arXiv subjects

Rohit Dhir

Publications and source records attributed to Rohit Dhir.

At least 19 recordsLinked to original sources

arXiv2026

Geometrical Tuning of Light-Matter Interaction in Atomic Trimer Antennas: A Symmetry-Resolved Modal Analysis

Atomic trimers constitute the smallest geometry in which collective electric and magnetic responses emerge from coupled electric dipoles. We present a theoretical study of collective mode excitation in atomic trimers as the geometry is continuously tuned from linear to equilateral, using the coupled-dipole method with a multipole expansion formulated about the optimal scattering center. By combining eigenmode analysis and symmetry classification, we provide a complete symmetry-resolved map of the six in-plane and three out-of-plane modes, revealing how symmetry reduction across the $D_{\infty h}$, $C_{2v}$, and $D_{3h}$ configurations governs the evolution of eigenmodes and their spectral features, lifting degeneracies, activating dark modes, and enabling full access to the modal spectrum. Based on this modal understanding, we demonstrate that forward-backward scattering can be switched solely by frequency detuning in a nearly linear trimer, without geometric reconfiguration. Furthermore, a linear trimer under s-polarized excitation supports a magnetic mode with a strongly enhanced magnetic field and a large Purcell factor, making it a promising platform for probing magnetic dipole transitions in atoms, with emission preferentially directed into the transverse plane. These results establish atomic trimers as a minimal platform where symmetry-controlled electric-magnetic mode engineering can be fully resolved and exploited for tailoring light-matter interaction at the atomic level.

physics.optics↗

arXiv2026

$\boldsymbol{B_c}$ Meson Spectroscopy from Bayesian MCMC: Probing Confinement and State Mixing

We present a Bayesian study of the $B_c$ meson spectrum using three non-relativistic confining potentials, namely the Cornell potential, a logarithmically modified extension, and a screened Cornell form. Parameters for each potential are sampled using Markov chain Monte Carlo (MCMC), retaining correlations among the fitted parameters. The resulting parameter distributions are used to calculate the $B_c$ spectrum through the $6D$ multiplet, including masses, spin-dependent splittings, mixing angles, and wave-function observables. The predicted masses are further examined through Regge trajectories. The low-lying spectrum is relatively stable across the three potentials, while their predictions become increasingly separated with excitation as the states probe larger distances, accompanied by growing parameter-induced uncertainties. The Regge trajectories show stronger non-linearity for low-lying states and progressively approach linear behavior with excitation. These results quantify the sensitivity of the predicted excited $B_c$ spectrum to the chosen confining interaction and provide uncertainty estimates for states that remain experimentally less explored.

hep-ph↗

arXiv2026

A baryon-calibrated unified quark-diquark effective mass formalism for heavy multiquarks

We present a unified framework for heavy tetraquark and pentaquark systems within the quark-diquark effective mass formalism, extending its baryon-calibrated construction to multiquark states without introducing sector-dependent parameters. Intra-diquark color-spin correlations are encoded in effective diquark masses fixed from baryon spectroscopy, while the inter-cluster chromomagnetic scale, independently determined from vector-pseudoscalar meson splittings, is propagated unchanged to exotic configurations, ensuring residual one-gluon exchange dynamics only between composite color sources. Within this framework, we compute the complete spectra for both $\bar{\mathbf{3}}_c\otimes\mathbf{3}_c$ and $\mathbf{6}_c\otimes\bar{\mathbf{6}}_c$ configurations in tetraquarks, whereas the pentaquark analysis focuses on the dominant $\bar{\mathbf{3}}_c\otimes\bar{\mathbf{3}}_c\otimes\bar{\mathbf{3}}_c$ clustering. Heavy-quark spin symmetry and flavor-symmetry breaking across light, charm, and bottom sectors emerge naturally through the explicit $1/(m_{D_1}m_{D_2})$ scaling of the calibrated couplings. The resulting spectra exhibit a coherent dynamical hierarchy spanning baryons and multiquark states. Established exotic candidates are reproduced within hadronic uncertainties, while the unified calibration enables quantitative predictive control across flavor sectors. The framework thus provides a parameter-economical, systematically constrained baseline with unified dynamical consistency for heavy multiquark spectroscopy.

