Photoproduction of π−-mesons on deuteron has been studied in the first resonance region with an annihilation photon beam with adjustable peak energy (from 250 MeV to 400 MeV). A coincidence detection of both outgoing π−-meson and forward proton has been performed with a set of 9 multiwire proportional chambers (1700 wires) inside the gap of a spectrometer. The momentum of the second proton is computed from three-body kinematics; their distribution is found in excellent agreement with the spectator model, even at the top of the resonance. The differential cross-sections of π− have been measured from 100° to 180° (center of mass); they are in reasonable agreement with conventional multipole calculations and do not indicate an appreciable isotensor term.
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Differential cross sections for coherent π0-photoproduction from deuterium have been measured in the photon energy range from 240 to 400 MeV and for pion c.m. angles between 70 ° and 160 °. The recoil deuterons were analysed in angle and momentum by a magnetic spectrometer. The cross sections obtained were higher by a factor of about 2 compared with the results from Stanford [7], the only data available up to now in the first resonance region. Below the resonance the measured cross sections give a smooth extension to the low energy data from Glasgow [5] and Orsay [6].
No description provided.
Inclusive π− distributions from 205-GeV/c pp interactions, covering the full range of longitudinal and transverse momenta, have been obtained using the 30-in. hydrogen bubble chamber at the National Accelerator Laboratory. These data provide new evidence for scaling in the fragmentation region and for a plateau in the central region of rapidity. The 90°-c.m. invariant cross section varies as exp[−(10±2)PT2] in the range PT2<~0.1 (GeV/c)2.
No description provided.
We have measured the cross section, the angular distribution, and the Λ polarization for the reaction π−p→ΛK0. A spark-chamber spectrometer was used to collect 8400 ΛK0 events at fourteen beam momenta near ΣK threshold. Our data do not show the prominent cross-section enhancement suggested by some previous experiments. However, detailed structure in the cross section and the angular distribution agrees well with a simple model which includes a cusp effect at ΣK threshold.
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BACKWARD-FORWARD PRODUCTION ASYMMETRY.
AVERAGE LAMBDA POLARIZATION.
The joint decay density-matrix elements have been measured for the ρ0Δ++ and ωΔ++ channels at 3.7 GeV/c. The data are presented as a function of momentum transfer in both the t-channel and s-channel coordinate systems. The presence of correlated decays is illustrated for both reactions by employing selective cuts on the decay angles of one resonance, and displaying the effects on the decay distribution of the opposing resonance. An amplitude analysis is performed with the data near 0° production angle, where we obtain a helicity decomposition of the scattering amplitude with no experimental ambiguity.
T-CHANNEL COORDINATE SYSTEM (XYZ=TH).
T-CHANNEL COORDINATE SYSTEM (XYZ=TH).
S-CHANNEL COORDINATE SYSTEM (XYZ=SH).
The ratio (p¯d→π−π0ps)(p¯d→π−π+n) at rest, with spectator momenta ≲300 MeVc, has been measured and found to be 0.68 ± 0.07. This implies that (75 ± 8)% of the annihilations in deuterium into two pions come from odd N¯N orbital angular momenta, in disagreement with the S-state-dominance hypothesis. It has also been observed that the p¯d→π−π0ps production rate depends on the spectator momentum, which suggests energy-sensitive N¯N phenomena near threshold.
RELATIVE ANNIHILATION FREQUENCY AT REST.
The inelastic reaction p+p→p+X is studied at 205 GeV/c. The distribution of the square of the missing mass, M2, shows a large diffractivelike peak at low M2 due to two-, four-, and six-prong events. The slope of the invariant cross section versus t decreases with increasing M2. The energy dependences of the multiplicity moments for the recoiling system X are similar to those for corresponding moments for p+p→(n chargedparticles).
No description provided.
The differential cross section for π−−p elastic scattering has been measured at 13.8 and 22.6 GeV/c up to −t=5 (GeV/c)2. The dips in the angular distribution at −t≈0.8 and 2.8 (GeV/c)2 previously observed at lower momenta become less prominent at higher momentum. The −t=2.8 (GeV/c)2 dip is still observed at 13.8 GeV/c, but at 22.6 GeV/c it has become a sharp kink in the angular distribution. At large momentum transfers, dσdt at fixed t is still decreasing with increasing s, but at a slower rate in the 14- to 23-GeV/c region than at lower momenta.
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We have measured the total cross section for electron-positron annihilation into three or more hadrons, with at least two charged particles in the final state. The measurement was made at a center-of-mass energy of 4 GeV with a 2π−sr nonmagnetic detector. With 88 events detected, we obtain a model-independent lower limit on the hadron production cross section of 9.6 ± 1.4 nb; a calculation of detection efficiency based on invariant phase-space production of pions leads to a total cross section of 26 ± 6 nb. This cross section is 4.7 ± 1.1 times the theoretical total cross section for e+e−→μ+μ−. The average charged multiplicity is n¯=4.2±0.6.
No description provided.
Momentum spectra for forward Σ− production on beryllium by protons of momentum 25.8 and 29.4 GeVc are presented. Data for the two primary proton momenta are compared for scaling behavior in the invariant cross section. In addition, the observed single-particle momentum distributions are compared with single-particle spectra from other inclusive reactions initiated by protons.
No description provided.
No description provided.
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