A complete set of polarization-transfer observables has been measured for quasifree (p→,n→) reactions on H2, C12, and Ca40 at a bombarding energy of 495 MeV and a laboratory scattering angle of 18°. The data span an energy-loss range from 0 to 160 MeV, with a corresponding momentum transfer range of qc.m.=1.7–1.9 fm−1. The laboratory observables are used to construct partial cross sections proportional to the nonspin response and three orthogonal spin responses. These results are compared to the transverse spin response measured in deep inelastic electron scattering and to nuclear responses based on the random phase approximation. The polarization observables for all three targets are remarkably similar and reveal no evidence for an enhancement of the spin-longitudinal nuclear response relative to the spin-transverse response. These results suggest the need for substantial modifications to the standard form assumed for the residual particle-hole interaction.
No description provided.
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No description provided.
The spin correlation parameter C NN has been measured for n-p elastic scattering at 181 MeV. A comparison with predictions from various phase shift sets and potential models reveals sizeable deviations from the for the data Paris potential and Saclay phase shifts. For the Paris potential the deviations are directly related to an overprediction of the 3 D 2 phase shift parameter.
Numerical values of data supplied by J. Sowinski.
The polarization of the Σ+ has been measured for the line-reversed reactions π+p→K+Σ+ and K−p→π−Σ+ at 7 and 11.6 GeV/c using the SLAC Hybrid Facility. Since the Σ+ decay is observed in the bubble chamber, the trigger of the flash lamps on a fast K+(π−) did not bias the polarization measurements. We find that the Σ+ polarizations from the two reactions have opposite signs but similar magnitudes and are in much better agreement with the predictions of weak exchange degeneracy than previous lower-energy comparisons.
No description provided.
Measurements have been made of the ratio of the π+ photoproduction cross sections at right angles to and along the electric field vector. Data have been taken at 45°, 90°, and 135° at energies of 227, 240, 342, and 373 MeV. A comparison of the data with the predictions of a phenomenological analysis using only S and P waves shows less than 0.1% chance of obtaining such results without the inclusion of higher angular momenta, and hence, demonstrates even more convincingly the need for a meson current term which has been indicated by other measurements. A comparison is made with the relativistic dispersion relations of McKinley which include an approximation for the γ, ρ, π coupling. At the resonance energy our polarization asymmetry is insensitive to this coupling and is in good agreement with the McKinley prediction. At lower energy the agreement is not as good but our data seem to substantiate the need for a negative γ, ρ, π coupling constant.
No description provided.
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We have measured the polarization parameter in neuton-proton charge-exchange scattering for incident neutron momenta of 2-12 GeVc and 0.01<~|t|<~1.0 (GeVc)2. Results based on 300 000 events show a negative polarization whose magnitude increases monotonically with |t| approaching 60% for |t|∼0.6 and which has little energy dependence.
No description provided.
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We have measured in a single experimental setup the differential cross sections and polarizations of the Y*(1385) produced in the two line-reversed reactions π+p→K+Y*(1385) (260 eV/μb) and K−p→π−Y*(1385) (180 eV/μb) at 11.5 GeV/c. We compare these results to Σ+ production in the same experiment. The data have been derived from a triggered bubble-chamber experiment using the SLAC Hybrid Facility. We find that both helicity-flip-dominated (Y*) and helicity-nonflip-dominated (Σ) processes are consistent with weak-exchange-degeneracy predictions.
Axis error includes +- 10/10 contribution.
Axis error includes +- 10/10 contribution.
Axis error includes +- 10/10 contribution.
The polarization of τ leptons produced in the reaction e + e − → τ + τ − at the Z resonance has been measured using the τ decay modes e ν e ν τ , μν μ ν τ , πν τ , ϱν τ , and a 1 ν τ . The mean value obtained is P τ = −0.152±0.045, indicating that parity is violated in the neutral current process e + e − → τ + τ − . The result corresponds to a ratio of a neutral current vector and axial vector coupling constants of the τ lepton g V τ (M 2 Z ) g A τ (M 2 Z ) = 0.076±0.023 and a value of the electroweak mixing parameter sin 2 θ w ( M 2 Z ) = 0.2302 ± 0.0058.
Results are for both TAU+ and TAU- decay. Final combined result contains statistical and systematic errors added in quadrature.
No description provided.
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POLARIZATION PARAMETER P(N000).
POLARIZATION PARAMETER A(00N0).
WOLFENSTEIN PARAMETER D(N0N0).
Results are presented on vector meson production in the hypercharge exchange reactions: π + p → K ∗+ (890) Y + and K − p→ ρ − Y + where Y + is either Σ + or Y ∗+ (1385). These reactions have been studied at 7 GeV/ c and 11.5 GeV/ c using the SLAC Hybrid Facility. Total and differential cross sections, hyperon polarization, and vector meson decay angular distributions are presented. We find that reactions with Σ + production are dominated by natural parity exchange. The Y ∗ (1385) reactions are consistent with substantial natural parity exchange contributions but also show significant unnatural parity exchange. The differential cross sections and polarization measurements for the vector meson production are compared to the pseudoscalar production reactions.
Axis error includes +- 20/20 contribution.
Axis error includes +- 20/20 contribution.
Axis error includes +- 20/20 contribution.
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