Superheavy-quarkonium production and decays: A new Higgs-boson signal

We study the production and subsequent decays of the S- and P-wave quarkonium states of a heavy quark that may be produced at a multi-TeV hadron collider. Our considerations are focused on the lighter member of a fourth-generation doublet, for which the weak decays of the quark are expected to be suppressed by mixing angles. For quarkonium masses ≲1 TeV, the dominant production is via gluon fusion. In addition to the decay channels that are present in the charm and bottom systems, heavy quarkonia can decay into $W^{+}$ $W^{\mathrm{-}}$, $Z^0$ $Z^0$, and $Z^0$γ pairs. Furthermore, the latter decay rates may be enhanced due to couplings of the heavy quarks to the longitudinal components of the gauge bosons. We assess the prospects for discovery of a new heavy quark via its bound-state decays. Quarks with masses up to ≊100 GeV can be found from the decay of the $1^{\mathrm{-}\mathrm{-}}$ state (ψ) into lepton pairs. If the decay of the pseudoscalar quarkonium state into a Z boson and a Higgs boson is kinematically allowed, there is a rather clean signal for the Higgs boson, even for the intermediate-mass Higgs boson with 2$m_t$<$m_H$<2$M_W$. Furthermore, Hγ and HH pairs would also be present at fairly large rates.