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Register a new user$B_c$ meson exclusive decays to a $P$-wave charmonium and a pion at NLO accuracy
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In this paper, we calculate the next-to-leading order (NLO) quantum chromodynamics (QCD) corrections to the exclusive processes $B_c^+to chi_{cJ}(h_c)pi^+$ in the framework of the nonrelativistic QCD (NRQCD) factorization formalism. The results show that NLO QCD corrections markedly enhance the branching ratios with $K$ factors of about 2.5. In combination with the study of $B_c^+to J/psipi^+$, we find that the NLO NRQCD prediction for the ratio of branching fractions $frac{mathcal{B}(B_c^+to chi_{c0}pi^+)}{mathcal{B}(B_c^+to J/psi pi^+)}$ is then compatible with the experimental measurement.
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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 $U(r)=frac{1}{2}(1+gamma^0)(ar^2+V_0)$, where ($a$, $V_0$) are the potential parameters.The form factors for $B_c^+to eta_c /psi e^+ u_e$ 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($B_c^+to eta_c /psi (3S)$) $<$ BR($B_c^+to eta_c/ psi (2S)$) $<$ BR($B_c^+to eta_c /psi (1S)$). The longitudinal ($Gamma_L$) and transverse polarization ($Gamma_T$) for $B_c to psi(ns)$ 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 $frac {Gamma_L}{Gamma_T} < 1$ 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.
We calculate the next-to-leading order (NLO) quantum chromodynamics (QCD) corrections to inclusive processes $W^+to J/psi(eta_c)+c+bar{s}+X$ and $W^+to B_c(B_c^{*})+b+bar{s}+X$ in the framework of nonrelativistic QCD (NRQCD) factorization formalism. Result indicates that the NLO corrections are significant, and the uncertainties in theoretical predictions with NLO corrections are greatly reduced. The charmonium and $B_c$ meson yielding rates at the Large Hadron Collider (LHC) are given.
In this work, we discuss exclusive semileptonic $B_c$-meson decays: $B_cto eta_c(J/psi)l u$ and $B_cto D(D^*)l u$ 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 $tau^-$ 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 $tau^-$ 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 $tau^-$ 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.
We compute the exclusive electroproduction, $gamma^* p rightarrow V p$, of heavy quarkonia $V$ to NLO in the collinear factorisation scheme, which has been formally proven for this process. The inclusion of an off-shell virtuality $Q^2$ carried by the photon extends the photoproduction phase space of the exclusive heavy quarkonia observable to electroproduction kinematics. This process is relevant for diffractive scattering at HERA and the upcoming EIC, as well as at the proposed LHeC and FCC.
Recent studies of properties and decays of the $B_c^+$ meson by the LHC experiments are presented. Mass and lifetime measurements are discussed and some of the many new observed decays are reported.
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