M. Coupland

Direct observation of the decay of beauty particles into charm particles

Abstract The associated production of a pair of beauty particles B− and B 0 by a 350 GeV π− interaction has been observed in an emulsion target inserted in an array of silicon microstrip detectors. Both beauty particles decay into charm particles, both of which are also observed to decay in the emulsion. Two negative muons were identified and their momenta measured in a large muon spectrometer. One muon has a pT of 1.9 GeV/c and is associated with a beauty particle decay. The other, with a pT of 0.45 GeV/c is associated with a charm particle decay. The flight times of the two beauty particles are respectively (0.8 ± 0.1) × 10−13 s and (5+2−1) × 10−13 s. Alternative interpretations of this event have negligible probability.

THE DOUBLE ASSOCIATED PRODUCTION OF CHARMED PARTICLES BY THE INTERACTION OF 350 GEV/C PI-MESONS WITH EMULSION NUCLEI

Abstract Evidence is reported for the simultaneous production of four charmed particles in interactions induced by 350 GeV/ c π − mesons in stacks of nuclear emulsions. The events were found during a search for beauty particles among a sample of about 200 interactions with candidates for charmed particles. The events selected required the presence of at least one muon with a high component of momentum transverse to the beam direction.

The production of beauty particles in π−-U interactions at 320 GeV energy

Abstract B B production in π − -uranium interactions has been observed at 320 GeV beam energy looking at events with three muons in the final state. The cross section is found to be σ B B = 4.5±1.4±1.4 nb per nucleon (for a linear A -dependence) or σ B B = 17.6±5.5±5.5 nb per nucleon (assuming A 0.75 dependence). An estimate of x F distribution is given.

A Hybrid Experiment to Search for Beauty Particles

We give here a detailed description of experiment WA75, which was performed at CERN to search for beauty particles. Events containing at least one muon with a high momentum transverse to the beam direction were selected; then the primary interactions and decay vertices, located in stacks of nuclear research emulsions, were examined and analysed. The various parts of the apparatus are described and the off-line analysis and search in emulsion are discussed. An estimate is made of the sensitivity of the experiment to beauty- and charmed-particle production.

Experimental study of uranium-scintillator and iron-scintillator calorimetry in the energy range 135–350 GeV☆

Abstract Results are reported of measurements made using a sampling hadronic calorimeter in the energy range 135–350 GeV. The responses to hadronic showers at various energies using iron and uranium of different thicknesses as absorbers have been compared. The results obtained in iron are in substantial agreement with the existing data, while those in uranium show an unexpected overcompensation in the hadronic response. Direct measurement of the e π ratio is in agreement with this statement.

Experimental study of BB production π-U interactions at 320 GeV energy

Abstract A sample of 29 gu + υ + 35 υ − υ − coming from B B decay have been observed in π -U interactions at 320 GeV energy. The experimental distributions and the total cross section are found to be in good agreement with QCD predictions. The effect of B 0 B 0 mixing is discussed.

BB inclusive cross section in 320 GeV π−-uranium interactions

Abstract The inclusive cross section for B B production by 320 GeV π− on uranium has been measured, assuming different production models and a variable amount of B0− B 0 mixing. A comparison of our results with those of the NA10 Collaboration is performed. The J/Ψ inclusive production cross section has also been measured in our experiment and agrees well with existing data, thus confirming the accuracy of our overall normalization.

A Muon Spectrometer With Calorimeter Dump Used for the Beauty Search at the {CERN} Super Proton Synchrotron

Abstract A detailed description is given of the WA78 apparatus, which combines a dump calorimeter and a muon spectrometer and is used to measure the cross-section for B B production by a high-intensity 320 GeV π − beam. The performance of the various parts of the equipment is discussed. In particular, we consider all the problems related to the calorimetric measurement in high-rate conditions.

An attempt to observe directly beauty particles in nuclear emulsions

Abstract An attempt at the direct observation of the cascade decay of beauty particles, produced by π − of 350 GeV / c leading to 3 muons or 4 muons in the final state, has been made in an emulsion/counter hybrid experiment at CERN. Under the assumption that the lifetime of beauty particles is of the order of 10 −13 s the non-observation of any candidates provides an upper limit for beauty production of ∼90 nb at the 90% confidence level.

A-dependence of low-mass muon pair production in 300 GeV/c p and 320 GeV/cπ− interactions

Abstract The A-dependence of inclusive μ+μ− production is measured in the kinematical region 2mμ⩽m(μ+μ−) ⪅1.5 GeV/c2, 0.1≲xF(μ+μ−) ≲0.6, using a 300 GeV/cp beam and a 320 GeV/cπ− beam, on Al, Fe, and U targets. Assuming that the production cross section varies as Aα, we obtain α=0.68±0.03−0.05+0.02 for the beam and α=0.8+-0.02−0.05+0.02 for the the π− beam.