Hard diffraction in eA

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Hard diffraction in eA
Cyrille MarquetRIKEN BNL Research Center
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Inclusive and diffractivestructure functions
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Deep inelastic scattering (DIS)

• eh center-of-mass energyS (kP)2?h
  center-of-mass energyW2 (k-kP)2photon
  virtualityQ2 - (k-k)2 gt 0

x momentum fraction of the struck parton y
W²/S
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Diffractive DIS
when the hadron remains intact

• momentum transfert (P-P)2 lt 0diffractive
  mass of the final stateMX2 (P-Pk-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
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Inclusive diffraction at HERA
Diffractive DIS with proton tagging e p ? e X p
H1 FPS data ZEUS LPS data
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Collinear factorizationvsdipole factorization
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Collinear factorization
in the limit Q² ? ? with x fixed

• for inclusive DIS

a quarks, gluons

• perturbative evolutionof ? with Q2

Dokshitzer-Gribov-Lipatov-Altarelli-Parisi
not valid if x is too small
non perturbative

• for diffractive DIS

another set of pdfs, same Q² evolution
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Factorization with diffractive jets ?
you cannot do much with the diffractive pdfs
factorization does not hold for diffractive jet
production at low Q² diffractive jet production
in pp collisions
factorization also holds for diffractive jet
production at high Q²
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
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The QCD dipole picture in DIS
in the limit x ? 0 with Q² fixed

• deep inelastic scattering (DIS) at small xBj

sensitive to values of x as small as
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Hard diffraction and small-x physics
the dipole scattering amplitudfe
dipole size r
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Hard diffraction off nucleisome expectations
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The ratio F2D,A / F2 A
at HERA saturation naturally explains the
constant ratio
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The ratio F2D,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