arXiv subjects

Muhammad Jamil Aslam

Publications and source records attributed to Muhammad Jamil Aslam.

6 recordsLinked to original sources

arXiv2026

The Angular Observables of $\Lambda_b \to \Lambda_c(\to \Lambda^0 \pi^+) \, \tau^-(\to \pi^- \nu_\tau)\, \bar{\nu}_\tau$ within the Paradigm of FCCC Anomalies

We present a global analysis of the current $B$-meson flavor anomalies and extend it to the baryonic sector through the decay $\Lambda_b^0 \to \Lambda_c^+(\to \Lambda^0 \pi^+) \tau^-(\to \pi^- \nu_\tau)\bar{\nu}_\tau$. The lepton flavor universality ratios $R_{\tau/(\mu,e)}(D^{(*)})$, measured by BaBar, Belle, and LHCb, exhibit a combined $3.8\sigma$ deviation from Standard Model (SM) predictions. Using the latest HFLAV averages and $B_c$-lifetime constraints, $\mathcal{B}(B_c \to \tau \nu) < 60\%, 30\%, 10\%$, found new physics (NP) solutions to the cascade decay $\Lambda_b^0 \to \Lambda_c^+(\to \Lambda^0 \pi^+) \tau^-(\to \pi^- \nu_\tau)\bar{\nu}_\tau$. The scenario $(C_{V_L},C_{S_R})$ emerges as the most favored NP solution, largest pull from the SM and insensitive to branching-ratio constraints; followed by $C_{V_L}$ case. We study the impact of NP operators on a complete set of angular observables on the five-fold $\Lambda_b$ decay using Lattice-QCD form factors and find that the scenarios $(\Re[C_{S_L}=4C_T],\Im[C_{S_L}=4C_T])$ and $(C_{S_L},C_{S_R})$ generate the largest deviations from the SM predictions. In particular, the observables $\mathcal{K}_{1c}$, $\mathcal{K}_{2ss}$, $\mathcal{K}_{2cc}$, and $\mathcal{K}_{4s}$ show the highest sensitivity to NP effects. The correlation analysis reveals the $(\Re[C_{S_L}=4C_T],\Im[C_{S_L}=4C_T])$ scenario exhibits inverse correlations among $\mathcal{K}_{1c}$ and $\mathcal{K}_{2ss,2cc,4s}$ and direct correlations between $\mathcal{K}_{2ss}$ and $\mathcal{K}_{2cc,4s}$, pointing to a possible CP-violating phase, while the $(C_{S_L},C_{S_R})$ scenario displays complementary behavior consistent with CP-conserving dynamics. These results establish baryonic semileptonic decays as a powerful and independent probe of the $R_{\tau/(\mu,e)}(D^{(*)})$ anomalies, with future measurements providing critical tests of the underlying NP structure.

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arXiv2025

Addressing the $R_{\tau/{\mu,e}}\left(D^{(*)}\right)$ puzzle through New Physics four-fermion operators and their impact on $\Lambda_{b}\rightarrow\Lambda_{c}\tau\bar{\nu}_{\tau}$ decay