hep-ph↗

arXiv2026

Quark-diquark effective mass formalism for heavy baryon spectroscopy

We develop a quark-diquark effective mass formalism for heavy-flavor baryon spectroscopy and apply it to the $J^P = \tfrac{1}{2}^+$ and $J^P = \tfrac{3}{2}^+$ spectra across the singly, doubly, and triply heavy sectors. The analysis is carried out in two complementary scenarios: Scenario I treats all quark-quark diquark channels dynamically, while Scenario II restricts the dynamics to scalar and axial-vector diquarks, providing a more selective and physically transparent description. Constituent quark masses, effective diquark masses, and chromomagnetic couplings are extracted from known heavy-baryon masses, with the couplings determined solely by the quark content of each state and no sector-dependent adjustment introduced. A mass-dependent binding term is implemented to account for spin-independent chromoelectric effects and to describe the transition from chromomagnetic to color-Coulomb dominance across the light-to-heavy quark regime, ensuring consistency with heavy-quark spin symmetry in the heavy-quark limit. The resulting predictions are in good agreement with available experimental measurements and lattice QCD results across both charm and bottom sectors. The extracted diquark parameters remain stable across all heavy-flavor sectors, establishing the present framework as a symmetry-constrained spectroscopic baseline for heavy-baryon structure.

hep-ph↗

arXiv2025

Weak decays of $B_s$ meson in self-consistent covariant light-front approach

We present a comprehensive study of weak transition form factors and decay observables of the $B_s$ meson in transitions to pseudoscalar ($P$) and vector ($V$) mesons. The $B_s \to P(V)$ form factors are calculated using the self-consistent covariant light-front quark model, with a model-independent $z$-series expansion calibrated to lattice QCD and phenomenological inputs for quark masses and $\beta$ parameters. This enables reliable $q^2$-resolved predictions across the full kinematic range. Based on these form factors, we predict branching ratios and angular observables, including forward-backward asymmetries, polarization fractions, and leptonic convexity parameters for semileptonic decays. Nonleptonic two-body decay rates for $B_s \to PP$ and $B_s \to PV$ modes are also computed within the standard factorization framework using the same dynamical input. Comparisons with results from lattice QCD, light-cone sum rules, and other approaches are presented, highlighting both theoretical consistency and persistent tensions with experiment.

hep-ph↗

arXiv2025

Systematic study of light and charm meson M1 radiative transitions

Motivated by recent experimental advancements in the study of radiative decays of charmed mesons, we investigate the magnetic (transition) moments of vector mesons by applying the effective mass scheme, obtained from the one-gluon exchange interaction between quark-antiquark pairs. By incorporating high-precision experimental data from both heavy and light flavor sectors, we accurately account for the strong hyperfine interaction contributions to the quark and antiquark masses within mesons. We calculate the $V \to P$ effective transition magnetic moments to reliably predict M1 decay widths. Furthermore, to enhance the completeness of our analysis, we employ the non-relativistic potential model to calculate bound state isomultiplet masses and to predict the M1 decay widths of charmed mesons. Additionally, scale-dependent effects in both the effective mass scheme and the potential model are systematically analyzed and interpreted, emphasizing the decisive role of higher-order QCD corrections in determining M1 decay widths.

hep-ph↗

arXiv2024

Weak decays of $\pmb{B_c}$ involving vector mesons in self-consistent covariant light-front approach

We present a comprehensive analysis of weak transition form factors, semileptonic decays, and nonleptonic decays of $B_c$ meson involving pseudoscalar ($P$) and vector ($V$) meson for bottom-conserving and bottom-changing decay modes. We employ self-consistent covariant light-front quark model (CLFQM), termed as Type-II correspondence, to calculate the $B_c$ to $P(V)$ transition form factors. The Type-II correspondence in the CLF approach gives self-consistent results associated with the $B^{(i)}_j$ functions, which vanish numerically after the replacement $M^{\prime(\prime\prime)} \to M_0^{\prime(\prime\prime)}$ in traditional Type-I correspondence, and the covariance of the matrix elements is also restored. We investigate these effects on bottom-conserving $B_c$ to $P(V)$ form factors that have not yet been studied in CLFQM Type-II correspondence. In addition, we quantify the implications of self-consistency propagating to weak decays involving both bottom-conserving and bottom-changing $B_c$ transition form factors. We use two different parameterizations, the usual three-parameter function of $q^2$ and the model-independent $z$-series expansion, to establish a clear understanding of $q^2$ dependence. Using the numerical values of the form factors, we predict the branching ratios and other physical observables, such as forward-backward asymmetries, polarization fractions, etc., of the semileptonic $B_c$ decays. Subsequently, we predict the branching ratios of two-body nonleptonic weak decays using the factorization hypothesis in self-consistent CLFQM. We also compare our results with those of other theoretical studies.

hep-ph↗

arXiv2023

Spectroscopy and Annihilation Decay Widths of Charmonium and Bottomonium Excitations

