M. K. Jones

Measurement of GEp/GMp in ep → ep to Q2 = 5.6 GeV2

The ratio of the electric and magnetic form factors of the proton G(Ep)/G(Mp), which is an image of its charge and magnetization distributions, was measured at the Thomas Jefferson National Accelerator Facility (JLab) using the recoil polarization technique. The ratio of the form factors is directly proportional to the ratio of the transverse to longitudinal components of the polarization of the recoil proton in the elastic (e) over right arrowp --> e (p) over right arrow reaction. The new data presented span the range 3.5 < Q(2) < 5.6 GeV2 and are well described by a linear Q(2) fit. Also, the ratio rootQ(2) F-2p/F-1p reaches a constant value above Q(2) = 2 GeV2.The ratio of the electric and magnetic form factors of the proton G(E(p))/G(M(p)), which is an image of its charge and magnetization distributions, was measured at the Thomas Jefferson National Accelerator Facility (JLab) using the recoil polarization technique. The ratio of the form factors is directly proportional to the ratio of the transverse to longitudinal components of the polarization of the recoil proton in the elastic e(-->)p---> e(-->)p reaction. The new data presented span the range 3.5< Q(2)< 5.6 GeV(2) and are well described by a linear Q(2) fit. Also, the ratio sqrt[Q(2)] F(2(p))/F(1(p)) reaches a constant value above Q(2) = 2 GeV(2).

Induced Proton Polarization for pi0 Electroproduction at Q2 = 0.126 GeV2/c2 Around the Delta(1232) Resonance

We present a measurement of the induced proton polarization P{sub n} in {pi}{sup 0} electroproduction on the proton around the {Delta} resonance. The measurement was made at a central invariant mass and a squared four-momentum transfer of W = 1231 MeV and Q{sup 2} = 0.126 GeV{sup 2}/c{sup 2}, respectively. We measured a large induced polarization, P{sub n} = -0.397 {+-} 0.055 {+-} 0.009. The data suggest that the scalar background is larger than expected from a recent effective Hamiltonian model.

Calibration of the polarimeter POMME with polarized deuterons at 1.8 GeV

Abstract We report here the results of the calibration of the polarimeter POMME for vector polarized deuterons at an energy of 1.8 GeV. The results show that inclusive deuteron-carbon scattering has substantial vector analyzing power even at this high energy. The results obtained on two analyzers, carbon, which is generally used and a lighter material, paraffin, are found to be similar.

A vector and tensor polarimeter for high-energy deuterons

Abstract The characteristics of a polarimeter to measure the tensor polarization of deuterons with energy of a few GeV have been studied by Monte Carlo simulations. The analyzing reaction is forward elastic dp scattering. The results of the simulation have been verified with a prototype hydrogen cell and a recoil proton detector using drift tubes inserted in the polarimeter POMME. The test used a vector and tensor polarized deuteron beam of 1.6xa0GeV kinetic energy at the accelerator Saturne. The feasability of a vector and tensor deuteron high-energy polarimeter based on deuteron–proton elastic scattering reaction has been studied. We present here the prediction of a Monte Carlo simulation and the first results of a test made with a prototype, at the Saturne National Laboratory.

Cross sections and Rosenbluth separations in 1H(e, e'K+)Lambda up to Q2=2.35 GeV2

The kaon electroproduction reaction 1H(e,eK+)Lambda was studied as a function of the virtual-photon four-momentum, Q2, total energy, W, and momentum transfer, t, for different values of the virtual- photon polarization parameter. Data were taken at electron beam energies ranging from 3.40 to 5.75 GeV. The center of mass cross section was determined for 21 kinematics corresponding to Q2 of 1.90 and 2.35 GeV2 and the longitudinal, sigmaL, and transverse, sigmaT , cross sections were separated using the Rosenbluth technique at fixed W and t. The separated cross sections reveal a flat energy dependence at forward kaon angles not satisfactorily described by existing electroproduction models. Influence of the kaon pole on the cross sections was investigated by adopting an off-shell form factor in the Regge model which better describes the observed energy dependence of sigmaT and sigmaL.

G{sub E{sub p}}/G{sub M{sub p}} Ratio by Polarization Transfer in e(vector sign)p {yields} ep(vector sign)

The ratio of the protons elastic electromagnetic form factors, G{sub E{sub p}}/G{sub M{sub p}} , was obtained by measuring P{sub t} and P{sub l} , the transverse and the longitudinal recoil proton polarization, respectively. For elastic e(vector sign)p{yields}ep(vector sign) , G{sub E{sub p}}/G{sub M{sub p}} is proportional to P{sub t}/P{sub l} . Simultaneous measurement of P{sub t} and P{sub l} in a polarimeter provides good control of the systematic uncertainty. The results for the ratio G{sub E{sub p}}/G{sub M{sub p}} show a systematic decrease as Q{sup 2} increases from 0.5 to 3.5 GeV{sup 2} , indicating for the first time a definite difference in the spatial distribution of charge and magnetization currents in the proton. (c) 2000 The American Physical Society.The ratio of the protons elastic electromagnetic form factors was obtained by measuring the transverse and longitudinal polarizations of recoiling protons from the elastic scattering of polarized electrons with unpolarized protons. The ratio of the electric to magnetic form factor is proportional to the ratio of the transverse to longitudinal recoil polarizations. The ratio was measured over a range of four-momentum transfer squared between 0.5 and 3.5 GeV-squared. Simultaneous measurement of transverse and longitudinal polarizations in a polarimeter provides good control of the systematic uncertainty. The results for the ratio of the protons electric to magnetic form factors show a systematic decrease with increasing four momentum squared, indicating for the first time a marked difference in the spatial distribution of charge and magnetization currents in the proton.