Gluon poles and photon distribution amplitudes in Drell-Yan-like processes

We calculate the hadron tensor related to the photon-induced Drell-Yan process, with incoming nucleon being transversally polarised. We predict the new single spin asymmetry which probes gluon poles and which is expressed in terms of photon (both chiral-odd and chiral-even) distribution amplitudes and chiral-odd nucleon function stemming from the nucleon transverse polarization.Comment: 6 pages, 3 figures; Appendix has been adde

Non-factorized genuine twist 3 in exclusive electro-production of vector mesons

We present an analysis of genuine twist-3 quark contributions to the amplitude of exclusive electro-production of transversely polarized vector mesons. Using the formalism based on the momentum representation we calculated all the genuine twist-3 terms of quark contributions to gamma_T^* --> rho_T amplitude. We found that these terms can not be factorized owing to the existence of the infrared divergencies in the amplitude of hard sub-processes.Comment: 4 pages. Talk presented by I.V. Anikin at European Workshop on the QCD Structure of the Nucleon (QCD-N'02), Ferrara, Italy, 3-6 Apr 2002 (to appear in Nucl. Phys. A, Proc. Suppl.

New contributions to gluon poles in direct photon production

We consider the direct photon production in two hadron collision with one of the hadrons being transversely polarized. By using the contour gauge for gluon fields, we find that there are new twist-$3$ terms present in the hadron tensor of the considering process in addition to the standard twist-$3$ terms. In this work, we demonstrate that the significance of these new terms are two-fold: first, they are crucial to both the QED and QCD gauge invariance and, second, their contributions to the hadron tensor are at least the same as those from the standard ones. We also study the resuting effects which are responsible for the universality breaking of the corresponding twist-$3$ parton distributions.Comment: 19 pages, 5 figure

Strong and radiative decays of the Ds0*(2317) meson in the DK-molecule picture

We consider a possible interpretation of the new charm-strange meson Ds0*(2317) as a hadronic molecule - a bound state of D and K mesons. Using an effective Lagrangian approach we calculate the strong Ds0* to Ds pi0 and radiative Ds0* to Ds* gamma decays. A new impact related to the DK molecular structure of the Ds0*(2317) meson is that the presence of u(d) quarks in the D and K mesons gives rise to a direct strong isospin-violating transition Ds0* to Ds pi0 in addition to the decay mechanism induced by eta-pi0 mixing considered previously. We show that the direct transition dominates over the eta-pi0 mixing transition in the Ds0* to Ds pi0 decay. Our results for the partial decay widths are consistent with previous calculations.Comment: 22 pages, 4 figures, accepted for publication in Phys. Rev.