A peak is reported in the ηπ + π − system, produced in the reaction γ p→ ηπ + π − p, at a mass of 1.28 ± 0.01 GeV with a width of 0.08 ± 0.02 GeV. Possible spin-parity assignments for the peak are shown to be J π = 1 − , J π = 1 + or J π = 2 + and interpretations of these assignments are discussed.
No description provided.
No description provided.
The reactions γ p→K + K − π 0 (p) and γ p→ K s 0 K ± π ± (p) have been measured using tagged photons in the energy range 20 to 70 GeV. No resonance structure is observed in either of the K K π invariant mass distributions, which range from threshold up to ∼ 3 GeV. The photoproduction cross sections for φπ 0 and K ∗ (892)K are presented and are compared with theoretical predictions. No evidence has been found for the photoproduction of φ′ (1680).
No description provided.
No description provided.
NO EVIDENCE FOR RESONANT STRUCTURE AT PHIPRIME(1680).
Results on photoproduction of π + π − π 0 in the photon energy range 20–70 GeV are presented. For the ω meson, the production cross-section is found to be 1010±15 (statistical)±290 (systematic) nb and is constant over the incident photon energy range. Spin-density matrix elements are evaluated for ω meson production. The φ meson is observed with a total photoproduction cross section (corrected for branching ratio to π + π − π 0 ) of 610±35±170 nb. A third resonance, at 1.67 GeV, is seen in the mass spectrum and its interpretation is discussed. The production of a broad π + π − π 0 continuum, mainly via ϱπ, and peaking at 1.2 GeV, contributes with a cross section of about 2.5 ωb. The spin-parity content is analysed by the moments of the π + π − π 0 decay angular distribution in the helicity frame and by maximum likelihood fits to the π + π − π 0 Dalitz plot. It is found that production of J P = 1 − states accounts for less than half of the total mass spectrum above 900 MeV. There is a broad enhancement in the 1 + wave around 1.15 GeV indicating photoproduction of the H(1190) meson.
No description provided.
EXPONENTIAL FITS TO D(SIG)/DT IN OMEGA MASS REGION.
EXPONENTIAL FITS TO D(SIG)/DT OVER FULL ENERGY FOR THREE MASS REGIONS CORRESPONDING TO OMEGA, PHI AND OMEGA*.
Measurements of the reaction γ p → p ωπ + π − are reported for photon energies 25–50 GeV. Particular attention is paid to ωπ + π − masses < 2 GeV. A search is made for ω′ or φ′ partners of the ϱ′(1600). Evidence is presented against the existence of narrow states and against the production of a broad state by an s -channel helicity conserving mechanism.
No description provided.
A ϱπ enhancement with mass 1.67 ± 0.02GeV and width 0.16 ± 0.02GeV is observed in the channel γp→pπ + π − π 0 . Assuming an incoherent background, the cross section × branching ratio is 100 ± 20 nb. A spin-parity analysis favours J P = 1 − . The enhancement is most simply interpreted as a radial recurrence of the ω meson.
No description provided.
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.
Measured charged current total cross section.
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