Virtual photoproduction of J/ ψ mesons has been measured for 280 GeV muon iron interactions in an iron/scintillator calorimeter target. The J/ψ's were identified by their decay into muon pairs. 315 events were observed, about half of which were elastic. The t , Q 2 and v distributions of these elastic events are presented. The v dependence is measured between 40 and 180 Mev and compared with lower energy photoproduction results. The Q 2 dependence is compared with the predictions of the vector dominance model.
TPRIME DISTRIBUTION OF ELASTIC J/PSI EVENTS FOR ALL Q2 AND NU WITH 280 GEV MUON BEAM.
NORMALIZED Q**2 DISTRIBUTION OF ELASTIC J/PSI EVENTS FOR ALL NU AND T WITH 280 GEV MUON BEAM.
EXTRAPOLATION OF Q**2 AND T DEPENDENCE TO CALCULATE D(SIG)/DT AT Q**2=0 AND T=0 FOR ELASTIC J/PSI PHOTOPRODUCTION PER NUCLEON.
Measurements of the production inp-BeO collisions of charged baryons and antibaryons with strangeness between −3 and +3 at\(\sqrt s= 21.2GeV\)x=0.48, andpT=600MeV/c are reported. The experimental results can be interpreted within the framework of a simple proton fragmentation-recombination model.
No description provided.
No description provided.
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We report a photon-photon experiment performed at the Orsay storage rings. 300e + e − , μ + μ − and π + π − pairs produced with low invariant masses have been observed. For each event, one or both protons have been tagged at a very small angle. The γγ→μ + μ − and γγ→π + π − cross-sections have been measured near threshold, the γγ→e + e − process being used as a normalization. The observed invariant mass distribution is compared to theoretical calculations for each of the three processes. The μ + μ − data are in good agreement with QED predictions. The π + π − cross-section, in our experimental acceptance, is somewhat larger than the one expected from the Born terms only.
EACH BEAM ENERGY VARIED BETWEEN 750 MEV AND 1 GEV.
The e + e − → K S 0 K L 0 cross section has been measured between 1400 and 2180 MeV. About 58 K S 0 K L 0 events were in the magnetic detector DM1 at the Orsay storage ring DCI. The charged and neutral kaon form factor behaviour suggests the existence of a new isoscalar vector meson at 1.65 GeV.
No description provided.
The e + e − → 3 π + 3 π − cross section has been measured between 1400 and 2180 MeV with the magnetic detector DM1 at the Orsay storage rings DCI. The cross section increases continuously above 1600 MeV and reaches 2 nb at the maximum explored energy, much larger than VDM previous estimates.
No description provided.
The e + e − → ωπ + π − → π + π − π + π − π 0 cross section has been measured at DCI by the DMI experiment in the 1.4–2.2 GeV energy range. A bump in this cross section appears at 1.65 GeV above a small background, with 6.2 s.d. statistical significance. It can be interpreted as a new isoscalar vector meson: ω ′ or ø ′.
THE INDIVIDUAL SYSTEMATIC ERRORS ARISE FROM THE UNCERTAINTY IN SUBTRACTING THE FIVE-PION (NON-OMEGA) BACKGROUND. THESE ERRORS ARE CORRELATED WITH THE STATISTICAL ERRORS.
New measurements of thee + e − → π + π − π + π − cross section have been performed by the magnetic detector DM1 at DCI (ORSAY) in the 1.4−2.18 GeV total energy range with statistics of 11000 events. Assuming the4 π ± production is dominated by the ϱ′(1.6) we determine its parameters: M = 1.57 ± 0.02 (stat.) −0.00 +0.06 (syst.) GeV,Γ = 0.51 ± 0.04 (stat.) −0.01 +0.04 (syst.)GeV,Γ ρ ′ee B ϱ′→ ρ 0 π + π − = 2.67 ± 0.19 (stat.) −0.36 +0.27 (syst.)keV.
No description provided.
First measurements of the e + e − → π + π − K + K − cross section have been performed by the DM1 on DCI in the total energy range 1.4–2.18 GeV. π + π − K + K − production is dominated by K ∗ Kπ dynamics. The cross section is rather large around 1.9 GeV. Comparison with K 0 S inclusive production shows an isospin interference. Upper limits on φππ production are compatible with the OZI rule.
No description provided.
UPPER LIMITS TO PHI CROSS SECTIONS WITH CL=90 PCT.
First measurements of the e + e − → K S 0 K ± π ∓ reaction in the 1.4–2.18 GeV energy range have been performed with the magnetic detector DM1 at the Orsay storage rings DCI. The cross section is rather large. The production is mainly K ∗0 K 0 which reveals an interference between isovector and isoscalar amplitudes. These results show again the existence of an isoscalar vector at 1.65 GeV shown to be a φ ′ meson.
No description provided.
The reactions e + e − → ρη , ρπ , φπ and φη have been studied with the magnetic detector DM1 at DCI in the total energy ranges between 1.4 and 2.18 GeV. The ρη signal is clearly seen. Upper limits for ρπ and φη channels as well as for the OZI forbidden φπ channel.
No description provided.
UPPER LIMIT TO SIG AS EXPLAINED IN SYSTEMATICS.
UPPER LIMIT TO CROSS SECTION AT CL=90 PCT.