The decay $b\to sγ$ and the charged Higgs boson mass without R-Parity

Abstract

The experimental measurement of $B(b \to sγ)$ imposes important constraints on the charged Higgs boson mass in the MSSM. We show that by adding bilinear R--Parity violation (BRpV) in the tau sector, these bounds are relaxed. The bound on $m_{H^{\pm}}$ in the MSSM--BRpV model is $\gsim 200-250$ GeV for the the heavy squark limit. For lighter squarks, light charged Higgs bosons can be reconciled with $B(b \to sγ)$ only if there is also a light chargino. In the BRpV model if we impose $m_{χ^{\pm}_1}>90$ GeV $m_{H^{\pm}} \gsim 75$ GeV, around 30 GeV down from the MSSM. In this case the charged Higgs bosons would be observable at LEP II. The relaxation of the bounds is due mainly to the fact that charged Higgs bosons mix with staus and they contribute importantly to $B(b \to sγ)$.