Bounds on QCD instantons from HERA Original Research Article

Signals for processes induced by QCD instantons are searched for in HERA data on the hadronic final state in deep-inelastic scattering. The maximally allowed fraction of instanton-induced events is found at 95% confidence level to be on the percent level in the kinematic domain 10−4 ≲ x ≲ 10−2 and 5 ≲ Q2 ≲ 100 GeV2. The most stringent limits are obtained from the multiplicity distributions.