arXiv subjects

M. Ali Paracha

Publications and source records attributed to M. Ali Paracha.

24 records · Page 2Linked to original sources

arXiv2011

K_1(1270)-K_1(1400) mixing and the fourth generation SM effects in B-->K_1l^+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 θ_{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 θ_{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.

hep-ph↗

arXiv2011

Analysis of B_{C} --> D_{s}^{*}l^{+}l^{-} in the Standard Model Beyond Third Generation

The weak decays of B_{c} --> D_{s}^{*}l^{+}l^{-} (l=mu,tau) are investigated in the Standard Model with fourth generation (SM4). Taking fourth generation quark mass m_{t'} of about 300 to 600 GeV with the CKM matrix elements V_{t'b}^{*}V_{t's} in the range (0.03-1.2)*10^{-2} and using the new CP odd phase (phi_{sb}) to be 90^{o} the analysis of decay rates, forward-backward asymmetries, lepton polarization asymmetries and the helicity fractions of D_{s}^{*} meson in B_{c} --> D_{s}^{*}l^{+}l^{-} (l=mu,tau) is made. It is shown that the values of these physical observables are greatly influenced by the effects of extra sequential quark generation in the SM. It is found that the zero position of the forward-backward asymmetry in B_{c} --> D_{s}^{*} mu^{+} mu^{-} deviates significantly from that of the SM value while the effects in the decay rate, helicity fractions of D_s^{*} meson and the lepton polarization asymmetries are also quite promising. In B_{c} --> D_{s}^{*} tau^{+} tau^{-} decay, the SM4 the NP effects are somewhat mild in the decay rate and forward-backward asymmetry but they have shown them up in the longitudinal and transverse lepton polarization and also in the helicity fractions of the D_{s}^{*} meson which differ distinctively from the SM values. Thus the study of these physical observables will provide us useful information to probe new physics and helps us to search for the fourth generation of quarks (t',b') in an indirect way.

hep-ph↗

arXiv2011

Semileptonic charmed $B$ meson decays in Universal Extra Dimension Model

Form factors parameterizing the semileptonic decay $B_{c}\rightarrow D_{s}^{\ast}l^{+}l^{-}$ ($l=μ,τ$) 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 $D_{s}^{\ast}$ 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 $D_{s}^{\ast}$ are quite sensitive to the UED model especially when have muons as the final state lepton. Therefore, these can serve as a useful tool to establish new physics predicted by the UED model.

hep-ph↗

arXiv2011

Model Independent Analysis of the Forward-Backward Asymmetry for the $B\to K_{1}μ^{+}μ^{-}$ Decay

The sensitivity of the zero position of the forward backward asymmetry $\mathcal{A}_{FB}$ for the exclusive $B\rightarrow K_{1}(1270)μ^{+}μ^{-}$ decay is examined by using most general non-standard 4-fermion interactions. Our analysis shows that the zero position of the forward backward asymmetry is very sensitive to the sign and size of the Wilson coefficients corresponding to the new vector type interactions, which are the counter partners of the usual Standard Model operators but have opposite chirality. In addition to these, the other significant effect comes from the interference of Scalar-Pseudoscalar and Tensor type operators. These results will not only enhance our theoretical understanding about the axial vector mesons but will also serve as a good tool to look for physics beyond the SM.

hep-ph↗

arXiv2008

Exclusive B-> K_{1}l ^{+}l ^{-} decay in model with single universal extra dimension

Decay rate and forward-backward asymmetries in B -> K_{1} l^{+} l ^{-}, K_{1} is the axial vector meson, are calculated in the universal extra dimension (UED) model. The dependence of these physical quantities on the compactification radius $R$, the only unknown parameter in UED model, is studied and it is shown that zero of forward-backward asymmetry is sensitive to the UED model, therefore they can be very useful tool to establish new physics predicted by the UED model. This work is briefly extended to B -> K^{*}l^{+}l^{-}.

hep-ph↗

arXiv2007

Form factors, branching ratio and forward-backward asymmetry in B -> K_{1}ell ^{+} ell ^{-} decays

We study long-distance effects in rare exclusive semileptonic decays B -> K_{1}ell ^{+}ell ^{-}, K_{1} is the axial vector meson.The form factors, describing the meson transition amplitudes of the effective Hamiltonian, are calculated using Ward identites which are then used to calculate branching ratio and forward-backward asymmetry in these decay modes. The zero of forward-backward asymmetry is of special interest and provide us the precission test of Standard model.

hep-ph↗