Analysis of the Bq→Dq(Dq∗)PB_q\to D_q(D_q^*) P and Bq→Dq(Dq∗)VB_q\to D_q(D_q^*) V decays within the factorization approach in QCD

Using the factorization approach and considering the contributions of the current-current, QCD penguin and electroweak penguin operators at the leading approximation, the decay amplitudes and decay widths of $B_q\to D_q(D_q^*) P$ and $B_q\to D_q(D_q^*) V$ transitions, where $q=u,d,s$ and P and V are pseudoscalar and vector mesons, are calculated in terms of the transition form factors of the $B_q\to D_{q}$ and $B_q\to D^{*}_{q}$. Having computed those form factors in three-point QCD sum rules, the branching fraction for these decays are also evaluated. A comparison of our results with the predictions of the perturbative QCD as well as the existing experimental data is presented.Comment: 18 Pages and 9 Table

Investigation of the Ds1D_{s1} structure via BcB_c to Ds1l+l−/ννˉD_{s1} l^+l^-/\nu\bar\nu transitions in QCD

We investigate the structure of the $D_{s1}(2460,2536) (J^P=1^+)$ mesons via analyzing the semileptonic $B_{c}\to D_{s1}l^+l^-$, $l=\tau, \mu, e$ and $B_{c}\to D_{s1}\nu\bar{\nu}$ transitions in the framework of the three--point QCD sum rules. We consider the $D_{s1}$ meson in two ways, the pure $|c\bar{s}>$ state and then as a mixture of two $|^3P_1>$ and $|^1P_1>$ states. Such type rare transitions take place at loop level by electroweak penguin and weak box diagrams in the standard model via the flavor changing neutral current transition of $b \to s$. The relevant form factors are calculated taking into account the gluon condensate contributions. These form factors are numerically obtained for $|c\bar s>$ case and plotted in terms of the unknown mixing angle $\theta_s$, when the $D_{s1}$ meson are considered as mixture of two $|^3P_1>$ and $|^1P_1>$ states. The obtained results for the form factors are used to evaluate the decay rates and branching ratios. Any future experimental measurement on these form factors as well as decay rates and branching fractions and their comparison with the obtained results in the present work can give considerable information about the structure of this meson and the mixing angle $\theta_s$.Comment: 33 Pages, 11 Figures and 5 Table

Exclusive Ds→(η,η′)lνD_{s} \to (\eta,\eta^{\prime}) l \nu decays in light cone QCD

Probing the $\bar ss$ content of the $\eta$ and $\eta'$ mesons and considering mixing between these states as well as gluonic contributions, the form factors responsible for semileptonic $D_s \to (\eta, \eta') l \nu$ transitions are calculated via light cone QCD sum rules. Corresponding branching fractions and their ratio for different mixing angles are also obtained. Our results are in a good consistency with experimental data as well as predictions of other nonperturbative approaches.Comment: 13 Pages, 2 Figure and 4 Table

gDs∗DK∗(892)g_{D^{\ast}_{s}D K^{\ast}(892)} and gBs∗BK∗(892)g_{B^{\ast}_{s}B K^{\ast}(892)} coupling constants in QCD sum rules

The coupling constants $g_{D^{\ast}_{s}D K^{\ast}(892)}$ and $g_{B^{\ast}_{s}B K^{\ast}(892)}$ are calculated in the framework of three-point QCD sum rules. The correlation functions responsible for these coupling constants are evaluated considering contributions of both $D(B)$ and $K^*(892)$ mesons as off-shell states, but in the absence of radiative corrections. The results, $g_{D^{\ast}_{s}D K^{\ast}(892)}=(4.31\pm1.42) GeV^{-1}$ and $g_{B^{\ast}_{s}B K^{\ast}(892)}=(3.24\pm1.08) GeV^{-1}$ are obtained for the considered strong coupling constants.Comment: 13 Pages and 11 Figure