Beam spin asymmetry measurements from deeply virtual meson production

Date of Completion

January 2008


Physics, Nuclear




Deeply virtual exclusive reactions γ* +N → N+M (M = γ, meson), where the γ* virtuality Q2 is large, offer a unique opportunity to probe the nucleon structure at the parton level, as described by Generalized Parton Distributions (GPDs). The object of this study is to measure the Beam Spin Asymmetry (BSA) in Deeply Virtual Meson Production (DVMP), in the pseudoscalar channels ep → epη and ep → epπ 0. The data came from the 2005 CLAS experiment of e1-dvcs, with a 5.776 GeV electron beam impinging on a liquid Hydrogen target. In this study, the Q2, xbj and t dependencies of the η and π0 BSAs in deep inelastic regime are measured and compared. For both of these channels, the measurements of non-zero BSA are the indicative of longitudinal-transverse (LT') interference, which is not in agreement with the prediction of the QCD factorization theorems. ^