Exclusive Diffraction at HERA Henri Kowalski DESY Ringberg October 2005

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

Gluon density Gluon density dominates F 2 for x < 0.01

Diffractive Scattering Non-Diffractive Event ZEUS detector Diffractive Event M X - 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

Non-Diffraction Diffraction - Rapidity uniform, uncorrelated particle emission along the rapidity axis => probability to see a gap  Y is ~ exp(-  Y) - average multipl. per unit of Y Diffractive Signature dN/dM 2 X ~ 1/M 2 X => dN/dlog M 2 X ~ const Non- diff ~  Y= log(W 2 /M 2 X )

Observation of diffraction indicates that single ladder may not be sufficient (partons produced from a single chain produce exponentially suppressed rap. gaps) Diffractive Structure Function Dipole Model Study of exclusive diffractive states may clarify which pattern is right Only few final states present in DiMo: qq, qqg (aligned and as jets) VM ______________ Initial Diff. SF Q 2 0 ~ 4 GeV 2

Dipole description of DIS equivalent to Parton Picture in the perturbative region Mueller, Nikolaev, Zakharov  r  Q 2 ~1/r 2 Optical T momentum space configuration space dipole preserves its size during interaction.   qq ~ r 2 xg(x,  ) for small r

Iancu, Itakura, Munier - BFKL-CGC motivated ansatz Forshaw and Shaw - Regge ansatz with saturation Dipole description of DIS GBW – first Dipole Saturation Mode ( rudimentary evolution) Golec-Biernat, Wuesthoff BGBK – DSM with DGLAP Bartels, Golec-Biernat, Kowalski

b – impact parameter Impact Parameter Dipole Saturation Model T(b) - proton shape Glauber-Mueller, Levin, Capella, Kaidalov… Kowalski Teaney

x < universal rate of rise of all hadronic cross-sections Total  * p cross-section

from fit to  tot predict  diff GBW, BGBK … Ratio of  tot to  diff  diff is not a square of  tot !

Diffractive production of a qq pair _ ~ probability to find a Pomeron(2g) in p ~ probability for a Pomeron(2g) to couple to a quark

spin 1/2 spin 1   ~ s  => dN/dlog M 2 X ~ const

Diffractive production of a qqg state

Inclusive Diffraction LPS — BGBK Dipole

Comparison with Data FS model with/without saturation and IIM CGC model hep-ph/ Fit F 2 and predict x IP F 2 D(3 ) F2F2 F2F2 FS(nosat) x CGC FS(sat)

Dipole cross section determined by fit to F 2 Simultaneous description of many reactions Gluon density test? Teubner  * p -> J/  p IP-Dipole Model F 2 C IP-Dipole Model

Exclusive  production

Modification by Bartels, Golec-Biernat, Peters, (first proposed by Nikolaev, Zakharov)

H. Kowalski, L. Motyka, G. Watt preliminary

Diffractive Di-jets Q 2 > 5 GeV 2 -RapGap Satrap

Diffractive Di-jets Q 2 > 5 GeV 2

Diffractive Di-jets Q 2 > 5 GeV 2

Dijet cross section factor 3-10 lower than expected using HERA Diffractive Structure Functions suppression due to secondary interactions ? Diffractive Di-jets at the Tevatron

H1 and ZEUS: NLO overestimates data by factor  1.6. Kaidalov et al.: resolved part needs to be rescaled by 0.34

scaled by factor 0.34

Dipole form double eikonal single eikonal Khoze Martin Ryskin t – distributions at LHC Effects of soft proton absorption modulate the hard t – distributions t-measurement will allow to disentangle the effects of soft absorption from hard behavior Survival Probability S 2 Soft Elastic Opacity

ZEUS-LPS

H1 VFPS at HERA

Conclusions Inclusive diffraction, exclusive diffractive VM and jet production can be successfully derived from the measured F 2 (Dipole Model with u. gluon densities obtained from F 2 ) Detailed VM-data from HERA should allow to pin down VM wave functions Diffractive Structure Function analysis describes well the inclusive diffractive processes and the exclusive diffractive jet production although it has some tendency to amplify small differences of the input distributions Exclusive diffractive processes give detailed insight into DIS dynamics

