arXiv subjects

Lopamudra Nayak

Publications and source records attributed to Lopamudra Nayak.

11 recordsLinked to original sources

arXiv2025

$B \to D^{(*)} τν_τ$ decay properties with RIQ model

In this work we compute the branching fraction of $B \to D^{(*)} \,τ\, ν_τ$ and $B_s \to D_s^{(*)}\, τ\, ν_τ$ within the Relativistic Independent Quark Model, emphasizing the harmonic potential model dependent analysis of these decay channels in the precision flavor physics era. Considering the experimental observation of longitudinal $τ$-polarization and fraction of longitudinal polarization at LHCb and Belle, we have also investigated these observables within our model framework which are aligning well with the standard model expectations. We perform a comprehensive analysis of the form factors across the whole accessible kinematic range of $q^2$. Our results are consistent and compatible with other theoretical approaches as well as with the experimental measurements. Furthermore, we evaluated the clean ratios of $B_s$ to $B_0$ in the semimuonic mode that are in accordance with the LHCb measurements, and support the validity of the SU(3) flavor symmetry. Although the concept of new physics is facing a significant challenge at the current TeV scale, semileptonic $B$ decays, nevertheless, always serve as a valuable probe to study the decay dynamics.

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arXiv2025

Mass spectrum of S-wave mesons in the relativistic independent quark model

The confining strength or model parameters and constituent quark masses are reparametrized for predicting the ground state meson masses. We analyzed these from the hyperfine splitting of $S$-wave heavy-flavored, heavy-light and light (except non-strange) mesons in the framework of a relativistic independent quark (RIQ) model with one gluon exchange and centre-of-mass correction. These mesons with spin parity $J^P=0^-$ and $1^-$, the masses obtained are in accordance with the experimental physical masses. The results will serve as good complementary tools in further study of hadron dynamics and will behave as a foundation for the higher excited and exotic states of hadrons.

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arXiv2024

Study of angular observables in exclusive semileptonic $B_c$ decays

In this work, we investigate angular observables such as the longitudinal polarization of charged leptons, $τ$-polarization, and forward-backward asymmetry in semileptonic $B_c$ decays. Additionally, we provide predictions for lepton flavor violating observables, the $\mathcal{R}$ ratios in the decay channels $B_c \rightarrow η_c (J/ψ) l ν_l$ and $B_c \rightarrow D (D^*) l ν_l$ across the entire $q^2$ region. Our analysis is conducted within the Relativistic Independent Quark Model, focusing on the potential model-dependent aspects of these observables. We compare our model predictions with existing lattice predictions, highlighting the strong applicability of our framework in describing $B_c$ decays. Considering the forthcoming experimental upgrades and the Run 3 data results on $B_c$ meson decays, rapid confirmation of these quantities could indicate significant discoveries of physics beyond the Standard Model. This will open up new avenues for understanding the complex flavor dynamics in heavy meson decays.

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arXiv2024

Study of exclusive decays of \texorpdfstring{$B_s \to ψ(1S,2S) K_s$}{Lg} and \texorpdfstring{$B_s \to η_c(1S,2S) K_s$}{Lg}

We analyze the exclusive two-body nonleptonic decays of $B_s$ meson to ground as well as radially excited $2S$ charmonium state with a light meson $K_s$, induced by the $b\to c\bar{c}d$ transition. Within the framework of relativistic independent quark (RIQ) model based on a flavor-independent interaction potential in scalar-vector harmonic form, we calculate the weak form factors from the overlapping integrals of meson wave function obtained in this model. Using the factorization approximation, we predict the branching fractions for the $B_s \to ψ(1S,2S) K_s$ and $B_s \to η_c(1S,2S) K_s$, which can be compared with future theoretical predictions. Branching fraction for $B_s\to J/ψK_s$ decay is found to be in good agreement with the data from LHCb Collaboration, whereas for $B_s\to ψ(2S) K_s$, it is found to be within the detection ability of the CMS Collaboration. We also predict the ratios of branching fractions $(\cal{R})$, which are in broad agreement with the data from LHCb Collaboration. These results indicate that the present approach works well in the description of exclusive nonleptonic $B_s$ decays within the framework of the RIQ model.

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arXiv2024

Assessing Lepton Flavor Universality Violations in Semileptonic Decays

In light of recent measurements suggesting potential lepton flavor universality violations in semileptonic decays at collider experiments, this article provides a concise study of tree- and loop-level $B$-hadron semileptonic decays, $b \to c l ν_l$ and $b \to s l^+ l^-$. We provide predictions for lepton flavor violating observables, $\mathcal{R}_{J/ψ}$ and $\mathcal{R}_{η_c}$, across the entire $q^2$ range. Our study employs the Relativistic Independent Quark Model (RIQM), highlighting a model-dependent approach to these observables. We compare our model's predictions with existing lattice predictions, demonstrating the strong applicability of the RIQM framework in describing $B_c$ decays. Additionally, we reassess global averages for $\mathcal{R}_{D(D^*)}$ and $\mathcal{R}_{K(K^*)}$ in semileptonic transitions. With the upcoming experimental upgrades and the anticipated Run 3 data on $B_c$ meson decays, rapid confirmation of these quantities could indicate significant evidence of physics beyond the Standard Model, thereby opening new pathways for understanding the complex flavor dynamics in $B$ meson decays.

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arXiv2023

Delving into the $ B_s \to \ell \ell^{\prime}$, $B_{(s)} \to (K^{()}, ϕ, f_2^{\prime}, K_2^) \ell \ell ^{\prime}$ processes

To shed light on the indirect search for new physics beyond the standard model, the long standing discrepancies between the theory and experiment mediated by FCNC $b\to s \ell \ell$ quark level transitions set an ideal testing ground. Though the very recent measurements of $R_K$ and $R_{K^*}$ are consistent with the standard model, still the excitements remain on the measurements of LHCb experiment with the observables $\mathcal{B} (B_s \to ϕμ^+ μ^-)$ which has deviations at the level of $3.6 σ$. Additionally, standard deviation of $\sim 3.3 σ$ and $1.2 σ$, respectively for $P_5^{\prime}$ in $B \to K^* μ^+ μ^-$ and the branching ratio in $B_s \to μ^+ μ^-$ processes are observed. Inspired by these discrepancies, we work out the constraints on the new physics coupling parameters in the presence of a non-universal $Z'$ model. We then probe the exclusive leptonic decay channels $ B_s \to \ell \ell^{\prime}$, $B_{(s)} \to (K^{(*)}, ϕ, f_2^{\prime}, K_2^*) \ell \ell ^{\prime}$ induced by the neutral current transition $b\to s \ell \ell^{\prime}$. We find that the $q^2$ variation of the observables, such as, branching ratio, forward-backward asymmetry, lepton polarization asymmetry, and the very sensible observable, so called non-universality observables for LFV decays display the sensitivity of new physics. In this analysis. we estimate above mentioned observables that could shed light on the window of new physics in the near future.

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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.

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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.

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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.

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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.

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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.

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