STUDY OF LEPTONIC AND RADIATIVE b QUARK DECAYS IN THE LIGHT OF up-QUARK FLAVOUR CHANGING CONTRIBUTIONS: MULTIDOUBLET MODEL

SURATH KUMAR BISWAS and V. P. GAUTAM

Theoratical Physics Department, Indian Association for the Cultivation of Science, Jadavpur, Calcutta 700 032, India

Received 27 March 1997

The effective bsZ vertex may be influenced by tree uu˘Z vertex formed by a mixing with heavy exotic isosinglet up-type quarks. The electroweak penguin diagrams involving one insertion of the uu˘Z vertex have been considered and we have calculated the contribution arising from those diagrams using the fourth generation Cabbibo-Kobayashi-Maskawa matrix elements; also the applicability of the generalized Glashow-Iliopoulos-Maiani mechanism is considered. The additional effects of the heavy isosinglets are compared with the effects of exotic heavy isodoublets appearing in multi-generational models. We see that in the effective vertex amplitude, the up-flavour-changing contribution interferes constructively and destructively with the one loop-penguin diagrams with and without any insertion of flavour changing coupling, respectively.

UDC 539.126
PACS 12.60.-i

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