Quasi-elastic pn scattering in ^6LiD and ^6LiH targets from 1.1 to 2.4 GeV

A polarized proton beam from SATURNE II, the Saclay polarized targets with Li compounds, and an unpolarized target were used to measure spin-dependent observables for protons scattered on bound nucleons. The beam and target polarizations were oriented vertically. The analyzing power and the depolarization were determined at seven energies between 1.1 and 2.4 GeV. The spin correlation parameter was measured at only 1.1 and 1.6 GeV. Measurements with the target at 1.1 GeV provided data for scattering of polarized protons on neutrons in carbon. The quasi-elastic observables are compared with previous elastic scattering measurements and at 1.1 GeV with predictions of phase shift analyses. Received: 19 April 1999 / Published online: 28 September 1999     

Angular dependence of pp spin correlation and rescattering observables between 1.80 and 2.10 GeV

A polarized proton beam extracted from SATURNE II and the Saclay polarized proton target were used to determine the spin correlation parameter Aoosk and the rescattering observablesK _os″ so; D_os″ok, N_os″sn, andN _onsk at 1.80 and 2.10 GeV. The beam polarization was oriented perpendicular to the beam direction in the horizontal scattering plane and the target polarization was directed either along the vertical axis or longitudinally. Left-right and up-down asymmetries in the second scattering were measured. A check for the beam optimization with the beam and target polarizations oriented vertically provided other observables, of which results forD _onon andK _onno at 1.80, 1.85, 2.04, and 2.10 GeV are listed here. The new data at 2.10 GeV suggest a smooth energy dependence of spin triplet scattering amplitudes at fixed angles in the vicinity of this energy.     

Measurement of the spin correlationA ookk innp elastic scattering between 0.63 and 1.08 GeV

We present the measurements of the spin correlation parameterA _ookk (np). A longitudinally polarized beam of free neutrons obtained from the break-up of polarized deuterons was scattered on the longitudinally polarized Saclay frozen-spin proton target. Measurements were carried out at SATURNE II, at neutron beam kinetic energies of 0.63, 0.88, 0.98 and 1.08 GeV. The data points cover the angular region from about 40° to 110° CM. The observed angular dependence ofA _ookk (np) at 0.63 GeV agree with the phase shift analysis predictions except at small angles.     

Elastic and quasi-elastic pp scattering in ^6LiH and ^6LiD targets between 1.1 and 2.4 GeV

A polarized proton beam extracted from SATURNE II, the Saclay polarized target with Li compounds, and a target were used to measure elastic and quasi-elastic pp spin-dependent observables in the angular region . The beam and/or target polarizations were oriented vertically. Accurate pp data for the analyzing power , spin-correlation parameter , and the polarization transfer were measured at 1.1 GeV. The observables and were determined at six other energies between 1.6 and 2.4 GeV. At 1.6 GeV, was also obtained. The individual contributions from H, Li, and LiD were deduced. The target provided results on free hydrogen and on protons in carbon. The elastic and quasi-elastic observables are compared with existing data and with phase-shift analysis predictions. Received: 19 April 1999 / Published online: 14 October 1999     

Measurement of the spin correlation parameter Aoonn and of the analyzing power for pp elastic scattering in the energy range from 0.5 to 0.8 GeV

The spin correlation parameter A_oonn and the analyzing powers A_oono and A_ooon were measured simultaneously, in the energy range 0.5–0.8 GeV and in the angular region 40°–80° CM. The experiment used the polarized proton beam of SATURNE II and the Saclay frozen spin polarized target.     

The pp elastic scattering analyzing power measured with the polarized beam and the unpolarized target between 1.98 and 2.80 GeV

A polarized proton beam extracted from SATURNE II was scattered on an unpolarized CH₂ target. The angular distribution of the beam analyzing power A_oono was measured at large angles from 1.98 to 2.8 GeV and at 0.80 GeV nominal beam kinetic energy. The same observable was determined at the fixed mean laboratory angle of 13.9° in the same energy range. Both measurements are by-products of an experiment measuring the spin correlation parameter A_oon.     

