M. Ali Paracha

Form factors, branching ratio and forward–backward asymmetry in B→K1ℓ+ℓ- decays

We study long-distance effects in the rare exclusive semileptonic decays B→K1ℓ+ℓ-, where K1 is the axial vector meson. The form factors describing the meson transition amplitudes of the effective Hamiltonian are calculated using the Ward identities, which are then used to calculate the branching ratio and the forward–backward asymmetry in these decay modes. The zero of the forward–backward asymmetry is of special interest and provides us with a precision test of the standard model.

K 1 ( 1270 ) − K 1 ( 1400 ) mixing and the fourth generation standard model effects in B → K 1 l + l − decays

The implications of the fourth generation quarks in the B-->K_{1}(1270,1400)l^{+}l^{-} with l=mu, tau decays are studied, where the mass eigenstates K_{1}(1270) and K_{1}(1400) are the mixture of ^{1}{P}_{1} and ^{3}{P}_{1} states with the mixing angle \theta_{K}. In this context, we have studied various observables like branching ratio (BR), forward backward asymmetry (A_{FB}) and longitudinal and transverse helicity fractions (f_{L,T}) of K_{1} meson in B-->K_{1}l^{+}l^{-} decays. To study these observables, we have used the Light Cone QCD sum rules form factors and set the mixing angle \theta_{K}=-34^{o}. It is noticed that the BR is suppressed for K_{1}(1400) as a final state meson compared to that of K_{1}(1270). Same is the case when the final state leptons are tauons rather than muons. In both the situations all the above mentioned observables are quite sensitive to the fourth generation effects. Hence the measurements of these observables at LHC, for the above mentioned processes can serve as a good tool to investigate the indirect searches for the existence of fourth generation quarks.

Semileptonic charmed

Form factors parameterizing the semileptonic decay

B

B_{c}\rightarrow D_{s}^{\ast}l^{+}l^{-}

meson decays in Universal Extra Dimension Model

(

Model independent analysis of the forward–backward asymmetry for the B→K 1 μ + μ − decay

l=\mu ,\tau

Effects of neutral

) are calculated using the frame work of Ward Identities. These form factors are then used to calculate the physical observables like branching ratio and helicity fractions of final state

Z^{\prime}

D_{s}^{\ast}

boson in

meson in these decay modes. The analysis is then extended to the the universal extra dimension (UED) model where the dependence of above mentioned physical variables to the compactification radius R, the only unknown parameter in UED model, is studied. It is shown that the helicity fractions of

B_{s} \to \phi \ell^{+} \ell^{-}

D_{s}^{\ast}