We present the first results of an experiment at the CERN intersecting storage rings, which measures the total cross-section in proton-proton collisions. The equivalent laboratory momenta are 291, 496, 1068 and 1480 GeV/c. We have made a direct measurement of αT as the ratio between the total interaction rate and the machine luminosity. The present paper gives a detailed description of the experimental apparatus and of the analysis procedure. We find that αT increases by about 10% in the energy region studied.
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The polarization of scattered antiproton in\(\bar pp\) elastic scattering has been measured at the kinetic energy of 220MeV by means of double scattering in a bubble chamber. The polarizations obtained are 0.28±0.11, 0.46±0.12, 0.51±0.19 and 0.38±0.31 at the scattering angles 28°, 42°, 56° and 73° in the c.m. system, respectively. These results do not seem to be in good agreement with a prediction given by Bryan and Phillips. We have also compared these data with a modified diffraction model.
POLARIZATION ASSUMED POSITIVE.
The reaction π-p→pωπ- has been studied at 9.1 GeV/c, its total cross-section is σ=(123±22) μb. The pB− and the quasi-three-body channels contribute with cross-section of σ=(24±7) μb and σ=(94±23) μb, respectively. The main features of the quasi-three-body pωπ- channel, displayed by some techniques of data presentation, are satisfactorily described by a double-Regge-pole model. In this model pomeron-meson and meson-meson exchanges are taken into account. An OPE modelà la Veneziano predicts a total cross-section too high and reproduces very poorly the observed features.
BREIT-WIGNER PLUS BACKGROUND FITS FOR B(1235)- AND OMEGA MESONS.
The final results of an experimental investigation of the reaction γ+n→p+π− performed with a deuterium bubble chamber at the 1 GeV Frascati electrosynchrotron are presented. Total and differential cross-sections on neutrons are extracted by means of the spectator model, the reliability of which has been checked by numerous tests and is extensively discussed. The problems of a possible isotensor component in the electromagnetic current, the time-reversal invariance of the electromagnetic interactions and the photoproduction of the Roper resonance are considered in detail.
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With an apparatus slightly improved with respect to a previous one we have studied multihadronic production at the Adone e + e − storage ring up to a maximum center of mass energy of 3 GeV.
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Multihadron production by electron-positron colliding beams has been investigated for total centre-of-mass energies ranging from 1.2 to 2.4 GeV. The total cross-section, σtot ≡ σ(e+e−→π+π−+ + anything), is of the order of σμμ ≡ σ(e+e−→μ+μ−), with a threshold near 1 GeV. Partial cross-sections for the various channels are also derived. The cross-section of the specific channel e+e−→π+π−π+π− exhibits an energy dependence which is suggestive of a heavier vector meson, ρ' (mρ,≈ 1.6 GeV,Гρ, ≈ 350 Mev), having the same quantum numbers as the ρ-meson. An upper limit is given for the coupling constantfρ′ (fρ′/4π<18, wherefρ′=mρ′2e/gγρ′). Final states withG+ parity are found to be much more abundant than those withG− parity. The average multiplicity (charged plus neutral final-state pions) is found to be betweet 4 and 5 over all the energy range explored.
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VALUES OF R CALCULATED FROM TOTAL CROSS SECTION.
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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.
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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 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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