arXiv subjects

Bilal Masud

Publications and source records attributed to Bilal Masud.

At least 19 recordsLinked to original sources

arXiv2025

Charmonium spectrum and its decay properties

In this work, we have calculated the mass spectrum, radiative decays, and strong decays of charmonium (cc) by using the non-relativistic quark potential(NRQP) model. The wave functions are calculated by solving the radial Schrodinger equation numerically, which are further used to compute the radiative decay widths of (cc) states. The 3P0 model is used to calculate the strong decay widths by using the simple harmonic (SHO) wave functions. The SHO parameter \b{eta} values for different cc states are calculated by fitting it to the numerical wave functions. We also compare our results with experimental data and other theoretically predicted results. We assign to the charmonium states X(3940), X(3872), X(3862), X(4350) likely quantum numbers of {\eta}c(3S), \c{hi}1(2P), \c{hi}0(2P) and \c{hi}2(3P) states.

hep-ph↗

arXiv2025

Study of excited $D$ and $D_s$ mesons in a relativized quark model

We use a modified relativistic quark model to study the properties of excited charmed and charmed strange mesons. We calculate the masses and wave functions of conventional charmed and charmed strange mesons incorporating both spin and $S$-$D$ mixing effects and fit parameters of the potential model with known experimental states using differential evolution technique. Using Leading Born-Oppenheimer expansion, we also compute the spectrum and wave functions of first gluonic excited state of charmed and charmed strange mesons. We examine the effects of gluonic excitation on the spectrum of resultant hybrid mesons. By using our calculated spectrum and wave functions, we determine the radiative transitions of the conventional and hybrid open charm mesons. We compare our calculations with experimental data and other works. We expect our results will be beneficial in the detection of the charmed and charmed strange conventional and hybrids mesons.

hep-ph↗

arXiv2025

Strong Decays of Charmonia

In this work, we calculate the charmonium spectrum and strong decay widths of cc states. The calculations are performed using the quark potential model with which incorporates the relativistic effects. The resulting cc spectrum exhibits a good agreement with experimental data. The open flavor strong decay widths are calculated employing the 3P0 model. We adopt two choices of wave functions to determine the observables: the first involves the utilization of realistic wave functions obtained by solving relativistic Schrodinger equation, while the second employs Simple harmonic oscillator (SHO) wave functions whose parameters are fitted to the realistic wave functions. We find that the decay widths of higher charmonia states above the threshold value of open charm mesons are well described with these wave functions. We provide a comprehensive analysis of the strong decay widths and assigned specific charmonium states: X(3940) is assigned to the {\eta}c(3S) state, Y (4660) to the {\psi}(5S) state, X(3915) to the \c{hi}0(2P) state, Zc(3900) to the hc(2P) state, X(4350) to the \c{hi}2(3P) state, and X(3842) to the {\psi}3(1D) state. We also compare our results with available experimental data and theoretical predictions of other models.

hep-ph↗

arXiv2024

$Υ$ absorption cross sections by nucleons

The cross sections of $Υ$\ absorption by nucleons are calculated in meson-baryon exchange model using an effective hadronic Lagrangian. Calculated cross sections are found to peak near threshold followed by an increase which tends to settle at large center of mass energy. Peak values are found in range about 1.8 to 4 mb when cutoff parameter of monopole form factor is varied from 1.2 to 1.8 GeV. The results disagree with pQCD calculations but are consistent with the effective value of the absorption cross section extracted from p-A scattering data in E772 experiment at $\sqrt{s_{NN}}=39$ GeV. We use this data value to find a best fit of the cutoff parameter which enables us provide definite predictions for the values of $Υ$ absorption cross sections by nucleons for upcoming p-A scattering experiments at RHIC and LHC energies for zero rapidity $b\bar{b}$ states. The results could be useful in studying the effect of $Υ$ absorption by nucleons at its production stage in relativistic heavy-ion collision experiments. We also find that thermal averaged values of total absorption cross sections are small enough to rule out the effect of absorption of $Υ$ by the comovers in the hadronic matter.

