21 differential cross section measurements of the np → pn charge-exchange reaction have been carried out at the synchrotron Saturne (Saclay), for incident neutron momenta between 1 and 2 GeV/ c and in the squared four-momentum transfer range 0 ⩽ −t ⩽ 0.4 (GeV/ c ) 2 . The π exchange peak is seen at all the incident momenta. The s dependence of the very forward slope of this peak shows weak structures near the threshold of inelastic channels.
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The π − p→n γ and π − p→n π ° differential cross sections have been measured for −0.9< cos θ ∗ <−0.45 (θ ∗ c.m. scattering angle) at 475 MeV/ c and 550 MeV/ c incident momenta. The π − p→n γ measurement is a good check of the detailed balance principle in the electromagnetic interactions of hadrons at these energies and is in good agreement with Walker's analysis. On the other hand the π − p→ π °n extrapolated values of 180° allows one to verify that the phases of the A 1 2 and A 3 2 amplitudes are equal.
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BACKWARD CROSS SECTION ESTIMATED BY LEGENDRE POLYNOMIAL FIT.
Experimental results are presented for the available channels in the 1.2 GeV/ c π + p interaction. An isobaric model with incoherent addition of the amplitudes is used to determine the π, Δ and N ∗ abundance rates in the π + π o p final state. The multipole parameters in the density matrix of the Δ ++ are determined as functions of its production angle.
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LEGENDRE POLYNOMIAL FIT USED TO CORRECT FOR ELASTIC EVENTS LOST FROM THE FORWARD BIN.
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The results are presented of two partial-wave analyses of the (3π) − system in 30 000 events of the reaction π − p → π − π − π + p at 11.2 GeV/ c . Both techniques incorporate the assumptions of the isobar model and are (a) the University of Illinois program which fits in terms of the (3π) density matrix elements and (b) an amplitude parametrisaton including possible effects of both spin non-flip and spin flip at the baryon vertex. The results obtained with these independent programs are found to be very close.
NORMALIZED TO A TOTAL REACTION CROSS SECTION OF 1.17 +- 0.24 MB. ALL QUOTED CROSS SECTIONS ARE FOR INTEGRATED BREIT-WIGNERS.
A2 2+D-WAVE FOR 1.2 < M(3PI) < 1.4 GEV. THE FIRST THREE COMBINATIONS OF DENSITY MATRIX ELEMENTS ARE FOR NATURAL PARITY EXCHANGE, AND THE REMAINDER UNNATURAL.
Neutron-proton differential cross sections have been measured with good statistics for four-momentum transfers 0.14<−t≲19.0 (GeV/c)2 at laboratory momenta ranging from 4.5 to 12.5 GeV/c. The experiment was carried out in a neutron beam at the Argonne National Laboratory zero-gradient synchrotron. These results in conjunction with previous n−p charge-exchange data provide almost complete elastic-scattering angular distributions in this momentum range.
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The forward production of charm states in 350 GeV p-Fe interactions has been studied via the production of prompt single muons with momentum p ≳ 20 GeV/ c . The data indicate equal production of single μ + and μ − events. The observed momentum distributions can be fit with the hypothesis that D mesons are produced with an invariant cross section proportional to (1 − x F ) 5.0±0.8 exp[−(2 ± 0.3) P t ] and do not favor a large diffractive cross section predicted by intrinsic charm models. Extrapolation of the distributions to x F = 0 yields a total D D production cross section of 22.6 ± 2.1(±3.6)ωb/nucleon on the assumption of a linear A dependence and 8% average semileptonic branching ratio of charm states.
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Differential cross sections for π + p elastic scattering were measured for seven incident energies from 65 to 140 MeV at laboratory scattering angles between 93° and 165°. The results are compared with previous results of Bertin et al. and the phase-shift analysis of Arndt and Roper. Agreement between the phase-shift analysis and the data is good.
ABSOLUTE NORMALIZATION UNCERTAINTY = 2.4 PCT.
ABSOLUTE NORMALIZATION UNCERTAINTY = 2.0 PCT.
ABSOLUTE NORMALIZATION UNCERTAINTY = 1.4 PCT.
We have measured the production polarization of 265- and 310-GeV/c Σ− in the inclusive reaction p+Cu→Σ−+X using 400-GeV/c protons. The polarization was analyzed via the asymmetry in the weak decay Σ−→n+π−, and has typical values of +0.20 with respect to the direction of the cross product of the incident-proton and Σ− momenta. Using the spin-precession technique, we have determined the Σ− magnetic moment to be -1.23±0.03±0.03 nuclear magnetons, where the statistical and systematic errors are shown separately.
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An absolute measurement of π0 photoproduction on the proton has been carried out in the threshold region (from 144.7 to 173 MeV) by use of tagged annihilation photons. The measured cross sections, differential in the recoiling-proton energy, are used to perform a multipole analysis which gives a value & &, in disagreement with low-energy-theorem predictions. Total cross sections and coefficients of the π0 angular distribution are presented.
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360 GeV/c proton interactions with aluminium (Al) and gold (Au) targets are studied using the European Hybrid Spectrometer (EHS) equipped with the Rapid Cycling Bubble Chamber (RCBC). Multiplicities, rapidity distributions and correlations between leading and other produced particles are presented and compared with Monte Carlo calculations based on the multi-chain and Lund models.
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