S. Beedoe

Measurement of tensor polarization in elastic electron–deuteron scattering at large momentum transfer

Tensor polarization observables ( t(20), t(21), and t(22)) have been measured in elastic electron-deuteron scattering for six values of momentum transfer between 0.66 and 1.7 (GeV/c)(2). The experiment was performed at the Jefferson Laboratory in Hall C using the electron High Momentum Spectrometer, a specially designed deuteron magnetic channel and the recoil deuteron polarimeter POLDER. The new data determine to much larger Q2 the deuteron charge form factors G(C) and G(Q). They are in good agreement with relativistic calculations and disagree with perturbative QCD predictions.

Measurements of Deuteron Photodisintegration up to 4.0 GeV

The first measurements of the differential cross section for the d(γ,p)n reaction up to 4.0 GeV were performed at the Continuous Electron Beam Accelerator Facility (CEBAF) at Thomas Jefferson Laboratory. We report the cross sections at the proton center-of-mass angles of 36°, 52°, 69°, and 89°. These results are in reasonable agreement with previous measurements at lower energy. The 89° and 69° data show constituent-counting-rule behavior up to 4.0 GeV photon energy. The 52° and 36° data disagree with the counting-rule behavior. The quantum chromodynamics (QCD) model of nuclear reactions involving reduced amplitudes disagrees with the present data.

Electroproduction of kaons on light nuclei

The A(e,e{prime}K{sup +})YX reaction on H, D, {sup 3}He, and {sup 4}He was investigated in Hall C at CEBAF. Data were obtained for Q{sup 2} {approx} 0.35 and 0.5 GeV{sup 2} at 3.245 GeV. The missing mass spectra for both H and D are fitted with Monte-Carlo simulations incorporating peaks corresponding to {Lambda} production on the proton and {Sigma} production on both the proton and neutron. For D, the cross section ratio {Sigma}{sup 0}/{Sigma}{sup {minus}} {approx} 2, and excess yield close to the thresholds for {Lambda} and {Sigma} production can be attributed to final-state interactions that are compared to the data. The analysis of the data for the He targets is in a more preliminary state with broader quasi-free peaks resulting from the higher Fermi momenta. Evidence for bound {Lambda}-hypernuclear states is seen and other structure may be present.

Tensor polarization in elastic electron-deuteron scattering to the highest possible momentum transfers

In elastic electron-deuteron scattering, the tensor polarization moments t 20 , t 21 and t 22 , together with the unpolarized cross-sections, have been measured up to a momentum transfer of 1.8 (GeV/c) 2 , or 6.8 fm −1 . The experiment was performed at Jefferson Laboratory using the recoil deuteron polarimeter POLDER. Preliminary results are presented and discussed, especially in view of their significance concerning the applicability of perturbative QCD to this exclusive process.

Electroproduction of strangeness on (Lambda)H-3,4 bound states on helium

The A(e,e′K+)X reaction has been investigated at Jefferson Laboratory. Data were taken for Q2 ≈ 0.35 GeV2 at a beam energy of 3.245 GeV for 1H,3He and 4He targets. Evidence for Λ‐hypernuclear bound states is seen for 3,4He targets. This is the first time that the electroproduction of these hypernuclei has been observed.

Electroproduction of strangeness on Λ3,4H bound states on Helium

The A(e,e′K+)X reaction has been investigated at Jefferson Laboratory. Data were taken for Q2 ≈ 0.35 GeV2 at a beam energy of 3.245 GeV for 1H,3He and 4He targets. Evidence for Λ‐hypernuclear bound states is seen for 3,4He targets. This is the first time that the electroproduction of these hypernuclei has been observed.

ELECTROPRODUCTION OF STRANGENESS ON LIGHT NUCLEI

The A(e,e{prime} K{sup +})YX reaction has been investigated in Hall C at Jefferson Laboratory for 6 different targets. Data were taken for Q{sup 2} {approx} 0.35 and 0.5 GeV{sup 2} at a beam energy of 3.245 GeV for {sup 1}H, {sup 2}H, {sup 3}He, {sup 4}He, C and Al targets. The missing mass spectra are fitted with Monte Carlo simulations taking into account the production of {Lambda} and {Sigma}{sup 0} hyperon production off the proton, and {Sigma}{sup -} off the neutron. Models for quasifree production are compared to the data, excess yields close to threshold are attributed to FSI. Evidence for {Lambda}-hypernuclear bound states is seen for {sup 3,4}He targets.

Longitudinal and Transverse Cross Sections in the 1H(e,e′K+)Λ Reaction

U.S. Department of Energy, National Science Foundation, Stichting voor Fundamenteel Onderzoek der Materie (Netherlands), Korean Science and Engineering Foundation

Associated Λ production at Jefferson lab

Abstract The 1 H(e, e′K + )Λ and 1 H(e,e′K + )Σ 0 reactions were studied as a function of the squared four-momentum-transfer, Q 2 , and the virtual photon polarization, e, thus enabling the separation of the longitudinal and transverse parts of the cross section. The existence of a sizable longitudinal component for the 1 H(e,e′K + )Λ reaction seems to be indicated by these data.

Results from CEBAF experiment E89-012: Measurements of deuteron photo-disintegration up to 4 GeV

The first measurements of differential cross sections for deuteron photo-disintegration at photon energies up to 4 GeV were performed at the Thomas Jefferson National Accelerator Facility early in 1996. Cross section results for D(γ,p)n at proton center of mass angle of 35°, 53° and 90° will be presented. These results are in good agreement with previous measurements at low energy and extend to higher energies where data were previously unavailable. The 90° degree data show behavior consistent with the constituent counting rules up to 4 GeV and are also in fair agreement with the asymptotic meson exchange model. The 37° and 53° data do not show clear signs of counting rule behavior, although a threshold in transverse momentum for the onset of scaling cannot be excluded.