Press Release: The 2005 Nobel Prize in Physics 4 October 2005 The Royal Swedish Academy of Sciences The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics for 2005 with one half to Roy J. Glauber Harvard University, Cambridge, MA, USA " for his contribution to the quantum theory of optical coherence"

Glauber wrote his formula for heavy nuclei and for deuteron. He was the first who realized that his formula in the case of deuteron describes both the elastic cross section and the diffractive dissociation of the deuteron. Genya Levin

Roy Glauber's recent research has dealt with problems in a number of areas of quantum optics, a field which, broadly speaking, studies the quantum electrodynamical interactions of light and matter. He is also continuing work on several topics in high- energy collision theory, including the analysis of hadron collisions, and the statistical correlation of particles produced in high-energy reactions. Specific topics of his current research include: the quantum mechanical behavior of trapped wave packets; interactions of light with trapped ions; atom counting-the statistical properties of free atom beams and their measurement; algebraic methods for dealing with fermion statistics; coherence and correlations of bosonic atoms near the Bose- Einstein condensation; the theory of continuously monitored photon counting-and its reaction on quantum sources; the fundamental nature of “quantum jumps”; resonant transport of particles produced multiply in high-energy collisions; the multiple diffraction model of proton-proton and proton-antiproton scattering Roy Glauber’s Harvard Webpage

Saturation and Absorptive corrections Example in Dipole Model F 2 ~ - Single inclusive linear QCD evolution Diffraction High density limit —> Color Glass Condensate McLerran coherent gluon state Venogopulan

2-Pomeron exchange in QCD Final States (naïve picture ) 0-cut 1-cut 2-cut Diffraction

QCD diagrams

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

GBW Model IP Dipole Model less saturation (due to IP and charm) strong saturation

Saturation scale ( a measure of gluon density) HERA RHIC Q S RHIC ~ Q S HERA

Geometrical Scaling A. Stasto & Golec-Biernat J. Kwiecinski

Geometrical Scaling can be derived from traveling wave solutions of non-linear QCD evolution equations  Velocity of the wave front gives the energy dependence of the saturation scale Munier, Peschanski L. McLerran +… Al Mueller +.. Question: Is GS an intrinsic (GBW) or effective (KT) property of HERA data ? Dipole X-section —— BGBK ---- GBW

2-Pomeron exchange in QCD Final States (naïve picture ) 0-cut 1-cut 2-cut Diffraction

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

HERA Result Unintegrated Gluon Density Dipole Model Example from dipole model - BGBK Another approach (KMR) Active field of study at HERA: UGD in heavy quark production, new result expected from high luminosity running in 2005, 2006, 2007

Exclusive Double Diffractive Reactions at LHC low x QCD reactions : pp => pp + g Jet g Jet  ~ 1 nb for M(jj) ~ 50 GeV   ~ 0.5 pb for M(jj) ~ 200 GeV  JET | < 1 x IP =  p/p, p T x IP ~ % High momentum measurement precision pp => pp + Higgs   3) fb SM  O(100) fb MSSM 1 event/sec x IP =  p/p, p T x IP ~ %

t – distributions at HERA t – distributions at LHC with the cross-sections of the O(1) nb and L ~ 1 nb -1 s -1 => O(10 7 ) events/year are expected. For hard diffraction this allows to follow the t – distribution to t max ~ 4 GeV 2 For soft diffraction t max ~ 2 GeV 2 Saturated gluons Non-Saturated gluons t-distribution of hard processes should be sensitive to the evolution and/or saturation effects see: Al Mueller dipole evolution, BK equation, and the impact parameter saturation model for HERA data

Dipole form double eikonal single eikonal Khoze Martin Ryskin t – distributions at LHC Effects of soft proton absorption modulate the hard t – distributions t-measurement will allow to disentangle the effects of soft absorption from hard behavior Survival Probability S 2 Soft Elastic Opacity

L. Motyka, HK preliminary Gluon Luminosity Q T 2 (GeV 2 ) Dipole Model F2F2 Exclusive Double Diffraction f g – unintegrated gluon densities

Conclusions We are developing a very good understanding of inclusive and diffractive g * p interactions: F 2, F 2 D(3), F 2 c, Vector Mesons (J/Psi)…. Observation of diffraction indicates multi-gluon interaction effects at HERA HERA measurements suggests presence of Saturation phenomena Saturation scale determined at HERA agrees with RHIC HERA determined properties of the Gluon Cloud 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!!!!

