arXiv subjects

Sudhansu S. Biswal

Publications and source records attributed to Sudhansu S. Biswal.

18 recordsLinked to original sources

arXiv2026

Probing $Υ({1S})$, $η_b$ and $h_b$ resonances in proton-lead collisions at the LHCb

We explore the production of bottomonium states in proton--lead (pPb) collisions at the Large Hadron Collider (LHC) within the frameworks of Non-Relativistic Quantum Chromodynamics (NRQCD) and modified NRQCD (MNRQCD). In this work, we present theoretical predictions for the production cross-section, the nuclear modification factor $R_{\rm pPb}$ and the forward-to-backward production ratio $R_{\rm FB}$ of $Υ(1S)$ as functions of transverse momentum and rapidity in the LHCb kinematic region. The MNRQCD framework, which incorporates perturbative soft-gluon emissions from color-octet states, provides description of quarkonium production in heavy-ion collision. Furthermore, using heavy-quark spin symmetry, we estimate the production cross-sections and expected event yields of the spin-singlet bottomonium states $η_b$ and $h_b$ within both NRQCD and MNRQCD. The predictions show significant differences between the two approaches in the integrated cross-sections and transverse momentum distributions of these resonances. Therefore, these results could provide important benchmarks for future experimental measurements at LHCb and contribute to a deeper understanding of bottomonia production and nuclear modifications in proton--lead collisions.

hep-ph↗

arXiv2025

Probing charmonia resonances in proton-lead collisions at the LHC

After achieving a successful description of charmonia production in proton-proton (pp) collisions within Non-Relativistic Quantum Chromodynamics (NRQCD) and modified NRQCD (MNRQCD) frameworks, we now extend our study to proton-lead (p-Pb) collisions at the Large Hadron Collider (LHC). In this context, theoretical predictions for the production cross-section, the nuclear modification factor $R_{pPb}$ and forward -to-backward production ratio $R_{FB}$ of $J/ψ$ have been made as a function of transverse momentum and rapidity at the LHC. MNRQCD provides a reasonable agreement with the available LHC data for $J/ψ$ production. Furthermore, using the heavy quark symmetry relation, we have estimated the production cross sections and expected number of events of $η_{c}$ and $h_{c}$ production in both NRQCD and MNRQCD. Notably, the predictions exhibit substantial differences in the integrated cross-sections as well as in the $p_T$ distributions for these states at the LHC, highlighting the importance of further experimental and theoretical studies of these resonances to advance our understanding of quarkonium production.

hep-ph↗

arXiv2024

Predictions for $h_c$ and $h_b$ production at the LHC

The production cross sections of $h_c$ and $h_b$, the ${}^1P_1$ quarkonia can be predicted in Non-Relativistic Quantum Chromodynamics (NRQCD) using heavy quark symmetry. Our study includes predictions for both the integrated cross-section and the transverse momentum ($p_T$) distribution of $h_c$ ($h_b$) production at the Large Hadron Collider (LHC), using the decay process $h_c (h_b) \rightarrow η_c (η_b) + γ$, $η_c (η_b) \rightarrow p \overline{p}$. We demonstrate substaintial discrepancies in integrated cross-section and the $p_T$ distribution of ${}^1P_1$ quarkonia production at the LHC using Colour-Singlet Model (CSM), NRQCD and modified NRQCD. Measuring these resonances at the LHC could discriminate between these models, thereby offering further insights into the dynamics of quarkonium production. In addition, we compare the recent LHCb data for the integrated cross-section of $h_c$ production at $\sqrt{s}$ = 13 TeV in the kinematic range 5.0 $<$ $p_T$ $<$ 20.0 GeV and 2.0 $<$ $y$ $<$ 4.0 with the theoretical predictions using NRQCD and modified NRQCD. Modified NRQCD gives an agreement with the recent LHCb experimental data.