The Lepton Flavor Universality ratio $R_{\tau/{\mu,e}}\left(D^{(*)}\right)$ poses a challenge to the Standard Model (SM), as B-factory experiments, BaBar, Belle, and the LHCb show $3.31\sigma$ deviations from their theoretical predictions. Utilizing the latest HFLAV averages and incorporating the branching ratio constraints $60\%$, $30\%$ and $10\%$ from the lifetime of the $B_c$ meson, we determine the values of the Wilson coefficients (WCs) for different New Physics (NP) four-fermion operator with specific Lorentz structures. Our analysis finds that the WC scenario $\left(C_{S_{L}},C_{S_{R}}\right)$ is the most probable, the maximum pull from the SM, and strongly influenced by branching ratio constraints. Furthermore, we identify three degenerate solutions involving $C_{V_{L}}$, $C_{V_{L}}^{\prime}$, $C_{V_{L}}^{\prime\prime}$, and $C_{S_{R}}^{\prime\prime}$ as the second most probable NP scenarios. We then studied the influence of these NP operators on various physical observables in $\Lambda_{b}\rightarrow\Lambda_{c}\tau\bar{\nu}_{\tau}$ decay by using the Lattice QCD form factors. Our results highlighted $C_{S_{L}}^{\prime\prime}$, $C_{S_{R}}$, $C_{T}$, $\left(C_{S_{L}},C_{S_{R}}\right)$, $\left(C_{S_{R}},C_{T}\right)$, and the three degenerate scenarios involving $\left(C_{S_{L}},C_{T}\right)$, $\left(C_{S_{L}}^{\prime},C_{T}^{\prime}\right)$ and $\left(C_{S_{L}}^{\prime\prime},C_{T}^{\prime\prime}\right)$ as strong indicators of NP. The correlation of different physical observables shows a direct correlation between $d\Gamma/dq^{2}$ and $P_{L}^{\tau}$ for WC $\left(C_{S_{L}},C_{S_{R}}\right)$; and between $A_{FB}$ and $P_{L}^{\Lambda_{c}}$ for three degenerate WCs involving $\left(C_{S_{L}},C_{T}\right)$. We hope that the measurements of these observables in ongoing and future experiments will help us scrutinize these constraints on the various NP couplings.

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arXiv2024

Signature decay modes of the compact doubly-heavy tetraquarks $T_{bb\bar{u} \bar{d}}$ and $T_{bc\bar{u} \bar{d}}$

Based on the expectations that the lowest-lying doubly-bottom tetraquark $T_{bb\bar u \bar d}$ ($J^P = 1^+$) and the bottom-charm tetraquark $T_{bc\bar u \bar d}$ ($J^P = 0^+$) are stable against strong and electromagnetic decays, we work out a number of semileptonic and non-leptonic weak decays of these hadrons, making use of the heavy quark symmetry. In doing this, we concentrate on the exclusive decays involving also tetraquarks in the final states, i.e., transitions such as $T_{bb\bar u \bar d} \to T_{bc\bar u \bar d}\, (\ell^- \nu_\ell,\, h^-)$ and $T_{bc\bar u \bar d} \to T_{cc\bar u \bar d}\, (\ell^- \nu_\ell,\, h^-)$, where $h^- = \pi^-, \rho^-, a_1^-, D^-_s, D^{*-}_s$. So far, only the $J^P = 1^+$ tetraquark $T_{cc\bar u \bar d}$ has been discovered, which we identify with the $I = 0$ $T_{cc}^+$ object, compatible with $J^P = 1^+$ and having the pole mass relative to the $D^{*+} D^0$ mass threshold and decay widths $\delta m = M (T_{cc}^+) - ( M (D^{*+}) + M (D^0) ) = - 360 \pm 40^{+4}_{-0}$ keV and $\Gamma (T_{cc}^+) = 48^{+2}_{-14}$ keV. Experimental discoveries of the transitions worked out here, and related ones involving doubly-heavy baryons, will quantify the diquark-antidiquark component of these tetraquarks.

hep-ph↗

arXiv2024

Probing New Physics in light of recent developments in $b \rightarrow c \ell \nu$ transitions

