The Effects of Fourth Generation on the Total Branching Ratio and the Lepton Polarization in $Λ_b \rar Λ\ell^+ \ell^-$ decay

Abstract

This study investigates the influence of the fourth generation quarks on the total branching ratio and the single lepton polarizations in Λ_b --> Λ\ell^+ \ell^- decay. Taking $|V_{t's}V_{t'b}| {0.01-0.03} with phase just below $90^\circ$, which is consistent with the b\to s\ell^+\ell^- rate and the B_s mixing parameter Δm_{B_s}, we obtain that the total branching ratio and the single lepton(μ, τ) 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').