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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 Odderon Searches and Hadronic Final States in Diffractive Scattering at HERA Karlheinz Meier Kirchhoff-Institut für Physik Ruprecht-Karls-Universität Heidelberg Vth Workshop on Small-x and Diffractive Physics

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 M x (exclusive final state mass) M i (inclusive final state mass) M ≥ m p (proton or excited and decaying nucleon resonance) W ( p mass) Language of Diffraction in a factorized view x momentum fraction wrt. proton, only energy, momentum, angular momentum transferred here z momentum fraction wrt. pomeron Q 2 (momentum transfer describing photon virtuality

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 M x (exclusive final state mass) M i (inclusive final state mass) M ≥ m p (proton or excited and decaying nucleon resonance) W ( p mass) Language of Diffraction in a factorized view x momentum fraction wrt. proton, only energy, momentum, angular momentum transferred here z momentum fraction wrt. pomeron Q 2 (momentum transfer describing photon virtuality ?

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 H1 : Excl. Meson Production via C = +1 and C = -1 Exchange Idea : Unambiguous measurement of final state charge conjugation C look into pure photonic decays, count photons ODD number photons means POMERON exchange EVEN number of photons means ODDERON exchange „2 gluons“ C = +1 1 photon C = -1 „3 gluons“ C = -1

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 Quantitative prediction for exclusive meson production via Odderon exchange based on a non-perturbative QCD approach exists : Stochastic Vacuum Model (SVM) Dosch and Simonov, Phys.Lett. B205 (1988) Nachtmann, Ann.Phys. 209 (1991) Dosch Phys.Rev. D50 (1994) Berger, Donnachie, Dosch, Kilian, Nachtmann, Rüter, Eur. Phys. J. C9 (1999) Berger et al. Eur.Phys. J. C14 (2000) Model has successfully described a variety of high energy reactions (e.g. J/ Production at HERA) Donnachie, Dosch, Phys. Rev., D65 (2002) The H1 approach of photon counting is a clean test of this non-perturbative QCD approach based of purely electromagnetic probes with small experimental ambiguity Problem : No prediction of energy dependence, SVM calculations carried out for W = 20 GeV, Regge-Theory used for extrapolation, Odderon Intercept ?? The Stochastic Vacuum Model (SVM) of Dosch and Simonov

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 H1 : Expected Signals, Backgrounds and Topologies

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 Search for Odderon-Induced Contributions to Exclusive Photoproduction at HERA H1 Collaboration, C. Adloff et al., Phys. Lett. B544 H1 : Excl. 2 Production (C = -1 Exchange, Odderon) no signal observed, limit at 95% C.L. ( p) + N* + N* < 49 nb expectation from SVM is 200 nb Ensure exclusive final states via longitudinal momentum balance Explicit detection of neutron in upstream 0-degree calorimeter L = 30.6 pb -1 important cross-check : inclusive is clearly seen at correct rate

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 H1 : Excl. 3 Production (C = +1 Exchange, Pomeron) clear signal observed ( p) + X + X = 1250 180 (sta.) 220 (sys.) nb well in line with Regge fits (e.g. Cudell et al. Phys.Rev. D61 (2000). Ensure exclusive final states via longitudinal momentum balance L = 4.95 nb -1 clear intermediate signal seen and used for event selection

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 H1 : Excl. f 2 4 Production (C = -1 Exchange, Odderon) no clear signal observed, limit at 95% C.L. ( p) f 2 + X + X < 16 nb expectation from SVM is 21 nb Ensure exclusive final states via longitudinal momentum balance L = 4.95 nb -1 mass windows used for event selection

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 H1 : Excl. a 2 4 Production (C = -1 Exchange, Odderon) no signal observed, limit at 95% C.L. ( p) a 2 + X + X < 96 nb expectation from SVM is 190 nb Ensure exclusive final states via longitudinal momentum balance L = 4.95 nb -1 and mass windows used for event selection

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 H1 : Excl. (b 1 ) 5 Production (C = +1 Exchange, Pomeron) clear signal observed ( p) + + X + X = 980 200 (stat.) 200 (sys.) nb compatible with dominant resonant part from b 1 + (1 - - pseudovector) expect 190 nb from non-resonant PYTHIA generator, 660 nb from Regge fit to low energy data (Omega-Photon Collaboration : Nucl.Phys. B243 (1984)) Ensure exclusive final states via longitudinal momentum balance L = 4.95 pb -1 and mass windows used for event selection

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 Summary H1 Analysis of Exclusive Multiphoton Final States Clear Picture : A very clean test of a non- perturbative QCD prediction (SVM) has been performed. Only exclusive final states with odd number of photons are observed and in good agreement with expectations from Pomeron exchange. Even number states can be detected but are not seen. Limits clearly exclude the predictions from the SVM model (Dosch, Berger) The Odderon has not been seen

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 M x (exclusive final state mass) M i (inclusive final state mass) M ≥ m p (proton or excited and decaying nucleon resonance) W ( p mass) Language of Diffraction in a factorized view x momentum fraction wrt. proton, only energy, momentum, angular momentum transferred here z momentum fraction wrt. pomeron Q 2 (momentum transfer describing photon virtuality

