DOI 10.1007/s100529800763
Internal down quark's flavour changing contribution to the effective tcZ vertex
Surath Kumar Biswas - V.P. Gautam
Theoretical Physics Department, Indian Association for the
Cultivation of Science, Jadavapur, Calcutta, 700032, India
(e-mail: tpvpg@iacs.ernet.in)
Received: 21 March 1997 / Revised version: 19 August 1997 / Published online: 20 February 1998
Abstract
The effective tcZ vertex may be influenced by tree
vertex formed by a mixing with heavy exotic isosinglet
down
type quarks. To study that the electroweak penguin diagrams involving
one insertion of the vertex have been considered and we
have calculated the contribution arising out of those diagrams using the
Fourth Generation CKM matrix elements; also the applicability of the
generalized GIM 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 down flavour changing contribution
interferes constructively with the one loop penguin diagrams and
experimental data may put constraint on the fourth generation down quark
mass.
Copyright Springer-Verlag
