Charged Higgs mass bounds from b → sγ in a bilinear R-parity violating model

The experimental measurement of B(b --> s gamma) imposes important constraints on the charged Higgs boson mass in the MSSM. If squarks are in the few TeV range, the charged Higgs boson mass in the MSSM must satisfy m(H+/-) greater than or similar to 440 GeV. For lighter squarks, then light charged Higgs bosons can be reconciled with B(b --> s gamma) only if there is also a light chargino. In the MSSM if we impose m(chi 1+/-) > 90 eV then we need m(H+/-) greater than or similar to 110 GeV. We show that by adding bilinear R-parity violation (BRpV) in the tau sector, these bounds are relaxed. The bound on m(H+/-) in the MSSM-BRpV model is greater than or similar to 340 GeV for the heavy squark case and m(H+/-) greater than or similar to 75 GeV for the case of light squarks. 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 --> s gamma). (C) 1999 Published by Elsevier Science B.V. All rights reserved.