M. Rollier

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

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.

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 an excess of νe, νe events in a beam dump experiment at 400 GeV

Abstract A beam dump experiment has been performed at CERN in Gargamelle using the neutrino facility to look for penetrating particles produced either directly in the beam interaction or by prompt decay of new particles. A total of 32 interactions with a visible energy greater than 10 GeV has been found, classified, aftercorrections, into 18 charged current ν μ or ν μ , 5.1 neutral current and 8.9 ν e or ν e charged current events. An excess of ν e events remains after all subtractions from any established sources. Results are presented in terms of the product of the cross section and the leptonic decay branching ratio of the possible source.

Observation of an Excess of electron-neutrino, anti-electron-neutrino Events in a Beam Dump Experiment at 400-GeV

Abstract A beam dump experiment has been performed at CERN in Gargamelle using the neutrino facility to look for penetrating particles produced either directly in the beam interaction or by prompt decay of new particles. A total of 32 interactions with a visible energy greater than 10 GeV has been found, classified, aftercorrections, into 18 charged current ν μ or ν μ , 5.1 neutral current and 8.9 ν e or ν e charged current events. An excess of ν e events remains after all subtractions from any established sources. Results are presented in terms of the product of the cross section and the leptonic decay branching ratio of the possible source.

Charged current elastic antineutrino interactions in propane

Abstract A sample of 766 antineutrino charged current elastic events has been used to extract the variation of the elastic cross section with antineutrino energy and the distribution of d N /d q 2 . The best fit value for the parameter M A obtained from these measurements is M A = 0.91 ± 0.04 GeV/ c 2 for M V = 0.84 GeV/ c 2 . A simultaneous determination of M A and M V gives M A = 0.94 ± 0.07, M V = 0.81

Production of strange particles in antineutrino interactions at the CERN PS

Abstract We have studied neutral strange particle production in the bubble chamber Gargamelle filled with propane and exposed to antineutrinos from the CERN PS. Cross sections are presented for Λ, Σ0 and K0 production. Associated production reactions (ΔS = 0) have been observed in the charged and the neutral current channels. From 45 candidates for the quasi-elastic reaction ν p → μ + Λ , on bound and free protons, estimates of the axial transition form factor MA have been made using the total cross section and the t distribution. The weighted average from the two methods is MA = 862 ± 190 MeV. From a subsample of 15 candidates for ν interactions on free protons in propane, with (28±6)% background from ν interactions on bound protons, we obtain MA = 883 ± 243 MeV. The polarization of the Λ hyperons has been studied for the quasi-elastic reaction. We observe a significant Λ polarization in the production plane, normal to the Λ line of flight. The observed polarizations agree well with the predicted theoretical polarizations without any contribution from second-class axial coupling.

ANTINEUTRINO-NUCLEON TOTAL CROSS-SECTION AND RATIO OF ANTINEUTRINO CROSS-SECTION ON NEUTRONS AND PROTONS

Abstract On a selected sample of 2171 events, observed in the big heavy liquid bubble chamber Gargamelle at CERN, the charged current total cross section for antineutrino on nucleons has been determined up to the laboratory energy E v = 8 GeV . The total cross section is found to be a linear function of the antineutrino energy expressed by σ tot (E v ) = (0.26 ± 0.020) × 10 −38 × E v ( GeV ) cm 2 . The energy dependence of 〈q 2 〉 v is found to be given by 〈q 2 〉 v = (0.15 ± 0.04)E v + (0.05 ± 0.12) ( GeV /c) 2 . With a simplified nuclear model the ratio of cross sections on neutrons andprotons has been estimated as a function of energy and for two different values of the scaling variable x . The results are compared with the prediction of the naive quark parton model.

Experimental results on one-pion neutral current reaction in all channels induced by antineutrinos at CERN PS

Single pion production, in antineutrino-nucleon interactions via the neutral current, has been studied in the bubble chamber Gargamelle, filled with propane. Complete analysis of the secondaries, including π0,s, has allowed a detailed study of all channels. After background and nuclear corrections, results are obtained which can be interpreted in terms of isospin structure of the neutral weak current and of the Salam-Weinberg angle. Agreement is found with the currently accepted value of sin2θW and the data suggest an important contribution of I = 32 final states.