High Energy Photon Deep Inelastic Scattering at Small and Large Q^2 with Soft Plus Hard Pomeron
Abstract
We show how the sum of a hard singularity,
F
2H
(x,
Q
2
0
)∼
x
−λ
and a soft Pomeron
F
2P
(x,
Q
2
0
)∼Const.
for the singlet piece of the structure function
F
2S
=
F
2H
+
F
2P
for
Q
2
0
∼afewGe
V
2
, plus a saturating expression for the strong coupling,
α
~
s
(
Q
2
)=4π/
β
0
log[(
Q
2
+
Λ
2
)/
Λ
2
]
give an excellent description of experiment
i) For small Q^2, $0\lsim Q^2\leq 8.5 GeV^2$, and
ii) For large Q^2, $10\lsim Q^2\leq 1 500 GeV^2$ if evolved with QCD. The x range is $6\times10^{-6}\lsim x \lsim 0.04$. The description for low Q^2 implies self-consistent values for the parameters in the exponents of x both for singlet and nonsinglet. One has to have
α
ρ
(0)=0.48
and
λ=0.470[
α
P
(0)=1.470]
, in uncanny agreement with other determinations of these parameters, and in particular the results of the large Q^2 fits. The fit to data is so good that we may look for signals of a ``triple Pomeron" vertex, for which some evidence is found.