We present results from a high momentum resolution measurement of the π − p elastic differential cross section near the η production threshold. By analysing the cusp discontinuity in the elastic cross section we deduce the non-spin-flip elastic amplitude and compare it with solutions from phase-shift analyses.
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Measurements are reported of the differential cross section for the reaction π − +p→ ω +n from threshold to a final-state c.m. momentum P ∗ of 200 MeV /c . The previously reported fall in total cross section σ/P ∗ below about 100 MeV/ c is again seen. The differential cross section remains close to isotropic over the entire range. A paralle experiment on the variation in the elastic differential cross section across the threshold shows evidence of this threshold. The elastic data cover a range of incident moments from 1010 to 1180 MeV/ c in steps of 5 MeV/ c .
CROSS SECTION DEPENDENCE ON FINAL STATE CENTRE OF MASS MOMENTUM.
ANGULAR DISTRIBUTIONS ARE ALMOST ISOTROPIC.
LEGENDRE POLYNOMIAL COEFFICIENTS NORMALIZED SUCH THAT SIG = 4*PI*LEG(L=0).
Polarized cross sections for the reaction π − p → η n have been measured at 12 incident momenta between 1171 and 2267 MeV/ c . The data show that the polarization is small in the forward direction and there is a general trend for it to be large and positive near cos θ ∗ = 0.2 . These are the first published results on polarization effects in this channel in the resonance region. An energy-dependent partial-wave analysis has been performed and the couplings and branching fractions for decays of nucleon resonances to this channel are presented.
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High-statistics measurements of the absolute differential cross section for n−p scattering have been made over neutron c.m.-system scattering angles 9.5°<θ*<64.5°. The statistical error is 1.7 to 3.3% for 2°-wide angular bins, and the systematic error is 2.7 to 3.3%. The cross section is fitted by dσdΩ*=A exp(bt), with A=10.27±0.36 mb/sr, b=5.00±0.05, and 0.01<−t<0.39 (GeV/c)2. For the ratio of the real to the imaginary part of the forward-scattering amplitude we obtained αn>~−0.43±0.04, consistent with other less precise determinations of αn.
EXPONENTIAL FIT TO D(SIG)/DOMEGA OVER -T = 0.01 TO 0.39 GEV**2 (THETA = 9.5 TO 64.5 DEG).
We present measurements of the differential and polarization cross sections for the reactions KL0p→Ks0p, Λπ+, Σ0π+, and Λπ+π0 made in a hydrogen bubble chamber exposed to a beam of KL0 with incident momentum 550±35 MeV/c. The quasielastic data imposes additional constraints on the partial-wave analyses of the KN and K¯N systems. Our data show no strong energy-dependent effects in the region of the reported Σ(1580), JP=32− state. The phase of the forward regeneration amplitude was found to be about - 160° independent of KL0 momentum.
SYSTEMATIC ERRORS INCLUDED.
ROUGH FIT - POSSIBLY OTHER SYSTEMATIC ERRORS.
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p-He4 elastic scattering has been measured at 1.05-GeV incident proton energy, close to 180° in the center of mass. The steep backward peak observed at lower energies is still present, but its slope appears to decrease.
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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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Using a secondary pion beam from the Argonne Zero Gradient Synchrotron we have studied the process π−p→φn in the region of the cross-section enhancement near kinematic threshold. For incident momenta between 1.6 and 2 GeV/c, we have determined production and decay angular distributions and extrapolated total cross sections from a sample of about 160 φ's above background. The production and decay distributions are consistent with isotropy over this entire incident-momentum range. The extrapolated total cross section varies between 19 and 25 μb.
Axis error includes +- 16/16 contribution (RES-DEF(RES=PHI,BACK=CORRECTED)).
Axis error includes +- 16/16 contribution (RES-DEF(RES=PHI,BACK=CORRECTED)).
The angular distribution of the inclusive reaction 4 He + p → 3 He + X was measured with 6.85 GeV/ c incident alphas. At large angles, the observed kinematics corresponds to the elastic scattering on the target proton of an 3 He present in the incoming 4 He, the remaining neutron being a spectator. This shows the presence of an important component of 3 He in 4 He. The integrated cross section for 3 He production is σ 3He = 24.1 ± 1.9 mb.
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