hep-ph↗

arXiv2023

Bottomonia production in Modified NRQCD

Motivated by the success of Modified Non-Relativistic Quantum Chromodynamics (Modified NRQCD) in explaining data from experiments at the Large Hadron Collider (LHC) for charmonia, we now turn to the study of bottomonium production at the LHC. Modified NRQCD does very well in explaining $Υ$ data from the LHC. But this is true also of NRQCD which explains the $Υ$ data equally well. Where the two models differ substantially is in their predictions for $η_b$ production. As was the case with $η_c$, the measurement of $η_b$ production at the LHC will be another decisive test of Modified NRQCD.

hep-ph↗

arXiv2023

Resolution of the LHCb $η_c$ anomaly

Due to the heavy-quark symmetry of Non-Relativistic Quantum Chromodynamics (NRQCD), the cross-section for the production of $η_c$ can be predicted. This NRQCD prediction when confronted with data from the LHCb is seen to fail miserably. We address this LHCb $η_c$ anomaly in this paper using a new approach called modified NRQCD, an approach that has been shown to work extremely well for studying $J/ψ$, $ψ^{\prime}$ and $χ_c$ production at the LHC. We show, in the present paper, that the predictions for $η_c$ production agrees very well with LHCb measurements at the three different values of energy that the experiment has presented data for. Modified NRQCD also explains the intriguing agreement of the LHCb $η_c$ data with the colour-singlet prediction. The remarkable agreement of the theoretical predictions with the LHCb data suggests that modified NRQCD is closer to apprehending the true dynamics of quarkonium production.

hep-ph↗

arXiv2022

$χ_c$ production in modified NRQCD

In a previous paper, we had modified Non-Relativistic QCD as it applies to quarkonium production by taking into account the effect of perturbative soft-gluon emission from the colour-octet quarkonium states. We tested the model by fitting the unknown non-perturbative parameter in the model from Tevatron data and using that to make parameter-free predictions for $J/ψ$ and $ψ'$ production at the LHC. In this paper, we study $χ_c$ production: we fit as before the unknown matrix-element using data from Tevatron. We, then, extend the results of the previous paper for $J/ψ$ production by calculating the effect of $χ_c$ feed-down to the $J/ψ$ cross-section, which, by comparing with CMS results at $\sqrt{s}=$ 13 TeV, we demonstrate to be small. We have also computed $χ_c^1$ and $χ_c^2$ at $\sqrt{s}=$7 TeV and find excellent agreement with data from the ATLAS experiment.

hep-ph↗

arXiv2022

Understanding $J/ψ$ and $ψ'$ production using a modified version of Non-Relativistic Quantum Chromodynamics

There is serious disagreement between the predictions of Non-Relativistic Quantum Chromodynamics (NRQCD) and the data on $J/ψ$ polarisation which has persisted for almost a quarter of a century. We find that if we account for the effect of perturbative soft gluons on the intermediate charm-anticharm octet states in NRQCD then the polarisation problem can be resolved. In addition, this model, when used to fit the Run 1 data on $J/ψ$ and $ψ'$ production from the CDF experiment at Tevatron, gives good fits and yields values of (energy-independent) non-perturbative parameters. These, in turn, can be used to make parameter-free predictions for $J/ψ$ and $ψ'$ data from the CMS experiment at the Large Hadron Collider and the predictions are in excellent agreement with the CMS data.

hep-ph↗

arXiv2017

Probing Left-Right Seesaw using Beam Polarization at an $e^+e^-$ Collider

We show that the longitudinal beam polarization option at a future electron-positron collider provides an unambiguous distinction between low-scale seesaw models of neutrino mass. This is possible due to the fact that the pair production cross section of the heavy neutrinos in seesaw models is sensitive to the polarization of the initial lepton beams, and for a suitable choice of the polarization, shows a clear enhancement over the unpolarized cross section. More interestingly, the choice of the beam polarization for which the enhancement is maximum is governed by the size of the light-heavy neutrino mixing parameter. We also find that using this effect, one can probe a previously uncharted parameter space of the left-right seesaw model, which is complementary to the existing searches at both energy and intensity frontiers.

