Probing the exotic particle content beyond the standard model

Abstract

We explore the possible exotic particle content beyond the standard model by examining all its scalar bilinear combinations. We categorize these exotic scalar fields and show that without the suppression of (A) their Yukawa couplings with the known quarks and leptons, and (B) the trilinear couplings among themselves, most are already constrained to be very heavy from the nonobservation of proton decay and neutronantineutron oscillations, the smallness of K⁰-K̅⁰, D⁰-D̅⁰ and B⁰_d-B̅⁰_d mixing, as well as the requirement of a nonzero baryon asymmetry of the universe. On the other hand, assumption (B) may be naturally violated in many models, especially in supersymmetry, hence certain exotic scalars are allowed to be below a few TeV in mass and would be easily detectable at planned future hadron colliders. In particular, large cross sections for the distinctive processes like p̅p→tt, t̅c and pp→tt, bb would be expected at the Fermilab Tevatron and CERN LHC, respectively.