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 H1 : LO and NLO Fits of Diffractive Parton Distributions LO and NLO QCD fits to inclusive diffractive DIS data Contributions from light flavour singlet and gluons (+ reggeon contribution for high x P ) Evolution based on DGLAP equations Theoretical uncertainties from QCD and charm- quark mass Gluon dominance Use for calculation of various diffractive cross sections (2-Jets, charmed mesons)

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 M x (exclusive final state mass) M i (inclusive final state mass) M ≥ m p (proton or excited and decaying nucleon resonance) W ( p mass) Language of Diffraction in a factorized view x momentum fraction wrt. proton, only energy, momentum, angular momentum transferred here z momentum fraction wrt. pomeron Q 2 (momentum transfer describing photon virtuality

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 H1 : Diffractive 2-Jet Production in Deep Inelastic Scattering Data from H1 Eur.Phys.J. C20 (2001) 4 < Q 2 < 80 GeV 2 Use both, NLO ( s 2 ) QCD matrix elements for parton scattering (DISENT implementation) and NLO diffractive parton distributions in addition to Regge-factorisation for the Pomeron DISENT NLO set-up : µ T 2 = p T 2 (varied for systematics) µ f 2 = 40 GeV 2 4 QCD = 200 MeV Hadronisation corrections LO (without parton shower) far below data, better description with full NLO including errors from renormalization scale (20%) but not from diffractive parton distributions

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 H1 : Other 2-Jet DIS distributions compared to full NLO Consistent picture Decrease of NLO corrections for larger Q2 NLO describes all distributions in shape and normalisation reasonable well

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 H1 : Diffractive 2-Jet Production with Real Photons (Q 2 ≈ 0) Jets : pT,1(2) > 5(4) GeV Compare to leading order matrix element Monte-Carlo with parton showers taking care of higher order effects : RAPGAP Use new LO fit for diffractive parton distributions from H1 and compare to previous fit. New LO fit with LO Monte- Carlo including parton shower describes data well, major improvement compared to old fit.

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 H1 : Diffractive 2-Jets (Q 2 ≈ 0) for different x x = 1 : Direct, DIS like Interaction x < 1 : Resolved, Hadron- Hadron like Interaction Continuous (all x ) good description of H1 photoproduction 2-Jet data with model based on new LO Fit Fit equally well suited for DIS and photoproduction, no indication of factorisation failure

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 H1 : Diffractive D* Production in Deep Inelastic Scattering Data from H1 Phys.Lett. B520 (2001) 2 < Q 2 < 100 GeV 2 Use both, NLO calculation for D* (HVQDIS) and NLO diffractive parton distributions in addition to Regge-factorisation for the Pomeron HVQDIS NLO set-up : µ T 2 = Q 2 + 4m c 2 (m c = 1.5 GeV) (varied for systematics) µ f 2 = µ T 2 4 QCD = 200 MeV Peterson fragmentation function Good agreement between full NLO calculation and data in shape and normalisation, NLO correction smaller than for jet production

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 Consistent picture Some decrease of NLO corrections for larger Q2 NLO describes all distributions in shape and normalisation reasonable well H1 : Other D* DIS distributions compared to full NLO

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 ZEUS : Diffractive D* Production in Deep Inelastic Scattering DESY-03-094 1.5 < Q 2 < 200 GeV 2 0.02 < y < 0.7 X P < 0.035 < 0.8 p T (D*) > 1.5 GeV | (D*)| < 1.5 Signal of 4976 103 Mesons (cross section 0.521 nb)

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 ZEUS : Diffractive Event Fraction for Open Charm Diffractive fraction of of open charm is 6.4% No strong dependence on W, Q2, x(D) Rather distinct dependence on pT and , well understood in the framework on NLO QCD

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 NLO calculation with (old) gluon dominated fit to diffractive parton distribution functions (ACTW-B) gives good description of data Two gluon echange models SATRAP and BJLW. BJLW with gluon p T cut describes data only for low x P ZEUS : Differential Open Charm Cross-Section

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 ZEUS : Extraction the Open Charm Contribution to F 2 D Compare to NLO QCD with different fits to diffractive structure function (ACTW) Clear preference for gluon dominated fit B, other fits completely excluded Consistent set of diffractive structure function found (e.g. jets and open charm) Rather strong dependence on gluon behaviour in structure function

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Karlheinz Meier - Kirchhof-Institut für Physik - Heidelberg University - Vth Workshop on Small-x and Diffractive Physics - Fermilab - September 2002 Conclusions Final States from (real) Diffraction have reached a very detailed level of understanding The factorisation picture works at HERA for virtual as as well as for real photons Consistent modelling of jets and charmed meson production in complete NLO is in agreement with the data taken. The exchange of „vacuum quantum numbers“ (i.e. the Pomeron) is sufficient to describe all HERA data. There is so far no experimental hint for the existence of the Odderon (3 gluons....?). However, statistics only allows to probe the level of the SVM prediction. There is a lot to gain from HERA II in this area.

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