New Results on the π+π−\pi^{+}\pi^{-} Electroproduction Cross Sections off Protons

In these proceedings we present preliminary $\pi^{+}\pi^{-}$ electroproduction cross sections off protons in the kinematical area of 1.4 GeV $< W <$ 1.8 GeV and 0.4 GeV$^{2}$ $< Q^{2} < 1.1$ GeV$^{2}$. Our results extend the kinematical coverage for this exclusive channel with respect to previous measurements. Furthermore, the $\pi^{+}\pi^{-}$ electroproduction cross sections were obtained for $Q^2$-bins of much smaller size. The future analysis of this data within the framework of the JLAB-MSU reaction model (JM) will considerably improve our knowledge on the $Q^2$ evolution of the transition $\gamma_{v}NN^*$ electrocouplings, in particular for the resonances with masses above 1.6 GeV.Comment: Will be published in proceedings of NSTAR 2011 conference. 4 pages, 4 figure

Measurements of the γv p → p\u27π+π− Cross Section with the CLAS Detector for 0.4 GeV\u3csup\u3e2\u3c/sup\u3e \u3c Q\u3csup\u3e2\u3c/sup\u3e \u3c 1.0 GeV\u3csup\u3e2\u3c/sup\u3e and 1.3 GeV \u3c W \u3c 1.825 GeV

New results on the single-differential and fully integrated cross sections for the process γvp → p\u27π+π− are presented. The experimental data were collected with the CLAS detector at Jefferson Laboratory. Measurements were carried out in the kinematic region of the reaction invariant mass W from 1.3 to 1.825 GeV and the photon virtuality Q2 from 0.4 to 1.0 GeV2. The cross sections were obtained in narrow Q2 bins (0.05 GeV2) with the smallest statistical uncertainties achieved in double-pion electroproduction experiments to date. The results were found to be in agreement with previously available data where they overlap. A preliminary interpretation of the extracted cross sections, which was based on a phenomenological meson-baryon reaction model, revealed substantial relative contributions from nucleon resonances. The data offer promising prospects to improve knowledge on the Q2 evolution of the electrocouplings of most resonances with masses up to ∼1.8 GeV

Hard Exclusive Pion Electroproduction at Backward Angles With CLAS

We report on the first measurement of cross sections for exclusive deeply virtual pion electroproduction off the proton, ep → e\u27nπ+, above the resonance region at backward pion center-of-mass angles. The ϕ∗ π-dependent cross sections were measured, from which we extracted three combinations of structure functions of the proton. Our results are compatible with calculations based on nucleon-to-pion transition distribution amplitudes (TDAs). These non-perturbative objects are defined as matrix elements of threequark-light-cone-operators and characterize partonic correlations with a particular emphasis on baryon charge distribution inside a nucleon

Measurements of the Gamma(Upsilon)p -\u3e p ’pi(+)Pi(- )Cross Section with the CLAS Detector for 0.4 GeV2 \u3c Q(2) \u3c 1.0 GeV2 and 1.3 GeV \u3c W \u3c 1.825 GeV

New results on the single-differential and fully integrated cross sections for the process γvp -\u3e p\u27π+π- are presented. The experimental data were collected with the CLAS detector at Jefferson Laboratory. Measurements were carried out in the kinematic region of the reaction invariant mass W from 1.3 to 1.825 GeV and the photon virtuality Q2 from 0.4 to 1.0 GeV2. The cross sections were obtained in narrow Q2 bins (0.05 GeV2) with the smallest statistical uncertainties achieved in double-pion electroproduction experiments to date. The results were found to be in agreement with previously available data where they overlap. A preliminary interpretation of the extracted cross sections, which was based on a phenomenological meson-baryon reaction model, revealed substantial relative contributions from nucleon resonances. The data offer promising prospects to improve knowledge on the Q2 evolution of the electrocouplings of most resonances with masses up to similar to ~ 1.8 GeV

Measurement of the Generalized Form Factors Near Threshold Via ˠ*p→nπ+ at High Q²

We report on the first measurement of the F2 structure function of the neutron from the semi-inclusive scattering of electrons from deuterium, with low-momentum protons detected in the backward hemisphere. Restricting the momentum of the spectator protons to ≲ 100  MeV/c and their angles to ≳ 100° relative to the momentum transfer allows an interpretation of the process in terms of scattering from nearly on-shell neutrons. The Fn2 data collected cover the nucleon-resonance and deep-inelastic regions over a wide range of Bjorken x for 0.65 \u3c Q2 2, with uncertainties from nuclear corrections estimated to be less than a few percent. These measurements provide the first determination of the neutron to proton structure function ratio Fn2 / Fp2 at 0.2 ≲ x ≲0.8 with little uncertainty due to nuclear effects