[en] Coherent single-pion production on neon nuclei is studied using the Fermilab 15-ft bubble chamber filled with a heavy Ne-H₂ mixture and exposed to the Tevatron neutrino beam. In the neutrino energy range 40--300 GeV, the net signal is 20±6 events, giving a corrected rate per charged-current event of (0.26±0.10)%. The cross section and kinematic distributions agree with the predictions of a model based on partial conservation of axial-vector current and meson dominance

[en] Neutral strange particle production in anti ν Ne charged current interactions is studied using the bubble chamber BEBC, exposed to the CERN SPS antineutrino wide band beam. From a sample of 1191 neutral strange particles, the inclusive production rates are determined to be (15.7±0.8)% for K⁰ mesons, (8.2±0.5)% for Λ, (0.4±0.2)% for anti Λ and (0.6±0.3)% for Σ⁰ hyperons. The inclusive production properties of K⁰ mesons and Λ hyperons are investigated. The Λ hyperons are found to be polarized in the production plane. (orig.)

[en] The Fermilab 15-ft bubble chamber has been exposed to a quadrupole triplet neutrino beam produced at the Tevatron. The ratio of ν to bar ν in the beam is approximately 2.5. The mean event energy for ν-induced charged-current events is 150 GeV, and for bar ν-induced charged-current events it is 110 GeV. A total of 64 dimuon candidates (1 μ⁺μ⁺, 52 μ^-μ⁺ and μ⁺μ^-, and 11 μ^-μ^-) is observed in the data sample of approximately 13 300 charged-current events. The number and properties of the μ^-μ^- and μ⁺μ⁺ candidates are consistent with their being produced by background processes, the important sources being π and K decay and punchthrough. The 90%-C.L. upper limit for μ^-μ^-/μ^- for muon momenta above 4 GeV/c is 1.2x10^-3, and for momenta above 9 GeV/c this limit is 1.1x10^-3. The opposite-sign-dimuon--to--single-muon ratio is (0.62±0.13)% for muon momenta above 4 GeV/c. There are eight neutral strange particles in the opposite-sign sample, leading to a rate per dimuon event of 0.65±0.29. The opposite-sign-dimuon sample is consistent with the hypothesis of charm production and decay

[en] The coherent production of π and ρ mesons in ν_μ(bar ν_μ)--neon charged-current interactions has been studied using the Fermilab 15-foot bubble chamber filled with a heavy Ne-H₂ mix and exposed to the Teva- tron quadrupole triplet (anti)neutrino beam. The ν_μ (bar ν_μ) beam had an average energy of 80 GeV (70 GeV). From a sample corresponding to approximately 28 000 charged-current interactions, net signals of (53±9) μ^±π^minus-plus coherent events and (19±7) μ^±π^minus-plusπ⁰ coherent events are extracted. For E>10 GeV, the coherent pion production cross section is determined to be (3.2±0.7)x10^-38 cm² per neon nucleus whereas the coherent ρ production cross section is (2.1±0.8)x10^-38 cm² per neon nucleus. These cross sections and the kinematical characteristics of the coherent events at |t|<0.1 GeV² are found to be in general agreement with the predictions of a model based on the hadron dominance and, in the pion case, on the partially conserved axial-vector current hypothesis. Also discussed is the coherent production of systems consisting of three pions

[en] A study has been made of neutral strange particle production in ν_μNe and bar ν_μNe charged-current interactions at a higher energy than any previous study. The experiment was done at the Fermilab Tevatron using the 15-ft. bubble chamber, and the data sample consists of 814(154) observed neutral strange particles from 6263(1115) ν(bar ν) charged-current events. For the ν beam (average event energy left-angle E_ν right-angle=150 GeV), the average multiplicities per charged-current event have been measured to be 0.408±0.048 for K⁰, 0.127±0.014 for Λ, and 0.015±0.005 for bar Λ, which are significantly greater than for lower-energy experiments. The dependence of rates on kinematical variables has been measured, and shows that both K⁰ and Λ production increase strongly with E_ν, W², Q², and y_B. Compared to lower-energy experiments, single-particle distributions indicate that there is much more K⁰ production for x_F>-0.2, and the enhanced Λ production spans most of the kinematic region. bar Λ production is mostly in the region |x_F|<0.3. The Lund model is shown to be in qualitative agreement with the data, but does not reproduce single-particle distributions in detail. For x_F>-0.2 there is a significant excess of Λ production over the model's prediction. The Λ hyperons are found to be polarized in the production plane

