K. Niu

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.

Interactions of 60 and 200 A GeV 16O Ions in Nuclear Emulsion

A survey of the interactions of 16O nuclei of energies 60 and 200 A GeV in nuclear emulsions is presented. Correlations between projectile fragments and target evaporation are studied. The electromagnetic dissociation of 16O, mainly ascribed to absorption in the giant-resonance region, is found to contribute to a sizeable fraction of the cross-section, and increases with increasing energy.

Cross sections for charm production by neutrinos

The production of charmed particles has been measured using a hybrid emulsion spectrometer in the Fermilab wide-band neutrino beam. The relative cross section for charged current charmed particle production is σ(v → μ−c)/σ(v → μ−) = 6.5 ±1.91.8%, and the energy dependence of the cross section is presented. One event with charm pair production was observed. A limit of σ(v → μcc)/σ(v → μc) < 6% (90% CL) is found for the ratio of charged current pair and single charm production.

Interactions of 200 GeV/nucleon 16O and 32S ions in nuclear emulsions

Abstract This paper presents and contrasts features of the inelastic nuclear reactions of 200 GeV/nucleon 16O and 32S ions with emulsion nuclei. Both the multiplicities of shower particles and the extent of target fragmentation have been studied for varying degress of disruption of the projectile nuclei. The results may be interpreted within a simple geometrical model. In particular the rapidity distributions of those events which exhibit complete projectile break-up without any overt sign of low-energy target fragmentation have been determined. The interaction of secondary projectile fragments of charge two or more issuing from oxygen interactions were also studied and the mean free paths in emulsion of the primary 16O and 32S ions and all such fragments have been compared to those predicted by a simple Glauber model.

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.

The electromagnetic and hadronic diffractive dissociation of 16O ions

Abstract Events which satisfy the kinematics of p( 16 O,CHep), with low excitation energy in the (CHe) system and a low-energy recoil proton, have been identified in the interactions of 200 GeV/nucleon 16 O ions with nuclear emulsion. An eikonal DWIA estimate of the target A -dependence of strong-interaction diffractive dissociation suggests that, on the basis of these hydrogen data, most of the (CHe) final states, previously ascribed to electromagnetic dissociation on heavy nuclei, might rather be hadronic in character. This contamination is very much less important in the dominant (NH) channel.