The experimental studies of the observables associated with the $b \rightarrow c$ transitions in the semileptonic $B-$ meson decays at BaBar, Belle and LHCb have shown some deviations from the Standard Model (SM) predictions, consequently, providing a handy tool to probe the possible new physics (NP). In this context, we have first revisited the impact of recent measurements of $R({D^{(*)}})$ and $R(\Lambda_c)$ on the parametric space of the NP scenarios. In addition, we have included the $R(J/\psi)$ data in the analysis and found that their influence on the best-fit points and the parametric space is mild. Using the recent HFLAV data, after validating the well established sum rule of $R(\Lambda_c)$, we derived the similar sum rule for $R(J/\psi)$. Furthermore, according to the updated data, we have modified the correlation among the different observables, giving us their interesting interdependence. Finally, to discriminate the various NP scenarios, we have plotted the different angular observables and their ratios for $B \to D^* \tau\nu_\tau$ against the transfer momentum square $\left(q^2\right)$, using the $1\sigma$ and $2\sigma$ parametric space of considered NP scenarios. By implementing the collider bounds on NP Wilson coefficients, we find that, in the parametric space of some NP WCs is significantly restrained. To see the clear influence of NP on the amplitude of the angular observables, we have also calculated their numerical values in different $q^2$ bins and shown them through the bar plots. We hope their precise measurements will help to discriminate various NP scenarios.

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arXiv2023

Analysis of $b\rightarrow c\tau\bar{\nu}_\tau$ anomalies using weak effective Hamiltonian with complex couplings

Recently, the experimental measurements of the branching ratios and different polarization asymmetries for the processes occurring through flavor-changing-charged current $b\rightarrow c\tau\overline{\nu}_{\tau}$ transitions by BABAR, Belle, and LHCb show some sparkling differences with the corresponding SM predictions. Assuming the left handed neutrinos, we add the dimension-six vector, (pseudo-)scalar, and tensor operators with complex WCs to the SM WEH. Together with 60%, 30% and 10% constraints coming from the branching ratio of $B_{c}\to\tau\bar{\nu}_{\tau}$, we analyze the parametric space of these new physics WCs accommodating the current anomalies in the purview of the most recent HFLAV data of $R_{\tau/{\mu,e}}\left(D\right)$, $R_{\tau/{\mu,e}}\left(D^*\right)$ and Belle data of $F_{L}\left(D^*\right)$ and $P_{\tau}\left(D^*\right)$. Furthermore, we derive the sum rules which correlate these observables with $R_{\tau/{\mu,e}}\left(D\right)$ and $R_{\tau/{\mu,e}}\left(D^*\right)$. Using the best-fit points of the new complex WCs along with the latest measurements of $R_{\tau/{\mu,e}}\left(D^{(*)}\right)$, we predict the numerical values of the observable $R_{\tau/\ell}\left(\Lambda_c\right)$, $R_{\tau/\mu}\left(J/\psi\right)$ and $R_{\tau/\ell}\left(X_c\right)$ from the sum rules. Apart from finding the correlation matrix among the observables under consideration, we plot them graphically which is useful to discriminate different NP scenarios. Finally, we study the impact of these NP couplings on various angular and the CP triple product asymmetries, that could be measured in some ongoing and future experiments. The precise measurements of these observables are important to check the SM and extract the possible NP.

hep-ph↗

arXiv2017

Constraints on Two Higgs Doublet Model Parameters in the light of rare $B$-Decays

We established the allowed parameters of two-Higgs doublet model(2HDM) from flavor physics observables, precisely from rare $B$ meson decays. In our analysis most formidable constraints on the 2HDM parameters arise from the branching ratio of rare radiative $B$ meson decay i.e., $B\to X_{s}γ$. However, the constraints arising from the branching ratio of $B_{s}\toμ^{+}μ^{-}$ decay in $m_{H^{\pm}}-\tanβ$ plane give $m_{H^{\pm}} >$ 80 GeV for the value of $\tanβ\sim 2$, that is in agreement with large electron-positron collider (LEP) data. Furthermore, we also investigate the bounds on the $CP$-even $m_{H}$ and $CP$-odd $m_{A^{0}}$ Higgs boson not only from above mentioned physical observables, but also from the zero crossing of the forward-backward asymmetry of $B\to K^{\ast}μ^{+}μ^{-}$ decay. Therefore, these bounds on parameters of the 2HDM will provides a fertile ground to test the 2HDM at current and future $B$-physics experiments.

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