hep-ph↗

arXiv2014

Anomalous Triple Gauge Vertices at the Large Hadron-Electron Collider

At a high energy $ep$ collider, such as the Large Hadron-Electron Collider (LHeC) which is being planned at CERN, one can access the $WWγ$ vertex exclusively in charged current events with a radiated photon, with no interference from the $WWZ$ vertex. We find that the azimuthal angle between the jet and the missing momentum in each charged current event is a sensitive probe of anomalous $WWγ$ couplings, and show that for quite reasonable values of integrated luminosity, the LHeC can extend the discovery reach for these couplings beyond all present experimental bounds.

hep-ph↗

arXiv2013

Probing chromomagnetic and chromoelectric couplings of the top quark using its polarization in pair production at hadron colliders

The Tevatron, where the top quark was discovered, and the currently functional Large Hadron Collider (LHC), with copiously produced top pairs, enable a detailed study of top-quark properties. In particular, they can be used to test the couplings of the top quark to gauge bosons. Several extensions of the standard model (SM) can give rise to anomalous couplings of the top quark to gauge bosons, in particular, the gluons. In this work we examine how top-quark polarization, which is predicted to be negligibly small in the SM, can be used to measure chromomagnetic and chromoelectric couplings of the top quark to gluons. We lay special emphasis on the use of angular distributions and asymmetries of charged leptons arising from top decay as measures of top polarization and hence of these anomalous couplings. Sensitivities that may be reached at the Tevatron and the LHC are obtained.

hep-ph↗

arXiv2012

Azimuthal Angle Probe of Anomalous HWW Couplings at the LHeC

A high energy ep collider, such as the proposed LHeC, possesses the unique facility of permitting direct measurement of the HWW coupling without contamination from the HZZ coupling. At such a machine, the fusion of two W bosons through the HWW vertex would give rise to typical charged current (CC) events accompanied by a Higgs boson. We demonstrate that azimuthal angle correlations between the observable CC final states could then be a sensitive probe of the nature of the HWW vertex and hence of the CP properties of the Higgs boson.

hep-ph↗

arXiv2012

New physics contributions to the forward-backward asymmetry at the Tevatron

The Tevatron has measured a discrepancy relative to the Standard Model prediction in the forward-backward asymmetry in top quark pair production. This asymmetry grows with the rapidity difference of the two top quarks. It also increases with the invariant mass of the tt pair, reaching, for high invariant masses, 3.4 standard deviations above the Next to Leading Order prediction for the charge asymmetry of QCD. However, perfect agreement between experiment and the Standard Model was found in both total and differential cross section of top quark pair production. As this result could be a sign of new physics we have parametrized this new physics in terms of a complete set of dimension six operators involving the top quark. We have then used a Markov Chain Monte Carlo approach in order to find the best set of parameters that fits the data, using all available data regarding top quark pair production at the Tevatron. We have found that just a very small number of operators are able to fit the data better than the Standard Model.

hep-ph↗

arXiv2011

Top quark forward-backward asymmetry at Tevatron and its implications at the LHC

The measurement of forward-backward asymmetry in the top and anti-top quark ($t \bar{t}$) production has been recently reconfirmed by the CDF Collaboration and shows a more than $3σ$ deviation from the Standard Model(SM) prediction in the large $t \bar{t}$ invariant mass region. Models with new W$^{\prime}$ or Z$^{\prime}$ bosons have been invoked to explain this deviation. In the context of these models we perform a $χ^2$ analysis with all the available experimental numbers in different $ΔY$ and $M_{t \bar{t}}$ bins. We show that for the $Z^{\prime}$ model the region of parameter space which explain the Tevatron asymmetry can be probed in the same sign top production channel by Tevatron itself. Moreover, we consider a recently proposed observable, the one sided forward-backward asymmetry ($A_{OFB}$) at the LHC and conclude that both the W$^{\prime}$ and Z$^{\prime}$ models can lead to sizable $A_{OFB}$ even at the LHC running at a center of mass energy of 7 TeV for the model parameters consistent with the Tevatron measurements.

