PHYSICAL REVIEW D VOLUME 35, NUMBER 11 1 JUNE 1987 Superheavy-quarkonium production and decays: A new Higgs-boson signal V. Barger Physics Department, University of Wisconsin, Madison, Wisconsin 53706 E. W. N. Crlover Physics Department, University of Wisconsin, Madison, Wisconsin 53706 and Cavendish Laboratory, University of Cambridge, Cambridge CB3 OHE, England K. Hikasa Physics Department, University of Wisconsin, Madison, Wisconsin 53706 and National Laboratory for High Energy Physics (KEK), Tsukuba, Ibaraki 305, Japan W. - Y. Keung Physics Department, University of Illinois, Chicago, Illinois 60680 M. G. Olsson, C. J. Suchyta III, and X. R. Tata Physics Department, University of Wisconsin, Madison, Wisconsin 53706 (Received 27 January 1987) 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 pro- duction is via gluon fusion. En addition to the decay channels that are present in the charm and bot- tom systems, heavy quarkonia can decay into 8'+ W, Z Z, and Z y pairs. Furthermore, the latter decay rates may be enhanced due to couplings of the heavy quarks to the longitudinal corn- ponents 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 state (1b) 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 2m, ~ m& ~ 2M~. Furthermore, Hy and 00 pairs would also be present at fairly large rates. I. INTRODUCTION The first signals in hadronic collisions for charm and bottom quarks were the leptonic decays of the J/f and Y bound states. Hence it is of particular interest to examine the possibilities for discovery of new heavy-quark flavors at hadronic colliders through the decays of their quar- konium bound states. The tt quarkonium signals were ex- amined previously' and found to be rather elusive. How- ever, in a recent Letter we showed that the prospects for simultaneously identifying a fourth-generation quarkoni- um state and the Higgs boson at supercollider energies were very promising, due to the possible dominance of the distinctive decay mode ri(QQ)~ZH of the pseudoscalar bound state q into a Z boson and a Higgs boson. In this paper we make a thorough study of production and de- cays of g(0 +), g(1 ), X(0++, I++, 2++), and h(1+ ) superheavy quarkonium states. Quarkonium states with masses M&& ( 1 TeV would be produced with substantial cross sections at hadron super- colliders with a center-of-mass energy of 10 — 40 TeV. For these energies, the gg luminosity exceeds the qq luminosi- ty by a factor ) 50, and gluon fusion is the dominant source of quarkonium production. The pseudoscalar state ri(QQ) and the scalar and tensor P wave states Xo(QQ-) and X2(QQ) couple directly to two gluons and are directly produced via the gluon-fusion mechanism. The vector state 1b(QQ) and the spin-1 P wave states Xt(QQ-) and h (QQ) couple only to the three-gluon or qqg system. Here the dominant production mechanism is the process gg~gg. This is so even though the decay width for g~qq exceeds that for tb~ggg because the gluon lumi- 35 3366 1987 The American Physical Society