Zooming-in on Instantons at HERA

In view of the intriguing, preliminary search results for instanton-induced events at HERA from the H1 collaboration, some important remaining theoretical issues are discussed. Notably, the question is addressed, to which extent the H1 analysis may be directly compared to our original predictions from instanton-perturbation theory, since certain fiducial cuts are lacking in the H1 data. Various theoretical uncertainties are evaluated and their impact on the observed excess is discussed. An improved understanding of the experimental findings along with an encouraging over-all agreement with our original predictions seems to emerge.Comment: 13 pages, 12 figure

QCDINS 2.0 - A Monte Carlo generator for instanton-induced processes in deep-inelastic scattering

We describe a Monte Carlo event generator for the simulation of QCD-instanton induced processes in deep-inelastic scattering (HERA). The QCDINS package is designed as an ``add-on'' hard process generator interfaced to the general hadronic event simulation package HERWIG. It incorporates the theoretically predicted production rate for instanton-induced events as well as the essential characteristics that have been derived theoretically for the partonic final state of instanton-induced processes: notably, the flavour democratic and isotropic production of the partonic final state, energy weight factors different for gluons and quarks, and a high average multiplicity O(10) of produced partons with a Poisson distribution of the gluon multiplicity. While the subsequent perturbative evolution of the generated partons is always handled by the HERWIG package, the final hadronization step may optionally be performed also by means of the general hadronic event simulation package JETSET.Comment: 51 pages, 3 figure

Theory and Phenomenology of Instantons at HERA

We review our on-going theoretical and phenomenological investigation of the prospects to discover QCD-instantons in deep-inelastic scattering at HERA.Comment: 18 pages, 15 figures; contribution to the Ringberg Workshop ``New Trends in HERA Physics'', Ringberg Castle, Tegernsee, Germany, May 30 - June 4, 1999; to be published in the proceeding

Towards the Phenomenology of QCD-Instanton Induced Particle Production

We present a first status report on a broad and systematic study of possible manifestations of QCD-instantons at HERA. Considerable motivation comes from the close analogy between instanton-induced $B+L$ violation in electroweak processes and effects of QCD-instantons in deep inelastic scattering. We concentrate on the high multiplicity final state structure, reminiscent of an isotropically decaying ``fireball''. A set of experimental isolation criteria is proposed. They serve to further enhance the striking event signature without significantly suppressing the expected rates.Comment: 32 pages, latex, epsfig, 11 uuencoded figure