We report Λ 0 -hyperon polarization measurements at the CERN intersecting storage rings from √ s of 31 to 62 GeV. P Λ 0 changes insignificantly, +(0.8±1.7)%, over this range of √ s . However, P Λ 0 is observed to grow with Feynman- x F and with transverse momentum. At an average p t of 1.1 GeV/ c , P Λ 0 depends linearly on x F and approaches −40% at x F =0.8.
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Axis error includes +- 0.0/0.0 contribution (?////).
Results onK0 and Λ production ine+e− annihilation at c.m. energies of 14, 22 and 34 GeV are presented. The shape of theK0 and Λ differential cross sections are very similar to each other and to those of π±,K± and\(p(\bar p)\). Scaling violations are observed forK0 production. We obtain a value for the probability to produce strange quark-antiquark pairs relative to that to produce up or down quark-antiquark pairs of 0.35±0.02±0.05. The value ofRh=σ(e+e-→hX)/σµµ is shown to rise steadily with c.m. energy for all particle species. At 34 GeV we find 1.48±0.05K0 and 0.31±0.03 Λ per event. We have searched for possible Λ polarization. The production ofK0's and Λ's in jets is examined as a function ofpT2 and rapidity and compared to that of all charged particles; the yields in two and three jets are also investigated. Results are presented from events with two baryons\((\Lambda ,\bar \Lambda ,por\bar p)\) observed.
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A new measurement of the differential cross section and of the analysing power A 0 n of the charge-exchange reaction p − p → n − n at 875 MeV/ c is presented. The A 0 n data cover the entire angular range and constitute a considerable improvement over previously published data, both in the forward and in the backward hemisphere. The cross-section data cover only the backward region, but are unique at this energy. A careful study of the long-term drifts of the apparatus has allowed to fully exploit the good statistics of the data.
Forward hemisphere measurement. Additional systematic error of 4 pct due to target polarization uncertainty.
Backward hemisphere measurement. Additional systematic error of 15 pct.
Differential cross section in the backward hemisphere. Additional systematic error of 15 pct.
The polarization parameter has been measured for π − p elastic scattering in the backward region at 3.5 GeV/ c incident momentum. The experimental set-up consisted of a polarized target in a spectrometer magnet, hodoscopes and wire spark chambers. Data are presented for the range −0.95< u ⩽−0.19 GeV 2 . An isospin analysis has been carried out to separate the I u = 1 2 and I u = 3 2 contributions.
BACKWARD SCATTERING.
We have measured the polarization parameter in π − p→K + Σ − backward scattering at 3.5 GeV/ c incident momentum, in the u -range −0.6< u <0.1 GeV 2 . The apparatus consisted of a polarized target in a spectrometer magnet, counter hodoscopes for time-of-flight measurements, a large water Čerenkov counter for kaon tagging, and wire spark chambers. After identification of the kaons, the reaction was selected by a missing-mass technique. An isospin analysis has been carried out to separate the contributions of the various isospin exchange amplitudes in the u -channel.
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A partial-wave analysis of the (3 π ) 0 system produced peripherally in the reaction K − p → π + π − π 0 Λ at 4.2 GeV/ c is presented. The observation of the weak Λ decay allows a determination of all the transversity production amplitudes except for two phases. The production of known resonances having decay modes other than 3 π is used to test the isobar model ansatz. Significant ω(783), φ(1020) and A 2 (1310) production is observed. The spin parity of the ω ∗ (1675) is established as 3 − . No evidence for production of other resonances, such as axial vector-mesons, is found.
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The angular distributions of the analyzing power for the pp → dπ + reaction have been measured at seven energies T p = 1.2, 1.4, 1.6, 1.7, 1.8, 2.0 and 2.3 GeV. The data show a strong energy dependence with a structure centered at √ s π d = 2.66 GeV. Possible interpretations are presented in the frame of the OPE model and involving the question of the excitation of a dibaryon resonance.
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We have searched for signatures of polarization in hadronic jets from $Z~0 \rightarrow q \bar{q}$ decays using the ``jet handedness'' method. The polar angle asymmetry induced by the high SLC electron-beam polarization was used to separate quark jets from antiquark jets, expected to be left- and right-polarized, respectively. We find no evidence for jet handedness in our global sample or in a sample of light quark jets and we set upper limits at the 95\% C.L. of 0.063 and 0.099 respectively on the magnitude of the analyzing power of the method proposed by Efremov {\it et al.}
Polarized E- beam. Events were classified as being of light or heavy flavors based on impact parameters of charged tracks measured in the vertex detector. Jet handedness are measured for helicity-based and chirality-based analysis (seetext). C=95PCT CL indicates the upper limits at the 95 PCT C.L. on the magnitudes.
Inclusive Λ production has been studied in K − p interactions at 8.25 GeV/ c using about 69 000 events; the total cross section is found to be 3.35 ± 0.20 mb. A comparison has been made with Σ 0 and Σ(1385) inclusive production. Their influence on the inclusive Λ production is discussed. The inclusive Λ cross section and polarization is interpreted in terms of the triple-Regge model. In the target fragmentation region an effective Regge trajectory is determined which lies closer to the K than to the K ∗ . In the beam fragmentation region the cross-section data indicate an effective Regge trajectory which corresponds to the nucleon, while the polarization data require additional Regge exchanges to be present.
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