nucl-th↗

arXiv2023

Effect of the Quark-Gluon Vertex on Dynamical Chiral Symmetry Breaking

In this work, we investigate how the details of the quark-gluon interaction vertex affect the quantitative description of chiral symmetry breaking through the gap equation for quarks. We start from two gluon propagator models widely used in literature and constructed in direct connection with our gradually improved understanding of infrared quantum chromodynamics coupled with its exact one-loop limit. The gap equation is then solved by employing a variety of vertex \emph{Ansätze}, which have been constructed in order to implement some of the key aspects of quantum chromodynamics, namely, multiplicative renormalizability of the quark propagator, gauge invariance, matching with perturbation theory in the weak coupling regime, independence from unphysical kinematic singularities as well as manifestly correct transformation properties under charge conjugation and parity operations. On general grounds, all truncation schemes exhibit the same qualitative and quantitative pattern of chiral symmetry breaking, ensuring the overall robustness of this approach and its potentially reliable description of the hadron spectrum and properties.

nucl-th↗

arXiv2022

Charmonium spectrum in an unquenched quark model

The effects of virtual light quark pairs on the charmonium spectrum are studied. Pair creation is modelled with a ``$^{3}P_{0}$" vertex and intermediate states are summed up to 2S excitations. Quark model parameters are obtained by fitting to 12 well-known charmonium states, allowing for feedback between the decaying particle and the induced mass shifts. Both of these technical steps are new and improve agreement with the experimental spectrum. In general, the masses receive small shifts once model parameters are refit. This is true in almost cases except the $χ_{cJ}(2P)$ multiplet, which experiences upwards mass shifts of order 150 MeV, has the ordering of the multiplet rearranged, and pushes the erstwhile $c\bar{c}$ ${2}^3P_1$ state well above $D^*\bar{D}$ threshold--observations that clarify the nature of the enigmatic $X(3872)$

hep-ph↗

arXiv2022

Quarkonium in a spin dependent quark anti-quark potential at finite temperature

We study the states of $c\bar{c}$ and $b\bar{b}$ system in a non-relativistic a spin dependent potential model at finite temperature. The potential incorporate color screening effect through a parameter $μ$. The parameter $μ$ along with strong coupling constant $α_s$ and string tension $σ$ are taken temperature dependent and their values are fitted to the Lattice data of quark anti-quark potential available at different values of temperature. The applied potential include spin-spin, spin-orbital, tensor interactions which allow us to study spin singlet and triplet states of quarkonia. By solving non-relativistic Schr{ö}dinger equation, we find the spectrum of quarkonium states at different temperature and also determine the critical temperature at which each state is dissolved. We find the critical temperature is decreased with orbital and radial excitations, however, for spin singlet and triplet states it remains same.

hep-ph↗

arXiv2019

Properties of excited charmed-bottom mesons

We calculate the spectrum of $B_c$ mesons using a non-relativistic quark potential model. Using the calculated wave functions, we compute the radiative widths of $B_c$ excited states. The strong decay widths are calculated in a modified $^3P_0$ model, assuming harmonic oscillator wave functions. The hadronic transition rates of $B_c$ mesons are calculated using the Kuang-Yan approach. These results are used to determine branching ratios of possible decay channels of several $B_c$ excited states. Calculated branching ratios are then combined with production cross section of $B_c$ states at the LHC to suggest strategies to find missing excited states of $B_c$ mesons.

hep-ph↗

arXiv2018

Conventional and Hybrid $B_c$ Mesons in an Extended Potential Model

Using our analytical expressions that well model the lattice simulations of the gluonic excitations, we use the extended quark potential model to study the effects of orbital and radial excitations on the masses and sizes of conventional and hybrid $B_c$ mesons. A non relativistic formalism is used to numerically calculate the wave functions using the shooting method; this allows us also calculating the $E1$, $M1$ radiative partial widths for conventional meson to meson and hybrid to hybrid transitions. We incorporate spin mixing and compare our calculated spectrum and decay widths with the available experimental $B_c$ masses and the theoretically predicted spectra and the decay widths by other groups. Our results can help consider both conventional and hybrid quantum numbers to $B_c$ mesons as experimental results become available.

