This analysis is based on data from neutrino and antineutrino scattering on hydrogen and deuterium, obtained with BEBC in the (anti) neutrino wideband beam of the CERN SPS. The parton momentum distrib
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Evidence is presented for diffractive production of ρ-mesons and of ρπ-systems invp and\(\bar \nu p\) chargedcurrent interactions. In the (anti-)neutrino energy range 10 GeV<Ev<60 GeV the cross sections for diffractive ρ and diffractive ρπ production are found to be (0.64±0.14 (stat.)±0.08 (syst.))% and (0.28±0.08 (stat.)±0.04 (syst.))% of the charged-current cross section. The diffractive ρπ signal is consistent with being entirely due to diffractivea1 production. However, the data cannot distinguish between diffractivea1 and diffractive nonresonant ρπ production. The experimental distributions ofW, Q2,xBj andyBj for diffractive ρ and ρπ events are consistent with model predictions.
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We report a study of electron proton collisions at very low Q 2 , corresponding to virtual photoproduction at centre of mass energies in the range 100–295 GeV. The distribution in transverse energy of the observed hadrons is much harder than can be explained by soft processes. Some of the events show back-to-back two-jet production at the rate and with the characteristics expected from hard two-body scattering. A subset of the two-jet events have energy in the electron direction consistent with that expected from the photon remnant in resolved photon processes.
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The total photoproduction cross section is determined from a measurement of electroproduction with the ZEUS detector at HERA. The Q 2 values of the virtual photons are in the range 10 −7 < Q 2 <2×10 −2 GeV 2 . The γp total cross section in the γp centre of mass energy range 186–233 GeV is 154 ± 16 (stat.) ± 32 (syst.) μ b.
Scattered electron in range 10 to 16 GeV.
The coherent production of π and ρ mesons in νμ (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 Tevatron quadrupole triplet (anti)neutrino beam. The νμ (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∓ coherent events and (19±7) μ±π∓π0 coherent events are extracted. For E>10 GeV, the coherent pion production cross section is determined to be (3.2±0.7)×10−38 cm2 per neon nucleus whereas the coherent ρ production cross section is (2.1±0.8)×10−38 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.
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Neutral strange particle production in\(\bar v\) 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)% forK0 mesons, (8.2±0.5)% for Λ, (0.4±0.2)% for\(\bar \Lambda \) and (0.6±0.3)% for Σ0 hyperons. The inclusive production properties ofK0 mesons and Λ hyperons are investigated. The Λ hyperons are found to be polarized in the production plane.
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Using data onvp and\(\bar vp\) charged current interactions from a bubble chamber experiment with BEBC at CERN, the average multiplicities of charged hadrons and pions are determined as functions ofW2 andQ2. The analysis is based on ∼20000 events with incidentv and ∼10000 events with incident\(\bar v\). In addition to the known dependence of the average multiplicity onW2 a weak dependence onQ2 for fixed intervals ofW is observed. ForW>2 GeV andQ2>0.1 GeV2 the average multiplicity of charged hadrons is well described by〈n〉=a1+a2ln(W2/GeV2)+a3ln(Q2/GeV2) witha1=0.465±0.053,a2=1.211±0.021,a3=0.103±0.014 for thevp anda1=−0.372±0.073,a2=1.245±0.028,a3=0.093±0.015 for the\(\bar vp\) reaction.
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The Fermilab 15-ft bubble chamber has been exposed to a quadrupole triplet neutrino beam produced at the Tevatron. The ratio of ν to ν¯ in the beam is approximately 2.5. The mean event energy for ν-induced charged-current events is 150 GeV, and for 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 1.2×10−3, and for momenta above 9 GeV/c this limit is 1.1×10−3. 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.
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The production of the meson resonances ϱ(770) (all three charge states), η(550), ω(783) andf2(1270) in\(\bar v\) Ne and ν Ne charged current interactions is investigated in a bubble chamber experiment with BEBC at CERN. Except for thef2, the main features of resonance production are reasonably well described by the Lund model, although the average resonance multiplicities are overestimated by the model by (67±30)%. The average multiplicities of all resonances, including thef2, are well reproduced by a semiempirical model, whose parameters were determined from hadron interaction data.
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Usind data from avp and\(\bar v\)p experiment with BEBC at CERN, the rates for inclusive production ofD*+,Λc+ andD0 invp scattering and ofD*− in\(\bar v\)p scattering are measured. Some examples of the exclusive production ofD*+,Λc+ and∑c++ are given. The cross section for the reactionvp→μ−c++ is estimated.
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