arXiv subjects

A. K. Rai

Publications and source records attributed to A. K. Rai.

8 recordsLinked to original sources

arXiv2026

A Unified Study of Hidden-Charm and Hidden-Bottom Mesons

We present a unified phenomenological analysis of hidden-charm and hidden-bottom mesons, treating the $c\bar c$ and $b\bar b$ sectors within a common screened-potential and QCD sum-rule framework. The mass spectra are obtained from a screened Coulomb-plus-confining interaction with spin-dependent corrections, while the short-distance decay constants, annihilation widths and electromagnetic transition form factors are organized through two-point and three-point QCD sum rules. The same calculated states are then used to study E1 and M1 radiative transitions, Regge trajectories and finite-spectrum thermodynamic observables constructed from excitation energies relative to the corresponding ground states. The results are discussed together rather than as disconnected outputs: the mass spectra determine the state assignments, the Regge plots test the global level ordering, the radiative widths probe orbital and spin-flip overlap integrals, and the QCD sum-rule quantities connect the spectrum to current-coupled observables. The comparison of the two hidden-flavour sectors shows the expected compression and stronger spin suppression in bottomonium, while charmonium remains more sensitive to fine-structure, radial-node and medium-related effects. The resulting picture provides a coherent vacuum benchmark for $c\bar c$ and $b\bar b$ spectroscopy, radiative transitions and QCD sum-rule observables.

hep-ph↗

arXiv2026

A unified study of the $B_c$ meson: from spectrum and form factors to weak and radiative decays

The $B_c$ meson constitutes a unique system for investigating heavy-hadron dynamics, since it exhibits quarkonium-like bound-state structure while decaying predominantly through weak interactions. In this work, we present a unified study of $B_c$-meson spectroscopy, decay constants, weak decays, radiative transitions, and Regge trajectories within a single framework. The mass spectrum is computed in a screened potential model including relativistic kinetic-energy corrections and spin-dependent interactions, from which we obtain both spin-averaged and spin-resolved states together with the corresponding pseudoscalar and vector decay constants. Using these spectroscopic inputs, we then analyze weak decays within a mass-updated three-point QCD sum-rule framework for transitions to $S$-, $P$-, and $D$-wave charmonium states, as well as to final states containing charmonium and $D^{(*)}_{(s)}$ mesons. In this part of the analysis, the hadronic thresholds, Borel-window prescriptions, Lorentz decompositions, and decay-width expressions of the underlying sum-rule formulations are retained, while the heavy-quark masses are updated to $m_c=1.48~\mathrm{GeV}$ and $m_b=4.90~\mathrm{GeV}$, leading to a controlled refit of the overall normalization rather than a full rederivation of all perturbative and condensate contributions. We further investigate purely leptonic decay widths and radiative $E1$ and $M1$ transitions, and examine the Regge behavior of the resulting spectrum. The present study therefore provides a coherent description of the $B_c$ meson in which the spectroscopic wave functions determine the short-distance couplings that enter both weak and electromagnetic observables, while the Regge analysis serves as a complementary global consistency test of the same dynamical picture.

hep-ph↗

arXiv2023

Properties of N, $Δ$ Baryons with Screened Potential

N and $Δ$ baryons hold an important place towards understanding the quark dynamics inside hadrons. The hypercentral Constituent Quark Model (hCQM) has been employed in various studies ranging from light to heavy hadrons. In the present article, screened potential has been used to study light baryon resonances. The Regge trajectories have been plotted alongwith the details of slopes and intercepts. The strong decay widths to pion have been calculated for some channels using the present masses.

