Report

Hard diffraction in eA Cyrille Marquet RIKEN BNL Research Center Inclusive and diffractive structure functions Deep inelastic scattering (DIS) k’ k eh center-of-mass energy S = (k+P)2 size resolution 1/Q *h center-of-mass energy W2 = (k-k’+P)2 photon virtuality Q2 = - (k-k’)2 > 0 p Q2 Q2 x 2 2P.(k k ' ) W M h2 Q2 x ~ momentum fraction of the struck parton P.(k k ' ) Q2 / x y P.k S M h2 y ~ W²/S Diffractive DIS k’ when the hadron remains intact k momentum transfer t = (P-P’)2 < 0 diffractive mass of the final state MX2 = (P-P’+k-k’)2 p p’ Q2 Q2 2( P P' ).(k k ' ) M X2 t Q2 ~ momentum fraction of the struck parton with respect to the Pomeron xpom = x/ rapidity gap : = ln(1/xpom) xpom ~ momentum fraction of the Pomeron with respect to the hadron Inclusive diffraction at HERA Diffractive DIS with proton tagging e p e X p H1 ZEUS FPS data LPS data Diffractive DIS without proton tagging e p e X Y with MY cut H1 ZEUS LRG data MY < 1.6 GeV FPC data MY < 2.3 GeV Collinear factorization vs dipole factorization Collinear factorization in the limit Q² with x fixed • for inclusive DIS *p X tot (x, Q2) 1 d (, Q2)ˆa(x/, Q2) O(1/Q2) a/ p partons a x a = quarks, gluons • perturbative evolution of with Q2 : ln(Q2) Κ DGLAP Dokshitzer-Gribov-Lipatov-Altarelli-Parisi not valid if x is too small non perturbative • for diffractive DIS another set of pdf’s, same Q² evolution perturbative Factorization with diffractive jets ? you cannot do much with the diffractive pdfs factorization also holds for factorization does not hold for diffractive jet production at high Q² diffractive jet production at low Q² diffractive jet production in pp collisions for instance at the Tevatron: predictions obtained with diffractive pdfs overestimate CDF data by a factor of about 10 a very popular approach: use collinear factorization anyway, and apply a correction factor called the rapidity gap survival probability The QCD dipole picture in DIS in the limit x 0 with Q² fixed • deep inelastic scattering (DIS) at small xBj : photon virtuality Q2 = - (k-k’)2 >> 2QCD *p collision energy W2 = (k-k’+p)2 sensitive to values of x as small as xBj k’ k Q size resolution 1/Q 2 W2 Q 2 p k’ • diffractive DIS : k diffractive mass MX2 = (k-k’+p-p’)2 Q2 M Q 2 X 2 xpom = x/ rapidity gap = ln(1/xpom) p p’ Hard diffraction and small-x physics the dipole scattering amplitudfe T=1 T << 1 dipole size r Q2 DIS Q2 DDIS 1 1 Q2 ln(Q2 /QS2 ) 1 1 1 hard diffraction is directly sensitive to the saturation region Forshaw and Shaw no good fit without saturation effects contribution of the different r regions in the hard regime Q2 Q2S DIS dominated by relatively hard sizes 1 Q r 1 QS DDIS dominated by semi-hard sizes r ~ 1 QS Hard diffraction off nuclei some expectations D,A The ratio F2 / F2 A following the approach of Kugeratski, Goncalves and Navarra (2006) ratio ~ 35 % from Kowalski-Teaney model at HERA saturation naturally explains the constant ratio plots from Tuomas Lappi The ratio F2 • D,A / F2 D,p x dependence following Kugeratski, Goncalves and Navarra Au / d full : Iancu-Itakura-Munier model linear : linearized version of IIM shape and normalization influenced by saturation • scheme dependence for naive : FRWS : Freund, Rummukainen, Weigert and Schafer ASW : Armesto, Salgado and Wiedemann Pb / p