J/ ψ production at 40 GeV/ c by π ± , K ± , p and p incident on hydrogen has been studied and results compared with those obtained on tungsten in the same experiment. On hydrogen, J/ψ cross-section ratios relative to π − have been measured to be (for x F > 0) σ(π − ) : σ(π + ) : σ( p ) : σ( p ) = 1 : (0.78 ± 0.09) : (0.83 ± 0.35) : (0.07 ± 0.04) . The suppression of the proton induced cross sections shows the importance of calence quark-antiquark fusiin J/ψ production at this energy (i.e. M J 2 / ψ / s =0.13).
ERRORS ONLY STAT.
ERRORS ONLY STAT.
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Data at nine π+ momenta are presented in the following three-body final states: Σ+K+π0, Σ+K0π+, Σ0K+π+, ΛK+π+, pK+K¯0. The data consist of cross sections, Dalitz plots, and angular distributions for the quasi-two-body final state Y*+(1385)K+. In the channel Y*+(1385)K+ the production and Y* decay distributions are compared with the predictions of Stodolsky and Sakurai.
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EVENTS ABOVE BACKGROUND - NO FIT.
DATA VALUES TAKEN FROM PDG2 CHEW 73B COMPILATION WHICH READ THEM FROM THE GRAPH AND CONVERTED TO MUB. BACKGROUND NOT SUBTRACTED.
Based on a sample of 22 four-prong D 0 / D 0 decays produced in hydrogen by 360 GeV/ c π − , we present the following new results: mean lifetime τ = (3.5 −0.9 +1.4 ) x 10 −13 s ; production cross section for x F > 0.0, σ = (10.3 ± 3.5) ωb ; the D → K ± π ± π + π − branching ratio = (7.1 ± 2.5)%.
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The production of the f 0 (1270) has been studied in the reaction π − p → π + π − n at 12 and 15 GeV/ c in the momentum transfer range 0.02 to 0.80 GeV 2 . Differential and total cross sections for the reaction π − p → f 0 n have been determined. The f 0 decay density matrix elements have been evaluated requiring all the matrix eigenvalues to be non-negative. The relative unnatural and natural parity exchange contributions to the f 0 production have been studied. The results are compared with a Regge exchange model formulated in terms of the pion and A 2 exchanges including cut contributions.
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We have analyzed the two-prong final states in π+p interactions at 3.9 GeVc. Our result for elastic scattering is σ (elastic) = 6.50±0.1 mb (statistical error only). We find the elastic slope to be 6.61±0.14 (GeVc)−2. We find the elastic forward cross section to be 40.0±1.4 mb(GeVc)2. We have applied a longitudinal-momentum analysis to the one-pion-production channel. We find the cross section for the reaction π++p→π++π0+p to be 2.30±0.06 mb and that for π++p→π++π++n to be 1.45±0.05 mb. For resonance-production cross sections in these channels we find Δ(1236)=0.60±0.07 mb, ρ(760)=0.86±0.06 mb, and diffraction dissociation = 1.69±0.11 mb. We find that we can satisfactorily fit all distributions in the one-pion-production channel without assuming any phase-space production. In the missing-mass channel we observe dominant Δ++(1236) production plus evidence for A2+ production.
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Data on the reaction π − p → π + π − π 0 have been taken at 12 and 15 GeV/ c with the CERN Omega multiparticle spectrometer. In a 3-pion partial-wave analysis strong production of A 2 0 (1310) and ω ∗ (1675) is observed. Total and differential cross sections are determined and density matrix elements presented as a function of t in the t - and s -channel frames. The energy dependence of A 2 0 production is studied, and a comparison of ω(780), A 2 0 (1310) and ω ∗ (1675) production is made.
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We have observed the D(1285), E(1420) and δ(975) mesons produced in 12 and 15 GeV/ c π − p interactions at the CERN Omega Spectrometer. Production cross sections and decay branching ratios are presented. Analysis of the decay D(1285) → δ (975) π favours a spin-parity assignment of 1 + .
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CORRECTED FOR DECAY MODES OTHER THAN <ETA PI+ PI-> AND FOR THE UNOBSERVED PARTS OF THE T-DISTRIBUTION.
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We report on a measurement for the branching-ratio X 0 → 2γ X 0 ar all. Our result is X 0 → 2γ X 0 → all = (2.9 ± 0.9)% .
BY COMPARISON WITH THE KNOWN ETA PRODUCTION CROSS SECTION.
The production of ρ 0 (770) and f(1270) is studied in π − p interactions at 16 GeV/ c . By comparison with inclusive K ∗0 production in the reaction K − p → K ∗0 + anything, and with inclusive ρ 0 production in the reaction pp → ρ 0 + anything, it is found that the data can be interpreted in terms of two production processes: the central production of resonances and the fragmentation of the beam particle. For the π − p reaction, the inclusive ρ 0 beam fragmentation cross section is 3.1 ± 0.3 mb while that for central production is 1.6 ± 0.5 mb. The ρ 0 central production cross section is consistent with increasing with energy as ln s behaviour. The ratio of ρ 0 to π − inclusive cross sections (excluding the leading π − ) is ∼0.2, independent of energy. The ρ 0 to π − ratio increases as a function of p T to a constant value of ∼ 1 2 above 1 GeV/ c . The ρ (charged and neutral) and f decays account for (25 ± 4)% and (1.4 ± 0.3)%, respectively, of all pions produced.
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We have studied the reactionspp→ppπ+π-,K+p→K+pπ+π−π, π+p→ π+,pπ+π− and π−p →π+π− at 147 GeV/c using the 30-inch Fermilab hybrid system. All four reactions were detected with the same apparatus and analyzed in the same way. The energy dependence of the channel cross section was found to beAp−0.6+B for thepp reaction andAp−1+B for the other three. About 90% of the cross section at 147 GeV/c can be accounted for by either beam or target diffraction. Some of the remaining cross section may come from double Pomeron exchange reactions which we tried to isolate. We have tested the hypothesis of a factorizable Pomeron and our data indicates a violation of this hypothesis. We show that the 3π mass enhancement in the mass region 1.2–1.4 GeV is diffractively produced in the π± beam reactions. Fourprong, four-constraint and six-prong, four-constraint cross sections are reported.
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CROSS SECTIONS FOR DIFFRACTION DISSOCIATION OF BEAM. FEYNMAN X OF OUTGOING PROTON <-0.96.
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