International Journal of Modern Physics A

In this paper, we have employed HQET to determine the masses of radially excited ($n=2$) S-wave charm and bottom baryons. The HQET Lagrangian containing the non-perturbative parameters is shown with heavy baryon fields. The non-perturbative parameters, couplings, and decay widths are also studied for the S-wave singly heavy baryons. The HQET parameters $\overline{\mathrm{\Lambda }}$, ${\lambda }_1$ and ${\lambda }_2$ are calculated for the ground state ($n=1$) using the masses of S-wave baryons. The $1S$ mass short-distance mass scheme is employed to estimate the heavy quark masses and non-perturbative parameters. The mass term ratios of $n=1$ and $n=2$ mesons and baryons containing parameters $\overline{\mathrm{\Lambda }}$ and ${\lambda }_1$ are studied by varying the bottom quark mass. This analysis shows that heavy quarks behave the same inside mesons and baryons in both 1S and 2S states. The HQET symmetry of $\overline{\mathrm{\Lambda }}$ is used to find the parameters and masses for $n=2$ S-wave baryons. The variation of mass of 2S baryons with the non-perturbative parameters ${\lambda }_1$ and ${\lambda }_2$ is discussed. The Regge trajectories are also plotted in the $(n,M^2)$ plane using masses of $n=1$ and 2 charm and bottom baryons. The Regge trajectories are parallel and equidistant lines in the $(n,M^2)$ plane. We have also studied the strong decays of charm and bottom baryons for both $n=1$ and $n=2$ states. We have estimated the coupling constants $g_1=0.913_{-0.017}^{+0.010}$ and $g_2=0.559_{-0.010}^{+0.006}$ for $n=1$, and $\frac{{\tilde{g}}_1}{{\tilde{g}}_2}=1.52$ for $n=2$. We have also shown the semi-electronic decay rates of charm baryons in the spectator heavy quark approximation for $1S\to 1S$, $2S\to 1S$, and $2S\to 2S$ transitions. The decay rates for $1S\to 1S$ transitions are of the same order as $2S\to 2S$ transitions. This analysis agrees well with the available theoretical and experimental data.

Weakly interacting massive particles (WIMPs) and axions are arguably the most compelling dark matter (DM) candidates in the literature. Here, we consider a model where the Peccei–Quinn (PQ) symmetry solves the strong CP problem, generates radiatively Dirac neutrino masses and gives origin to a multicomponent dark sector. Specifically, scotogenic Dirac neutrino masses arise at one-loop level. The lightest fermionic mediator acts as the second DM candidate due to a residual $Z_2$ symmetry resulting from the PQ symmetry breaking. The WIMP DM component resembles the well-known singlet–doublet fermion DM. While the lower WIMP dark mass region is usually excluded, our model reopens that portion of the parameter space (for DM masses below $\lesssim 100$GeV). Therefore, we perform a phenomenological analysis that addresses the constraints from direct searches of DM, neutrino oscillation data and charged lepton flavor violating processes. The model can be tested in future facilities where neutrino telescopes search for DM annihilation into Standard Model particles.

We have obtained charged asymptotically anti-de Sitter (AdS) black hole solutions in Einstein–Gauss–Bonnet gravity in the presence of string cloud. It turns out that there exist three black holes in certain range of parameters for small enough chemical potential. However, for large chemical potential, these black holes merge into a single one. The free energy of the black holes is computed from the on-shell Euclidean action by subtracting the contribution of an extremal black hole. We have studied the free energy and specific heat of the solutions, which shows that the medium-sized black hole is unstable. As an application, we have studied the quark–antiquark potential in the dual gauge theory. This study provides necessary ingredients for the study of the dual theories in the context of condensed matter systems.

In this work, the spectra and decay properties of $B_c$ mesons $(c\overline{b}$) have been investigated using a nonrelativistic potential model incorporating corrections from LQCD. The nonrelativistic Schrödinger wave equation is solved numerically using the Matrix Numerov Method. Using the obtained masses and wave functions, decay widths, lifetime, branching ratios and radiative decay widths are computed for the $c\overline{b}$ system. Influence of the bound state effect on decay width of $B_c$ mesons is also analyzed. We compare the obtained results with the experimental data and with other theoretical models.

Without adhering to any specific model, we have presented 4 $\times$ 4 quark mixing matrix as an extension of the 3 $\times$ 3 Particle Data Group (PDG) parametrization of the Cabibbo–Kobayashi–Maskawa (CKM) matrix Using unitarity constraints as well as the hierarchy among the elements of the 3 $\times$ 3 CKM matrix, we have found the hierarchy among the fourth row and fourth column elements of the 4 $\times$ 4 quark mixing matrix. Further, for the fourth generation case, we have explicitly found the nine independent rephasing invariant parameters $J_{4\times 4}$. Also, using phenomenological estimates of the fourth row and fourth column elements, we have numerically evaluated these nine parameters.

The tunneling of scalar particles and fermions across the event horizon of KN-AdS black hole surrounded by perfect fluid in Rastall theory are investigated in the frame dragging coordinate systems by applying modified Klein–Gordon equation and modified Dirac equation under the influence of Lorentz symmetry violation in curved spacetime. The Hawking temperature and the heat capacity of the black hole are modified due to the influence of Lorentz symmetry violation. The Hawking temperature and the Bekenstein–Hawking entropy of the black hole beyond the semiclassical approximation are also derived by taking the effects of Planck constant $\hslash$. The modified Hawking temperature and entropy correction of the black hole are dependent on the Lorentz violation parameter $\lambda$, the ether-like vectors $u^{\alpha }$ and Planck constant $\hslash$.

In this paper, our focus lies in investigating nonrelativistic quantum systems under external potentials by solving the Schrödinger wave equation within a topological defect background. We opt for a class of Yukawa potential (CYP) and substitute the screening parameter with the Debye mass, which varies with temperature. Employing a Taylor series expansion to simplify the exponential term, we solve the radial wave equation, yielding an analytical solution for the quantum system in question, referred to as the Quarkonium system. Our analysis reveals that the presence of a topological defect modifies the energy profile of the Quarkonium system, consequently disrupting the degeneracy of the energy spectra.