arXiv subjects

N. Barik

Publications and source records attributed to N. Barik.

17 recordsLinked to original sources

arXiv2024

Exclusive rare semileptonic decays of $B$ and $B_c$ mesons in the relativistic independent quark model

We investigate the exclusive rare semileptonic decays: $B(B_c)\to K(D_{(s)})l\bar{l}/\Sigma\nu_l\bar{\nu_l}$ ($l=\mu, \tau$) in the framework of relativistic independent quark (RIQ) model based on an average flavor independent confining potential in equally mixed scalar-vector harmonic form. The invariant weak form factors, parametrising the matrix elements between participating meson states are calculated in the parent meson rest frame. The momentum transfer dependence of the form factors is reliably determined in the whole accessible kinematical range: $q^2_{min}\leq 0\leq q^2_{max}$. Our predicted branching fractions for $B\to K\mu^+\mu^-/\tau^+\tau^-(\Sigma\nu_l\bar{\nu_l})$, $B_c\to D(D_s)\mu^+\mu^-$, $B_c\to D(D_s)\tau^+\tau^-$ and $B_c\to D(D_s)\Sigma\nu_l\bar{\nu_l}$, obtained in order of $10^{-7}(10^{-6})$, $10^{-9}(10^{-7})$, $10^{-9}(10^{-8})$ and $10^{-8}(10^{-7})$, respectively are in reasonable agreement with other Standard Model predictions and Lattice QCD results. The averaged values of the lepton polarization asymmetries for decay modes are obtained as $\langle P_L(B\to K\mu^+\mu^-)\rangle$=-0.97, $\langle P_L(B_c\to D_{(s)}\mu^+\mu^-)\rangle$=-0.972, $\langle P_L(B\to K\tau^+\tau^-)\rangle$=-0.224, $\langle P_L(B_c\to D\tau^+\tau^-)\rangle$=-0.275 and $\langle P_L(B_c\to D_s\tau^+\tau^-)\rangle$=-0.194.

hep-ph↗

arXiv2023

Purely leptonic decays of heavy-flavored charged mesons

We study the purely leptonic decays of heavy-flavored charged pseudoscalar (P) and vector (V) mesons ($D_{(s)}^{(*)+}$, $B_{(c)}^{(*)+}$) in the relativistic independent quark (RIQ) model based on an average flavor-independent confining potential in equally mixed scalar-vector harmonic form. We first compute the mass spectra of the ground-state-mesons and fix the model parameters necessary for the present analysis. Using the meson wave functions derivable in the RIQ model, and model parameters so fixed from hadron spectroscopy, we predict the decay constants: $f_{P(V)}$, ratios of decay constants: $f_{V}/f_{P}$, $f_{P_1}/f_{P_2}$, $f_{V_1}/f_{V_2}$, and the branching fractions (BFs): ${\cal B}(P(V)\to l^+\nu_l)$, $l=e, \mu, \tau$, which agree with the available experimental data and other Standard Model (SM) predictions. For the unmeasured decay constants especially in the purely leptonic decays of the charged vector mesons, our predictions could be tested in the upcoming Belle-II, SCTF, CEPC, FCC-ee and LHCb experiments in near future.

hep-ph↗

arXiv2023

The nonleptonic decays of $b$-flavored mesons to $S$-wave charmonium and charm meson states

The detection of radially excited heavy meson \\states in recent years and measurement of heavy meson decays, particularly $B_c^+\to J/ψD_s^+$ and $B_c^+\to J/ψD_s^{*+}$, by the LHCb and ATLAS Collaborations, have aroused a lot of theoretical interest in the nonleptonic decays of $b$-flavored mesons. In this paper, we study the exclusive two-body nonleptonic $\bar{B}^0$, $\bar{B_s^0}$, $B^-$ and $B_c^-$-meson decays to two vector meson ($V_1(nS)V_2$) states. Assuming the factorization hypothesis, we calculate the weak-decay form factors from the overlapping integrals of meson wave functions, in the framework of the relativistic independent quark (RIQ) model. We find a few dominant decay modes: $B^-\to D^{*0}ρ^-$, $\bar{B^0}\to D^{*+}ρ^-$, $\bar{B_s^0}\to D_s^{*+}ρ^-$, $B^-\to J/ψK^{*-}$ and $B_c^-\to J/ψD_s^{*-}$ with predicted branching fractions of 1.54, 1.42, 1.17, 0.53 and 0.52 (in $\%$), which are experimentally accessible. The predicted branching fractions for corresponding decay modes to excited ($2S$) states, obtained in the order ${\cal O }(10^{-3}-10^{-4})$ lie within the detection accuracy of the current experiments at LHCb and Tevatron. The sizeable $CP$-odd fractions predicted for $B_c^-$-meson decay to two charmful states: $D^{*0}D^{*-}_{(s)}$ and $\bar{D}^{*0}D^{*-}_{(s)}$ indicate significant $CP$-violation hinting at the so-called new physics beyond the standard model.

