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

We report the measurement of near-threshold neutral pion electroproduction cross sections and the extraction of the associated structure functions on the proton in the kinematic range Q2 from 2 to 4.5 GeV2 and W from 1.08 to 1.16 GeV. These measurements allow us to access the dominant pion-nucleon s-wave multipoles E0+ and S0+ in the near-threshold region. In the light-cone sum-rule framework (LCSR), these multipoles are related to the generalized form factors Gπ0p1(Q2) and Gπ0p2(Q2). The data are compared to these generalized form factors and the results for Gπ0p1(Q2) are found to be in good agreement with the LCSR predictions, but the level of agreement with Gπ0p2(Q2) is poor.