Speaker
Abstract:
Supersymmetric grand unified models based on the gauge group SU (5) often require in addition to gauge coupling unification, the unification of b-quark and τ -lepton Yukawa couplings. We examine SU (5) SUSY GUT parameter space under the condition of b − τ Yukawa coupling unification using 2-loop MSSM RGEs including full 1-loop threshold effects. The Yukawa-unified solutions break down into two classes. Solutions with low tan β ∼ 3 − 11 are characterized by mg ∼ 1 − 4 TeV and mq ∼ 1 − 5 TeV. Many of these solutions would be beyond LHC reach, although they contain a light Higgs scalar with mh < 123 GeV and so may be excluded should the LHC Higgs hint persist. The second class of solutions occurs at large tan β ∼ 35 − 60, and are a subset of t − b − τ unified solutions. Constraining only b − τ unification to ∼ 5% favors a rather light gluino with mg ∼ 0.5−2 TeV, which should ultimately be accessible to LHC searches. While our b − τ unified solutions can be consistent with a picture of eutralino-only cold dark matter, invoking additional moduli or Peccei-Quinn superfields can allow for all of our Yukawa-unified solutions to be consistent with the measured dark matter abundance. In second part of the talk some new results for NLSP gluino in Patti-Salam model will be discussed briefly.
