussed, together with new results on the nuclear modification factors of the $Υ$(1S) and $Υ$(2S) states measured at forward and backward $y$. All the results will be compared to those obtained at lower energies and with available theoretical calculations.

nucl-ex↗

arXiv2022

$ψ$(2S) production and nuclear modification factor in nucleus--nucleus collisions with ALICE

Charmonium production is a probe sensitive to deconfinement in nucleus--nucleus collisions. The production of J/$ψ$ via regeneration within the QGP or at the phase boundary has been identified as an important ingredient for the description of the observed centrality and $p_{\rm T}$ dependence at the LHC. $ψ$(2S) production relative to J/$ψ$ is one possible discriminator between the two different regeneration scenarios. At RHIC and at the LHC, there is so far no significant observation of the $ψ$(2S) in nucleus--nucleus collisions in central events at low transverse momentum, where regeneration is the dominating process. The combined Run 2 data set of ALICE allows to extract a significant $ψ$(2S) signal in such a kinematic region at forward rapidity in the dimuon decay channel. In this contribution, we present for the first time results on the $ψ$(2S)-to-J/$ψ$ double ratio and the $ψ$(2S) nuclear modification factor in Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV, calculated with respect to a new pp reference with improved precision. Results are compared with model calculations.

nucl-ex↗

arXiv2022

Recent ALICE results on quarkonium production in nuclear collisions

Quarkonium production has long been regarded as a potential signature of deconfinement in nucleus-nucleus collisions. Recently, the production of J/$ψ$ via regeneration within the quark-gluon plasma (QGP) or at the phase boundary has been identified as an important ingredient for the interpretation of quarkonium production results from lead-lead collisions at the Large Hadron Collider (LHC). Quarkonium polarization could also be used to investigate the properties of the hot and dense medium created at the LHC energies. In this contribution, the latest ALICE results on quarkonium will be presented and discussed. These include, among others, the nuclear modifications of (prompt and non-prompt) J/$ψ$ and $ψ$(2S) production, and the J/$ψ$ polarisation, all measured with lead-lead collisions at the LHC. The results will be compared with available theoretical model calculations.

nucl-ex↗

arXiv2021

Prospects for quarkonium studies at the high-luminosity LHC

Prospects for quarkonium-production studies accessible during the upcoming high-luminosity phases of the CERN Large Hadron Collider operation after 2021 are reviewed. Current experimental and theoretical open issues in the field are assessed together with the potential for future studies in quarkonium-related physics. This will be possible through the exploitation of the huge data samples to be collected in proton-proton, proton-nucleus and nucleus-nucleus collisions, both in the collider and fixed-target modes. Such investigations include, among others, those of: (i) J/psi and Upsilon produced in association with other hard particles; (ii) chi(c,b) and eta(c,b) down to small transverse momenta; (iii) the constraints brought in by quarkonia on gluon PDFs, nuclear PDFs, TMDs, GPDs and GTMDs, as well as on the low-x parton dynamics; (iv) the gluon Sivers effect in polarised-nucleon collisions; (v) the properties of the quark-gluon plasma produced in ultra-relativistic heavy-ion collisions and of collective partonic effects in general; and (vi) double and triple parton scatterings.

hep-ph↗

arXiv2017

Charmonium production in p-Pb collisions with ALICE at the LHC

The suppression of quarkonium production with respect to pp collisions is one of the most distinctive signatures of the formation of quark-gluon plasma (QGP), a hot nuclear medium created in ultrarelativistic heavy-ion collisions. However, the suppression of heavy quarkonium production with respect to pp collisions can also take place in p-A collisions, where QGP is not expected to be created and only cold nuclear matter (CNM) effects, such as nuclear absorption, parton shadowing and parton energy loss in initial and final states occur. The study of p-A collisions is therefore important to disentangle the effects of QGP from the CNM ones, and to provide essential input to understand the nucleus-nucleus collisions. The ALICE Collaboration at the LHC has studied inclusive J/$ψ$ production, in the dimuon decay channel, at forward rapidity (2.03 $<$ $y_{\rm cms}$ $<$ 3.53) and backward rapidity ($-$4.46 $<$ $y_{\rm cms}$ $<$ $-$2.96) in p-Pb collisions at $\sqrt{s_{\rm NN}} = 8.16$ TeV with the Muon Spectrometer. In this contribution, we present the measurement of the nuclear modification factor of inclusive J/$ψ$ as a function of the centrality and we show the comparison of this result with the one at $\sqrt{s_{\rm NN}} = 5.02$ TeV.