hep-ph↗

arXiv2022

Exclusive semileptonic $B_c$-meson decays to radially excited charmonium and charm meson states

In the wake of recent measurements of ratios of semileptonic branching fractions: ${\cal R}_{J/ψ}, {\cal R}_D$ and ${\cal R}_{D^*}$ reported by the LHCb, BELLE and HFLAV Collaborations, we calculate invariant form factors for the exclusive semileptonic $B_c$-meson decays to radially excited charmonium and charm meson states in the full kinematical region within the framework of relativistic independent quark (RIQ)model. We evaluate the lepton mass effect in the decay processes induced by $b\to c,u$ transition at the quark level. Our predictions on branching fractions for $B_c\to η_c/ψ(nS)$ are found $\sim10^{-2}-10^{-4}$ and that for $B_c\to D^*(nS)$ are $\sim 10^{-4}$ in their $e^-$ decay modes, which lie within the detection accuracy of current experiment. Our predictions on branching fractions, forward backward asymmetry and asymmetry parameter are found in reasonable agreement with other model predictions; which can hopefully be tested in future experiments at LHC and Tevatron. Our predicted observable ${\cal R}$ in this sector are found comparable to other standard model (SM) predictions that violate the lepton flavor universality hinting at new physics beyond SM.

hep-ph↗

arXiv2022

Exclusive nonleptonic Bc-meson decays to S-wave charmonium states

We study the exclusive two-body nonleptonic $B_c\to X_{c\bar{c}}M$ decays, where $X_{c\bar{c}}$ is either a ground(1S) or a radially excited (2S or 3S) charmonium and $M$ is a pseudoscalar $(P)$ or a vector $(V)$ meson. We consider here three categories of decays: $B_c \to PP, PV, VP$ decays within the framework of relativistic independent quark(RIQ) model based on a flavor-independent interaction potential in scalar-vector harmonic form. Using the factorization approximation, we calculate the weak form factors from the overlapping integrals of meson wave functions obtained in the RIQ model and predict the branching fractions for a set of exclusive nonleptonic $B_c$-decays in reasonable agreement with other model predictions. Some of the decays of interest are found to have branching fractions $\sim (10^{-3}-10^{-4})$ within the detection ability of the current experiments and can be precisely measured at LHCb in near future. In the wake of the recent measurement of $B_c\to J/ψπ(K)$, $B_c\to J/ψπ(D_s)$, $B_c\to π(J/ψ,ψ(2S))$ and $B_c\to J/ψ(π,μν)$ reported by the LHCb Collaborations, we predict the ratios: ${\cal R}_{K/π}$, ${\cal R}_{D_s/π}$ and ${\cal R}_{ψ(2S)/{J/ψ}}$ in broad agreement with the LHCb data though our predicted ratio ${\cal R}_{π/{μν}}$ is found to be underestimated. The results indicate that the present approach works well in the description of exclusive nonleptonic $B_c$-decays within the framework of the RIQ model.

hep-ph↗

arXiv2021

Lepton mass effects in exclusive semileptonic $B_c$-meson decays

In this work, we discuss exclusive semileptonic $B_c$-meson decays: $B_c\to η_c(J/ψ)lν$ and $B_c\to D(D^*)lν$ in the framework of the relativistic independent quark(RIQ) model based on an average flavor independent confining potential in equally mixed scalar-vector harmonic form. We calculate the invariant form factors representing decay amplitudes from the overlapping integrals of meson wave functions derivable in the RIQ model. To evaluate the lepton mass effects in the semileptonic decays, we first study the $q^2$-dependence of the form factors in the accessible kinematic range of $q^2$ involved in the decay process in its $e^-$ and $τ^-$ mode separately. Similar studies on helicity amplitudes, $q^2-$spectra for different helicity contributions, and total $q^2$-spectra for each decay process are carried out separately in their $e^-$ and $τ^-$ modes. We predict the decay rates/ branching fractions, forward-backward asymmetry, and the asymmetry parameter in reasonable agreement with other model predictions, which can hopefully be tested in future experiments at the Tevatron and LHC. We also predict the observable $'R'$ which corresponds to the ratio of branching fractions for the decay process in its $e^-$ mode to its corresponding value in the $τ^-$ mode. Our results are comparable to another standard model(SM) predictions which highlight the failure of the lepton flavor universality hinting at new physics beyond SM for the explanation of the observed deviation of observable $'R'$ value from the corresponding SM predictions.

