The measurement of the nonelectromagnetic forward-backward charge asymmetry in the reaction e+e−→μ+μ− at s∼34.6 GeV and in the angular region 0<|cosθ|<0.8 is reported. With a systematic error less than 1%, we observe an asymmetry of (-8.1±2.1)%. This is in agreement with the standard electroweak theory prediction of (-7.6±0.6)%. The weak-current coupling constants are also reported.
No description provided.
No description provided.
With a PETRA energy scan in ≤30-MeV steps, the continuum production of open top quark up to 38.54 GeV is excluded. Over regions of energy scan from 29.90 to 38.63 GeV limits are set on the product of hadronic branching ratio and electronic width BhΓee for toponium to be less than 2.0 keV at the 95% confidence level. By a search for flavor-changing neutral currents in b decay, models without a top quark are excluded.
MEASUREMENT OF R IN ENERGY SCAN FROM SQRT(S) = 29.9 TO 3.146 AND 33.0 TO 36.72.
MEASUREMENT OF R IN THE RANGE SQRT(S) 37 TO 38.63 GEV.
THRUST DISTRIBUTION FOR EVENTS IN THE RANGE SQRT(S) 37.94 TO 38.63 AND 38.54 TO 38.63.
The differential and total corss sections and the decay density matrix elements have been measured for the reactions, γp→ωp and γp→ωΔ+ (1232) in the photon energy range 2.8 to 4.8 GeV. The total cross sections for ωΔ+ (1232) photo-production are found to be slightly larger than those for elastic ω photo-production in this energy range. The data are compared to the predictions of a theoretical model and the contributing exchange mechanics are discussed.
No description provided.
No description provided.
No description provided.
A tagged photon beam (2.8<Eγ<4.8 GeV) and multiparticle spectrometer have been used to study the photoproduction in hydrogen ofK+Λ(1520). Precise values for the mass and width of the Λ(1520) are given. The total cross-section is found to fall with increasing photon energy like (6.5±0.7)Eγ−(2.1±0.2) μb. The differential cross sectiondσ/dt indicates peripheral forward production and exhibits no evidence for shrinkage when compared with higher energy data. The Λ(1520) spin density matrix shows thatK exchange alone cannot account for the production mechanism. The reaction is found to resemble the process γp→K+ Λ(1115) in all measurable respects.
FITTED CROSS SECTION ENERGY DEPENDENCE IS SIG = (6.7 +- 0.7 MUB*GEV**2) * P**(-2.1 +- 0.2), INCLUDING HIGHER ENERGY DATA.
EXPONENTIAL SLOPE IS 6.1 +- 2.0 GEV**-2 FOR -T = 0.2 TO 0.7 GEV**2.
No description provided.
The results of an experiment to study elasticK+K− photoproduction are presented. Differential cross sections and spin density matrix elements for ϕ(1.019) production are stddied as a function of incident photon energy and over a wide range of momentum transfer,t (tmin>t>−1.5(GeV/c)2). Helicity conserving amplitudes are observed to dominate ϕ production throughout this range and the differential cross sections exhibit a forward diffractive peak which cannot be understood in terms of a simple exponential dependence. A new value of the photon ϕ coupling constant is determined and shown to be consistent withe+e− annihilation measurements. A detailed study of the energy dependence of the differential cross sections is made, including other experimental data, and the extracted effective Regge trajectory compared with other diffractive processes. A study of the dependence of theK+K− decay angular distribution on invariant mass reveals evidence for ans wave contribution interfering with thep wave ϕ which may be attributable to theS* meson.
LOWER LIMIT OF ABS(T) IN TABLE IS TMIN.
No description provided.
LOW T VARIATION WITH ELAB. LOWER LIMIT OF ABS(T) IN TABLE IS TMIN.
None
DATA ARE CORRECTED FOR TWO-PHOTON AND TAU PRODUCTION EFFECTS, ACCEPTANCE AND QED RADIATIVE EFFECTS UP TO ORDER ALPHA**3. THERE IS ALSO A 6 PCT NORMALISATION ERROR NOT INCLUDED. THE OVERALL AVERAGE VALUE OF R FROM THIS DATA IS 3.88 +- 0.04 +- 0.22.
No description provided.
ERRORS CONTAIN BOTH STATISTICS AND SYSTEMATICS.
We have searched for resonances in the reaction e+e−→hadrons, γγ, μμ, and ee, in the energy range 39.79<s<45.52 GeV, using the Mark J detector at PETRA. We obtain stringent upper limits on the production of toponium and particles postulated to explain Z0→leptonpair+γ events observed at the CERN p―p collider. We also set limits on the mass and coupling constant of excited electrons.
The elastic photoproduction of four pions has been studied at incident photon energies between 2.8 and 4.8 GeV. Production cross-sections are presented and an analysis of the angular decay correlations is also described, indicating a large 1− contribution in both final states, π+ π− π+ π− and π+ π− π0 π0. A quantitative understanding of these and other available 4π photoproduction data in terms of the ρ′(∼1.2GeV) and the ρ′(∼1.6) is presented.
WITH OMEGA/RHO DECAY PARAMETRIZATION.
WITH OMEGA/A1 DECAY PARAMETRIZATION.
We have performed a high-statistics measurement of Bhabha scattering and of the production of hadrons in electron-positron annihilation at PETRA energies (12 GeV<~s<~36.7 GeV). Combining the results with measurements of μ+μ− and τ+τ− production enables us to compare our results with electroweak theory. We find sin2θw=0.27±0.08. This is in good agreement with the value obtained from neutrino experiments which were carried out in entirely different kinematic regions.
ASYMMETRY WAS USED.
OVERALL FIT USED.
No description provided.
We have performed a high statistics measurement of the production rate and the energy flow pattern of hadron events between √ s =33 and 36.7 GeV. The data show no evidence for the production of a new quark with charge 2 3 e . Planar events in e + e − →hadrons are shown to have three well separated jets. The production rate and the shape of three-jet events are compared with many models and we find that only the QCD model can explain the data.
ENERGY SCAN WITH 7077 HADRON EVENTS.
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