D. Cundy

Observation of Neutrino Like Interactions Without Muon Or Electron in the Gargamelle Neutrino Experiment

Abstract Events induced by neutral particles and producing hadrons, but no muon or electron, have been observed in the CERN neutrino experiment. These events behave as expected if they arise from neutral current induced processes. The rates relative to the corresponding charged current processes are evaluated.

Search for elastic muon-neutrino electron scattering

Abstract One possible event of the process ν − μ + e − → v − μ + e − has been observed. The various background processes are discussed and the event interpreted in terms of the Weinberg theory. The 90% confidence limits on the Weinberg parameter are 0.1 2 θ W

First Evidence for Direct CP Violation

Since CP violation was first observed in the decay of the long-lived neutral kaon into two pions [1], it remains one of the enigmas in particle physics. Whilst CP violation is manifest in neutral kaon decays, the search for CP-violating effects has elsewhere been unsuccessful. In the phenomenology of CP violation in the neutral kaon system [2], the short- and long-lived mass eigenstates are usually defined in terms of the CP eigenstates K1 (CP = + 1) and K2 (CP = - 1) as Ks ≈ K1 + ?K2 and KL ≈ K2 + ?K1. The parameter ? describes CP violation induced by kaon state-mixing. Direct CP violation may also occur in the decay of K2 into two pions with a relative amplitude ?′, which is non-zero in the case of a phase difference between the amplitudes A0 and A2 for the decay into isospin O and 2 states of two pions. Before the present measurement, all experimental results were compatible with ? = 2.27 × 10-3 exp (i 43.70) and with the Superweak Model [3], in which state-mixing is the only source of CP violation and ?′ = 0. In the Standard Model with six weakly interacting quarks [4], direct CP violation as well as state-mixing is introduced by transitions via heavy-quark intermediate states. Based on this, a small, but non-zero, value of ?′ is predicted [5]. To a good approximation, ?′ /? is related to the double ratio R of the relative decay rates of the long- and short-lived neutral kaons into two neutral and two charged pions as Re (?′/?) = 1/6 × (1 - R).

Experimental Study of Atmospheric Neutrino Flux in the NUSEX Experiment

The fully contained events detected in the NUSEX nucleon stability experiment have been analysed to search for possible anomalies in the fluxes of atmospheric neutrinos. The measured flux of muon neutrinos is in very good agreement with predictions and no anomaly has been found in the ratio between the rate of electron and muon neutrino events.

Analysis of nucleon structure functions in CERN bubble chamber neutrino experiments

Abstract We present results for the differential cross sections of neutrinos and antineutrinos on nucleons in the energy range E = 2−200 GeV, from the BEBC and Gargamelle experiments. The structure functions F2, 2χF1 and χF3 have been evaluated as a function of χ and q2. Deviations are observed from Bjorken scaling, which are very similar to those found in electron and muon inelastic scattering. For the Callan-Gross ratio, we find 2χF 1 F 2 = 0.80 ± 0.12 and the corresponding value for 〈R〉 = 〈 σ S σ T 〉 = 0.15 ± 0.10 . Our results are consistent with the Gross-Llewellyn-Smith sum rule; we measure ⩾2.5 ± 0.5 valence quarks per nucleon. Quark and antiquark distributions are given. The Nachtmann moments of F2 and χF3 are quantitatively consistent with the predictions from QCD. The value of the strong interaction parameter is λ = 0.74 ± 0.05 GeV without corrections, and 0.66 ± 0.05 GeV including αS2 corrections. The moments of the gluon distribution are found to be positive and indicate an χ distribution of gluons which is comparable with that of the valence quarks.

Measurement of the neutrino--nucleon and antineutrino--nucleon total cross sections

Abstract The v and v nucleon total cross-sections have been determined as a function of energy using a sample of 2500 v and 950 v event. The results are compared with predictions of scaling and charge symmetry hypotheses.

A measurement of the phases of the CP-violating amplitudes in K0→2π decays and a test of CPT invariance

Abstract The phases of the CP-violating amplitudes in K0→π+π− and K0→2π0 decays, φ+−=46.9°±2.2° and φ00=47.1°±2.8°, have been measured in the same experiment, and a direct comparison gives the phase difference φ00−φ+−=0.2°±2.9°. This result leads to an upper limit on possible CPT violation in the K0 mass matrix, of |(m K 0 −m K 0 )/m K 0 | −18 at the 95% confidence level and is the most stringent test of the equality of particle and antiparticle masses.

Observation of Prompt Neutrinos from 400-GeV Proton Nucleus Collisions

Abstract In 70 000 photos taken in BEBC during an experiment in which the 400 GeV proton beam of the CERN SPS was dumped into a massive Cu target 820 m upstream of BEBC, 70 interactions induced by neutral primaries above 10 GeV were observed. In 11 events the secondary charged lepton is an e − , in four events an e + . This number of electron events cannot be due to electron neutrinos from conventional sources (K, Λ, Σ − decays). The flux of the additional (prompt) neutrinos is evaluated. Possible origins are discussed in terms of charmed particles, τs, and as yet undiscovered particles. Limits are given on axion production.

Observation of neutrino-like interactions without muon or electron in the Gargamelle neutrino experiment

Events induced by neutral particles and producing only hadrons, but no muon or electron, have been observed in the heavy liquid bubble chamber Gargamelle exposed to neutrino (v) and antineutrino (v) beams at CERN. A study of the various sources which could give rise to such events reveals that less than 20% could be attributed to neutrons or KL°. The events behave as expected if they arise from neutral current processes induced by neutrinos and antineutrinos. The ratio of the number of these events to the number of corresponding events with charged lepton is 0.22 ± 0.04 for v and 0.43 ± 0.12 for v.

Observation of a time modulated muon flux in the direction of Cygnus X-3

Abstract The analysis of angular and phase distribution is reported for high energy muons recorded in the NUSEX nucleon decay detector, located in the Mont Blanc tunnel at a depth of about 5000 hg of standard rock. Evidence is found for a signal correlated to the direction and time modulation of Cygnus X-3.