542 research outputs found
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 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
Instanton-Induced Cross-Sections in Deep-Inelastic Scattering
We present our results for inclusive instanton-induced cross-sections in
deep-inelastic scattering, paying in particular attention to the residual
renormalization-scale dependencies. A ``fiducial'' kinematical region in the
relevant Bjorken variables is extracted from recent lattice simulations of QCD.
The integrated instanton-contribution to the cross-section at HERA
corresponding to this fiducial region is surprisingly large: It is in the
O(100) pb range, and thus remarkably close to the recently published
experimental upper bounds.Comment: 13 pages, 10 figure
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