Measurement of Exclusiveπ0Electroproduction Structure Functions and their Relationship to Transverse Generalized Parton Distributions

I. Bedlinskiy, V. Kubarovsky, S. Niccolai, P. Stoler, K. P. Adhikari, M. Aghasyan, M. J. Amaryan, M. Anghinolfi, H. Avakian, H. Baghdasaryan, J. Ball, N. A. Baltzell (+142 others)
2012 Physical Review Letters  
Exclusive π^0 electroproduction at a beam energy of 5.75 GeV has been measured with the Jefferson Lab CLAS spectrometer. Differential cross sections were measured at more than 1800 kinematic values in Q^2, x_B, t, and ϕ_π, in the Q^2 range from 1.0 to 4.6 GeV^2, -t up to 2 GeV^2, and x_B from 0.1 to 0.58. Structure functions σ_T +ϵσ_L, σ_TT and σ_LT were extracted as functions of t for each of 17 combinations of Q^2 and x_B. The data were compared directly with two handbag-based calculations
more » ... luding both longitudinal and transversity GPDs. Inclusion of only longitudinal GPDs very strongly underestimates σ_T +ϵσ_L and fails to account for σ_TT and σ_LT, while inclusion of transversity GPDs brings the calculations into substantially better agreement with the data. There is very strong sensitivity to the relative contributions of nucleon helicity flip and helicity non-flip processes. The results confirm that exclusive π^0 electroproduction offers direct experimental access to the transversity GPDs.
doi:10.1103/physrevlett.109.112001 pmid:23005620 fatcat:cuiqsbqiznd6ndcdccdy5fki3e