1 / 50

Proton

Small-x and Diffraction in DIS at HERA II Henri Kowalski DESY 12 th CTEQ Summer School Madison - Wisconsin June 2004. Dipole Saturation Models. Proton. GBW. b – impact p. BGBK. DGLAP. IIM Model with BFKL & CG evolution. KT. Glauber Mueller. T(b) - proton shape.

infinity
Download Presentation

Proton

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Small-x and Diffraction in DIS atHERAIIHenri KowalskiDESY 12thCTEQ Summer School Madison - Wisconsin June 2004

  2. Dipole Saturation Models Proton GBW b – impact p. BGBK DGLAP IIM Model with BFKL & CG evolution KT Glauber Mueller T(b) - proton shape

  3. Derivation of the GM dipole cross section probability that a dipole at b does not suffer an inelastic interaction passing through one slice of a proton Uncorrelated scatterings S2 -probability that a dipole does not suffer an inelastic interaction passing through the entire proton • NOTE: the assumption of • uncorrelated scatterings is • not valid for BK and JIMWLK • equations • Correlations from evolution • IIM Dipole fit GM Dipole + DGLAP mimics full evolution <= Landau-Lifschitz

  4. Data precision is essential to the progress of understanding GBW GBW GBW Parameters fitted to HERA DIS data: c2 /N ~ 1 s0 = 23 mb l = 0.29 x0 = 0.0003

  5. lGBW=0.29 ----- universal rate of rise of all hadronic cross-sections Smaller dipoles  steeper rise Large spread of leff characteristic for Impact Parameter Dipole Models (KT)

  6. Analysis of data within Dipole Models BGBK lGBW=0.29 KT GBW In GBW Model change of l with Q2 is due to saturation effects In IP Saturation Model (KT) change of l with Q2 is mainly due to evolution effects In BGBK Model change of l with Q2 is due to saturation and evolution effects Theory (RV): evolution leads to saturation - Balitzki- Kovchegov and JIMWLK

  7. GBW - - - - - - - - - - - - - - - - - - - - - x = 10-6 BGBK ___________________________________ x = 10-2 Evolution increases gluon density => smaller dipoles scatter stronger, gluons move to higher virtualities Fourier transform x = 10-4 - numerical evaluation x = 10-2 In Color-Glass gluons occupy higher momentum states

  8. A glimpse into nuclei Naïve assumption for T(b): Wood-Saxon like, homogeneous, distribution of nuclear matter

  9. Smooth Gluon Cloud Q2 (GeV2) C 0.74 1.20 1.70 Ca 0.60 0.94 1.40

  10. Lumpy Gluon Cloud Q2 (GeV2) C 0.74 1.20 1.70 Ca 0.60 0.94 1.40

  11. Saturation Scale at RHIC

  12. _ Diffractive production of a qq pair

  13. Diffractive production of a qqg system

  14. Inclusive Diffraction

  15. Non-DiffractionDiffraction <=p e => Select diffractive events by requirement of no forward energy deposition called hmaxcut Q: what is the probability that a non-diff event has no forward energy deposition?

  16. MX Method Non-Diffractive Event Diffractive Event detector detector log W2 log MX2 DY Y Y DY g* g* p p g*p-CMS g*p-CMS non-diff events are characterized by uniform, uncorrelated particle emission along the whole rapidity axis => probability to see a gap DY is ~ exp(-lDY) l – Gap Suppression Coefficient diff events are characterized by exponentially non-suppressed rapidity gap DY since DY ~ log(W2/M2X) – h0 dN/dlogM 2X ~exp( l log(M 2X)) dN/ dM 2X ~ 1/ M 2X => dN/dlogM2X ~ const

  17. MX Method diff diff diff Non- diff Non- diff Non- diff Non-Diffraction dN/dM 2X ~exp( l log(M 2X)) Gap suppression coefficient l independent of Q2 and W2 for Q2 > 4 GeV2 Diffraction dN/dlog M 2X ~ const

  18. Gap Suppression in Non-Diff MC ---- Generator Level CDM ---- Detector Level CDM Detector effects cancel in Gap Suppression ! dN/dM 2X ~exp( llog(M 2X)) In MC l independent of Q2 and W2 l~ 2 in MC l~ 1.7 in data