hep-ph↗

arXiv2022

Bottomonium spectroscopy using Coulomb plus linear (Cornell) potential

The coulomb plus linear (Cornell) potential is used to investigate the mass spectrum of bottomonium. Gaussian wave function is used in position and momentum space to estimate values of potential and kinetic energies, respectively. Based on our calculations, we study newly observed ${{\mathit Υ}{(10860)}}$ as an admixture of $4^{3}S_{1}$ with $4^{3}D_{1}$, and ${{\mathit Υ}{(10753)}}$ as an admixture of $6^{3}S_{1}$ with $4^{3}D_{1}$ also, we try to assign ${{\boldsymbol Υ}{(11020)}}$ as a pure $4^{3}D_{1}$ bottomonium state. We also study the Regge trajectories in the $(J,M^{2})$ and $(n_r,M^{2})$ planes to help prove our association. We estimate the pseudoscalar and vector decay constants, the radiative (Electric and Magnetic Dipole) transition rates, and the annihilation decay width for bottomonium states.

hep-ph↗

arXiv2022

Spectroscopic Properties of $\mathit {B}$ and $\mathit {B_s}$ meson using Screened Potential

Inspired by the recent observations of $B$ and $B_s$ meson states at LHCb\cite{Aaij:2020hcw} we calculate the masses of ground, orbitally, and radially excited states. Also, we estimate the mixing parameters, decay constant, leptonic decay width, and corresponding branching ratios, as well as electromagnetic transition widths. ${\cal{O}}\left(\frac{1}{m}\right)$ and ${\cal{O}}(p^{10})$ relativistic corrections to potential and kinetic energy terms have been added to the Hamiltonian. The screening potential employed is solved by applying the gaussian wave function. The estimated masses are used to construct the Regge trajectories, which help us in the association of some newly observed states to $B$ and $B_s$ meson family. Overall, the results from the present study are in fair agreement with available experimental and theoretical studies.

hep-ph↗

arXiv2015

Decay rates and electromagnetic transitions of heavy quarkonia

The electromagnetic radiative transition widths for heavy quarkonia, as well as digamma and digluon decay widths, are computed in the framework of the extended harmonic confinement model (ERHM) and Coulomb plus power potential (CPP$_ν$) with varying potential index $ν$. The outcome is compared with the values obtained from other theoretical models and experimental results. While the mass spectra, digamma and digluon widths from ERHM as well as CPP$_{ν=1}$ are in good agreement with experimental data, the electromagnetic transition widths span over a wide range for the potential models considered here making it difficult to prefer a particular model over the others because of the lack of experimental data for most transition widths.

hep-ph↗

arXiv2012

Many-body correlations of electrostatically trapped dipolar excitons

We study the photoluminescence (PL) of a two-dimensional liquid of oriented dipolar excitons in In_{x}Ga_{1-x}As coupled double quantum wells confined to a microtrap. Generating excitons outside the trap and transferring them at lattice temperatures down to T = 240 mK into the trap we create cold quasi-equilibrium bosonic ensembles of some 1000 excitons with thermal de Broglie wavelengths exceeding the excitonic separation. With decreasing temperature and increasing density n <= 5*10^10 cm^{-2} we find an increasingly asymmetric PL lineshape with a sharpening blue edge and a broad red tail which we interpret to reflect correlated behavior mediated by dipolar interactions. From the PL intensity I(E) below the PL maximum at E_{0} we extract at T < 5 K a distinct power law I(E) \sim (E_{0}-E)^-|α| with -|α|\sim -0.8 in the range E_{0}-E of 1.5-4 meV, comparable to the dipolar interaction energy.

cond-mat.mes-hall↗

arXiv2012

Single exciton emission from gate-defined quantum dots

With gate-defined electrostatic traps fabricated on a double quantum well we are able to realize an optically active and voltage-tunable quantum dot confining individual, long-living, spatially indirect excitons. We study the transition from multi excitons down to a single indirect exciton. In the few exciton regime, we observe discrete emission lines reflecting the interplay of dipolar interexcitonic repulsion and spatial quantization. The quantum dot states are tunable by gate voltage and employing a magnetic field results in a diamagnetic shift. The scheme introduces a new gate-defined platform for creating and controlling optically active quantum dots and opens the route to lithographically defined coupled quantum dot arrays with tunable in-plane coupling and voltage-controlled optical properties of single charge and spin states.

cond-mat.mes-hall↗