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F 2 is dominated by single ladder exchange ladder symbolizes a QCD evol. process

Overview of low-x and diffraction at HERA Henri Kowalski DESY Rencontres de Moriond La Thuile, March 2006. F 2 is dominated by single ladder exchange ladder symbolizes a QCD evol. process ( DGLAP or others ). Gluon density. Gluon density dominates F 2 for x < 0.01.

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F 2 is dominated by single ladder exchange ladder symbolizes a QCD evol. process

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  1. Overview of low-x and diffraction atHERAHenri KowalskiDESY Rencontres de Moriond La Thuile, March 2006

  2. F2 is dominated by single ladder exchange ladder symbolizes a QCD evol. process ( DGLAP or others )

  3. Gluon density Gluon density dominates F2 for x < 0.01

  4. Diffractive Scattering Non-Diffractive Event ZEUS detector Diffractive Event MX - invariant mass of all particles seen in the central detector t - momentum transfer to the diffractively scattered proton t - conjugate variable to the impact parameter

  5. Diffractive Signature diff Non- diff ~ DY= log(W2/M2X) Non-Diffraction Diffraction - Rapidity uniform, uncorrelated particle emission along the rapidity axis => probability to see a gap DY is ~ exp(-<n>DY) <n> - average multipl. per unit of Y dN/dM2X ~ 1/M2X => dN/dlog M2X ~ const

  6. Observation of diffraction indicates that single ladder may not be sufficient (partons produced from a single chain have exponentially suppressed rap. gaps) Optical T Inclusive DIS Hard Diffraction Dipole Models equivalent to LO perturbative QCD for small dipoles Glauber Mueller GBW – first Dipole Saturation Mode Golec-Biernat, Wuesthoff BGBK – DSM with DGLAP Bartels, Golec-Biernat, Kowalski IIM - BFKL-CGC motivated ansatzIancu, Itakura, Munier FS – Regge ansatz with saturation Forshaw and Shaw

  7. KT - Kowalski Teaney KMW – Kowalski, Motyka, Watt Impact Parameter Dipole Saturation Model proton shape

  8. Total g*p cross-section KT KMW universal rate of rise of all hadronic cross-sections x < 10-2

  9. from fit to stot predict sdiff GBW, BGBK, …. Inclusive Diffraction -LPS

  10. Dipole cross section determined by fit to F2 Simultaneous description of many reactions KT F2 C KMW

  11. KMW

  12. Description of the size of interaction region BD Modification by Bartels, Golec-Biernat, Peters KMW proton size BG BG

  13. Diffractive Di-jets Q2 > 5 GeV2 -RapGap Satrap

  14. Saturation scale (a measure of gluon density) HERA RHIC QSRHIC ~ QSHERA

  15. Geometrical Scaling A. Stasto & Golec-Biernat J. Kwiecinski GS is an effective property of HERA data b-Dipole Model analysis: GS seen in the center of the proton Theoretical importance: property of non-linear evolution in QCD BK, JIMWLK

  16. Multiple Interactions and Long Range Correlation 2-Pomeron exchange in QCD Final States (naïve picture) Diffraction 0-cut 1-cut <n> 2-cut <2n>

  17. QCD diagrams

  18. AGK rules in the Dipole Model Note: AGK rules underestimate the amount of diffraction in DIS

  19. Exclusive Double Diffractive Reactions at LHC xIP = Dp/p, pT xIP ~ 0.2-1.5% xIP = Dp/p, pT xIP ~ 0.2-1.5% High momentum measurement precision 1 event/sec low x QCD reactions: pp => pp + gJet gJets ~ 1 nb for M(jj) ~ 50 GeV s ~ 0.5 pb for M(jj) ~ 200 GeV hJET| < 1 pp => pp + Higgs s ~ O(3) fb SM ~ O(100) fb MSSM

  20. Absorptive corrections from BK equation Resummation of BFKL pomeron fan diagrams

  21. Conclusions We are developing a very good understanding of inclusive and diffractive DIS interactions: F2 , F2D(3) , F2c , Vector Mesons (J/Psi,f,r) HERA measurements suggests presence of Saturation phenomena Saturation scale determined at HERA agrees with RHIC Observation of diffraction indicates multi-gluon interaction effects -> Underlying events at LHC may be process dependent Diffractive LHC ~ pure Gluon Collider => investigations of properties of the gluon cloud in the new region Gluon Cloud is a fundamental QCD object - SOLVE QCD!!!! _____________________________________________________ Diffractive vector mesons scattering - an excellent probe of nuclear matter Ideal device: e-RHIC like machine with ~1/3 of HERA energy

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