Higgs bosons in left-right-symmetric models.

Abstract

In the context of minimal left-right-symmetric extensions of the standard $\mathrm{SU}{(2)}_{L}\ifmmode\times\else\texttimes\fi{}\mathrm{U}(1)$ model, four possible scenarios emerge depending upon the number of neutral Higgs fields that acquire nonzero vacuum expectation values. We examine these four scenarios in the case of a simple form for the scalar potential of the model. We find that by combining the minimization conditions appropriate to each of these scenarios with constraints coming from ${K}_{L}\ensuremath{-}{K}_{S}$ mixing and the absence of flavor-changing neutral currents, two of the scenarios are ruled out. For the allowed scenarios rather definitive consequences for the Higgs sector can be obtained. For instance, several of the scalar bosons are forced to be very heavy by flavor-changing neutral-current constraints. Aside from the Higgs boson which plays the role of the standard-model Higgs fields, the three left-handed triplet members are most likely to be light. Indeed, in one of the vacuum-expectation-value scenarios they are forced to be light (the neutral member being massless at the tree level). We catalogue the constraints from low-energy experiments on a doubly charged Higgs triplet and a very light neutral Higgs triplet, when these couple to two leptons (as in the left-right model). Many of the constraints we obtain are new. A new lower bound on the ${W}_{R}$ mass, related to the strength of these lepton-lepton couplings, is derived. The cross sections for these bosons are large out to masses of order several TeV and signatures for their decay are striking and essentially background-free.