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SUMMARY:Diffractive Dijets and Gap Survival Probability at HERA
DTSTART:20080421T143000Z
DTEND:20080421T153000Z
DTSTAMP:20261008T160300Z
UID:indico-event-32566@indico.cern.ch
DESCRIPTION:Speakers: Sebastian Schaetzel (CERN)\n\nThe study of diffracti
 ve proton scattering is one of the main successes of the electron-proton c
 ollider HERA.  In these diffractive collisions\, the proton stays intact b
 ut a hard scatter occurs which allows comparison with perturbative QCD cal
 culations.  The universality of the diffractive proton structure is invest
 igated by comparing different hard scattering final states\, and by compar
 ing collisions initiated through the exchange of point-like photons with t
 hose induced by real photons.\n\nIn this talk I will review the HERA resul
 ts which can be summarised as follows: While all point-like photon scatter
 ing processes (deep-inelastic scattering\, DIS) can be described using the
  same diffractive parton densities (factorisation)\, the situation is diff
 erent in real photon scattering where the diffractive dijet cross section 
 measured by H1 for E_T(jet1)>5 GeV\, E_T(jet2)>4 GeV is a factor of approx
 imately 0.5 lower than expectations based on the DIS parton densities (fac
 torisation breaking).  Strikingly\, this gap survival probability factor i
 s independent of the photon energy that manifests itself outside the jet s
 ystem---direct and resolved photon processes are equally suppressed. This 
 behaviour is unexpected\, but can be understood qualitatively in the dipol
 e picture of photon-proton scattering.  I will also present latest results
  which indicate that the survival probability depends on the transverse en
 ergy of the jets.\n\nhttps://indico.cern.ch/event/32566/
LOCATION:Council Chamber ** (CERN)
URL:https://indico.cern.ch/event/32566/
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