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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THESE VALUES OF R = SIG(HAD)/SIG(MU) ARE TABULATED IN THE RECORD OF THE THESIS OF A. BACKER, DESY-F33-77-03 (1977).
PRELIMINARY DATA.
DATA GIVEN IN J. BURMESTER ET AL., PL 68B, 283 (1977).
Measurements of flux-normalized neutrino and antineutrino total charged-current cross sections (σ) in the energy range 45<E<205 GeV are presented. We see no evidence for the anomalous sharp rise in σν¯σν reported by earlier authors. The neutrino cross section rises linearly with energy and with σE about 18% smaller than other measurements below 10 GeV. The average antineutrino slope at 55 GeV is consistent with measurements at low energy; however, a (20 ± 10)% increase is indicated over our energy range.
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As a part of the study of the inclusive production of electron pairs in pp collisions at the CERN Intersecting Storage Rings (ISR), a search has been performed for additional photons accompanying J/ψ particles. The results suggest that (43±21)% of the J/ψ's are produced via the photonic decay of one of the χ(3.5) states.
The cross section times branching ratio.
The cross section ratio of the elastic neutral current reaction ν p→ ν p to the quasi-elastic charged current reaction ν n→ μ − p has been measured in the kinematical region 0.3⩽ q 2 ⩽1.0 (GeV/ c ) 2 . The measured value is R M =0.17±0.08. Model dependent corrections are applied, especially for ν n→ ν n contamination, and the result is compared to various models.
(C=OBSERVED) and (C=CORRECTED) are the observed and corrected for the nuclear effects ratios.
The inclusive reactions pn → p s + x and π + n → p s + x at incident momentum of 195 GeV/ c have been studied in an exposure of the Fermilab 30 inch deuterium filled bubble chamber to a mixed ( π + , p) beam. Analysing the t and M 2 dependence of our data within the framework of triple-Regge models we conclude that pion exchange yields a dominating contribution. Comparing our data with the pp results we conclude that isoscalar Regge exchange, ω, is much larger than isovector, ϱ, Regge exchange. We observe significant leading π − emission from the recoiling mass x, comparable to that observed in on-mass-shell π − p → π − experiments. This verifies our conclusions about pion-exchange dominance in the above reactions.
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Interference between the I u = 1 2 and I u = 3 2 baryon exchange amplitudes is observed in the reaction π − p → p π − π 0 , with the proton produced forward with cos θ p ∗ >0.8 . The Dalitz plot shows that the reaction is dominated by the quasi two body final states ρ − p( δ exchange) and N ∗0 (1670)π 0 ( N exchange ) , with δ(1238), N ∗ (1520) and higher mass N ∗ 's also produced. The relative phase between the ρ and the N ∗ (1670) production amplitudes is measured to be 135° ± 10° and is compared with the Regge pole signature factor phase predictions.
THE RELATIVE PRODUCTION AMPLITUDE PHASE FROM INTERFERENCE IS 135 +- 10 DEG.
A precision measurement of the μ + momentum in π + decay at rest has been made with a magnetic spectrometer. The result is p μ + = (29.7873 ± 0.0014) MeV/c. The consequences of thisresult for the rest masses of the muon neutrino and of the positive pion are discussed.
DECAY AT REST WAS STUDIED.
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The rates for forward electroproduction of single charged pions from deutrium have been measured in the resonance region, at a virtual photon mass squared ≈−0.5( GeV/ c 2 ) 2 . Results are presented in the form of a π − to π + cross-section ratio.
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We have investigated inclusive Λ , Λ and Σ ± (1385) productions in 405 GeV/ c pp interactions. The observed cross sections are σ ( Λ )=4.05±0.39 mb, σ( Λ =0.63±0.17 mb, σ ( Σ + (1385))=0.74±0.17 mb and σ ( Λ − (1385))=0.56±0.17 mb. Λ production is dominant in a central region of ∣ x ∣≤0.4. The Λ/ Λ production ratio at ∣ x ∣≈0 is found to be 1.2±0.5. The excess, about 0.2 mb, of σ ( Λ + (1385)) over σ ( Λ − (1385)) is most likely attributed to proton fragmentations (∣ x ∣≥0.4), and gives an evidence for scaling.
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