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Search for QCD Instantons in DIS |
| Reference |
N.N., to be presented at DIS 2002, Spring 2002 |
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| Contact |
B.Koblitz, S.Mikocki |
| Abstract |
Signals of QCD instanton-induced processes are searched for in deep-inelastic scattering (DIS) at the electron-proton collider HERA in a kinematic region defined by the Bjorken-scaling variables x > 10^-3, 0.1 < y < 0.6 and photon virtualities 10 < Q^2 < 100 GeV^2. Several observables characterising hadronic final state properties of QCD instanton-induced events are exploited to identify a potentially instanton enriched domain. Despite an excess of observed events in the instanton signal region, within the accuracy of the standard DIS background simulation this is not significant. An instanton cross-section between 60 pb and 1000 pb, depending on the kinematic domain considered for instanton-induced processes, is excluded. The data do not contradict the instanton production cross-section predicted by instanton perturbation theory for small instanton sizes. However, the steep rise of the cross-section towards large instanton sizes corresponding to a naive extrapolation of instanton perturbation theory is not observed in agreement with non-perturbative lattice simulations of the QCD vacuum. |
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