An analysis of the production ofKS0KS0 andK±Ks0π∓ by two quasi-real photons is presented. The cross section forγγ→K0\(\overline {K^0 } \), which is given for the γγ invariant mass range fromK\(\bar K\) threshold to 2.5 GeV, is dominated by thef′(1525) resonance and an enhancement near theK\(\bar K\) threshold. Upper limits on the product of the two-photon width times the branching ratio intoK\(\bar K\) pairs are given forΘ(1700),h(2030), and ξ(2220). For exclusive two-photon production ofK±Ks0π∓ no significant signal was observed. Upper limits are given on the cross section ofγγ→K+\(\overline {K^0 } \)π− orK−K0π+ between 1.4 and 3.2 GeV and on the product of the γγ width times the branching ratio into theK\(\bar K\)π final states for theηc(2980) and the ι(1440), yieldingΓ(γγ)→i(1440))·BR(i(1440)→K\(\bar K\)π<2.2 keV at 95% C.L.
Data read from graph.. Corrected for the angular distribution, which is assumed to be sin(theta)**4 for W > 1.14 GeV and isotropic in the first bin.
Data read from graph.
We have observed exclusive production of K + K − and K S O K S O pairs and the excitation of the f′(1515) tensor meson in photon-photon collisions. Assuming the f′ to be production in a helicity 2 state, we determine Λ( f ′ → γγ) B( f ′ → K K ) = 0.11 ± 0.02 ± 0.04 keV . The non-strange quark of the f′ is found to be less than 3% (95% CL). For the θ(1640) we derive an upper limit for the product Λ(θ rarr; γγ K K ) < 0.03 keV (95% CL ) .
Data read from graph.. Errors are the square roots of the number of events.
Data read from graph.. Errors are the square roots of the number of events.
Additional systematic uncertainty 25% not included.
The Λ-proton elastic scattering cross section has been measured between 1 and 17 GeV/c in a bubble chamber experiment. These are the first measurements of the elastic cross section for pΛ>5 GeV/c. The Λ's were produced by 25-GeV/c proton interactions in a platinum target. The cross section falls from 22 to 4 mb over the region. No significant polarization is observed.
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CORRECTION MADE FOR KL P --> KS P.
The polarisation of the recoil sigma in the reaction π + p → K + Σ + has been measured at 12 production angles at a beam momentum of 1.11 GeV /c using counters and spark chambers. The new data are compared with existing phase shift solutions of π p → K Σ channels in the low energy region.
THE ASYMMETRY PARAMETER, ALPHA, FOR SIGMA+ --> P PI0 IS CLOSE TO -1. THE LAST DATA VALUE IS DEDUCED FROM ALL THE EXPERIMENTAL EVENTS.
The polarization of recoiling protons from the photoproduction of π0 mesons on liquid hydrogen has been measured for primary photon energies between 500 and 1000 MeV over a range of π0 c.m. angles from 55° to 130°. The results show structure not observed previously in experiments of less precision. In particular, the polarization at 90° c.m. is close to zero at a primary photon energy of 900 MeV. Also, a strong dependence of polarization on π0 c.m. angle between 600 and 900 MeV was observed. A subsidiary measurement of the polarization of the recoil protons from elastic e−p scattering at 900 MeV and q2=10 F−2 gave a value (1.3±2.0)%.
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The cross section for the elastic scattering of positrons from protons has been compared with the corresponding electron cross section using secondary beams derived from the photon beam of the Cornell 2-GeV synchrotron. The paths of the scattered leptons (positrons or electrons) and recoil protons were recorded in spark chambers and were used to determine the incident lepton energy of each event. Elastic scatterings were identified by requiring coplanarity and a fit to the scattering kinematics. The detection system was sensitive to scattering angles between 25° and 75°. The ratio of the positron cross section to the corresponding electron cross section was 0.992±0.017 at 800 MeV and 0.987±0.019 at 1200 MeV. No significant variation of the ratio with angle of scattering was found.
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