Search for QCD instanton-induced processes in deep-inelastic scattering at HERA

  • The H1 Collaboration
  • C. Adloff et al.
Experimental Physics


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 &gt; 10-3, 0.1 &lt; y &lt; 0.6 and photon virtualities \(\) < 100 GeV2. Several observables characterising hadronic final state properties of QCD instanton-induced events are exploited to identify a potentially instanton-enriched domain. While an excess of events with instanton-like topology is observed it cannot be claimed significant given the uncertainty of the standard DIS background simulation. Upper limits on the cross-section for instanton-induced processes of between 60 pb and 1000 pb are set dependent on the kinematic domain considered. The data do not exclude the cross-section predicted by instanton perturbation theory for small instanton sizes. At large instanton sizes a naive extrapolation of instanton perturbation theory yields a cross-section in the range of sensitivity of this study. Such a cross-section is not observed, in agreement with non-perturbative lattice simulations of the QCD vacuum.


Perturbation Theory Photon Virtuality Kinematic Region Lattice Simulation Hadronic Final State 
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Copyright information

© Springer-Verlag Berlin Heidelberg / Società Italiana di Fisica 2002

Authors and Affiliations

  • The H1 Collaboration
  • C. Adloff et al.
    • 1
  1. 1.Fachbereich Physik, Bergische Universität Gesamthochschule Wuppertal, Wuppertal, Germany DE

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