We have made a study of the coherent reaction K + d → K 0 π + d at 2 GeV/ c , using data obtained in the Lawrence Berkeley Laboratory 25 inch bubble chamber. The cross section for this reaction is 324 ± 25 μ b, after correction for invisible K 0 decays. This reaction is dominated primarily by vector exchange. We determine the parameters of the ω trajectory to be α ω = (0.33 ± 0.04) + t .
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SLOPE IS 9.4 +- 0.5 GEV**-2 FOR -T > 0.02 GEV**2 AND 10.4 +- 0.6 GEV**-2 FOR -TP > 0.
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Data are presented which firmly establish the existence of the double charge exchange reaction p p → Σ − Σ − at 3.6 GeV/ c . The forward cross section was found to be (5.9 ± 1.1) μb and the ratio of the “forbidden” to “allowed” forward cross section is R = σ( Σ − Σ − σ( Σ + Σ + ) = 0.09 ± 0.02 .
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We have measured dσ du for π − p elastic scattering at 3 and 4 GeV c in the ranges −0.119⩽ u ⩽0.113 and −0.233⩽ u ⩽0.088, respectively. A fit of the form d σ /d u = A exp ( Bu + Cu 2 ) gives B = 4.34±0.42 and C = 7.0±3.5 at 4 GeV c with χ 2 = 5.7 for 9 degrees of freedom; the simpler form d σ /d u = A exp( Bu ) gives B = 3.7 ± 0.3 with χ 2 = 9.6. At 3 GeV c we confirm with high statistics the structures already observed.
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The average multiplicities 〈 n c 〉 and 〈n〉, of charged-plus-neutral pions produced in e + e − collisions, have been determined for total center-of-mass energies ranging from 1.2 to 2.4 GeV. No appreciable multiplicity variation is observed over this energy range, where the mean values 〈; n c 〉 = 3.3 +0.3 −0.2 and 〈 n 〉 = 4.4 +0.4 −0.2 are found.
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VALUES OF R CALCULATED FROM TOTAL CROSS SECTION.
We have measured with good statistics the differential cross section for p p →π + π − , K + K − around 0°. Our data and previous results show that the s -dependence of dσ/d t has a value compatible with the appropriate baryon exchange.
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We report our first measurements of the polarization in the elastic scattering of negative pions from polarized protons at an incident pion momentum of 40 GeV/ c . The momentum-transfer region covered was 0.08 < | t | < 1.3 (GeV/ c ) 2 . The angular distribution of the polarization exhibits a first minimum of ∼ − 5% and the well-known zero around t ≈ − 0.6 (GeV/ c ) 2 . The energy variation of the first minimum (at around t = − 0.2) may be expressed in a simple form, P avr = −(0.48±0.06) s −0.52±0.05 .
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The p p → n n polarization has been measured at 8 GeV/ c and for − t values ranging from 0 up to 0.8 (GeV/ c ) 2 . A small and negative polarization has been found.
ERRORS INCLUDE STATISTICAL AS WELL AS RELATIVELY SMALL SYSTEMATIC EFFECTS.
The observation of 21 K + K − pairs in 38 hadron pair events produced at 1.5, 1.6, and 1.7 GeV total centre-of-mass energies in e + e − annihilations, establishes that time-like photons produce K pairs and π pairs with comparable rates in this energy range. The K-meson electromagnetic form factor at a mean s -value of 2.4 GeV 2 is measured to be | F K | = 0.50±0.08. The number of e + e − pairs observed in the same angular and energy range is 5148.
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Invariant cross-sections are presented for the inclusive reaction p + p → π o + anything, Measurements of large transverse momentum π o 's (2.5 GeV/ c < p ⊥ <9 GeV/ c ) were made near 90° at the CERN ISR at five centre-of-mass energies (√ s = 23.5, 30.6, 44.8, 52.7 and 62.4 GeV. At large p ⊥ , the invariant cross-sections are seem to vary with s and p ⊥ , in good agreement with a fit of the form Ap ⊥ − n F ( p ⊥ /√ s ), with n ≈8 and F ( p ⊥ /√ s )≈ exp (−26 p ⊥ /√ s ).
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Data on polarization in backward elastic π + p scattering at 2.0, 3.5 and 4.0 GeV/ c are presented. The data at 2.0 GeV/ c are compared with the result of a recent phase-shift analysis. Our data at 3.5 and 4.0 GeV/ c , and existing data above 3 GeV/ c , show no significant energy dependence of the polarization over the measured u -range. A comparison with Regge models and with results from amplitude analysis is made.
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