Y. Homma

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.

Measurement of R and search for new heavy quarks in e+e- annihilation at 50 and 52 GeV centre-of-mass energies

Abstract The total cross section for the process of the e+e- annihilation into hadrons has been measured at the centre-of-mass energies of 50 GeV and 52 GeV and a search has been made for new heavy quarks. The ratios R = σ(e+e- → hadrons)/σpoint(e+e- → μ+μ-) obtained are 4.4±0.5 at 50 GeV and 4.7±0.3 at 52 GeV, respectively. An additional systematic uncertainty is 10%. From the event shape analysis we found no evidence for a new quark with charge 2 3 e .

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.

Measurement of the proton-antiproton pair production from two-photon collisions at TRISTAN

Abstract The cross section of the γγ → p p reaction was measured at two-photon center-of-mass energy (Wγγ) between 2.2 and 3.3 GeV, using the two-photon process at an e+e− collider, TRISTAN. The Wγγ dependence of the cross section integrated over a c.m. angular region of | cos θ ∗ | is in good agreement with the previous measurements and the theoreticalv prediction based on diquark model in the high Wγγ region.

Determination of the QCD scale parameter ΛMS with QCD cascade on the basis of the next-to-leading logarithmic approximation

Abstract The relative production ratio of 3-jet events to the total number of hadronic events was studied in e+e− annihilations at centre-of-mass energies between 54 and 61.4 GeV. The QCD scale parameter has been determined to be Λ MS =254 −47 +55 ±56 MeV on the basis of a QCD cascade with the next-to-leading logarithmic approximation.

Measurement of the differential cross sections ofe+e−→γγ ande+e−→γγγ at\(\sqrt s = 55,56,56.5\) and 57 GeV and search for unstable photino pair production

AbstractDifferential cross sections fore+e−→γγ have been measured at center-of-mass energies of 55, 56, 56.5 and 57 GeV. The results are in good agreement with those predicted by QED. Possible deviations from QED are studied in terms of contact interactions, and the limits on compositeness scales are obtained. Using events with a gramma pair in the final state, a search is made for the pair production of unstable photons,

Measurement of the Differential Cross-sections of

e^ + e^ - \to \tilde \gamma \tilde \gamma