Glueball Production in High Energy e+e- Collision

Abstract

Inclusive glueball production via two· photon subprocess in high energy e+ e- collision is discussed. Formulae for the cross section are shown and then numerically evaluated. It is demonstrated that considerably large cross section can be expected with feasible rate for near future experiments. The quantum chromodynamics (QCD) strongly suggests the existence of glueballs (gluonic bound states with no valence quarks). Such entities are analogues to quarkonia and expected to gain an equal footing in particle physics. We think it is crucial to the well-tried QCD whether the glueball can really be established, for gluons in the color singlet sector should necessarily make bound states by virtue of the non-linear strong self-couplings among themselves. Masses of glueballs have been conjectured, on the basis of various models,1)-5) to lie near those of usual quarkonia (typically say, 1.5 Ge V or so). If it is the case, some of those glueballs may have already been detected and mistaken for quarkonia (e. g., t(1440) in ¢~rKKJ[6),7) and 8(1640) in ¢~rrJ7J;7) these being likely to be regarded as pseudoscalar and tensor glueballs, respectively). Since the 021 rule forbids the glueballs to decay fast into conventional hadrons, the low lying levels should appear as fairly narrow states. This narrowness becomes an effective clue for glueball search. At the same time, this means the glueball production should be quite suppressed as far as its experiments are done with use of the hadronic collisions. Then it may be difficult to find good signals for glueballs out of considerably large background noises. On the contrary, we should be able to evade such disadvantage if we avail high energy e+ e- collision for the observation of glueballs. Its reason is, as elucidated soon,*) that the high energy e+ e- collision becomes predominated by two almost real photons which are rich in soft gluons. Then it is of much interest *) In this context, it is quite important to observe that the photon is a fundamental 0. e., pointlike) particle as well as the quark and the gluon. This fact means, in the Kogut-Susskind picture for the partonometry or the extended version of the equivalent quantum approximation, that the photon itself behaves as a kind of parton and turns out, in contrast with the composite hadrons, to be able to evolve through the relevant QED Born term by virtue of the perturbative QeD interaction (see Ref. 10) for further details).