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

2. Inclusive and diffractive structure functions

3. 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

4. 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

5. 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

6. Collinear factorization vs dipole factorization

7. 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

8. 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

9. 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 :

10. 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

11. Hard diffraction off nuclei some expectations

12. 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

13. 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 :