Production and Decay of Scalar Stoponium Bound States

In this paper we discuss possible signatures for the production of scalar t̃1t̃ ∗ 1 (stoponium) bound states σt̃1 at hadron colliders, where t̃1 is the lighter scalar top eigenstate. We first study the decay of σt̃1 ; explicit expressions are given for all potentially important decay modes. If t̃1 has unsuppressed two–body decays, they will always overwhelm the annihilation decays of σt̃1 . Among the latter, we find that usually either the gg or hh final state dominates, depending on the size of the off–diagonal entry of the stop mass matrix; h is the lighter neutral scalar Higgs boson of the minimal supersymmetric model. If mσt̃ happens to be close to the mass of one of the neutral scalar Higgs bosons, QQ̄ final states dominate (Q = b or t). W+W− and ZZ final states are subdominant. We argue that σt̃1 → γγ decays offer the best signal for stoponium production at hadron colliders. The tevatron should be able to close the light stop window left open by LEP searches, but its mass reach is limited to mσt̃ ≤ 90 GeV. In contrast, at the LHC one should ultimately be able to probe the region mσt̃ ≤ 700 GeV, if the hh partial width is not too large. We also comment on the feasibility of searching for σt̃1 production at hadron colliders in the ZZ, Zγ and τ +τ+τ−τ− final states, and briefly mention σt̃1 production at γγ colliders. Heisenberg Fellow E–mail: NOJIRIN@JPNKEKVX