Theory Seminar DATE: 2005-09-06 11:00 - PLACE: Kenkyu Honkan 2F RM 220 TITLE: Large electroweak penguin effects in B and K physics CONTACT: Tango SPEAKER: Dr. Makiko Nagashima  (National Taiwan University) LANGUAGE: English ABSTRACT: Recent decay rate and direct CP violation measurements in B-> K\pi decays hint at possible new physics that carry near maximal CP phase in electroweak penguin operators. This can be realized by the existence of fourth generation, where e.g. m_{t^\prime}￣ 300 GeV and |V_{t^\prime s}^\ast V_{t^\prime b}|￣ 0.02-0.03. The constraints of B-> X_s \ell^+\ell^- and B_s mixing independently require V_{t^\prime s}^\ast V_{t^\prime b} to be nearly imaginary if the strength is sizable. Such large effects in b->s transitions are bound to spill over into s->d transitions, and V_{t^\prime b} -> 0 is not an option because of unitarity and kaon constraints. By taking account of \epsilon_K, K^+-> \pi^+\nu\bar\nu and \epsilon^\prime/\epsilon constraints, we find that K_L-> \pi^0\nu\bar\nu gets enhanced by two order of magnitude in comparison with the SM expectation. Back