nucl-ex↗

arXiv2016

Charmonium production in Pb-Pb collisions at $\sqrt{s_{\rm NN}} =$ 2.76 and 5.02 TeV with ALICE

The production of charmonium states, J/$ψ$ and $ψ$(2S), in heavy-ion collisions, is an important probe to investigate the formation of a plasma of quarks and gluons (QGP). In a hot and deconfined medium, quarkonium production is, indeed, expected to be significantly modified, with respect to the pp yields, due to a balance of color screening and charm-quark recombination mechanisms. The ALICE Collaboration at the LHC has measured charmonium production in Pb-Pb collisions at $\sqrt{s}_{\rm NN} =$ 2.76 and 5.02 TeV. The nuclear modification factor of inclusive J/$ψ$, evaluated at forward ($-4<η<-2.5$) rapidity, is measured as a function of the centrality of the collision and of the J/$ψ$ kinematic variables as transverse momentum and rapidity. In this article, we report on the new J/$ψ$ results, obtained at forward rapidity, at $\sqrt{s}_{\rm NN} = 5.02$ TeV. These new results are compared to the J/$ψ$ nuclear modification factor obtained at $\sqrt{s}_{\rm NN} =$ 2.76 TeV and to the available theoretical predictions.

nucl-ex↗

arXiv2016

Inclusive $ψ$(2S) production at forward rapidity in pp, p-Pb and Pb-Pb collisions with ALICE at the LHC

The ALICE Collaboration has studied inclusive $ψ$(2S) production in pp, p-Pb and Pb-Pb collisions with the ALICE Muon Spectrometer which covers the rapidity range 2.5 $<$ $y_{\rm lab}$ $<$ 4. The $ψ$(2S) measurement was performed in the dimuon decay channel. The $ψ$(2S) production cross-section and $ψ$(2S) to J/$ψ$ cross-section ratio in pp collisions will be presented, both integrated and differential in rapidity and in transverse momentum. In p-Pb collisions, $ψ$(2S) results will be compared to the J/$ψ$ ones by means of the production cross-section ratio and the double ratio [$ψ$(2S)/J/$ψ$]$_{\mathrm {pPb}}$/[$ψ$(2S)/J/$ψ$]$_{\mathrm {pp}}$ studied as a function of the resonance transverse momentum and event activity of the collision. The $ψ$(2S) nuclear modification factor, $R_{\mathrm {pPb}}$, will also be presented. Theoretical models based on nuclear shadowing, coherent energy loss or both cannot describe our results. Therefore other mechanisms must be invoked in order to describe the $ψ$(2S) production. Finally, results on $ψ$(2S) production in Pb-Pb collisions will be shown in two transverse momentum ranges as a function of centrality.

nucl-ex↗

arXiv2014

Systematic study of Charmonium production in pp collisions at the LHC energies

We have performed a systematic study of $J/ψ$ and $ψ(2S)$ production in $p-p$ collisions at different LHC energies and at different rapidities using the leading order (LO) non-relativistic QCD (NRQCD) model of heavy quarkonium production. We have included the contributions from $χ_{cJ}$ ($J$ = 0, 1, 2) and $ψ(2S)$ decays to $J/ψ$. The calculated values have been compared with the available data from the four experiments at LHC namely, ALICE, ATLAS, CMS and LHCb. In case of ALICE, inclusive $J/ψ$ and $ψ(2S)$ cross-sections have been calculated by including the feed-down from $B$ meson using Fixed-Order Next-to-Leading Logarithm (FONLL) formalism. It is found that all the experimental cross-sections are well reproduced for $p_T >$ 4 GeV within the theoretical uncertainties arising due to the choice of the factorization scale. We also predict the transverse momentum distributions of $J/ψ$ and $ψ(2S)$ both for the direct and feed-down processes at the upcoming LHC energies of $\sqrt{s} =$ 5.1 TeV and 13 TeV for the year 2015.

