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HERA Physics and Gustav Kramer Alice Valk árová , Charles University, Prague

HERA Physics and Gustav Kramer Alice Valk árová , Charles University, Prague. Gustav Kramer has more than 5000 citations to his papers….(h-ind. 38). A lot of citations to G. Kramer and co - authors in H1 and ZEUS publications !. Photoproduction dijets , inclusive..

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HERA Physics and Gustav Kramer Alice Valk árová , Charles University, Prague

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  1. HERA Physics and Gustav KramerAlice Valkárová, Charles University, Prague Festkolloquium - G.Kramer

  2. Gustav Kramer has more than 5000 citations to his papers….(h-ind. 38). A lot of citations to G.Kramer and co-authors in H1 and ZEUS publications! • Photoproductiondijets, inclusive.. • Fragmentation functions, charm • Isolated photons in DIS • Diffraction, dijets, factorization Festkolloquium - G.Kramer

  3. Dijet photoproduction In LO! Q2 ~ 0 GeV2 xγ - fraction of photon’s momentum inhard subprocess hadron –like component (resolved) photon fluctuates into hadronic system, which takespart in hadronicscattering xγ<0.2(at parton level) point –like component of resolved photon dominates in the region of 0.2<xγ<1 direct photoproduction photon directly involved in hard scattering xγ=1(at parton level) Festkolloquium - G.Kramer

  4. Photoproduction, NLO QCD calculations Measurement of the Inclusive Di-Jet Cross Section in Photoproduction and Determination of an Effective Parton Distribution in the Photon, H1 Collab., C. Adloff et al., Eur. Phys. J. C1 (1998) 97-107 ,   09/97 H1 H1 – untagged photoproduction Q2<4 GeV2 Compared to KK NLO calculations Hadronization correction not taken into account…… Festkolloquium - G.Kramer

  5. Low Q2 - dijets Program for NLO QCD calculations JETviP (Kramer,Poetter) (the only program with resolved contribution included). G. Kramer and B. Poetter, Eur. Phys. J. C 5 (1998) 665 used for comparison with dijet photoproduction. Measurement of Dijet Production at Low Q2 at HERA H1 Collab., A. Aktas et al., Eur. Phys. J. C37 (2004) 141-159 The asymmetric ET cuts avoid regions of instability in the NLO calculations! M. Klasen and G. Kramer, Phys. Lett. B 366 (1996) 385 Incorporationof resolved component to NLO brings predictions closer to the data! Festkolloquium - G.Kramer

  6. Inclusive photoproduction of jets ZEUS Coll., Inclusive –jet photoproduction at HERA and determination of αs, Nucl.Phys.B 864,1 (2012) (reference to:M.Klasen,T.Kleinwort,G.Kramer, Eur.Phys.J C1,(1998),1.) Untagged photoproduction Festkolloquium - G.Kramer

  7. Inclusive particle photoproduction Charged Particle Cross Sections in Photoproduction and Extraction of the Gluon Density in the Photon Tagged photoproduction H1 Collab., C. Adloff et al., Eur. Phys. J. C10 (1999) 363 B.A.Kniehl,G.Kramer, Z.Physik C62 (1994),53. Inclusive particle production at HERA: Resolved and direct quasireal photon contributions in NLO QCD Testing the universality of fragmentation functions – B.A.Kniehl,G.Kramer,B.Poetter Nucl.Phys. B597 (2001), 337. 150 citations Festkolloquium - G.Kramer

  8. Fragmentation functions Three different parameterisations of the FF are used which are obtained from NLO fits to e+e- data: KKP,KRETZER and AKK In Breit frame,the measured normalized distribution of the scaled momentum 1/N dn/dxp, N is the total number of events, dn is the total number of charged tracks with scaled momentum xp in the interval dxp, x p=p h/(Q/2) KKP B.A.Kniehl,G.Kramer,B.Potter,Nucl.Phys.B582(2000)514 with 314 citations…. AKK S.Albino,B.A.Kniehl,G.Kramer,Nucl.Phys.B725(2005) 181 Charged Particle Production in High Q2 Deep-Inelastic Scattering at HERA H1 Collab., Phys.Lett.B654:148-159,2007. Festkolloquium - G.Kramer

