Ds+→ϕρ+D_s^+ \to \phi \rho^+ Decay

Motivated by the experimental measurement of the decay rate, $\Gamma$, and the longitudinal polarization, $P_L$, in the Cabibbo favored decay $D_s^+\to \phi {\rho}^{+}$, we have studied theoretical prediction within the context of factorization approximation invoking several form factors models. We were able to obtain agreement with experiment for both $\Gamma$ and $P_L$ by using experimentally measured values of the form factors $A_1^{D_s\phi}(0)$, $A_2^{D_s\phi}(0)$ and $V^{D_s\phi}(0)$ in the semi-leptonic decay $D_s^+\to \phi l^{+}\nu_{l}$. We have also included in our calculation the effect of the final state interaction ($fsi$) by working with the partial waves amplitudes $S$, $P$ and $D$. Numerical calculation shows that the decay amplitude is dominated by $S$ wave, and that the polarization is sensitive to the interference between $S$ and $D$ waves. The range of the phase difference $\delta_{SD} = \delta_S - \delta_D$ accommodated by experimental error in $P_L$ is large.Comment: 7 pages, LaTe

Resonant final-state interactions in D^0 -> \bar{K}^{0} {\eta}, \bar{K}^{0} \eta' Decay

We have investimated the effect of the isospin 1/2, J^P = 0^+ resonant state K^*_0(1950) on the decays D^0 ->\bar{K}^{0}\eta and D^0 ->\bar{K}^0 \eta' as a function of the branching ratio sum r =Br(K^*_0(1950)->\bar{K}^0\eta)+ Br(K^*_0(1950)->\bar{K}^0 \eta' and coupling constants g_{K^*_0\bar{K}^0\eta}, g_{K^*_0\bar{K}^0\eta'}. We have used a factorized input for D^0 -> K^*_0(1950) weak transition through a \pi K loop. We estimated both on- and off-shell contributions from the loop. Our calculation shows that the off-shell effects are significant. For $r\geq 30$ a fit to the decay amplitude A(D^0 -> \bar{K}^0 \eta') was possible, but the amplitude A(D^0 ->\bar{K}^0 \eta) remained at its factorized value. For small values of r, $r\leq 18$, we were able to fit A(D^0 -> \bar{K}^0 \eta), and despite the fact that A(D^0 -> \bar{K}^0 \eta') could be raised by almost 100 % over its factorized value, it still falls short of its experimental value. A simultaneous fit to both amplitudes A(D^0 -> \bar{K}^0 \eta') and A(D^0 -> \bar{K}^0 \eta) was not possible. We have also determined the strong phase of the resonant amplitudes for both decays. PACS numbers:13.25.Ft, 13.25.-k, 14.40.LbComment: 16 pages, 6 figures, 3 table

Potential Models for Radiative Rare B Decays

We compute the branching ratios for the radiative rare decays of B into K-Meson states and compare them to the experimentally determined branching ratio for inclusive decay b -> s gamma using non relativistic quark model, and form factor definitions consistent with HQET covariant trace formalism. Such calculations necessarily involve a potential model. In order to test the sensitivity of calculations to potential models we have used three different potentials, namely linear potential, screening confining potential and heavy quark potential as it stands in QCD.We find the branching ratios relative to the inclusive b ->s gamma decay to be (16.07\pm 5.2)% for B -> K^* (892)gamma and (7.25\pm 3.2)% for B -> K_2^* (1430)gamma for linear potential. In the case of the screening confining potential these values are (19.75\pm 5.3)% and (4.74\pm 1.2)% while those for the heavy quark potential are (11.18\pm 4.6)% and (5.09\pm 2.7)% respectively. All these values are consistent with the corresponding present CLEO experimental values: (16.25\pm 1.21)% and (5.93\pm 0.46)%.Comment: RevTeX, 6 pages, 1 eps figur

Covariant and Heavy Quark Symmetric Quark Models

There exist relativistic quark models (potential or MIT-bag) which satisfy the heavy quark symmetry (HQS) relations among meson decay constants and form factors. Covariant construction of the momentum eigenstates, developed here, can correct for spurious center-of-mass motion contributions.Proton form factor and M1 transitions in quarkonia are calculated. Explicit expression for the Isgur-Wise function is found and model determined deviations from HQS are studied. All results depend on the model parameters only. No additional ad hoc assumptions are needed.Comment: 34 pages (2 figures not included but avaliable upon request), LATEX, (to be published in Phys.Rev.D