hep-ph↗

arXiv2020

A New Set of Maxwell-Lorentz Equations and Rediscovery of Heaviside-Maxwellian (Vector) Gravity from Quantum Field Theory

We show that if we start with the free Dirac Lagrangian, and demand local phase invariance, assuming the total phase coming from two independent contributions associated with the charge and mass degrees of freedom of charged Dirac particles, then we are forced to introduce two massless independent vector fields for charged Dirac particles that generate all of electrodynamics and gravitodynamics of Heaviside's Gravity of 1893 or Maxwellian Gravity and specify the charge and mass currents produced by charged Dirac particles. From this approach we found: (1) a new set of Maxwell-Lorentz equations, (2) two equivalent sets of gravito-Maxwell-Lorentz equations (3) a gravitational correction to the standard Lagrangian of electrodynamics, which, for a neutral massive Dirac particle, reduces to the Lagrangian for gravitodynamics, (4) attractive interaction between two static like masses, contrary to the prevalent view of many field theorists and (5) gravitational waves emanating from the collapsing process of self gravitating systems carry positive energy and momentum in the spirit of Maxwell's electromagnetic theory despite the fact that the intrinsic energy of static gravitoelectromagnetic fields is negative as dictated by Newton's gravitational law and its time-dependent extensions to Heaviside-Maxwellian Gravity (HMG). Fundamental conceptual issues in linearized Einstein's Gravity are also discussed.

physics.gen-ph↗

arXiv2019

Semileptonic $B_c$ meson decays to S-wave charmonium states

We study the semileptonic decays of $B_c$ meson to S-wave charmonium states in the framework of relativistic independent quark model based on an average flavor-independent confining potential $U(r)$ in the scalar-vector harmonic form $U(r)=\frac{1}{2}(1+γ^0)(ar^2+V_0)$, where ($a$, $V_0$) are the potential parameters.The form factors for $B_c^+\to η_c /ψe^+ν_e$ transitions are studied in the physical kinematic range. Our predicted branching ratios (BR) for transitions to ground state charmonia are found comparatively large $\sim $ $10^{-2}$, compared to those for transitions to radially excited 2S and 3S states. Like all other mpdel predictions, our predicted BR are obtained in the hierarchy: BR($B_c^+\to η_c /ψ(3S)$) $<$ BR($B_c^+\to η_c/ ψ(2S)$) $<$ BR($B_c^+\to η_c /ψ(1S)$). The longitudinal ($Γ_L$) and transverse polarization ($Γ_T$) for $B_c \to ψ(ns)$ decay modes are predicted in the small and large $q^2$ - region as well as in the whole physical region. The ratios for such transitions are obtained $\frac {Γ_L}{Γ_T} < 1$ throughout the kinematic range which means the $B_c^+$ meson transitions to vector meson charmonium states take place predominantly in transverse polarization mode. The theoretical predictions on these transitions could be tested in the on-going and forthcoming experiments at LHCb.

hep-ph↗

arXiv2018

Neutron star matter with strange interactions in a relativistic quark model

The effect of strange interactions in neutron star matter and the role of the strange meson-hyperon couplings are studied in a relativistic quark model where the confining interaction for quarks inside a baryon is represented by a phenomenological average potential in an equally mixed scalar-vector harmonic form. The hadron-hadron interaction in nuclear matter is then realized by introducing additional quark couplings to $σ$, $ω$, $ρ$, $σ^*$ and $ϕ$ mesons through mean-field approximations. The meson-baryon couplings are fixed through the SU(6) spin-flavor symmetry and the SU(3) flavor symmetry to determine the hadronic equation of state (EoS). We find that the SU(3) coupling set gives the potential depth between $Λ$s around $-5$ MeV and favours a stiffer EoS.The radius for the canonical neutron star lies within a range of $12.7$ to $13.1$ km.