  9. Charm production H1 Collab., F.D. Aaron et al.,Eur. Phys. J. C72 (2012) 1995 Measurement of Inclusive and Dijet D*-Meson Cross Sections in Photoproduction at HERA Single differential D* cross sections compared to NLO calculations B.A. Kniehl, G. Kramer, I. Schienbein and H.Spiesberger, Eur. Phys. J.C62 (2009), 365 Difficult, due to the presence of two scales, mass of quark and pT Festkolloquium - G.Kramer

  10. Isolated photons and jets in DIS Quark radiative diagrams Photon plus jet cross-sections in DIS ep Collisions A. Gehrmann-De Ridder, G. Kramer, H.Spiesberger, Nucl. Phys. B 578 (2000) 326 LO Lepton radiative diagrams ZEUS Collab. Phys.Lett. B596 (2004), 86 Observation of isolated high-ET photons in deep inelastic scattering Photons with 5 GeV < ETγ< 10 GeV accompanied by jet Festkolloquium - G.Kramer

  11. Isolated photons and jets in DIS Measurement of isolated photons accompanied by jets in deep inelastic ep scattering, ZEUS collab.,Phys.Lett.B 715 (2012),88. The GKS predictions describe shapes quite well… H1 Collab., F.D. Aaron et al., Eur.Phys.J.C54:371,(2008). The production of isolated photons in DIS with at least one jet compared to NLO calculations A. Gehrmann-De Ridder, G. Kramer and H.Spiesberger, Nucl. Phys. B 578 (2000) 326 Festkolloquium - G.Kramer

  12. W Diffraction Diffraction was not expected to play so important role at HERA experiments! Two classes of diffractive events: Q2~0 → photoproduction Q2>>0 → deep inelastic scattering (DIS) Large rapidity gap HERA:~10% of low-x DIS events are diffractive Festkolloquium - G.Kramer

  13. σ (data) S2= σ (theory) ep pp → DPDFs – obey DGLAP, universal for diff. ep DIS (inclusive,dijet,charm) → universal hard scattering cross section (same as in inclusive DIS) Diffraction and questions of factorization QCD factorization theoretically proven for DIS (Collins, 1998) It allows the extraction of DPDFs from the (DIS) data Exporting DPDFs fromHERA toTevatrondoes not work! Factorisation broken -> S2 ~ 0.1. Factorisation in dijet photoproduction (resolved component similar to hadron-hadron collisions) - interactions of spectators filling rapidity gap? Factorization in photoproduction checked by both H1 and ZEUS…. Festkolloquium - G.Kramer

  14. Factorization in diffractive photoproduction H1 -diffractive dijet photoproduction results compared to Frixione and Kramer-Klasen NLO QCD calculations. The same conclusion also for ZEUS, however without suppression! H1 Collab., Eur.Phys.J. C70 (2010) 15 Data suppressed by factor ~ 0.58 Festkolloquium - G.Kramer

  15. Factorization in diffraction M.Klasen, G.Kramer, Suppression factors in diffractive photoproduction of dijets Suppression factor R Eur.Phys.J. C70 (2010) 91-106 An attempt to explain the difference in conclusions of both experiments. The hint that suppression depends on ET of jets…. (e.g. H1 Collab. Eur.Phys.J. C70 (2010) 15) This puzzle not solved yet, new H1 experimental results will come soon… (DIS 2013, Marseille). Festkolloquium - G.Kramer

  16. Summary • both HERA experiments profited a lot from the • close relations with G.Kramer and his group • H1 and ZEUS used frequently the predictions of • G.Kramer and co-authors for the interpretation • of the experimental results • In the name of both experiments • - best wishes for the next • fruitful years and good health! Festkolloquium - G.Kramer

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