hep-ph↗

arXiv2014

Suppression of inclusive J/$\mathbfψ$ and $\mathbfψ$(2S) production in p-Pb collisions with ALICE at the LHC

The ALICE Collaboration has studied inclusive J/$ψ$ and $ψ$(2S) production in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV with the Muon Spectrometer. The measurement was performed at forward (2.03 $<$ $y_{\rm cms}$ $<$ 3.53) and backward ($-$4.46 $<$ $y_{\rm cms}$ $<$ $-$2.96) centre of mass rapidities. The nuclear modification factor of J/$ψ$ and $ψ$(2S) has been measured as a function of transverse momentum and event activity. Theoretical models based on nuclear shadowing, coherent energy loss or both are in reasonable agreement with the J/$ψ$ results but cannot describe the $ψ$(2S) behaviour. Other mechanisms must be invoked in order to explain the $ψ$(2S) suppression in p-Pb collisions.

nucl-ex↗

arXiv2014

Inclusive J/$ψ$ and $ψ$(2S) production in pp collisions at $\sqrt{s} = 7$ TeV at forward rapidity with ALICE at LHC

The ALICE collaboration has studied inclusive J/$ψ$ and $ψ$(2S) production at forward rapidities in pp collisions at $\sqrt{s} = 7$ TeV with the ALICE Muon Spectrometer. The analysis has been carried out on a data sample corresponding to an integrated luminosity $\mathcal{L}_{\rm int}$ = 1.35 pb$^{-1}$. The production cross-sections of J/$ψ$ and $ψ$(2S), integrated over \pt\ (0 $<$ \pt\ $<$ 20 GeV/$c$) and \y\ (2.5 $<$ \y\ $<$ 4), have been measured. The J/$ψ$ and $ψ$(2S) differential cross-sections, in transverse momentum and rapidity, have also been measured. The results have been compared with the previous ALICE published results at $\mathcal{L}_{\rm int}$ = 15.6 nb$^{-1}$ and also with the measurement performed by LHCb collaboration. The $ψ$(2S)/J/$ψ$ production ratio (acceptance corrected) integrated over \pt\ and \y\ has been measured. This ratio have also been measured as a function of transverse momentum and rapidity. The ratio as a function of transverse momentum has been compared with the LHCb measurement.

nucl-ex↗

arXiv2014

Inclusive J/$ψ$ and $ψ$(2S) production in pp and p-Pb collisions at forward rapidity with ALICE at the LHC

The ALICE collaboration has studied inclusive J/$ψ$ and $ψ$(2S) production at forward rapidities in pp collisions at $\sqrt{s} = 7$ TeV with the ALICE Muon Spectrometer. The analysis has been carried out on a data sample corresponding to an integrated luminosity $\mathcal{L}_{\rm int}$ = 1.35 pb$^{-1}$. The production cross-sections of J/$ψ$ and $ψ$(2S), integrated over the transverse momentum (0 $<$ $p_{\mathrm T}$ $<$ 20 GeV/$c$) and rapidity (2.5 $<$ $y$ $<$ 4), have been measured. The J/$ψ$ and $ψ$(2S) differential cross-sections, in transverse momentum and rapidity, have also been measured, significantly extending the $p_{\mathrm T}$ reach of previous measurements performed in the same $y$-range. The results have been compared with the previously published ALICE results ($\mathcal{L}_{\rm int}$ = 15.6 nb$^{-1}$) and also with the measurement performed by the LHCb collaboration. The $ψ$(2S)/J/$ψ$ ratio, integrated over $p_{\mathrm T}$ and $y$, has been measured. This ratio has also been evaluated as a function of transverse momentum and rapidity and compared with the LHCb measurement. Finally, recent results on cross-sections, $ψ$(2S)/J/$ψ$ production ratio, nuclear modification factor ($R_{\rm pPb}$) and forward-to-backward yield ratio ($R_{\rm FB}$) in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV will be discussed.

nucl-ex↗