An experiment has been performed to study the inclusive photoproduction of π 0 mesons. Photoproduced π 0 's were detected in a hodoscope consisting of 14 lead glass Cerenkov counters. To obtain the cross sections at a photon energy of 6 GeV we used the photon-difference method. Data are presented in terms of the Feynman variable x = q ‖ ∗ (√s/2) and the trnasverse momentum q⊥. We have measured four q ⊥ distributions at x = 0.2, 0.4, 0.6 and 0.8. The results dhow that the π 0 rate at small values of q ⊥ is smaller than the π± rate. The data can be fitted smoothly by a form A exp (− Bq ⊥ 2 ) with a value about 3.5 GeV −2 for the slope parameter B .
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We have studied K+π− elastic scattering in the reaction K+p→K+π−Δ++ at 12 GeVc and in the Kπ mass interval 800 to 1000 MeV. We have performed a partial-wave analysis in this Kπ mass region, dominated by the p-wave resonance K*(890), in order to obtain information about the s-wave amplitude. We have extrapolated the K+π− moments, the total cross section, and p-wave cross section to the pion pole. The p-wave cross section is close to the unitarity limit and can be described by a Breit-Wigner resonance form, with parameters M=896±2 MeV and Γ=47±3 MeV. We then perform an energy-independent phase-shift analysis of the extrapolated moments and total cross section using this Breit-Wigner form for the p wave and a previously determined small negative phase shift for the I=32s wave. For the I=12s-wave phase shift we find the so called "down" solution, which has a phase shift that rises slowly from 20° at M(Kπ)=800 MeV to 60° at M(Kπ)=1000 MeV. The energy dependence of this phase shift is well described by an effective range form, with a scattering length a01=−0.33±0.05 F. The so-called "up" solution is eliminated or has large χ2 everywhere except for two overlapping mass intervals at M(Kπ)=890 and 900 MeV. However, due to limited statistics, we expect two solutions for the s wave very near the mass where the p wave is resonant. We then perform an energy-dependent partial-wave analysis and find again no evidence for an s-wave resonance although, due to limited statistics, we could not exclude one at 890 MeV with Γ<7 MeV.
Extrapolation.
Extrapolation. Initial K+ PI- system in P-wave state.
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Data read off graph.
Data read off graph.
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A set of two natural abundance Ge detectors of 1.1 kg each, located in the Homestake mine, and one small, 0.253 kg, Ge detector operating in the Canfranc railway tunnel in Spain, have been used to obtain bounds on the stability of the electron against the decay modes e − → γν e and e − → ν e ν e ν e . The bounds on the mean lifes are τ ( γν e ) > 3.7(2.1) × 10 25 yr , 68%(90%) CL and τ(ν e ν e ν e > 4.3(2.6) × 10 23 yr , 68%(90%) CL, which are at present the most stringent laboratory limits for these decays.
Lifetime in years (YR).
Inclusive charged-current interactions of high-energy neutrinos and antineutrinos have been studied with high statistics in a counter experiment at the CERN Super Proton Synchrotron. The energy dependence of the total cross-sections, the longitudinal structure function, and the nucleon structure functionsF2,xF3, and\(\bar q^{\bar v} \) are determined from these data. The analysis of theQ2-dependence of the structure functions is used to test quantum chromodynamics, to determine the scale parameter Λ and the gluon distribution in the nucleon.
ABSOLUTE FLUXES HAVE NOT BEEN MEASURED. NORMALISED TO OLD RESULTS.
STUCTURE FUNCTIONS ARE EVALUATED ASSUMING R=SIG(L)/SIG(T)=0.1 AND M(W) IS INFINITE. NO CORRECTION FOR FERMI MOTION APPLIED. ERRORS ARE STATISTICAL AND SYSTEMATIC POINT-TO-POINT ERRORS. IN ADDITION OVER-ALL SCALE ERROR OF 6 PCT. FOR F2 , 8 PCT. FOR XF3.
STUCTURE FUNCTIONS ARE EVALUATED ASSUMING R=SIG(L)/SIG(T)=0.1 AND M(W) IS INFINITE. NO CORRECTION FOR FERMI MOTION APPLIED. ERRORS ARE STATISTICAL AND SYSTEMATIC POINT-TO-POINT ERRORS. IN ADDITION OVER-ALL SCALE ERROR OF 6 PCT. FOR F2 , 8 PCT. FOR XF3.
We report measurements of the two-photon processes e+e−→e+e−π+π− and e+e−→e+e−K+K−, at an e+e− center-of-mass energy of 29 GeV. In the π+π− data a high-statistics analysis of the f(1270) results in a γγ width Γ(γγ→f)=3.2±0.4 keV. The π+π− continuum below the f mass is well described by a QED Born approximation, whereas above the f mass it is consistent with a QCD-model calculation if a large contribution from the f is assumed. For the K+K− data we find agreement of the high-mass continuum with the QCD prediction; limits on f′(1520) and θ(1720) formation are presented.
Data read from graph. Additional overall systematic error 20% not included.
Data read from graph.. Additional overall systematic error 20% not included.
Data read from graph.. Additional overall systematic error 20% not included.. The Q**2 dependence is normalized to unity for the bin centred on Q**2 = 0.
We measure an inclusive branching fraction of (13.9 ± 2.0−2.2+1.9)% for the decay τ−→ντπ−π0+nh0(n>~1), where h0 is a π0 or an η. The data sample, obtained with the time-projection-chamber detector facility at the SLAC e+e− storage ring PEP, corresponds to an integrated luminosity of 72 pb−1 at 29 GeV center-of-mass energy. The measured branching fraction is somewhat greater than the theoretical prediction and, with errors taken into account, could resolve the present difference between the inclusive and the sum of the exclusive τ± branching fractions into one charged prong.
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We compare the particle flow in the event plane of three-jet qq¯g (quark-antiquark-gluon) events with the particle flow in radiative annihilation events qq¯γ (quark-antiquark-photon) for similar kinematic configurations. In the angular region between quark and antiquark jet, we find a significant decrease in particle density for qq¯g as compared to qq¯γ. This effect is predicted in QCD as a result of destructive interference between soft-gluon radiation from quark, antiquark, and hard gluon.
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