We have identified 262 doubly tagged two-photon events. A subset of the data shows an enhancement of 21 events in the inclusive two-photon mass squared distribution between 0.8 and 2.2 GeV 2 . If these events result from spin 2 resonance production then Γ γγ = 9.5 ± 3.9 ± 2.4 keV (statistical and systematic). From another subset of 58 events in which the final state could be classified we determine the two-photon hadron to muon cross section ratio R γγ = 1.1 ± 0.3 ± 0.3.
ELECTRON BEAM ENERGIES OF 3.0 AND 3.6 GEV.
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DOMINANT NATURAL PARITY EXCHANGE.
EVIDENCE FOR FORWARD DIP FOR -TP < 0.1 GEV**2.
We observe production of a Ξ * (2370) in the reactions K − p→ [YK¯π] K, [YK¯π] Kπ and [ΩK] (K or Kπ) at 8.25 GeV/ c in a high statistics bubble chamber experiment. The mass and width are determined to be 2373 ± 8 MeV and 80 ± 25 MeV, respectively. The I = 1/2 assignment is strongly favoured.
CROSS SECTIONS FOR PRODUCTION OF XI(2370) --> (LAMBDA + SIGMA) AK PI. BREIT-WIGNER FIT WITH POLYNOMIAL BACKGROUND. XI(2370) PRODUCED BY BARYON EXCHANGE. CORRECTED FOR NEUTRAL DECAYS AND GEOMETRICAL LOSSES. <OMEGA-KAON> DECAY SEEN. OBSERVED RATIO OF CHARGED TO NEUTRAL XI(2370) PRODUCTION IS 2.7 +- 0.9.
Measurements have been made of the polarisation parameters Σ , T and P for the process γ p → π + n in the photon energy range 520–2250 MeV at c.m. angles between 30° and 120°. These data were obtained in a double polarisation experiment, using the polarised photon beam from the Daresbury electron synchrotron incident on a polarised proton target. The data are compared with predictions from current theoretical analyses.
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The polarisation parameters Σ, P and T have been measured for the process γ p→ π 0 p in the photon energy range 1300–2100 MeV and c.m. angles between 30° and 110°, in an experiment with a polarised beam and polarised target. The results are compared with a recent theoretical analysis which fits data from threshold to 16 GeV. The new data are in general agreement with the analysis, but with some significant discrepancies in detail.
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Inclusive Λ production has been studied in K − p interactions at 8.25 GeV/ c using about 69 000 events; the total cross section is found to be 3.35 ± 0.20 mb. A comparison has been made with Σ 0 and Σ(1385) inclusive production. Their influence on the inclusive Λ production is discussed. The inclusive Λ cross section and polarization is interpreted in terms of the triple-Regge model. In the target fragmentation region an effective Regge trajectory is determined which lies closer to the K than to the K ∗ . In the beam fragmentation region the cross-section data indicate an effective Regge trajectory which corresponds to the nucleon, while the polarization data require additional Regge exchanges to be present.
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The production of strange particles in π + d interactions has been examined at 4 GeV/ c where no previous data exist. Careful attention has been given to the resolution of ambiguities and to corrections for losses in a total sample of about 22 000 events which have been used to determine channel cross sections. Where they can be checked, the cross sections fit well into the observed variation of existing cross sections at higher and at lower energies.
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We present differential cross-sections for pp elastic scattering at eight laboratory momenta from 1.50 to 2.06 GeV/c. The data are analysed using an 8-parameter optical modelà la Frahn and Venter. However, the best representation of the differential cross-sections is obtained by combining the glory model with a parametrization of the scattering amplitude in terms of coherent exponentials. Both representations show the dominance of the partial wave with orbital angular momentum equal to four.
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The reaction\(\bar pp \to \bar \Lambda \Lambda \) has been studied in a bubble chamber experiment at eight incident momenta between 1.50 and 2.06 GeV/c. The differential cross-section, the polarization and the spin correlation coefficients have been measured. They have been compared with the prediction of two theoretical models: the K-meson conspiracy and the exchange of the K*K** degenerate trajectory associated with a Regge cut. The latter model gives the best representation of the data.
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POLARIZATION AND SPIN CORRELATION COEFFICIENTS. AVERAGED OVER ALL ANGLES. SEE PAPER FOR DEFINITIONS, MORE DETAILS AND POSSIBLE T-DEPENDENCE.