Z0Z^0--Z0′{Z^0}^\prime and ordinary-exotic fermion mixings revisited using some special observables

We investigate the mixing of an extra ${Z^0}^\prime$ with the standard $Z^0$ and mixings of exotic fermions with their standard counterparts through some precisely measured electroweak observables. These observables are geared to search for physics beyond the Standard Model. We observe that although most of such mixings are severely constrained by the recent LEP data, some of the mixing angles could still be rather large, awaiting future tests.Comment: 11 pages, CERN-TH. 7196/94, Late

LEP- and low energy-bounds on R-parity-violating supersymmetric Yukawa couplings

Electroweak precision data at LEP are used to place bounds on some $\lambda'$-type ($L$-violating) and $\lambda''$-type ($B$-violating) $R$-parity violating supersymmetric Yukawa couplings. We consider one-loop corrections (triangles and self-energies) induced by these couplings to the $Z$-partial widths. The couplings involving the top quark induce stronger loop effects and hence are more strongly constrained than others. On the other hand, information on $D$- and $\tau$-decays are used to constrain some of the $\lambda'$-type couplings which are complementary to the ones constrained from LEP. Among the bounds we have derived, many are new from a phenomenological view-point.Comment: 2 pages, postscript (uucompressed), to appear in the Proceedings of the International Europhysics Conference on High Energy Physics, Brussels, 27 July - 2 August, 199

Nondecoupling of charged scalars in Higgs decay to two photons and symmetries of the scalar potential

A large class of two- and three-Higgs-doublet models with discrete symmetries has been employed in the literature to address various aspects of flavor physics. We analyse how the precision measurement of the Higgs to diphoton signal strength would severely constrain these scenarios due to the nondecoupling behavior of the charged scalars, to the extent that the number of additional scalar doublets can be constrained no matter how heavy the nonstandard scalars are. We demonstrate that if the scalar potential is endowed with appropriate global continuous symmetries together with soft breaking parameters, decoupling can be achieved thanks to the unitarity constraints on the mass-square differences of the heavy scalars.Comment: 9 pages, 2 figures, several clarifying remarks and references added, to appear in Phys Rev

Chasing the light-gluino scenario through b→sγb\rightarrow s \gamma

We investigate the impact of a light gluino, which might have escaped detection at colliders, on inclusive radiative $B$-decays mediated through penguin-like diagrams. We find that the viability of the scenario depends largely on the magnitude of the flavour-violating $c$-parameter. Some previously allowed regions of parameter space are now ruled out.Comment: Latex, 8 pages + 1 Figure available upon request, CERN-TH. 7245/94, DAMTP 94-3

Pushing the SUSY Higgs mass towards 125 GeV with a color adjoint

We show that inclusion of a TeV scale chiral superfield transforming in the adjoint representation of the color SU(3) to the MSSM particle content modifies the renormalization group running of some parameters in such a way that a 125 GeV mass of the light Higgs boson is accommodated more comfortably than in cMSSM / mSUGRA. Put differently, the introduction of a color adjoint TeV scale superfield helps resurrecting lighter choices for the stop and gluino which are otherwise disfavored in cMSSM / mSUGRA.Comment: v2: 6 pages, 4 figures, estimate of fine-tuning and some more clarifying remarks added, published in PR