Double Lepton Polarization in Λb−−>Λl+l−\Lambda_b -->\Lambda l^+ l^- Decay in the Standard Model with Fourth Generations Scenario

This study investigates the influence of the fourth generation quarks on the double lepton polarizations in \Lambda_b --> \Lambda \ell^+ \ell^- decay by taking |V^\ast_{t's}V_{t'b}|= 0.005,0.01,0.02,0.03 with phase \{60^\circ,90^\circ,120^\circ\}. We will try to obtain a constrain on the mass of the 4th generation top like quark t', which is consistent with the $b--> s\ell^+\ell^- rate . With the above mentioned parameters, we will try to show that the double lepton(muon, tau) polarizations are quite sensitive to the existence of fourth generation. It can serve as a good tool to search for new physics effects, precisely, to search for the fourth generation quarks(t', b') via its indirect manifestations in loop diagrams.Comment: 36 pages, 33 figure

Exclusive B \rar \rho \ell^+ \ell^- Decay in the Standard Model with Fourth--Generation

We investigate the influence of the fourth generation of quarks on the branching ratio, the CP-asymmetry and the polarization asymmetries in B \rar \rho \ell^+ \ell^- decay. Taking $|V_{t'd}V_{t'b}|\sim 0.001$ with phase about $10^\circ$, which is consistent with the $sin2\phi_1$ of the CKM and the $B_d$ mixing parameter $\Delta m_{B_d}$, we obtain that for both ($\mu, \tau$) channels the branching ratio is increased and the magnitude of CP-asymmetry and polarization asymmetries decreased by the mass and mixing parameters of the 4th generation of quarks . These results can serve as a good tool to search for new physics effects, precisely, to search for the fourth generation of quarks($t', b')$ via its indirect manifestations in loop diagrams.Comment: 17 pages, 7 figure

Form factors and decay rate of Bc∗→Ds l+l−B_c^\ast \rightarrow D_{s}~l^+ l^- decays in the QCD sum rules

Rare exclusive $B_c^\ast \rightarrow D_{s}~l^+ l^-$ decays are analyzed in the framework of the three--point QCD sum rules approach. The two gluon condensate corrections to the correlation function are included and the form factors of this transition are evaluated. Using the form factors, the decay width and integrated decay rate for these decays are also calculated.Comment: 17 pages, 3 figure

CP-Conserving Unparticle Phase Effects on the Unpolarized and Polarized Direct CP Asymmetry in b→dℓ+ℓ−b \to d \ell^+\ell^- Transition

We examine the unparticle CP-conserving phase effects on the direct CP asymmetry for both polarized and unpolarized lepton in the inclusive $b\to d \ell^+ \ell^-$ transition, where the flavor changing neutral currents are forbidden at tree level but are induced by one-loop penguin diagrams. The averaged polarized and unpolarized CP asymmetries depict strong dependency on the unparticle parameters. In particular, a sizable discrepancy corresponding to the standard model is achieved when the scale dimension value is 1. We see that the unparticle stuff significantly enhances, suppresses or changes the sign of the CP asymmetry depending on the definite value of the scaling dimension d_{\UP}. Especially, when d_{\UP}\sim 1.1 the CP asymmetries vanish.Comment: 10 figures, PRD Published versio

Analysis of the B --> \pi \ell^+ \ell^- Decay in the Standard Model with Fourth Generation

We investigate the influence of the fourth generation quarks on the branching ratio and the CP-asymmetry in B -->\pi \ell^+ \ell^- decay. Taking the |V_{t'd}V_{t'b}| ~ 0.001 with phase about 10 degree, which is consistent with the sin2\phi_1 of the CKM and the B_d mixing parameter \Delta m_{B_d}, we obtain that for both muon and tau channels the branching ratio, the magnitude of CP-asymmetry and lepton polarization depict strong dependency on the 4th generation quarks mass and mixing parameters. These results can serve as a good tool to search for new physics effects, precisely, to search for the fourth generation quarks($t', b')$ via its indirect manifestations in loop diagrams.Comment: 17 pages, 8 figure

The Effects of Fourth Generation on the double Lepton Polarization in B \rar K \ell^+ \ell^- decay

This study investigates the influence of the fourth generation quarks on the double lepton polarizations in B \rar K \ell^+ \ell^- decay. Taking |V_{t's}V_{t'b}|\sim \{0.01-0.03\} with phase about 100^\circ, which is consistent with the b\to s\ell^+\ell^- rate and the B_s mixing parameter Delta m_{B_s}$, we obtain that the double lepton(muon and tau) polarizations are quite sensitive to the existence of fourth generation. It can serve as a good tool to search for new physics effects, precisely, to indirect search for the fourth generation quarks(t', b').Comment: 30 pages, 27 figure

Analysis of \Lambda_b \rar \Lambda \ell^+ \ell^- transition in SM4 using form factors from Full QCD

Using the responsible form factors calculated via full QCD, we analyze the $\Lambda_{b}\rightarrow \Lambda \ell^{+}\ell^{-}$ transition in the standard model containing fourth generation quarks (SM4). We discuss effects of the presence of $t'$ fourth family quark on related observables like branching ratio, forward-backward asymmetry, baryon polarization as well as double lepton polarization asymmetries. We also compare our results with those obtained in the SM as well as with predictions of the SM4 but using form factors calculated within heavy quark effective theory. The obtained results on branching ratio indicate that the $\Lambda_{b}\rightarrow \Lambda \ell^{+}\ell^{-}$ transition is more probable in full QCD comparing to the heavy quark effective theory. It is also shown that the results on all considered observables in SM4 deviate considerably from the SM predictions when $m_{t'}\geq 400 GeV$.Comment: 22 Pages and 21 Figure