J. Ellis, HERA-LHC Workshop Higher symmetries (e.g. Supersymmetry) lead to existence of several scalar, neutral, Higgs states, H, h, A.... Higgs Hunter Guide, Gunnion, Haber, Kane, Dawson 1990 In MSSM Higgs x-section are likely to be much enhanced as compared to Standard Model (tan  large because M Higgs > 115 GeV) CP violation is highly probable in MSSM all three neutral Higgs bosons have similar masses ~120 GeV can ONLY be RESOLVED in DIFFRACTION Ellis, Lee, Pilaftisis Phys Rev D, 70, , (2004), hep-ph/ Correlation between transverse momenta of the tagged protons give a handle on the CP-violation in the Higgs sector Khoze, Martin, Ryskin, hep-ph Precise measurement of the Higgs Mass

Gluon density Gluon density dominates F 2 for x < 0.01

Smaller dipoles  steeper rise Large spread of eff characteristic for IP Dipole Models universal rate of rise of all hadronic cross-sections The behavior of the rise with Q 2

GBW Model KT-IP Dipole Model less saturation (due to charm) strong saturation

Unintegrated Gluon Densities Exclusive Double Diffraction Note: xg(x,.) and P gg drive the rise of F 2 at HERA and Gluon Luminosity decrease at LHC Dipole Model

Saturation Model Predictions for Diffraction

Absorptive correction to F 2 Example in Dipole Model F 2 ~ - Single inclusive pure DGLAP Diffraction

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

A. Martin M. Ryskin G. Watt

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

2-Pomeron exchange in QCD Final States (naïve picture) 0-cut 1-cut 2-cut p   * p-CMS  YY detector p   * p-CMS  p  detector Diffraction

0-cut 1-cut 2-cut 3-cut Feynman diagrams QCD amplitudes J. Bartels A. Sabio-Vera H. K.

Probability of k-cut in HERA data Dipole Model

Problem of DGLAP QCD fits to F 2 CTEQ, MRST, …., IP-Dipole Model at small x valence like gluon structure function ? Remedy: Absorptive corrections? MRW Different evolution? BFKL, CCSS, ABFT

BFKL from Gavin Salam - Paris2004 LO DGLAP --- at low x Next to leading logs NLLx -----

from Gavin Salam - Paris 2004 Ciafalloni, Colferai, Salam, Stasto Similar results by Altarelli, Ball Forte, Thorn

Density profile grows with diminishing x and r approaches a constant value Saturated State - Color Glass Condensate multiple scattering S – Matrix => interaction probability Saturated state = high interaction probability S 2 => 0 r S - dipole size for which proton consists of one int. length

Saturation scale = Density profile at the saturation radius r S S = 0.15 S = 0.25

Saturated state is partially perturbative cross-sectiom exhibits the universal rate of growth

RHIC

Conclusions We are developing a very good understanding of inclusive and diffractive  * p interactions: F 2, F 2 D(3), F 2 c, Vector Mesons (J/Psi)…. Observation of diffraction indicates multi-gluon interaction effects at HERA Open problems: valence-like gluon density? absorptive corrections low-x QCD-evolution HERA measurements suggests presence of Saturation phenomena Saturation scale determined at HERA agrees with the RHIC one HERA+NMC data => Saturation effects are considerably increased in nuclei

Diffractive Scattering Non-Diffractive Event ZEUS detector Diffractive Event M X - 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

Non-Diffraction Diffraction - Rapidity uniform, uncorrelated particle emission along the rapidity axis => probability to see a gap  Y is ~ exp(-  Y) - average multiplicity per unit of rapidity Diffractive Signature dN/ dM 2 X ~ 1/ M 2 X => dN/dlog M 2 X ~ const note :  Y ~ log(W 2 / M 2 X ) Non- diff

Slow Proton Frame Transverse size of the quark-antiquark cloud is determined by r ~ 1/Q ~ cm/ Q (GeV ) Diffraction is similar to the elastic scattering: replace the outgoing photon by the diffractive final state , J/  or X = two quarks incoming virtual photon fluctuates into a quark-antiquark pair which in turn emits a cascade-like cloud of gluons Rise of   p tot with W is a measure of radiation intensity