nucl-th↗

arXiv2018

Electromagnetic transitions of $(b{\bar c})$ bound system

We study electromagnetic transitions: $B_c^*(ns)\to B_c(ns) e^+ e^-$, $B_c^*(ns)\to B_c(n^{\prime}s) e^+ e^-$ and $B_c(ns)\to B^*_c(n^{\prime}s) e^+ e^-$ in the relativistic independent quark (RIQ) model based on a flavor-independent potential in the scalar-vector harmonic form. The transition form factors for energetically possible transitions involving $B_c$ - and $B_c^*$- mesons in ground as well as orbitally excited states are predicted in their respective kinematic range. Our predictions on decay width for the allowed and hindered transitions are found compatible with those of the model calculations based on Bethe-Salpeter approach. Predictions in this sector would not only provide more information about members of the $B_c$-family including mass splitting between vector mesons and corresponding pseudoscalar counterparts but give hints for experimental determination of unknown masses of other excited $B_c$ - and ground state of $B_c^*$-meson, which is expected at LHCb and $Z^0$ factory in near future.

hep-ph↗

arXiv2017

Attractive Heaviside-Maxwellian (Vector) Gravity from Special Relativity and Quantum Field Theory

Adopting two independent approaches (a) Lorentz-invariance of physical laws and (b) local phase invariance of quantum field theory applied to the Dirac Lagrangian for massive electrically neutral Dirac particles, we rediscovered the fundamental field equations of Heaviside Gravity (HG) of 1893 and Maxwellian Gravity (MG), which look different from each other due to a sign difference in some terms of their respective field equations. However, they are shown to represent two mathematical representations of a single physical theory of vector gravity that we name here as Heaviside-Maxwellian Gravity (HMG), in which the speed of gravitational waves in vacuum is uniquely found to be equal to the speed of light in vacuum. We also corrected a sign error in Heaviside's speculative gravitational analogue of the Lorentz force law. This spin-1 HMG is shown to produce attractive force between like masses under static condition, contrary to the prevalent view of field theorists. Galileo's law of universality of free fall is a consequence of HMG, without any initial assumption of the equality of gravitational mass with velocity-dependent mass. We also note a new set of Lorentz-Maxwell's equations having the same physical effects as the standard set - a byproduct of our present study.

physics.gen-ph↗

arXiv2017

Magnetic Dipole Transitions of $B_c$ and $B_c^*$ mesons in the Relativistic Independent Quark Model

We study M1-transitions involving mesons: $B_c(1s)$, $B_c^*(1s)$, $B_c(2s)$, $B_c^*(2s)$, $B_c(3s)$ and $B_c^*(3s)$ in the relativistic independent quark (RIQ) model based on a flavor independent average potential in the scalar-vector harmonic form. The transition form factor for $B_c^*\to B_cγ$ is found to have analytical continuation from spacelike to physical timelike region. Our predicted coupling constant $g_{B_c^* B_c}$ = 0.34 Ge$V^{-1}$ and decay width $Γ(B_c^*\to B_cγ)$ = 23 eV agree with other model predictions. In view of possible observation of $B_c$ and $B_c^*$ s-wave states at LHC and Z-factory and potential use of theoretical estimate on M1-transitions, we investigate the allowed as well as hindered transitions of orbitally excited $B_c$-meson states and predict their decay widths in overall agreement with other model predictions. We consider the typical case of $B_c^*(1s)\to B_c(1s)γ$, where our predicted decay width which is found quite sensitive to the mass difference between $B_c^*$ and $B_c$ mesons may help in determining the mass of $B_c^*$ experimentally.

hep-ph↗

arXiv2017

$Δ$ isobars in hyperon stars in a modified quark meson coupling model

The possibility of the appearance of $Δ$ isobars in neutron star matter and the so called {\it $Δ$ puzzle} is studied in a modified quark meson coupling model where the confining interaction for quarks inside a baryon is represented by a phenomenological average potential in an equally mixed scalar-vector harmonic form. The hadron-hadron interaction in nuclear matter is then realized by introducing additional quark couplings to $σ$, $ω$, and $ρ$ mesons through mean-field approximations. The couplings of the $Δ$ to the meson fields are fixed from available constraints while the hyperon couplings are fixed from the optical potential values. It is observed that within the constraints of the mass of the precisely measured massive pulsars, PSR J0348+0432 and PSR J1614-2230, neutron stars with a composition of both $Δ$ isobars and hyperons is possible. It is also observed that with an increase in the vector coupling strength of the $Δ$ isobars there is a decrease in the radius of the neutron stars.

