E. Lesquoy

Production of d, t, 3He, d, t and 3He by 200 GeV protons

Abstract Data are presented on the yields of d, t, 3He, d , t and 3 He with laboratory momenta between 12 and 37 GeV/c produced by 200 GeV protons on beryllium and aluminium. The production yield of nuclei depends significantly on the target nucleus, while the d production is independent of target material. The mass dependence of the production cross section is exponential for both nuclei and antinuclei.

Particle production and search for long-lived particles in 200–240 GeV/c proton-nucleon collisions

Data are presented on the relative yields of π±, K±, p, p, d, d, t, t, 3He and 3He produced at 0° by 200–240 GeV/c protons on beryllium and aluminium targets. A search for the production of long-lived particles with charges ±23, ±1, ±43 and ±2 is described. The upper limits at the 95% confidence level are of the order of 10−11 with respect to the production of known particles.

Properties of the inelastic K+p reactions between 1.2 and 1.7 GeV/c

The observation of 70 000 K0 pπ+ events produced with K+ incident momenta of 1.21, 1.29, 1.38 and 1.69 GeV/c allows a detailed description of the production and decay of the Δ(1236) and K∗(892) resonances which dominate the K0pπ+ final state. No striking variations with energy are observed. The associated production of Δ and K∗ near threshold shows striking similarities with the same production at higher energy.

Experimental study of Ko → π+ π− πo decays and search for CP violation

The time distribution of 180 uniquely identified π+π−πo decays of the Ko meson between 0.04 and 20 KSo lifetimes has been studied. We find that the ratio η+−o of the KSo→π+π−πo to the KLo →π+π−πo amplitude is consistent with no CP violation. Our results confine η+−o to ∼0 < Reη+−o < −2 with small negative values of Imη+−o. If we set Reη−o = 0, we obtain Imη+−o = 0.37−-.34+0.47. If in addition we use the known value of Γ(KLo → π+π−πo) we obtain Imη = −0.23−0.25+0.31. Without these restrictions, a more accurate determination of η+−o can only be made, with the present statistics, by a combination of Ko and Ko data. Assuming η+−o = 0, we find Γ(KLo → π+π−πo = (2.35 ± 0.20) × 106 s−1.

Experimental study of the selection rule ΔS = ΔQ in Koe3 and Koμ3 decays

We have studied the time distribution of semi-leptonic decays of the neutral K meson produced in a hydrogen bubble chamber in the reaction K+p → Kopπ+ with K+ momenta between 1.2 and 1.7 GeV/c. We have identified 306 πev decays and 74 πμv decays of known lepton charge with proper times between 0.04 and 20 KS lifetimes. The results are compatible with no violation of the ΔS = ΔQ rule. For the ratio x of the ΔS = −ΔQ amplitude to the ΔS = ΔQ amplitude we find the values +0.06+0.13inKe3decays:Re⁡xe=0.05inKμ3decays:Re⁡xμ=0.10−0.07−0.16+0.06+0.16Im⁡xe=0.08Im⁡xμ=−0.03−0.07,−0.18. Assuming ΔS = ΔQ we find the rate Γ(KoL → πev + πμv) = (12.4 ± 0.7) × 106 s−1.

Measurement of the KSO mean life

We have measured theKSO mean life using a sample of 50 000 KO → π+π− decays in a hydrogen bubble chamber. We obtain τ = (0.8958 ± 0.0045) × 10−10 s. This value is significantly higher than the present world average of τ = (0.862 ± 0.006) × 10−10 s.

Search for CP-violation in K0 → π+π−π0 decays

Abstract We have studied the time distribution of π + π − π o decays of the neutral K meson produced in the reaction K + p → K o pπ + with K + momenta at 1.4 and 1.7 GeV/ c . Within our fiducial volume we have 98 uniquely identified π + π − π o decays with proper times between 0.04 and 20 K s lifetimes. For the ratio η +− o of the amplitude K s → π + π − π o to the amplitude K L → π + π − π o , it is found that: Re η +−0 = 0.01 ± 0.22 0.20 , Im η +−o = 0.33 ± 0.42 0.50 . This result is consistent with no CP -violation. Assuming η +− o = 0, we find the rate Г( K L → π + π − π o ) = (2.5 ± 0.3) 10 6 sec −1 .

Production of π±, K±, p and p̄ by 200 GeV/c protons

Abstract Data are presented on the relative yields of π ± , K ± , p and p with momenta between 6 and 37 GeV/ c produced at 0° by 200 GeV/ c protons on beryllium and aluminium.

Measurement of the KS0 → π+π−γ decay rate

Abstract From a study of 70 000 K° decays in the CERN 2m hydrogen bubble chamber, we have estimated the rate for KS0 → π+π−γ for different cuts in the γ momentum. The results are in good agreement with inner bremsstrahlung on KS0 → π+π−. For γ momentum in the K° c.m. greater than 50 MeV/c, we obtain the branching ratio: Γ(KS → π+π−γ, k>50 MeV/c)/Γ(KS→π+π−)=(2.8. ± 0.6)×10−3. This leads to an estimate for the direct γ emission process: Γ(KS→π+π−γ direct)/Γ(KS → π+π−)=(0.3 ± 0.6) × 10−3.

Search for long-lived particles in 200 GeV/c proton-nucleon collisions

A search for long-lived particles (τ ≳ 10−8 sec), with changes ±23, ± 1, ±43 and ± 2, produced in 200 GeV pN collisions was performed at the CERN-SPS in a secondary beam equipped with superconducting r.f. separators. Upper limits were obtained for the production of long-lived hadrons and leptons. For charge - 1 particles the limits are at the level of 10−7 of the pions at a mass m = 0.2 GeV and reach the 10−11 level from 3 to 8 GeV. The production of light antinuclei was measured. The cross sections for 3He production are (1.3 ± 0.3) and (1.9 ± 0.3) × 10−34 cm2/sr · GeV/c at 21 and 47.4 GeV/c respectively; for t the cross section is (7.6 ± 0.9) × 10−34 cm2/sr · GeV/c at 23.7 GeV/c.