Measurement of Exclusive ${\pi }^0$ Electroproduction Structure Functions and their Relationship to Transversity GPDs

Abstract

Exclusive ${\pi }^0$ 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 ${\varphi }_{\pi }$, 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 ${\sigma }_T+\epsilon {\sigma }_L,{\sigma }_{TT}$ and ${\sigma }_{LT}$ 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 including both longitudinal and transversity GPDs. Inclusion of only longitudinal GPDs very strongly underestimates ${\sigma }_T+\epsilon {\sigma }_L$ and fails to account for ${\sigma }_{TT}$ and ${\sigma }_{LT}$, 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 ${\pi }^0$ electroproduction offers direct experimental access to the transversity GPDs.

6 pages, 2 figures

References in corpus (4)

• Transverse spin structure of the nucleon from lattice QCD simulations
• Nucleon Tensor Charge from Exclusive ${\pi }^o$ Electroproduction
• Deeply inelastic pions in the exclusive reaction $p(e,e^{\prime }{\pi }^{+})n$ above the resonance region
• Unitarity constraints on neutral pion electroproduction

Cited by in corpus (1)

• Near Threshold Neutral Pion Electroproduction at High Momentum Transfers and Generalized Form Factors