Angela Biselli

Measurement of ep→e′pπ+π− and Baryon Resonance Analysis

The cross section for the reaction ep-->e()ppi(+)pi(-) was measured in the resonance region for 1.4<W<2.1 GeV and 0.5<Q2<1.5 GeV(2)/c(2) using the CLAS detector at Jefferson Laboratory. The data show resonant structures not visible in previous experiments. The comparison of our data to a phenomenological prediction using available information on N(*) and Delta states shows an evident discrepancy. A better description of the data is obtained either by a sizable change of the properties of the P13(1720) resonance or by introducing a new baryon state, not reported in published analyses.

SPIN ASYMMETRIES FOR EXCLUSIVE AND SEMI-EXCLUSIVE REACTIONS WITH CLAS

An extensive experimental program to measure the spin structure of the nucleons is being carried out with the CLAS detector at Jefferson Lab using a longitudinally polarized electron beam incident on a longitudinally polarized target. Spin degrees of freedom offer new tools to explore the baryon structure and test the many theoretical approaches that attempt to characterize it, such as effective Lagrangian models and transverse momentum dependent parton distributions. I will present preliminary results for single and double spin asymmetries for exclusive T O , T+, and 7 electroproduction in the resonance region compared with unitary isobar and dynamical models, as well as p electroproduction for DIS kinematics. I will also report on an analysis of the semi-inclusive and exclusive channels where double and single spin asymmetries were used to study transverse momentum dependent parton distributions.

Measurement of the proton spin structure function g1(x;Q2) for Q2 from 0.15-GeV2 to 1.6-GeV2 with CLAS

Double-polarization asymmetries for inclusive ep scattering were measured at Jefferson Lab using 2.6 and 4.3 GeV longitudinally polarized electrons incident on a longitudinally polarized NH3 target in the CLAS detector. The polarized structure function g(1)(x,Q2) was extracted throughout the nucleon resonance region and into the deep inelastic regime, for Q(2)=0.15-1.64 GeV2. The contributions to the first moment Gamma(1)(Q2)= integral g(1)(x,Q2) dx were determined up to Q(2)=1.2 GeV2. Using a parametrization for g(1) in the unmeasured low x regions, the complete first moment was estimated over this Q2 region. A rapid change in Gamma(1) is observed for Q2<1 GeV2, with a sign change near Q(2)=0.3 GeV2, indicating dominant contributions from the resonance region. At Q(2)=1.2 GeV2 our data are below the perturbative QCD evolved scaling value.

Measurement of the polarized structure function σLT′ for p(e⃗ ,e′p)π0 in the Δ(1232) resonance region

The polarized longitudinal-transverse structure function

ep⃗ epπ0 reaction studied in the Δ (1232) mass region using polarization asymmetries

sigma_{LT^prime}

GDH 2004: Proceedings of the Third International Symposium on the Gerasimov-drell-hearn Sum Rule And Its Extensions

has been measured using the

STUDY OF THE Δ(1232) USING DOUBLE-POLARIZATION ASYMMETRIES

p(vec e,epi^+)n

Baryons 2002 : proceedings of the 9th International Conference on the Structure of Baryons

reaction in the

GDH 2002: Proceedings of the Second International Symposium on the Gerasimov-Drell-Hearn Sum Rule and the Spin Structure of the Nucleon

Delta(1232)

HELICITY STRUCTURE OF BARYON RESONANCES

resonance region at