Jet structure ine+e−annihilation as a test of quantum chromodynamics and the quark-confining string

Abstract

We examine the jet structure in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation from two processes: (a) the bremsstrahlung of a hard gluon and (b) the emission of a meson at wide angle via the constituent-interchange model (CIM). At center-of-mass energies from 12 to 25 GeV, both processes, if present, are found to broaden the sharp transverse-momentum damping of jets observed at SPEAR. At lower energies and large transverse momentum we find that the CIM process prevails. But by center-of-mass energies greater than 30 GeV the gluonic process should be dominant. We also examine the jet structure generated by the decay of a bound state of new heavy quarks into three gluons. Should such quarks (${m}_{q}\ensuremath{\gtrsim}5$ GeV) exist, this bound state would provide an ideal place to look for gluon-induced jets. Other topics we have studied include (i) jet structure via the production of four quarks and (ii) different possible gluonic fragmentation functions. Jet structure in deep-inelastic lepton-hadron scattering processes is also briefly considered. We conclude that ${e}^{+}{e}^{\ensuremath{-}}$ annihilation is probably the cleanest place to search for gluonic structure, whose existence would be striking evidence in favor of quantum chromodynamics (QCD). On the other hand, the absence of such structure would necessitate a reexaminat on of our intuitive understanding of QCD and a serious consideration of other field-theoretical hadronic models, e.g., the quark-confining string, which, unlike QCD, does not possess gluonic degrees of freedom.