Measurements of the two and three spin-index observables inn p elastic scattering between 0.80 and 1.10 GeV

We present data of several rescattering observables measured inn p elastic scattering between 0.80 and 1.10 GeV. The SATURNE II polarized beam of free neutrons obtained from the break-up of polarized deuterons was scattered on the Saclay polarized frozen-spin proton target. Three different configurations of beam and target polarization directions were used: the observablesD _onon andK _onno were measured with the normal-normal spin configuration at eight energies;N _onkk ,D _os″ok andK _os″ko were determined with the longitudinal-longitudinal configuration at six energies;N _onsk ,D _os″ok andK _os″so with the sideway-longitudinal configuration at six energies. Part of the data was obtained with an unpolarized CH₂ target where only the two spin-index polarization transfer parametersK _os″ko andK _os″so were determined. Data are compared with phase shift analyses predictions and with the LAMPF results at 0.788 GeV. Present results are the first measurements of rescattering observables above 0.80 GeV. They provide an important contribution to any future theoretical or phenomenological analysis.

     

Measurement of the spin correlation parameters Aoosk and Aookk in pp elastic scattering at 0.84 and 1.0 GeV

The spin correlation parameters A_oosk and A_ookk were measured at 0.834 and 0.995 GeV using the SATURNE II polarized proton beam and the Saclay frozen spin polarized target. The measurements were carried out in the angular region φ_CM from 50° to ≃ 90°. The shape of the angular distribution A_oosk (pp) = f(θ_CM) changes rapidly from 0.8 to 1.0 GeV. The A_ookk data points specify our previous measurements.     

Measurement of the pp analyzing power in the vicinity of 2.20 GeV

The pp elastic scattering analyzing power was measured in small energy steps in the vicinity of the accelerator depolarizing resonance at 2.202 GeV. A vertically polarized proton beam was extracted from SATURNE II at energies above the resonance and passed through different copper degraders. The beam was focused on the beam line polarimeter CH target. Its halo was removed by four powerful magnets. Measurements at degraded energies were complemented by data obtained with the directly extracted polarized beam outside the resonance region. Analyzing power results at fixed laboratory angles are compared with existing data in the region under discussion, with polynomial fits from 1.6 to 3.5 GeV, and with phase shift analysis predictions. Received: 24 March 1999 / Published online: 12 August 1999     

Measurement of the spin correlation Aookk in pp elastic scattering from 0.88 to 2.7 GeV

The spin correlation parameter A_ookk in pp elastic scattering was measured using the SATURNE II polarized proton beam and the Saclay frozen spin polarized target. The measurements at 0.88 and 1.1 GeV were carried out in the angular region θ_CM from 28° to ⋍ 50° and complete our previous measurements from 45° to 90°. Above 1.1 GeV the measurements presented here cover both regions, extending from θ_CM = 28° (at the lower energies) or θ_CM = 18° (at the higher energies) to θ_CM > 90°. The shape of the angular distribution A_ookk (pp) = f(θ_CM) changes considerably between in our energy region.     

Measurements of the total cross section differenceΔσ Т innp transmission between 0.86 and 0.94 GeV

We present results of the total cross section differenceΔσ _Т obtained in transmission measurements at the energies 0.86, 0.88, 0.91 and 0.94 GeV. The SATURNE II polarized beam of free neutrons obtained from the break-up of polarized deuterons was transmitted through the polarized Saclay frozen-spin proton target. The beam and target polarizations were oriented in the vertical direction. The present results agree with previous SATURNE measurements and improve the amplitude analysis in the forward direction.     

Measurement of spin-correlation parameters ANN,ASS, and ASL at 2.1 GeV in proton-proton elastic scattering

At the Cooler Synchrotron COSY/Jülich spin-correlation parameters in elastic proton-proton (pp) scattering have been measured with a 2.11 GeV polarized proton beam and a polarized hydrogen atomic beam target. We report results for A(NN), A(SS), and A(SL) for c.m. scattering angles between 30 degrees and 90 degrees. Our data on A(SS)--the first measurement of this observable above 800 MeV--clearly disagrees with predictions of available pp scattering phase-shift solutions while A(NN) and A(SL) are reproduced reasonably well. We show that in the direct reconstruction of the scattering amplitudes from the body of available pp elastic scattering data at 2.1 GeV the number of possible solutions is considerably reduced.     

Measurement of the total cross section difference ΔσT(pp) in the energy range from 0.43 to 2.4 GeV

The SATURNE II polarized proton beam and the Saclay frozen spin polarized proton target were used to measure the total cross section difference Δσ_T = −2σ_{1 tot} at 26 energies between 0.43 and 2.4 GeV. Here Δσ_T is the total cross section difference for transverse beam and target spins parallel and antiparallel, respectively, and σ_1tot is one of spin-dependent terms in the total cross section σ_tot. The energy dependence of Δσ_T below 1 GeV shows similar structures as for Δσ_L. An additional minimum appears at about 1.3 GeV, which involves a structure in singlet spin partial waves.     