hep-ph↗

arXiv2018

Decays and spectrum of bottom and bottom strange mesons

The strong decay amplitudes and radiative partial widths of orbital and radially excited states of $B$ and $B_s$ mesons are presented. These results are obtained with a nonrelativistic potential quark model, the nonrelativistic reduction of the electromagnetic transition operator, and the "$^3P_0$" model of strong decays. The predictions are compared to experiment where possible and assignments for the recently discovered states, $B_1(5721)$, $B_2^*(5747)$, $B_J(5840)$, $B_J(5970)$, $B_{s1}(5830)$, and $B_{s2}^*(5840)$, are made.

hep-ph↗

arXiv2018

$ρJ/Ψ$ Scattering in an Improved Many Body Potential

We calculate the cross-sections for the processes $ρJ/ψ\rightarrow D^0\bar{D}^0$, $ρJ/ψ\rightarrow D^0\bar{D}^{0*}$ ($D^{0*}\bar{D}^{0}$) and $ρJ/ψ\rightarrow D^{0*}\bar{D}^{0*}$ using a QCD-motivated many-body overlap factor to modify the usual sum of two-body interaction model. The realistic Cornell potential has been used for pairwise interaction in the four quark Hamiltonian and noted to give lesser cross-sections as compared to the quadratic potential. The Resonating group method is employed along with the Born approximation which decouples its integral equations. It is pointed out that the additional QCD effect (a gluonic field ovelap factor) result in a significant suppression in the cross sections as compared to the more popular sum of two-body interaction.

hep-ph↗

arXiv2017

Interactions of $B_{c}$ Meson in Relativistic Heavy-Ion Collisions

We calculate the absorbtion cross-sections of $B_{c}$ mesons by $π$ and $ρ$ mesons including anomalous processes using an effective hadronic Lagrangian. The enhancement of Bc production is expected due to QGP formation in heavy-ion experiments. However it is also expected that the production rate of Bc meson can be affected due to the interaction with comovers. These processes are relevant for experiments at RHIC. Thermal average cross-sections of $B_{c}$ are evaluated with form factor when a cut off parameter in it is 1 and 2 GeV. Using these thermal average cross-sections in the kinetic equation we investigate the time evolution of $B_{c}$ mesons due to dissociation in the hadronic matter formed at RHIC.

nucl-th↗

arXiv2017

Higher Hybrid Bottomonia in an Extended Potential Model

Using our extension of the quark potential model to hybrid mesons that fits well to the available lattice results, we now calculate the masses, radii, wave functions at origin, leptonic and two photon decay widths, E1 and M1 radiative transitions for a significant number of bottomonium mesons. These mesons include both conventional and hybrid ones with radial and angular excitations. Our numerical solutions of the Schrodinger equation are related to QCD through the Born-Oppenheimer approach. Relativistic corrections in masses and decay widths are also calculated by applying the leading order perturbation theory. The calculated results are compared with available experimental data and the theoretical results by other groups. We also identify the states of $Υ(10860)$, $Υ(11020)$, and $Y_b(10890)$ mesons by comparing their experimental masses and decay widths with our results.

hep-ph↗

arXiv2016

$\bar{D}^{0}D^{0}$ $(D^{0}\bar{D}^{0})$ System in QCD-Improved Many Body Potential

For a system of current interest (composed of charm, anticharm quarks and a pair of light ones), we show trends in phenomenological implications of QCD-based improvements to a simple quark model treatment. We employ resonating group method to render this difficult four-body problem manageable. We use a quadratic confinement so as to be able to improve beyond the Born approximation. We report the position of the pole corresponding to $\bar{D}^{0}D^{0*}$ molecule for the best fit of a model parameter to the relevant QCD simulations. We point out the interesting possibility that the pole can be shifted to $3872$ MeV by introducing another parameter $I_{0}$ that changes the strength of the interaction in this one component of $X(3872)$. The revised value of this second parameter can guide future trends in modeling of the full exotic meson $X(3872)$. We also report the changes with $I_{0}$ in the $S$-wave spin averaged cross sections for $\bar{D}^{0}D^{0*}\longrightarrowωJ/ψ$ and $\bar{D}^{0}D^{0*}\longrightarrowρJ/ψ$. These cross sections are important regarding the study of QGP (quark gluon plasma).

