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Register a new userStudy of Bc -> BP,BV Decays with QCD Factorization
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The Bc -> BP,BV decays are studied with the QCD factorization approach (where P and V denote pseudoscalar and vector mesons, respectively). Considering the contributions of both current-current and penguin operators, the amplitudes of branching ratios are estimated at the leading approximation. We find that the contributions of the penguin operators are very small due to the serious suppression by the CKM elements. The most promising decay modes are Bc -> Bs Pi, Bs rho, which might be easily detected at hadron colliders.
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The Bc --> J/psi pi, etac pi decays are studied with the perturbative QCD approach. It is found that form factors and branching ratios are sensitive to the parameters w, v, f_J/psi and f_etac, where w and v are the parameters of the charmonium wave functions for Coulomb potential and harmonic oscillator potential, respectively, f_J/psi and f_etac are the decay constants of the J/psi and etac mesons, respectively. The large branching ratios and the clear signals of the final states make the Bc --> J/psi pi, etac pi decays to be the prospective channels for measurements at the hadron colliders
In the framework of the perturbative QCD approach, we study the charmless pure weak annihilation Bc->KK decay and find that the branching ratio BR(Bc->KK) O(10^-7). This prediction is so tiny that the Bc->KK decay might be unmeasurable at the Large Hadron Collider.
We report on the calculation of the two-loop penguin amplitudes in non-leptonic B decays in the framework of QCD factorization. We discuss the computation of this genuine two-loop, two-scale problem and provide details on the matching from QCD onto SCET, the evaluation of the master integrals, and the convolution of the hard scattering kernels with the light-cone distribution amplitude of the light meson. Preliminary results on the size of the two-loop correction are given.
We evaluate in the framework of QCD factorization the two-loop vertex corrections to the decays $bar{B}_{(s)}to D_{(s)}^{(ast)+} , L^-$ and $Lambda_b to Lambda_c^+ , L^-$, where $L$ is a light meson from the set ${pi,rho,K^{(ast)},a_1}$. These decays are paradigms of the QCD factorization approach since only the colour-allowed tree amplitude contributes at leading power. Hence they are sensitive to the size of power corrections once their leading-power perturbative expansion is under control. Here we compute the two-loop ${cal O}(alpha_s^2)$ correction to the leading-power hard scattering kernels, and give the results for the convoluted kernels almost completely analytically. Our newly computed contribution amounts to a positive shift of the magnitude of the tree amplitude by $sim 2$%. We then perform an extensive phenomenological analysis to NNLO in QCD factorization, using the most recent values for non-perturbative input parameters. Given the fact that the NNLO perturbative correction and updated values for form factors increase the theory prediction for branching ratios, while experimental central values have at the same time decreased, we reanalyze the role and potential size of power corrections by means of appropriately chosen ratios of decay channels.
In this work, we study the localized $CP$ violation in $B^-rightarrow K^-pi^+pi^-$ and $B^-rightarrow K^- sigma(600)$ decays by employing the quasi two-body QCD factorization approach. Both the resonance and the nonresonance contributions are studied for the $B^-rightarrow K^-pi^+pi^-$ decay. The resonance contributions include those not only from $[pipi]$ channels including $sigma(600)$, $rho^0(770)$ and $omega(782)$ but also from $[Kpi]$ channels including $K^*(892)$, $K_0^*(1430)$, $K^*(1410)$, $K^*(1680)$ and $K_2^*(1430)$. By fitting the experimental data $mathcal{A_{CP}}(K^-pi^+pi^-)=0.678pm0.078pm0.0323pm0.007$ for $m_{K^-pi^+}^2<15$ $mathrm{GeV}^2$ and $0.08<m_{pi^+pi^-}^2<0.66$ $mathrm{GeV}^2$, we get the end-point divergence parameters in our model, $phi_S in [4.75, 5.95]$ and $rho_Sin[4.2, 8]$. Using these results for $rho_S$ and $phi_S$, we predict that the $CP$ asymmetry parameter $mathcal{A_{CP}} in [-0.094, -0.034]$ and the branching fraction $mathcal{B} in [1.82, 20.0]times10^{-5}$ for the $B^-rightarrow K^-sigma(600)$ decay. In addition, we also analyse contributions to the localized $CP$ asymmetry $mathcal{A_{CP}}(B^-rightarrow K^-pi^+pi^-)$ from $[pipi]$, $[Kpi]$ channel resonances and nonresonance individually, which are found to be $mathcal{A_{CP}}(B^-rightarrow K^-[pi^+pi^-] rightarrow K^-pi^+pi^-)=0.585pm0.045$, $mathcal{A_{CP}}(B^-rightarrow [K^-pi^+] pi rightarrow K^-pi^+pi^-)=0.086pm0.021$ and $mathcal{A_{CP}}^{NR}(B^-rightarrow K^-pi^+pi^-)=0.061pm0.0042$, respectively. Comparing these results, we can see that the localized $CP$ asymmetry in the $B^-rightarrow K^-pi^+pi^-$ decay is mainly induced by the $[pipi]$ channel resonances while contributions from the $[Kpi]$ channel resonances and nonresonance are both very small.
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