  19. Uncorrelated Particle Emission (Longitudinal Phase Space Model) l – particle multiplicity per unit of rapidity Feynman (~1970): l depends on the quantum numbers carried by the gap l = 2 for the exchange of pion q.n. (a=0) = 1 for the exchange of rho q.n. (a=1/2) = 0 for the exchange of pomeron q.n. (a=1) l- is well measurable provided good calorimeter coverage Physical meaning of the Gap Suppression Coefficient l exp(- lDY ) = exp(-llog(W2/M2X)= (W2/M2X)-l from Regge point of view ~ (W2)-2(1-a)

  20. SR = SATRAP: MC based on the Saturated Dipole Saturation Model

  21. ~ H1 approach

  22. A. Martin M. Ryskin G. Watt

  23. A. Martin M. Ryskin G. Watt  BEKW

  24. Fit to diffractive data using MRST Structure Functions A. Martin M. Ryskin G. Watt

  25. Fit to diffractive data using MRST Structure Functions A. Martin M. Ryskin G. Watt

  26. Absorptive correction to F2 from AGK rules • Martin • M. Ryskin • G. Watt Example in Dipole Model F2 ~ - Single inclusive pure DGLAP Diffraction

  27. A. Martin M. Ryskin G. Watt

  28. AGK Rules QCD Pomeron The cross-section for k-cut pomerons: Abramovski, Gribov, KancheliSov. ,J., Nucl. Phys. 18, p308 (1974) 1-cut F (m) – amplitude for the exchange of m Pomerons 1-cut 2-cut

  29. Pomeron in QCD t-channel picture Color singlet dominates over octet in the 2-gluon exchange amplitude at high energies 3-gluon exchange amplitude is suppressed at high energies 2-gluon pairs in color singlet (Pomerons) dominate the multi-gluon QCD amplitudes at high energies

  30. 2-Pomeron exchange in QCD Final States (naïve picture) detector Diffraction 0-cut DY g* p g*p-CMS <n> 1-cut g* p g*p-CMS detector <2n> 2-cut g* p g*p-CMS

  31. 0-cut 1-cut 2-cut 3-cut

  32. AGK Rules in the Dipole Model Total cross section Mueller-Salam (NP B475, 293) Dipole cross section Amplitude for the exchange of m pomerons in the dipole model KT model

  33. AGK rules Dipole model Diffraction from AGK rules very simple but not quite right

  34. Q2~1/r2 exp(-mq r)

  35. All quarks Charmed quark

  36. Note: AGK rules underestimate the amount of diffraction in DIS

  37. Conclusions We are developinga very good understanding of inclusive and diffractive g*p interactions: F2 , F2D(3) , F2c , Vector Mesons (J/Psi)…. Observation of diffraction indicates multi-pomeron interaction effects at HERA HERA measurements suggests presence of Saturation phenomena Saturation scale determined at HERA agrees with the RHIC one Saturation effects in ep are considerably increased in nuclei

  38. Thoughts after CTEQ School George Sterman: Parton Model Picture (in Infinite Momentum Frame) is in essence probabilistic, non-QM. It is summing probabilities and not amplitudes F2 = f e2f x q(x,Q2) Parton Model Picture is extremely successful, it easily carries information from process to process, e.g. we get jet cross-sections in pp from parton densities detemined inep Dipole Models (Proton rest Frame) are very successful carrying information from process to process within ep. They are in essence QM, main objects are amplitudes: In DM Picture diffraction is a shadow of F2 . Many other multi-pomeron effects should be present

  39. Several attempts are underway to build a bridge over the gap between Infinite Momentum Frame and Proton Rest Frame Pictures Jochen Bartels, Lipatov & Co: Feynman diagrams for multi-pomeron processes… Raju Venogopulan & Co, Diffraction from Wilson loops, fluctuations from JIMWLK… ……………………………………..

  40. A new detector to study strong interaction physics p Si tracking stations EM Calorimeter Hadronic Calorimeter Compact – fits in dipole magnet with inner radius of 80 cm. Long - |z|5 m e

  41. Forward Detector e 27 GeV p 920 GeV

  42. HERA Interactions Collisions of e+ (e-) of 27.5 GeV with p of 920 GeV Increase of kinematic range by over 4 order of magnitude in x at moderate Q2 and6 order of magnitude in Q2

More Related