hep-ph↗

arXiv2015

Near-Stability of a Quasi-Minimal Surface Indicated Through a Tested Curvature Algorithm

We decrease the $rms$ mean curvature and area of a variable surface with a fixed boundary by iterating a few times through a curvature-based variational algorithm. For a boundary with a known minimal surface, starting with a deliberately chosen non-minimal surface, we achieve up to 65 percent of the total possible decrease in area. When we apply our algorithm to a bilinear interpolant bounded by four \emph{non-coplanar} straight lines, the area decrease by the same algorithm is only 0.116179 percent of the original value. This relative stability suggests that the bilinear interpolant is already a quasi-minimal surface.

math.DG↗

arXiv2014

Wave Function Based Characteristics of Hybrid Mesons

We propose some extensions of the quark potential model to hybrids, fit them to the lattice data and use them for the purpose of calculating the masses, root mean square radii and wave functions at the origin of the conventional and hybrid charmonium mesons. We treat the ground and excited gluonic field between a quark and an antiquark as in the Born-Oppenheimer expansion, and use the shooting method to numerically solve the required Schr$\ddot{\textrm{o}}$dinger equation for the radial wave functions; from these wave functions we calculate the mesonic properties. For masses we also check through a Crank Nichelson discretization. For hybrid charmonium mesons, we consider the exotic quantum number states with $ J^{PC} = 0^{+ -}, 1^{- +}$ and $2^{+ -}$. We also compare our results with the experimentally observed masses and theoretically predicted results of the other models. Our results have implications for scalar form factors, energy shifts, magnetic polarizabilities, decay constants, decay widths and differential cross sections of conventional and hybrid mesons.

hep-ph↗

arXiv2014

Higher Hybrid Charmonia in an Extended Potential Model

The quark potential model for mesons and its extension for hybrid mesons are used to study the effects of radial excitations on the masses, sizes and radial wave functions at the origin for conventional and hybrid charmonium mesons. These results can help in experimentally recognizing hybrid mesons. The properties of conventional and hybrid charmonium mesons are calculated for the ground and radially excited states using the shooting method to numerically solve the required Schrodinger equation for the radial wave functions. We compare our results with the experimentally observed masses and theoretically predicted results of the other models. Our results have implications for scalar form factors, energy shifts, and polarizabilities of conventional and hybrid mesons. The comparison of masses of conventional and hybrid charmonium meson with the masses of recent discovered XYZ-particles is also discussed.

hep-ph↗

arXiv2014

Variational Minimization on String-rearrangement Surfaces, Illustrated by an Analysis of the Bilinear Interpolation

In this paper we present an algorithm to reduce the area of a surface spanned by a finite number of boundary curves by initiating a variational improvement in the surface. The ansatz we suggest consists of original surface plus a variational parameter $t$ multiplying the numerator $H_{0}$ of mean curvature function defined over the surface. We point out that the integral of the square of the mean curvature with respect to the surface parameter becomes a polynomial in this variational parameter. Finding a zero, if there is any, of this polynomial would end up at the same (minimal) surface as obtained by minimizing more complicated area functional itself. We have instead minimized this polynomial. Moreover, our minimization is restricted to a search in the class of all surfaces allowed by our ansatz. All in all, we have not yet obtained the exact minimal but we do reduce the area for the same fixed boundary. This reduction is significant for a surface (hemiellipsoid) for which we know the exact minimal surface. But for the bilinear interpolation spanned by four bounding straight lines, which can model the initial and final configurations of re-arranging strings, the decrease remains less than 0.8 percent of the original area. This may suggest that bilinear interpolation is already a near minimal surface.

math.DG↗