W. Flauger

Parametrization of the q2 dependence of γvp total cross sections in the resonance region

Abstract All existing data on γvp total cross sections in the resonance region are fitted in the absolute value of the three-momentum transfers | q | independently for small bins of W in the range 1.11 ⩽ W ⩽ 1.99 GeV. The data are divided into three ranges of the polarization ϵ : ϵ ⩾ 0.9, 0.9 > ϵ > 0.6, ϵ ⩽ 0.6. Taking into account statistical and possible systematic errors, a comparison of the fits for different ranges of ϵ indicate that longitudinal contributions to the cross sections in the resonance region are in general small. In the range 1.3 2 GeV2 and above W = 1.6 GeV for q2 > 0.5 GeV2, up to 20% contribution of σl is possible.

πO electroproduction at Δ(1236) and a four-momentum transfer of 15 fm−2

The electroproduction of the Δ(1236) has been investigated through the π0 channel at a four-momentum transfer of 15 fm−2. Angles and momenta of the secondary electron and of the proton were measured in coincidence to obtain the differential cross section for the reaction ep→epπ0. The angular distribution for s- and p-waves of the outgoing pion and nucleon in their c.m. system was fitted to the cross sections. The resultant coefficients of the angular distributions are given as functions of the mass W of the pion nucleon system for 15 fm−2. In a small range of W around the resonance, the contributions of the resonant multipoles M1+, E1+ and S1+ to the cross section are also given. Further results with respect to non-resonant multipoles, as well as for momentum transfers of 25 and 40 fm−2, will be published later.

π0 electroproduction at the first resonance at momentum transfers q2 = 0.6, 1.0 and 1.56 GeV2

Abstract Recent measurements on electroproduction of π0 mesons in the region of the first pion nucleon resonance at four momentum transfers of q2 = 0.6 and q2 = 1 GeV are extended to q2 = 1.56 GeV2. All the results are discussed in terms of angular coefficients and multipole amplitudes. Assuming that the angular distributions are dominated by the magnetic dipole M1+, the square of the magnetic dipole amplitude and its interference terms with the multipoles E0+, S0+, E1+, S1+ and M1− are determined. The results are compared with theoretical models. The dependence of |M1+|2 on the invariant mass W at different q2 is discussed by comparison with a standard Breit Wigner formula.

Electroproduction of Δ(1236) in the π0 channel at a four momentum transfer of 25 fm−2

Abstract The electroproduction of the Δ(1236) has been investigated by measuring angular distributions of the outgoing proton. Coefficients of these angular distributions for a wide mass range around the resonance are given at a momentum transfer of 25 fm−2. Also given are the resonant multipoles in a small range around the resonance. The γNN∗ form factor obtained from our work at 15 and 25 fm−2 is compared with other results.

Measurements of inclusive hadron momentum distributions in deep inelastic electroproduction

In the deep inelastic region of electron scattering the distribution of hadrons in the direction of the virtual photon has been investigated. At q2 = 1.16 GeV2 and W = 2.63 GeV coincidence measurements between the scattered electron and photon, π± and K± have been made. Momentum and missing mass distributions are presented. They are compared with other electroproduction measurements, with photoproduction, and with hadronic reactions.

Separation of σL and σT in η electroproduction at the resonance S11 (1535)

Abstract The ratio R = σ L σ T of longitudinal and transverse cross sections for the reaction ep → ep η at the resonance S 11 (1535) was measured at momentum transfers q 2 = 0.6 and 1 GeV 2 . The transverse part dominates the longitudinal part of the cross-section. Averaging from W = 1.49 GeV to W = 1.58 GeV we obtain R = 0.22±0.23 at q 2 = 0.6 GeV 2 and R = −0.16 ± 0.16 at q 2 = 1 GeV 2 .

Separation of σ1 and σt at q2 ∼ 1 (GeV/c)2 in the resonance region

Abstract We report on some new values of R = σ1/σt taken in the resonance region from inelastic ep scattering at DESY. Cross sections were measured at θ = 57° and θ = 15° to 17° at q2 = 1 GeV2. R was calculated at masses 1495 ⩽ 1W⩽ 1715 MeV. It was found that the contribution of σ1 to the total cross section is small, below 20%. The errors are less than ΔR = 16%.