Cyrille Marquet RIKEN BNL Research Center Hard diffraction in eA Cyrille Marquet RIKEN BNL Research Center

Inclusive and diffractive structure functions

Deep inelastic scattering (DIS) k k’ p size resolution 1/Q eh center-of-mass energy S = (k+P)2 *h center-of-mass energy W2 = (k-k’+P)2 photon virtuality Q2 = - (k-k’)2 > 0 x ~ momentum fraction of the struck parton y ~ W²/S

rapidity gap :  = ln(1/xpom) Diffractive DIS k k’ p p’ when the hadron remains intact momentum transfer t = (P-P’)2 < 0 diffractive mass of the final state MX2 = (P-P’+k-k’)2  ~ 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 FPS data ZEUS LPS data Diffractive DIS without proton tagging e p  e X Y with MY cut H1 LRG data MY < 1.6 GeV ZEUS FPC data MY < 2.3 GeV

Collinear factorization vs dipole factorization

Collinear factorization in the limit Q²   with x fixed for inclusive DIS perturbative a = quarks, gluons perturbative evolution of  with Q2 : 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

Factorization with diffractive jets ? you cannot do much with the diffractive pdfs factorization also holds for diffractive jet production at high Q² factorization does not hold for 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 : k k’ p size resolution 1/Q photon virtuality Q2 = - (k-k’)2 >> QCD *p collision energy W2 = (k-k’+p)2 2 sensitive to values of x as small as xpom = x/ diffractive mass MX2 = (k-k’+p-p’)2 k k’ p p’ rapidity gap  = ln(1/xpom) diffractive DIS :

Hard diffraction and small-x physics the dipole scattering amplitudfe dipole size r contribution of the different r regions in the hard regime hard diffraction is directly sensitive to the saturation region DIS dominated by relatively hard sizes DDIS dominated by semi-hard sizes no good fit without saturation effects Forshaw and Shaw

Hard diffraction off nuclei some expectations

The ratio F2D,A / F2 A ratio ~ 35 % from Kowalski-Teaney model following the approach of Kugeratski, Goncalves and Navarra (2006) from Kowalski-Teaney model plots from Tuomas Lappi at HERA saturation naturally explains the constant ratio

The ratio F2D,A / F2 D,p x dependence scheme dependence for 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 Pb / p Armesto, Salgado and Wiedemann Freund, Rummukainen, Weigert and Schafer naive : FRWS : ASW :