Search for QCD instanton induced events in deep inelastic ep scattering at HERA

A search for QCD-instanton-induced events in deep inelastic ep scattering has been performed with the ZEUS detector at the HERA collider, using data corresponding to an integrated luminosity of 38 pb^{-1}. A kinematic range defined by cuts on the photon virtuality, Q^2 > 120 GeV^2, and on the Bjorken scaling variable, x > 10^{-3}, has been investigated. The QCD-instanton induced events were modelled by the Monte Carlo generator QCDINS. A background-independent, conservative 95% confidence level upper limit for the instanton cross section of 26 pb is obtained, to be compared with the theoretically expected value of 8.9 pb.

Note:

27 pages, 1 table, 6 figures

positron p: colliding beams
positron p: deep inelastic scattering
neutral current
quantum chromodynamics: instanton
jet: transverse momentum
hadron: multiple production
multiplicity: high
cross section: upper limit
numerical calculations: Monte Carlo
ZEUS

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