J.G. McEwen

Measurement of hadronic production of the χ1++(3507) and the χ2++(3553) through their radiative decay to Jϕ

Abstract The χ1++(3507) and the χ2++(3553) states have been observed in the Goliath spectrometer at the CERN SPS in 185 GeV/c π−-Be collisions. Their radiative decays contribute 27.7% (for the χ1++) and 12.8% (for the χ2++) to J ϕ production. At this energy, their cross sections are 65±19 nb and 96±29 nb, respectively

Production of J/ψ and ψ′ mesons in π−N scattering at 150 GeV/c

Abstract In a large-acceptance spectrometer, muon pairs and associated hadrons were observed with μμ masses up to 10 GeV/c2 and ΔM M = 0.015 resolution. We report here on the production of 4000 J/ψ and 80 ψ′ mesons.

High energy photoproduction of large transverse-momentum π0 mesons: A quantitative test of QCD

Abstract The first results on inclusive photoproduction of π 0 at transverse momenta up to 4 GeV/ c , using incident γ energies between 50 and 150 GeV are presented. A comparison is made with inclusive π 0 production obtained, in the same experiment, with incident π − . Using the π − data to parametrize the hadronic behaviour of the photon, significant differences are observed in quantitative agreement with QCD Compton scattering and corrections thereof.

A study of kinematical correlations between charmed particles produced in π-Cu interactions at s=26 GeV

Abstract A sample of 475 events, in which two charmed-particle decays are observed, is analyzed to determine distributions of two-particle kinematic variables. One charmed particle with x F > 0 is fully reconstructed and the other is at least partially recontructed. The distributions of Δo and p T 2 are compared with a next-to-leading order QCD calculation.

Meson mass spectrum near the X0 (958)

Abstract The meson mass spectrum near the X 0 (958) has been studied in the reaction π − + p → missing mass + n near threshold. A single peak, consistent with the X 0 , is seen. The mass obtained is 957.1 ± 0.45 MeV and the width is less than 1.9 MeV(95% C.L.).

Measurement of the beauty production cross section in 350 GeV / c π-Cu interactions

Abstract Using a sample of 108 triggered events, produced in π−−Cu interactions at 350 GeV/c, we have identified 26 beauty events. The estimated background in this sample is 0.6 ± 0.6 events. From these data, assuming a linear A-dependence, we measure a beauty production cross section integrated over all χF of 5.7−1.1+1.3 (stat.)−0.5+0.6 (syst.) nb/N.

Topological isolation of the deep inelastic QED Compton scattering

Abstract The NA14 photoproduction experiment, carried out at the CERN SPS, has measured the inclusive cross section of events with a prompt photon at high p T in the final state. Here we present a study of the topology of the final state of these events. The topology differs from that observed for events with an identified π 0 in the same kinematical domain. Using these differences we have extracted the contribution from the Born term to the inclusive prompt photon cross section. The result is in good agreement with theoretical predictions and supports the assignment of a fractional electric charge to the quarks.

Experimental estimate of the gluon structure function of the pion from J/Ψ production

Abstract In experiment WA11, preformed at the CERN Super Proton Synchroton, we have determined the shape of the gluon structure function of the pion to be (1−x1)1.9±0.3 from the longitudinal momentum distribution of 38000 J/Ψ produced by the collisions of negative pions of momentum 190 GeV/c with beryllium.

Search for the flavour-changing neutral-current decay D0 → μ+μ−

Abstract We have searched for the decay D 0 → μ + μ − among 2.0 × 10 5 μ + μ − pair produced, in the WA92 experiment, by 350 GeV/ c π − particles interacting in copper and tungsten targets. Using a high-resolution silicon-microstrip detector followed by a large-acceptance magnetic spectrometer and a muon filter we are able to measure the momentum of the muons, to visualize the event topology near their point of origin, and thus to discriminate between prompt and non-prompt muons. No D 0 → μ + μ − candidate has been found. This result allows us to set an upper limit on the branching fraction B( D 0 → μ + μ − ) of 4.1 × 10 −6 at 90 % confidence level.

WA92: A fixed target experiment to study beauty in hadronic interactions

Abstract The essential feature of the described experimental techniques is the use of two specially designed pieces of hardware: a high precision “decay detector” and a fast secondary vertex trigger processor. Experiment WA92 should be able to obtain a sufficient data sample to measure lifetimes of B ± and B 0 and the B hadroproduction cross section.