EUROPEAN PHYSICAL JOURNAL C, vol.27, no.3, pp.405-410, 2003 (SCI-Expanded)
The contribution of the fourth generation quarks to the rare B-s --> l(+)l(-) and B-s --> l(+)l(-)gamma decays are studied. Constraints on the extended Cabibbo-Kobayashi-Maskawa matrix elements \VtbV*(ts)\ and \Vt'bV*(t's)\, are obtained from the existing experimental result for the branching ratio of the B --> X(s)gamma decay. The branching ratios of the above-mentioned decays, as well as the photon spectrum in the B-s --> l(+)l(-)gamma decay, are studied. It is found that the results are sensitive to the existence of the fourth generation.