We study the charmonium ($c\bar{c}$) and bottomonium ($b\bar{b}$) spectra, using Cornell potential with additional constant potential term in a non-relativistic framework, with spin-dependent corrections corresponding to the spin-spin, spin-orbit, and tensor interactions added perturbatively. We predict the masses of low-lying and excited states of charmonium and bottomonium up to $n=6$ and $L=2$. We analyze the radial and orbital Regge trajectories of both the systems and investigate their departure from linearity. Further, we estimate the wave function at the origin and, consequently, predict the decay widths of charmonium and bottomonium states annihilating to leptons and photons. Also, we investigate the effect of scale dependence of the wave function at the origin and the strong coupling constant on the predictions of annihilation decay widths. We compare our predictions of heavy quarkonium spectra and decay widths with experimental results and other theoretical models.

hep-ph↗

arXiv2023

$B_c$ to $A$ Transition Form Factors and Semileptonic Decays in Self-consistent Covariant Light-front Approach

We present a comprehensive analysis of the semileptonic weak decays of $B_c$ meson decaying to axial-vector ($A$) mesons for bottom-conserving and bottom-changing decay modes. We employ self-consistent covariant light-front quark model (CLFQM) that uses type-II correspondence to eliminate inconsistencies in the traditional type-I CLFQM. As a fresh attempt, we test the self-consistency in CLFQM through type-II correspondence for $B_c \to A$ meson transition form factors. We establish that in type-II correspondence the form factors for longitudinal and transverse polarization states are numerically equal and are free from zero-mode contributions, which confirms the self-consistency of type-II correspondence for $B_c \to A$ transition form factors. Furthermore, we ascertain that the problems of inconsistency and violation of covariance of CLFQM within the type-I correspondence are resolved in type-II correspondence for $B_c \to A$ transitions. We thoroughly investigate the effects of self-consistency between type-I and type-II schemes using a comparative analysis. We also study the $q^2$ dependence of the form factors in weak hadronic currents for the whole accessible kinematic range $0 \leqslant q^2 \leqslant q^2_{max}$ for both bottom-conserving as well as bottom-changing transitions. In addition, we extend our analysis to predict the branching ratios of the semileptonic weak decays of $B_c$ meson involving axial-vector meson in the final state to quantify the effects of self-consistency in these decays that were not studied before. We evaluate the lepton mass effect on these branching ratios and various other important physical observables, such as forward-backward asymmetries, lepton-side convexity parameter, asymmetry parameter, and longitudinal polarization asymmetries and fractions. Finally, we obtain the lepton flavor universality ratios for various decays.

hep-ph↗

arXiv2022

Screening of quark charge and mixing effects on transition moments and M1 decay widths of baryons

Motivated by the precision measurements of heavy flavor baryon masses, we analyze the modification of quark charge by employing the screening effect inside the baryon. In addition, we calculate the isospin mass splitting up to charmed baryons employing isospin symmetry breaking. Consequently, we obtain the masses, magnetic moments, and transition moments of $J^P=\frac{1}{2}^+$ and $\frac{3}{2}^+$ baryons to predict radiative decay widths for $\frac{1}{2}^{\prime +} \to \frac{1}{2}^+$ and $\frac{3}{2}^+\to \frac{1}{2}^{(\prime)+}$ transitions. Finally, we include the effects of state mixing in flavor degenerate baryon magnetic and transition moments, as well as M1 transition decay widths.

hep-ph↗

arXiv2021

Radiative M1 transitions of heavy baryons: Effective Quark Mass Scheme

We calculate the magnetic moments of ground state $J^P=\frac{1}{2}^+$ and $J^P=\frac{3}{2}^+$ heavy flavor charm and bottom baryon states employing the concept of effective mass based on single gluon exchange interaction coupling to the spectator quarks in the non-relativistic quark model. We exploit the current experimental information in the heavy flavor sector to estimate the interaction contributions to get the effective masses of the quarks inside the baryons. We study the spin $\frac{1}{2}^{'+} \rightarrow \frac{1}{2}^+$, $\frac{3}{2}^+ \rightarrow \frac{1}{2}^+$, and $\frac{3}{2}^+ \rightarrow \frac{1}{2}^{'+}$ transition moments for these baryons. We make robust predictions of the radiative M1 decay widths of singly, doubly, and triply heavy flavored baryons.

hep-ph↗

arXiv2020

Gamma Ray Spectra from Thermal Neutron Capture on Gadolinium-155 and Natural Gadolinium