hep-ph↗

arXiv2010

eta_c production at the Large Hadron Collider

We have studied the production of the 1S_0 charmonium state, eta_c, at the Large Hadron Collider (LHC) in the framework of Non-Relativistic Quantum Chromodynamics (NRQCD) using heavy-quark symmetry. We find that NRQCD predicts a large production cross-section for this resonance at the LHC even after taking account the small branching ratio of eta_c into two photons. We show that it will be possible to test NRQCD through its predictions for eta_c, with the statistics that will be achieved at the early stage of the LHC, running at a center of mass energy of 7 TeV with an integrated luminosity of 100 pb^{-1}

hep-ph↗

arXiv2009

Use of transverse beam polarization to probe anomalous VVH interactions at a Linear Collider

We investigate use of transverse beam polarization in probing anomalous coupling of a Higgs boson to a pair of vector bosons, at the International Linear Collider (ILC). We consider the most general form of VVH (V = W/Z) vertex consistent with Lorentz invariance and investigate its effects on the process e+ e- --> f bar{f} H, f being a light fermion. Constructing observables with definite CP and naive time reversal (tilde T) transformation properties, we find that transverse beam polarization helps us to improve on the sensitivity of one part of the anomalous ZZH coupling that is odd under CP. Even more importantly it provides the possibility of discriminating from each other, two terms in the general ZZH vertex, both of which are even under CP and tilde T. Use of transverse beam polarization when combined with information from unpolarized and linearly polarized beams therefore, allows one to have completely independent probes of all the different parts of a general ZZH vertex.

hep-ph↗

arXiv2009

Role of polarization in probing anomalous gauge interactions of the Higgs boson

We explore the use of polarized $e^+/e^-$ beams and/or the information on final state decay lepton polarizations in probing the interaction of the Higgs boson with a pair of vector bosons. A model independent analysis of the process $e^+ e^- \to f \bar f H$, where $f$ is any light fermion, is carried out through the construction of observables having identical properties under the discrete symmetry transformations as different individual anomalous interactions. This allows us to probe an individual anomalous term independent of the others. We find that initial state beam polarization can significantly improve the sensitivity to CP-odd couplings of the $Z$ boson with the Higgs boson ($ZZH$). Moreover, an ability to isolate events with a particular $τ$ helicity, with even 40% efficiency, can improve sensitivities to certain $ZZH$ couplings by as much as a factor of 3. In addition, the contamination from the $ZZH$ vertex contributions present in the measurement of the trilinear Higgs-$W$ ($WWH$) couplings can be reduced to a great extent by employing polarised beams. The effects of initial state radiation (ISR) and beamstrahlung, which can be relevant for higher values of the beam energy are also included in the analysis.

hep-ph↗

arXiv2007

Effects of polarisation on study of anomalous VVH interactions at a Linear Collider

We investigate the use of beam polarisation as well as final state $τ$ polarisation effects in probing the interaction of the Higgs boson with a pair of heavy vector bosons in the process $e^+ e^- \to f \bar f H$, where $f$ is any light fermion. The sensitivity of the International Linear Collider (ILC) operating at $\sqrt s=500$ GeV, to such $VVH$($V = W/Z$) couplings is examined in a model independent way. The effects of ISR and beamstrahlung are discussed.

hep-ph↗

arXiv2007

Signatures of anomalous VVH interactions at a linear collider

We examine, in a model independent way, the sensitivity of a Linear Collider to the couplings of a light Higgs boson to gauge bosons. Including the possibility of CP violation, we construct several observables that probe the different anomalous couplings possible. For an intermediate mass Higgs, a collider operating at a center of mass energy of 500 GeV and with an integrated luminosity of 500 fb$^{-1}$ is shown to be able to constrain the $ZZH$ vertex at the few per cent level, and with even higher sensitivity in certain directions. However, the lack of sufficient number of observables as well as contamination from the $ZZH$ vertex limits the precision with which the $WWH$ coupling can be measured.

hep-ph↗