386,202 research outputs found
Gauge Invariance and QCD Twist-3 Factorization for Single Spin Asymmetries
The collinear factorization at twist-3 for Drell-Yan processes is studied
with the motivation to solve the discrepancy in literature about the single
spin asymmetry in the lepton angular distribution, and to show how QCD gauge
invariance is realized in the hadronic tensor. The obtained result here agrees
with our early result derived with a totally different approach. In addition to
the asymmetry we can construct another two observables to identify the spin
effect. We show that the gauge invariance of different contributions in the
hadronic tensor is made in different ways by summing the effects of gluon
exchanges. More interestingly is that we can show that the virtual correction
to one structure function of the hadronic tensor, hence to some weighted SSA
observables, is completely determined by the quark form factor. This will
simplify the calculation of higher order corrections. The corresponding result
in semi-inclusive DIS is also given for the comparison with Drell-Yan
processes.Comment: Small changes, accepted by JHE
Twist-3 Contributions in Semi-Inclusive DIS with Transversely Polarized Target
We study semi-inclusive DIS with a transversely polarized target in the
approach of collinear factorization. The effects related with the transverse
polarization are at twist-3. We derive the complete result of twist-3
contributions to the relevant hadronic tensor at leading order of ,
and construct correspondingly experimental observables. Measuring these
observables will help to extract the twist-2 transversity distribution, twist-3
distributions and twist-3 fragmentation functions of the produced unpolarized
hadron. A detailed comparison with the approach of
transverse-momentum-dependent factorization is made.Comment: discussions and references are added. Published version in PL
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