Alexander Savin

1
Diffractive Charm and Jet Production at HERA
Alexander A. Savin
on behalf of the H1 and ZEUS collaborations
ICHEP 2002, Amsterdam, Netherlands, 24-31 July
2002
2
The shape of diffractive events at HERA
27.5 GeV e
820/920 GeV P
Large Rapidity Gap
3
MC and Models
t
t
ltlt
(r ,t)
ltlt
(r ,t)
cross p
formation of qq
hard sc.
evolution of target
T
T
D
Two-gluon exchange models
F factorises into a Regge-inspired Pomeron
flux and a Pomeron structure function, analysed
using DGLAP evolution equation
2
Bartels et al.
BJLW
Golec-Biernat and Wusthoff
SATRAP
RAPGAP
Ingelman-Schlein
Alvero et al.
ACTW
4
Diffractive DIS Dijets Data
Using PDFs from LO fits to F2D and RAPGAP
H1
Shape is o.k. Normalization?
1996-97
5
Diffractive PHP Dijet Data
LO fits predictions for dijet production in pp
exceed the observed rate by a factor 10!
_
H1
1996-97
GAL Generalised Area Low model for pp
diff.scattering (fits to inclusive DIS ee data).
6
Diffractive PHP Dijet Data
Direct and resolved photon processes are
suppressed
7
Charm Production
H1
1996-97
8
Charm Production
ZEUS
1995-97
9
Charm Production
ZEUS
1998-2000
Forward Plug Calorimeter
10
Charm Production
ACTW NLO QCD prediction (gluon dominated Fit B)
11
Conclusion
The resolved gluon-dominated Pomeron models
are in good agreement with data. NLO describes
D data very well.
The PHP dijet rate is about factor 2 less then
expected from DIS data fits.
Data support gluon-dominated diffractive exchange
mechanism.
12
D(3)
PDF was assigned to the Pomeron and evolved using
DGLAP equation
F
QCD-fit to
2
Z is the fractional momentum of Pomeron carried
by the struck parton
The fraction of the momentum of the Pomeron
carried by gluons is smaller then for H1 Fit 2
and 3
2