nucl-th↗

arXiv2016

Hyperon star in a modified quark meson coupling model

We determine the equation of state (EOS) of nuclear matter with the inclusion of hyperons in a self-consistent manner by using a Modified Quark Meson Coupling Model (MQMC) where the confining interaction for quarks inside a baryon is represented by a phenomenological average potential in an equally mixed scalar-vector harmonic form. The hadron-hadron interaction in nuclear matter is then realized by introducing additional quark couplings to $σ$, $ω$, and $ρ$ mesons through mean-field approximations. The effect of a nonlinear $ω$-$ρ$ term on the equation of state is studied. The hyperon couplings are fixed from the optical potential values and the mass-radius curve is determined satisfying the maximum mass constraint of $2$~M$_{\odot}$ for neutron stars, as determined in recent measurements of the pulsar PSR J0348+0432. We also observe that there is no significant advantage of introducing the nonlinear $ω$-$ρ$ term in the context of obtaining the star mass constraint in the present set of parametrizations.

nucl-th↗

arXiv2015

Nuclear symmetry energy in a modified quark meson coupling model

We study nuclear symmetry energy and the thermodynamic instabilities of asymmetric nuclear matter in a self-consistent manner by using a modified quark-meson coupling model where the confining interaction for quarks inside a nucleon is represented by a phenomenologically averaged potential in an equally mixed scalar-vector harmonic form. The nucleon-nucleon interaction in nuclear matter is then realized by introducing additional quark couplings to $σ$, $ω$, and $ρ$ mesons through mean-field approximations. We find an analytic expression for the symmetry energy ${\cal E}_{sym}$ as a function of its slope $L$. Our result establishes a linear correlation between $L$ and ${\cal E}_{sym}$. We also analyze the constraint on neutron star radii in $(pn)$ matter with $β$ equilibrium.

nucl-th↗

arXiv2013

Nuclear equation of state in a relativistic independent quark model with chiral symmetry and variation with quark masses

We have calculated the properties of nuclear matter in a self-consistent manner with quark-meson coupling mechanism incorporating structure of nucleons in vacuum through a relativistic potential model; where the dominant confining interaction for the free independent quarks inside a nucleon, is represented by a phenomenologically average potential in equally mixed scalar-vector harmonic form. Corrections due to spurious centre of mass motion as well as those due to other residual interactions such as the one gluon exchange at short distances and quark-pion coupling arising out of chiral symmetry restoration; have been considered in a perturbation manner to obtain the nucleon mass in vacuum. The nucleon-nucleon interaction in nuclear matter is then realized by introducing additional quark couplings to sigma and omega mesons through mean field approximations. The relevant parameters of the interaction are obtained self consistently while realizing the saturation properties such as the binding energy, pressure and compressibility of the nuclear matter. We also discuss some implications of chiral symmetry in nuclear matter along with the nucleon and nuclear sigma term and the sensitivity of nuclear matter binding energy with variations in the light quark mass.

nucl-th↗

arXiv2001

Parton Distributions in Nucleon on the Basis of a Relativistic Independent Quark Model

At a low resolution scale with $Q^2=μ^2$ corresponding to the nucleon bound state; deep inelastic unpolarized structure functions $F_1(x,μ^2)$ and $F_2(x,μ^2)$ are derived with correct support using the symmetric part of the hadronic tensor under some simplifying assumptions in the Bjorken limit. For doing this; the nucleon in its ground state has been represented by a suitably constructed momentum wave packet of its valence quarks in their appropriate SU(6) spin flavor configuration with the momentum probability amplitude taken phenomenologically in reference to the independent quark model of scalar-vector harmonic potential. The valence quark distribution functions $u_v(x,μ^2)$ and $d_v(x,μ^2)$, extracted from the structure function $F_1(x,μ^2)$ in a parton model interpretation, satisfy normalization constraints as well as the momentum sum-rule requirements at a bound state scale of $μ^2=0.1 GeV^2$. QCD evolution of these distribution functions taken as the inputs; yields at $Q_0^2=15 GeV^2; xu_v(x,Q_0^2)$ and $xd_v(x,Q_0^2)$ in good qualitative agreement with the experimental data. The gluon distribution $G(x,Q_0^2)$ and the sea-quark distribution $q_s(x,Q_0^2)$; which are dynamically generated using the leading order renormalization group equation; also match reasonably well with the available experimental data.

hep-ph↗