C. Hebert

Nuclear interactions of 400 GeV protons in emulsion

Abstract We report on 400 GeV proton-emulsion nucleus reactions and compare the results to hadron-nucleus reactions at smaller energies. In particular we present results on the emission of fast target protons (essentially grey track particles) and on their correlation with the number of collisions inside the nucleus, ν, with the number of charged evaporated particles (essentially black track particles) and with the number of pions produced (essentially shower particles). We observe that the main features of the 200–400 GeV data are very similar. However, we find that the mean shower-particle multiplicity at 400 GeV is essentially higher than expected from the simple independent particle model prediction 〈ns〉 = 〈nch〉[1 + 0.5(〈ν〉 − 1)]. The shower particle multiplicities do not seem to follow a target mass dependence of the form 〈ns〉 = 〈nch〉 Aα with α = 0.14 or α = 0.19 as has been suggested in the literature. The pseudo-rapidity distribution shows limiting target and projectile fragmentation. The shower-particle multiplicity in the “central region” increases linearity with 〈ν〉 but faster than 0.5〈ν〉 times the corresponding multiplicity in pp reactions.

Cross-sections for Neutrino Production of Charmed Particles

Abstract We have found 122 charmed-particle decays among 3855 neutrino interactions located in the fiducial volume of a hybrid emulsion spectrometer installed in the Fermilab wide-band neutrino beam. We obtain an average relative charmed-particle production cross section of σ(ν μ → c μ − ) σ(ν μ →μ − ) =4.9 −0.6 +0.7 % , at an average neutrino energy of 22 GeV. We also obtain a production rate of σ(ν μ → c c ν μ ) σ(ν μ →ν μ ) =0.13 −0.11 +0.31 % , if we assume that there was an undetected muon, a limit of σ(ν μ → c c μ − ) σ(ν μ → c μ − ) CL ) can be obtained. Other cross section ratios and limits are also presented.

Measurement of the D+, F+, and Lambda(c)+ Charmed Particle Lifetimes

From the analysis of 685 neutrino and antineutrino interactions in an emulsion target, fifteen candidates for the multiprong decay of charged charmed particles are found. This Letter presents liketimes for the D/sup + -/, F/sup + -/, and ..lambda../sub c//sup +/ states based on the fitted events of the sample.

EXPERIMENTAL DETAILS ON LIFETIME MEASUREMENTS OF NEUTRINO PRODUCED CHARMED PARTICLES IN A TAGGED EMULSION SPECTROMETER

Abstract A new type of hybrid appaatus, which consisted of an emulsion target and a magnet spectrometer, was successfully used in an experiment to measure lifetimes of charmed particles produced by the wide-band neutrino beam from 350 GeV protons at Fermilab. The emulsion target was essential to find short distance decay vertices andthe counter spectrometer was used both to localize the neutrino events in the emulsion and also to identify the particles from weak decays and those produced in the neutrino interactions. Newly introduced emulsion techniques such as the changeable sheet as a low background interface to couple the emulsion target with the counter spectrometer, and the single track followback method to locate interaction and decay vertices in the emulsion, were proved to be very powerful. Details of the experimental apparatus and of the method of analysis employed are described.

Nuclear interactions of 200 GeV protons in emulsion

Abstract Proton-nucleus interactions have been studied in nuclear emulsion exposed to the NAL 200 GeV proton beam. The inelastic mean free path is found to be 35.5 ± 0.8 cm and the average shower particle multiplicity is 12.9 ± 0.2. The angular distribution reveals some characteristics features of proton-nucleus interactions.

Charmed hadron production by neutrinos

Abstract Charmed hadron production has been studied using a hybrid emulsion spectrometer in the Fermilab wide-band neutrino beam. The relative rates of D0, D+, F+, and Λ+c production have been measured - the fraction of D mesons is 69 ± 8 10 % . Momentum, transverse momentum, Feynman X, and fragmentation (Z) distributions are presented. The mean Z for charmed hadrons is 0.59 ± 0.03 (±0.03). Charmed target fragments have been observed.

Production characteristics of charmed particles in neutrino interactions

Abstract Using a hybrid emulsion spectrometer installed in the Fermilab wide-band neutrino beam, we located a total of 3855 neutrino interactions in the fiducial volume of our target. For 122 charmed-particle decays found in these interactions, we present distributions of x , y , charm-muon angular projection, Feynman- X , and the fragmentation Z . We find that the number of strange quarks in the nucleon sea is 4.2±2.1±2.6% of the number of down quarks.

Two-particle rapidity correlations in proton-nucleus interactions at 300 GeV

Abstract The single- and two-particle inclusive rapidity distributions for proton-nucleus interactions at 300 GeV in nuclear emulsions are presented. The analysis of the data with the two-particle rapidity correlation function R ( ν 1 , ν 2 ) shows clear evidence of short range correlations. A remarkable asymmetry between projectile and target hemisphere is found.

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.

200 GeV Proton Interactions in Nuclear Emulsion

The mean‐free‐path for inelastic interactions of 200 GeV protons in nuclear emulsion has been measured using the techniques of along‐the‐track scanning and area scanning. The results obtained are, respectively, λinel = 35.3 ± 1.0 cm and λinel = 33.1 ± 1.5 cm. The average charged multiplicities have been found to be 〈ns〉 = 8.2 ± 0.2 for ‘white’ stars and 〈ns〉 = 12.9 ± 0.15 for all events. A plot of ns versus Nh (where Nh is the number of black and grey tracks) shows a linear relation over the region 0 ≤ Nh ≤ 25. The Castagnoli method applied to ‘white’ stars overestimates the C.M. energy by ∼ 40%, however, for stars with Nh ≥ 1, there is good agreement.