Study of spin effects in neutron-proton interactions at intermediate energies at PSI

An intensive program of n-p measurement of spin observables in elastic and pion production reactions has been performed at the Paul Scherrer Institute taking advantage of the high intensity polarized neutron beam. In the elastic reaction 16 different spin observables have been measured for kinetic energies from 210 to 590 MeV with the centre of mass angular range from 60 to 180 degrees. This will allow to perform direct reconstruction in the model independent way of the isospin I=0 scattering amplitudes in elastic NN interaction. Three body final state process \(\vec np - pp\pi ^ - \) with polarized neutrons in exclusive experiment has been investigated.     

Measurement of the spin asymmetry in the photoproduction of pairs of high- p(T) hadrons at HERMES

We present a measurement of the longitudinal spin asymmetry A(||) in photoproduction of pairs of hadrons with high transverse momentum p(T). Data were accumulated by the HERMES experiment using a 27.5 GeV polarized positron beam and a polarized hydrogen target internal to the HERA storage ring. For h(+)h(-) pairs with p(h(1))(T)>1.5 GeV/c and p(h(2))(T)>1.0 GeV/c, the measured asymmetry is A(||) = -0. 28+/-0.12(stat)+/-0.02(syst). This negative value is in contrast to the positive asymmetries typically measured in deep inelastic scattering from protons, and is interpreted to arise from a positive gluon polarization.     

Asymmetry in the scattering of protons on polarized deuterons at 1.21 GeV/c

By using a polarized deuteron target we have measured the asymmetry in the differential cross section for elastic scattering of protons on deuterons and for quasi-elastic scattering of protons on protons bound in deuterons between the two states of opposite polarization, normal to the scattering plane of the initial deuteron. The beam momentum was 1.21 GeV/c. It is checked that the neutrons bound in the deuterons are polarized to approximately 20%.     

Measurement of spin-transfer observables in p p-->Lambda Lambda at 1.637 GeV/c

Spin-transfer observables for p p-->Lambda Lambda have been measured using a transversely polarized frozen-spin target and a beam momentum of 1.637 GeV/c. Current models of the reaction near threshold are in good agreement with existing measurements performed with unpolarized particles in the initial state but produce conflicting predictions for the spin-transfer observables Dnn and Knn (the normal-to-normal depolarization and polarization transfer), which are measurable only with polarized target or beam. Measurements of Dnn and Knn presented here are found to be in disagreement with predictions from these models.     

Parity-violating electron scattering from 4He and the strange electric form factor of the nucleon

We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from 4He at an average scattering angle = 5.7 degrees and a four-momentum transfer Q2 = 0.091 GeV2 . From these data, for the first time, the strange electric form factor of the nucleon G(E)s can be isolated. The measured asymmetry of A(PV) = (6.72 +/- 0.84(stat) +/- 0.21(syst) x 10(-6) yields a value of G(E)s = -0.038 +/- 0.042(stat) +/- 0.010(syst), consistent with zero.     

Measurement of the tensor analyzing powers T20 and T21 in elastic electron-deuteron scattering

The tensor analyzing power components T20 and T21 have been measured in elastic electron-deuteron scattering at the 2 GeV electron storage ring VEPP-3, Novosibirsk, in a four-momentum transfer range from 8.4 to 21.6 fm(-2). A new polarized internal gas target with an intense cryogenic atomic beam source was used. The new data determine the deuteron form factors G(C) and G(Q) in an important range of momentum transfer where the first node of the deuteron monopole charge form factor is located. The new results are compared with previous data and with some theoretical predictions.     

Spin-dependent electron-proton scattering in the Delta-excitation region

We report on measurements of the cross section and provide first data on spin correlation parameters A(TT') and A(TL') in inclusive scattering of longitudinally polarized electrons from nuclear-polarized hydrogen. Polarized electrons were injected into an electron storage ring operated at a beam energy of 720 MeV. Polarized hydrogen was produced by an atomic beam source and injected into an open-ended cylindrical cell, located in the electron storage ring. The four-momentum transfer squared ranged from Q2 = 0.2 GeV(2)/c(2) at the elastic scattering peak to Q2 = 0.11 GeV(2)/c(2) at the Delta(1232) resonance. The data provide a stringent test of pion electroproduction models.