#### Hard diffraction in eA Cyrille Marquet RIKEN BNL Research Center Inclusive and diffractive structure functions.

download report#### Transcript Hard diffraction in eA Cyrille Marquet RIKEN BNL Research Center Inclusive and diffractive structure functions.

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