The reaction e − + p → e − + p + η has been studied in the region of the S 11 (1535)-resonance by detecting the recoil proton in coincidence with the scattered electron. The reaction has been observed at three four-momentum transfers of the virtual photon: q 2 = 0.2, 0.28 and 0.4 (GeV/ c ). First results of the differential cross section measurements are given and compared with quark model calculations.
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Results are presented for the reactions (1) π+n→pπ+π−, (2) π+n→pπ+π−π0, at an incident pion beam momentum of 11.7 GeV/c. Both reactions show considerable resonance production. Reaction (1) is dominated by ρ0 and f0 production and there is evidence for the variation of the ρ00 width with momentum transfer. Decay angular distributions are presented for the dipion system observed in reaction (1). Reaction (2) shows the production of both dipion and tripion resonances and there is evidence for the associated production of\(\mathcal{N}\)-resonances with the dipion resonances.
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DN/DT PLOTTED. ALL RESONANCES ARE DEFINED JUST BY MASS CUTS.
RHO0 MASS REGION OF DIPION SYSTEM. NUMERICAL VALUES TAKEN FROM TABLE 6.1 OF THE THESIS BY D. KEMP (DURHAM 1974).
The invariant mass spectrum of neutral meson states from π − p interactions at 40 GeV/ c incident momentum has been investigated in a high statistics experiment performed at the 70 GeV IHEP accelerator. To detect the high energy photons coming from the produced neutral states, a hodoscope spectrometer with a computer on-line was used. A clear structure on the mass spectrum of dipions produced in the reaction π − p→π°π°n is observed at 2 GeV. The decay angular distributions show in this mass region the variation with mass typical of a state with a spin J = 4. The mass of the observed meson is found to be M = (2020±30)MeV and the estimate of the full width is (180±60) MeV.
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The total cross section for K ± production in e + e − collisions was measured for cms energies between 3.6 and 5 GeV and was found to increase by a factor of 2–3 from 3.6 to 4.1 GeV.
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The multiplicity distribution of inclusive electron events above 4 GeV cm energy shows two distinct classes of events: two prong no photon and high multiplicity events. If the high multiplicity events are attributed to the semi-leptonic decay of charmed particles the two prong no photon events must come from the weak decay of a different type of particle. The charged K to π ratio was measured for these events. The average number of charged kaons is 0.07 ± 0.06 per two prong event and 0.90 ± 0.18 per multiprong event. Thus the weak current responsible for the low multiplicity events has a small coupling to strange particles.
NUMBER OF CHARGED PARTICLES OBSERVED .EQ. 2.
NUMBER OF CHARGED PARTICLES OBSERVED .GE. 3.
New results on a high statistics measurement of pion-nucleon charge exchange scattering at 40 GeV/ c , extending in momentum transfer up to − t = 1.8 (GeV/ c ) 2 , are reported and compared with an optical impact parameter model, together with previous data for the reaction π − p → ηn at the same energy. The imaginary part of the pole trajectory b 0 ( s ) is determined from the slope of the tangent to the maxima of (−t) 1 2 d σ d t . The linear increase of Im b 0 ( s ) with log s , which has been observed at low energies, continues up to 40 GeV/ c .
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AT SMALL -T, THE BINNING TENDS TO SMEAR OUT THE FORWARD DIP.
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The invariant mass spectrum of neutral final states produced in π − p charge-exchange scattering at 40 GeV/ c has been studied, searching for heavy particles decaying in 2γ. A peak is observed around 2.85 GeV/ c 2 . The cross section of the reaction π − p→X(2.85)+n, times the branching ratio of the X→2 γ decay, is measured to be σ × BR ⋍ 2 × 10 −34 cm 2 .
MEAN VALUE OF -T = 0.28 +- 0.04 GEV**2.
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