Mass effects in the polarized virtual photon structure
Abstract
We discuss target mass effects in the polarized virtual photon structure functions
g
γ
1
(x,
Q
2
,
P
2
)
,
g
γ
2
(x,
Q
2
,
P
2
)
for the kinematic region
Λ
2
≪
P
2
≪
Q
2
, where
−
Q
2
(−
P
2
)
is the mass squared of the probe (target) photon. We obtain the expressions for the structure functions in closed form by inverting the Nachtmann moments for the twist-2 and twist-3 operators. Numerical analysis shows that target mass effects appear at large
x
and become sizable near the maximal value of
x
, as the ratio
P
2
/
Q
2
increases. Target mass effects for the QCD sum rules of
g
γ
1
and
g
γ
2
are also investigated.