We have measured the cross section σ for electron - positron annihilation into three or more hadrons, with at least two charged particles in the final state, at 5 GeV center-of-mass energy. We find a model-independent lower limit of σ>9.1±1.0nb; assuming invariant phase-space production of pions, we calculate the detection efficiency of our detector to be (45 ± 11)%, yielding a cross section σ=21±5nb. The average charged hadron multiplicity is found to be n¯=4.3±0.6.
No description provided.
Full angular distributions of the polarization parameter in elastic K+p scattering at 1.37, 1.45, 1.60, 1.71, 1.80, 1.89, 2.11, and 2.31 GeV/c are presented. These data were obtained in an experiment at the Zero Gradient Synchrotron using a polarized proton target with arrays of scintillation and Čerenkov counters to detect the scattered particles.
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We present here the results of an experiment to study the polarization in p−p elastic scattering at the incident momenta 5.15, 7.00, and 12.33 Ge V/c, at t values ranging between - 0.5 and - 6.5 (GeV/c)2. At each momentum we observe a relative maximum in the polarization around t=−1.8 (GeV/c)2. At 12.33 GeV/c the data exhibit a double zero near t=−2.4 (GeV/c)2 and another relative maximum near t=−2.9 (GeV/c)2. The results are discussed in terms of the Chu-Hendry optical model.
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We present herein the initial results of a large-angle elastic p−p polarization experiment which is now in progress at the Argonne ZGS (Zero-Gradient Synchrotron) accelerator. Data for the incident proton momentum of 5.15 GeVc are presented for 30∘≲θc.m.≲90∘. These results, which extend to t≈−4.0(GeVc)2, represent the first high-statistics p−p polarization measurements for |t| values greater than ∼2.5 (GeVc)2. We observe a minimum in the polarization near t=−0.8(GeVc)2, a smooth increase in the polarization until a maximum is attained near t=−1.8(GeVc)2, and then a monotonic decline in the polarization until the value of zero is reached at θc.m.=90∘. The data are analyzed in terms of an optical model.
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The charged-particle multiplicity distribution in 205−GeVc proton-proton interactions is presented. In addition, the total diffractive contributions to each charged multiplicity are estimated assuming a factorizable Pomeron.
THE TOTAL CROSS SECTION NORMALIZATION COMES FROM THIS AND OTHER EXPERIMENTS.
The angular dependence of the asymmetry for negative-pion photoproduction on neutrons by linearly polarized photons has been measured for photon energies 260, 300, 350, 400, 450, and 500 MeV at center-of-mass angles 60°, 75°, 90°, 150°, and 120°. The results are compared with theoretical models of low-energy single-pion photoproduction. The observed asymmetry below 400 MeV shows good agreement with predictions of dispersion-theoretical models by Berends, Donnachie, and Weaver and by Schwela. The asymmetry values in the 400-500 MeV energy region suggest that smaller M1− amplitude is more favorable.
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From an exposure of the Argonne National Laboratory 12-foot bubble chamber to a beam of 12.4-GeV/c protons we have obtained a 3649-event sample of the reaction pp→γ+anything, where we observe photon conversions into e+e− pairs in the liquid hydrogen. We find that the invariant cross section for this reaction does not separate in its x and P⊥ dependence at our energy. By setting upper bounds on the cross sections for inclusive η and Σ0 production, we show that π0 decay is the dominant source of photons and therefore measure the cross section for inclusive π0 production to be σ(π0)=(31.5±2.6) mb. Comparison with the inclusive π+ and π− cross sections at 12.0 GeV/c shows that the relation 2σ(π0)=σ(π+)+σ(π−) is well satisfied. We confirm earlier indications that the average number of π0's per inelastic pp interaction is approximately independent of the number of associated charged particles produced.
Axis error includes +- 8/8 contribution (THE CROSS SECTION FOR NON-PI0 GAMMA PRODUCTION IS LESS THAN 2.3 MB AND HAS BEEN NEGLECTED IN OBTAINING THE 31.5+-2.6 MB CROSS SECTION FOR THE INCLUSIVE PI0 PRODUCTION).
Results are presented on the elastic scattering of photons by protons. The incident photon energy ranged from 0.55 GeV to 4.5 GeV, and the four-momentum transfer t ranged from 0.12 to 1.0 (GeV/c)2. The data at large angles, 60°<θ*<115°, are characterized by a pronounced excitation of the D13(1518) resonance, a shoulder in the 1688-MeV mass region, and a precipitous drop thereafter in the cross section as a function of incident energy. The low-t data are characterized by a diffraction slope of 5 (GeV/c)−2. The data are inconsistent with the predictions of the vector-dominance model if the latter is restricted to ρ0, ω, and φ vector mesons.
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The reaction e − + p → e − + p + η has been studied in the region of the S 11 (1535)-resonance by detecting the recoil proton in coincidence with the scattered electron. The reaction has been observed at three four-momentum transfers of the virtual photon: q 2 = 0.2, 0.28 and 0.4 (GeV/ c ). First results of the differential cross section measurements are given and compared with quark model calculations.
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We have measured elastic pion-proton scattering in a 50 GeV/ c π − beam at the 76 GeV proton synchrotron in Serpukhov. Data are presented for four-momenta transfer squared in the range 0.03 < t < 0.4 (GeV/ c ) 2 .
SLOPE IS 9.1, +0.2, -0.4 GEV**-2 (INCLUDING SYSTEMATIC ERRORS).
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