Natural gadolinium is widely used for its excellent thermal neutron capture cross section, because of its two major isotopes: $^{\rm 155}$Gd and $^{\rm 157}$Gd. We measured the $γ$-ray spectra produced from the thermal neutron capture on targets comprising a natural gadolinium film and enriched $^{\rm 155}$Gd (in Gd$_{2}$O$_{3}$ powder) in the energy range from 0.11 MeV to 8.0 MeV, using the ANNRI germanium spectrometer at MLF, J-PARC. The freshly analysed data of the $^{\rm 155}$Gd(n, $γ$) reaction are used to improve our previously developed model (ANNRI-Gd model) for the $^{\rm 157}$Gd(n, $γ$) reaction, and its performance confirmed with the independent data from the $^{\rm nat}$Gd(n, $γ$) reaction. This article completes the development of an efficient Monte Carlo model required to simulate and analyse particle interactions involving the thermal neutron captures on gadolinium in any relevant future experiments.

nucl-ex↗

arXiv2019

Flavor Dependent Effects on Rare Weak Decays of $ B_c^{} $ and $B_s^{}$ Mesons

We investigate the effects of flavor dependence on the rare weak decays of $ B_c^{*} $ and $B_s^{*}$ mesons to psuedoscalar and vector mesons in the final state. We use the Bauer-Stech-Wirbel model framework to calculate the flavor dependent effects of transverse quark momentum on the form factors and consequently, the branching ratios of Cabibbo-Kobayashi-Maskawa favored and suppressed modes by employing the factorization hypothesis. We find that the flavor dependent effects significantly enhance the form factors and, consequently, the branching ratios. Some of the decay channels in $ B_c^{*} $ and $B_s^{*}$ have branching ratios $\mathcal{O}(10^{-5})$ to $\mathcal{O}(10^{-7})$, which are well within the reach of current experiments.

hep-ph↗

arXiv2017

Estimates of W-exchange contributions to $Ξ_{cc}$ decays

Encouraged by recent discovery of $Ξ_{cc}^{++}$ baryon, we investigate two body non-leptonic weak decays of doubly charmed, $Ξ_{cc}$, baryons. We calculate the branching ratios for CKM-favored and suppressed modes in factorization and pole model approach. We give the first estimates of nonfactorizable W-exchange contributions using pole model. We find that W-exchange contributions to $Ξ_{cc}$ decays being sizable can not be ignored.

hep-ph↗

arXiv2017

Charmed Axial Vector and Pseudoscalar Mesons Emitting Decays of Bottom Meson in NRQM

Two body nonleptonic weak decays of bottom mesons to a pseudoscalar meson and an axial-vector meson involving charmed states are studied using the non-relativistic quark model. We calculate the branching ratios of these decays by employing the factorization hypothesis. Obtained results are in good agreement with the existing experimental data. We also calculated the branching ratios in the light of heavy quark symmetry constraints and compared with the exiting theoretical analyses.

hep-ph↗

arXiv2015

Axial-Vector Emitting Weak Nonleptonic Deacys of $Ω_c^0$ Baryon

The axial-vector emitting weak hadronic decays of $Ω_c^0$ baryon are investigated. After employing the factorization and the pole model framework to predict their branching ratios, we derive the symmetry breaking effects on axial-vector-meson-baryon couplings and effects of flavor dependence on baryon-baryon weak transition amplitudes and, consequently, on their branching ratios. We found that the W-exchange process contributions dominate $p$-wave meson emitting decays of $Ω_c^0$ baryon.

hep-ph↗

arXiv2015

Model-Independent Analysis of CP Violation in Charmed Meson Decays

We present a model-independent analysis of CP violation, inspired by recent experimental observations, in charmed meson decays. The topological diagram approach is used to study direct CP asymmetries for singly Cabibbo-suppressed two-body hadronic decays of charmed mesons. We extract the magnitudes and relative phases of the corresponding topological amplitudes from available experimental information. In order to get more precise and reliable estimates of direct CP asymmetries, we take into account contributions from all possible strong penguin amplitudes, including the internal $b$-quark penguin contributions. We also study flavor SU(3) symmetry breaking effects in these decay modes and consequently, predict direct CP asymmetries of unmeasured modes.

hep-ph↗

arXiv2013

Magnetic Moments of Bottom Baryons: Effective mass and Screened Charge

We calculate the magnetic moments of low lying heavy flavor bottom baryons using effective quark mass and shielded quark charge scheme. We obtain the magnetic moments of both $J^P = 1/2^+$ and $J^P = 3/2^+$ baryon states. We compare our predictions with other theoretical approaches.

hep-ph↗