[en] From an exposure of the Fermilab 15-foot bubble chamber to the Tevatron quadrupole triplet neutrino beam, we have determined the ratio of neutral-current (NC) to charged-current (CC) interactions to be 0.288±0.032 for events with visible hadron momentum above 10 GeV/c. The mean ν(bar ν) event energy is 150 (110) GeV, which is higher than that for any previous beam. This result agrees with those from previous experiments at lower energies. The NC/CC ratio is derived for a combined sample of ν and bar ν events. A value of 0.274±0.038 is obtained for the dominant ν component assuming bar ν NC/CC=0.39±0.08. For events with visible hadron momentum above 25 GeV/c, where the neutral hadron contamination remaining in the NC sample is assumed to be negligible, the combined NC/CC is 0.323±0.025 and the K⁰ production rates are 0.375±0.064 per CC and 0.322±0.073 per NC event. The corresponding Λ rates are 0.161±0.030 per CC and 0.113±0.030 per NC event. The K⁰ and Λ distributions of the fractional hadron energy variable z in NC events are consistent with those in CC events

[en] The total cross section for the photoproduction process with a leading proton in the final state has been measured at γp centre-of-mass energies W of 91, 181 and 231 GeV. The measured cross sections apply to the kinematic range with the transverse momentum of the scattered proton restricted to p_T≤0.2 GeV and 0.68≤z≤0.88, where z=E_p'/E_p is the scattered proton energy normalised to the beam energy. The cross section dσ_γp→Xp'(W,z)/dz is observed to be independent of W and z within the measurement errors and amounts to (8.05±0.06 (stat)±0.89 (syst)) μb on average. The data are well described by a Triple Regge model in which the process is mediated by a mixture of exchanges with an effective Regge trajectory of intercept α_i(0)=0.33±0.04 (stat)±0.04 (syst). The total cross section for the interaction of the photon with this mixture (γα_i→X) can be described by an effective trajectory of intercept α_k(0)=0.99±0.01 (stat)±0.05 (syst). Predictions based on previous triple Regge analyses of pp→pX data assuming vertex factorisation are broadly consistent with the γp data. The measured cross sections are compared with deep inelastic scattering leading proton data in the same region of z and p_T for photon virtuality Q²>2.5 GeV². The ratio of the cross section for leading proton production to the total cross section is found to rise with Q²

[en] A measurement of the inclusive ep scattering cross section is presented in the region of low momentum transfers, 0.2 GeV²≤Q²≤12 GeV², and low Bjorken x, 5.10^-6≤x≤0.02. The result is based on two data sets collected in dedicated runs by the H1 Collaboration at HERA at beam energies of 27.6 GeV and 920 GeV for positrons and protons, respectively. A combination with data previously published by H1 leads to a cross section measurement of a few percent accuracy. A kinematic reconstruction method exploiting radiative ep events extends the measurement to lower Q² and larger x. The data are compared with theoretical models which apply to the transition region from photoproduction to deep inelastic scattering. (orig.)

[en] Events with high energy isolated electrons, muons or tau leptons and missing transverse momentum are studied using the full e^±p data sample collected by the H1 experiment at HERA, corresponding to an integrated luminosity of 474 pb^-1. Within the Standard Model, events with isolated leptons and missing transverse momentum mainly originate from the production of single W bosons. The total single W boson production cross section is measured as 1.14±0.25(stat.)±0.14(sys.) pb, in agreement with the Standard Model expectation. The data are also used to establish limits on the WWγ gauge couplings and for a measurement of the W boson polarisation. (orig.)

[en] A measurement of the inclusive deep inelastic neutral current e⁺p scattering cross section is reported in the region of four-momentum transfer squared, 12 GeV²≤Q²≤150 GeV², and Bjorken x, 2 x 10^-4≤x≤0.1. The results are based on data collected by the H1 Collaboration at the ep collider HERA at positron and proton beam energies of E_e=27.6 GeV and E_p=920 GeV, respectively. The data are combined with previously published data, taken at E_p=820 GeV. The accuracy of the combined measurement is typically in the range of 1.3-2%. A QCD analysis at next-to-leading order is performed to determine the parton distributions in the proton based on H1 data. (orig.)