Abstract
A review is given of measurements of hard exclusive π+ production on a hydrogen target, as well as of the production of exclusive π+π− pairs and light vector mesons on hydrogen and deuterium targets at HERMES using the 27.6 GeV HERA positron beam. First preliminary results for the unpolarized total π+ production cross section in the kinematic range 1.5<Q2<10.5 GeV2 and for 0.02<x<0.8 are presented and compared to GPD calculations. Furthermore, the first Legendre moment of the angular distributions of π+ mesons in the CM frame of the exclusively produced pion pairs is presented. Its dependence on the π+π− invariant mass can be understood as being due to the interference between relative P-wave (isovector) and S, D-wave (isoscalar) states of the two pions. From the exclusive light vector meson production preliminary results on the ratio of the longitudinal to transverse components of the ρ and ϕ production cross section, and the longitudinal component of the corresponding cross section are reported.
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