M. Defurne et al. (Jefferson Lab Hall A Collaboration)
We present deeply virtual π0 electroproduction cross-section measurements at xB=0.36 and three different Q2 values ranging from 1.5 to 2 GeV2,
obtained from Jefferson Lab Hall A experiment E07-007. The Rosenbluth
technique is used to separate the longitudinal and transverse responses.
Results demonstrate that the cross section is dominated by its
transverse component and, thus, is far from the asymptotic limit
predicted by perturbative quantum chromodynamics. Nonetheless, an
indication of a nonzero longitudinal contribution is provided by the
measured interference term σLT.
Results are compared with several models based on the leading-twist
approach of generalized parton distributions (GPDs). In particular, a
fair agreement is obtained with models in which the scattering amplitude
includes convolution terms of chiral-odd (transversity) GPDs of the
nucleon with the twist-3 pion distribution amplitude. This experiment,
together with previous extensive unseparated measurements, provides
strong support to the exciting idea that transversity GPDs can be
accessed via neutral pion electroproduction in the high-Q2 regime.
Voir en ligne : Phys. Rev. Lett. 117, 262001