Supergravity Grand Unification , Proton Decay and Cosmological Constraints

Properties and experimental predictions of a broad class of supergravity grand unified models possessing an SU(5)-type proton decay and R parity are described. Models of this type can be described in terms of four parameters at the Gut scale in addition to those of the Standard Model i.e. mo (universal scalar mass), m1/2 (universal gaugino mass), Ao (cubic soft breaking parameter) and tanβ =< H2 > / < H1 >. Thus the 32 SUSY masses can be expressed in terms of mo, m1/2, Ao tanβ and the as yet unknown t-quark mass mt. Gut thresholds are examined and a simple model leads to grand unification consistent with p-decay data when 0.114 < α3(Mz) < 0.135, in agreement with current values of α3(MZ). Proton decay is examined for the superheavy Higgs triplet mass MH3 < 10MG(MG ≃ 1.5 × 10 GeV) and squarks and gluinos lighter than 1 TeV. Throughout most of the parameter space chargino-neutralino scaling relations are predicted to hold: 2mZ̃1 ∼= mW̃1 ∼= mZ̃2 , mW̃1 ≃ (1/4)mg̃ (for μ > 0) or mW̃1 ≃ (1/3)mg̃ (for μ < 0), while mW̃2 ∼= mZ̃3 ∼= mZ̃4 >> mZ̃1 . Future proton decay experiments combined with LEP2 lead to further predictions, e.g. for the entire parameter space either proton decay should be seen at these or the W̃1 seen at LEP2. Relic density constraints on the Z̃1 further constrain the parameter space e.g. so that mt < 165 GeV, mh < 105 GeV, mW̃1 < 100 GeV and mZ̃1 < 50 GeV when MH3/MG < 6. † Talk at Les Rencontres de Physique de la Vallee D’Aoste ∗ PermanentAddress