$b-\tau$ Unification, $g_{\mu }-2$, the $b\to s+\gamma$ Constraint and Nonuniversalities

Abstract

An analysis is given of the $b-\tau$ Yukawa coupling unification in view of the recent result from Brookhaven on $g_{\mu }-2$ and under the constraint of $b\to s+\gamma$. We explore $b-\tau$ unification under the above constraints for nonuniversal boundary conditions for the soft SUSY breaking parameters. We find new regions of the parameter space where significant negative supersymmetric contribution to the b quark mass can arise and $b-\tau$ unification within SU(5) framework can occur with nonuniversal gaugino masses. Specifically we find that for the case where the gaugino mass matrix transforms like a 24 plet one finds a negative contribution to the b quark mass irrespective of the sign of the Higgs mixing parameter $\mu$ when the supersymmetric contribution to $g_{\mu }-2$ is positive. We exhibit regions of the parameter space where $b-\tau$ unification occurs for $\mu >0$ satisfying the constraints of $b\to s+\gamma$ and $g_{\mu }-2$. The $\mu <0$ case is also explored. The dependence of the accuracy of $b-\tau$ unification defined by $|{\lambda }_b-{\lambda }_{\tau }|/{\lambda }_{\tau }$ on the parameter space is also investigated and it is shown that unification with an accuracy of a few percent can be achieved in significant regions of the parameter space. The allowed parameter space is consistent with the naturalness constraints and the corresponding sparticle spectrum is accessible at the Large Hadron Collider.

Comments: 25 pages,Latex including 10 figs. TIFR/TH/01-04, NUB-TH/3222