Search

Evidence of the production of the Ds∗-(2111) meson in v μ Ne collisions is presented. The Ds∗- production rates the Ds−→φπ− branching fraction is estimated to be (2.3±0.7) × 10−3 of all charged currents having a hadronic mass W above 3 GeV.

Charged-current neutrino interactions have been analysed in a sample of pictures from BEBC equipped with a TST. Using a method independent of both the neutrino flux and nuclear interaction corrections, the ratio R= σn/σp has been measured. The result is R=1.98±0.19 for the ratio of total cross sections. Bjorken x distributions for proton and neutron targets and for u and d quarks are compared. © 1981., 0, SCOPUS: ar.j, info:eu-repo/semantics/published

A search for the purely leptonic neutral current process induced by antineutrinos: v μ + e − → v μ + e − , has been performed in the BEBC “TST” experiment. No contradiction has been observed with the Salam-Weinberg model.

Inclusive data for the production of γ rays and π 0 are presented from an experiment with a 4 GeV/ c π + beam, using a track-sensitive target. The results are compared with data at other energies and with π + and π − distributions.

We have investigated electron production in 4.0 GeV/ c π + pinteractions. Limits to direct electron pair production are measured and an example of ϱ 0 or ω 0 decay to e + e − is observed. The ratio of the number of singly produced electrons to the total number of charged pions is less than 6 × 10 -5 (at the 95% confidence level).

In a bubble chamber containing a neon-hydrogen mixture surrounding a hydrogen-filled track sensitive target, electrons with momenta above 100 MeV/ c are observed to have (1.25 ± 0.02) times more bubbles per unit length in neon-hydrogen than pions with momenta between 400 and 1500 MeV/ c . We interpret this difference as due to a relativistic rise in bubble density, such as has been observed previously in a freon bubble chamber. The total magnitude of the rise from minimum to plateau is estimated to be (28 ± 2)%. This should provide a method for distinguishing between relativistic pions, kaons and protons of the same momentum. It could in particular be exploited in high energy experiments using the track sensitive target technique in large bubble chambers such as BEBC.

First observation is reported of semi-inclusive coherent diffractive charged current interactions of antineutrinos on neon nuclei. A sharp peaking towards zero is observed in the, 0, SCOPUS: ar.j, info:eu-repo/semantics/published

Antineutrino interactions in BEBC are compared to look for differences between the differential cross sections per nucleon in neon and in deuterium. The identical geometries, beam spectra and muon identification criteria and acceptances allow comparison with very small systematic errors. The results are compared in detail with μ and e scattering data from EMC and SLAC. We find no rise in the ratio dσ/dx (ν Ne)/σ/dx (ν D2) at low x, independent of Q2 up to Q2 ∼ 14 GeV2. © 1984., 0, 58 auteurs, SCOPUS: ar.j, info:eu-repo/semantics/published

An event with the decay chain Σ c + → Λ c + + π 0 , Λ c + → K − + p + π + , has been observed in an exposure of BEBC, equipped with a track sensitive target, to the wide band neutrino beam from the SPS at CERN. The event has a unique three constraint kinematic fit to the ΔS = − ΔQ reaction v + p → μ − + p + K − + π + + π + + π 0 with both gammas from the π 0 decay detected. The proton and other final state particles are identified. The masses are M ( Λ c + ) = 2290 ± 3 MeV/ c 2 , M ( Σ c + ) = 2457 ± 4 MeV/ c 2 and M ( Σ c + ) − M ( Λ c + ) = 168 ± 3 MeV/ c 2 . Including other data one obtains M ( Σ c ++ ) − M ( Σ c + ) = 0 ± 4 MeV/ c 2 .

The Track Sensitive Target technique has been used to isolate 5000 events from the reaction π+p→π+pπ0π0 at 4 GeV/c. Channel cross sections are measured. The data agree with predictions from phase-shift analyses of π+π− data: the effect of the S∗ is clearly seen. There is strong evidence against any narrow ϵ below 1 GeV/c2.

For e + energy > 0.3 GeV and 10 GeV ƒ = (v μ + Ne → μ − e + )/(v μ + Ne → μ − ) = (0.41 ± 0.15)% ; (ii) 1.2 ± 0.5 neutral strange particles are produced per μ − e + event; (iii) the lifetime of possible positron-parent particles is −10 s (90% C.L.); (iv) the cross section for direct e + production via the neutral current is + , decaying into e + … is −3 times that for μ − production, implying M (L + ) > 10 GeV.

We have fully analysed all events with a single electron obtained in an exposure of BEBC to the 350 GeV wide-band neutrino beam at CERN. The data agrees well with expectations based on the calculated ν e flux and assuming μ−e universality. Using both the rate and the kinematic distributions, improved limits are set on ν e → ν X , ν μ → ν e , ν μ → ν τ mixing.

A study is presented of dimuon events from an exposure of BEBC to a wide band ν beam from the CERN SPS. These data double the available statistics on ν induced dilepton events observed in bubble chambers. The relative production rate and V0 yield have been measured and found to agree with previous experiments. The analysis of several kinematical variables shows that the gros features of the data agree with the predictions of the GIM model. Some indication exists that part of the signal could be due to quasi elastic production of the “beautiful baryon”, but the statistical significance is too weak to draw definitive conclusions. © 1980, All rights reserved., 0, SCOPUS: ar.j, info:eu-repo/semantics/published

A 2.1 GeV/ c K − exposure in a heavy-liquid bubble chamber has been used to search for the final state Y ∗ (1327) → Λγ . No evidence was found for the existence of this state; an upper limit is placed on the cross-section of the reaction K − + p → Y ∗ (1327) + π + + π − + nπ o , n ⩾ 0 .

In an experiment using a heavy liquid bubble chamber the Ξ hyperon lifetimes and α parameters were measured to be τΞo = (3.04 ± 0.230.26) × 10−10 sec, τΞ− = (1.73 ± 0.070.08) × 10−10 sec, αΞo = −0.84 ± 0.27 and αΞ− = −0.42 ± 0.11. These values agree with measurements which employed different techniques and are consistent with the predictions of the ΔI = 12 rule.

The S = −2 dibaryon states ΛΛ and Ξ − p have been studied with more than double previous statistics. Earlier indications of an enhancement at M ΛΛ = 2.37 GeV/ c 2 are not confirmed.

The reaction π+p → π+pπ0π0 is studied at an incident momentum of 4 GeV/c using the track-sensitive target technique. Peripheral Δ++π0π0 events are selected and comparisons made with predictions from π+π− data. These data allow a detailed analysis of the possible backgrounds contributing to the excess of events at low π0π0 masses.

SCOPUS: ar.j, info:eu-repo/semantics/published