Results on e + e − annihilation into hadrons at c.m. energies between 22 and 31.6 GeV are presented. The data were accumulated with the PLUTO detector at PETRA. The events are dominantly of the two-jet type. The value of the relative hadronic cross section R =3.88 ± 0.22 along with the details of the sphericity and thrust distribution rule out an open (tt̄) channel (Q t = 2 3 ) below 30 GeV. The inclusive muon results support the above conclusion.
In this Letter, a measurement of inclusive muon production (pμ>2 GeV/c) in e+e− annihilation into hadrons at center-of-mass energies from s=12 to 31.6 GeV is reported. The results agree with the expected semileptonic decays from charmed and bottom mesons.
MUONS PER HADRONIC EVENT.
INVARIANT CROSS SECTION, ASSUMING HADRONIC CROSS SECTION HAS R VALUE OF 3.9 +- 0.5.
We have measured the reaction ee → μμ and ee → ττ at center of mass energies from 9.4 to 31.6 GeV. The production cross sections are in agreement with the predictions of quantum electrodynamics, resulting in cutoff parameter limits of 70–100 GeV at 95% c.l. The branching ratio for τ → μν ν has been determined as [1.78 ± 2.0 (statist.) ± 1.8(syst.)]% The existence of a new sequential heavy lepton with a mass <14.5 GeV is excluded at 95% c.l.
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We have performed a search for narrow resonances in the center of mass energy range from 29.90 to 31.46 GeV using the e + e − storage ring PETRA at DESY. We present the total cross section for hadron production and an upper limit for resonance production, indicating that no bound state of charge- 2 3 quarks exists in this energy range.
First results from the magnetic detector PLUTO at the new e + e − storage ring PETRA are shown. The ratio R of the cross section for hadron production to that for μ-pair production has been measured to be R = 5.0 ± 0.5 at 13 GeV and 4.3 ±0.5 at 17 GeV. Both values have an additional systematic error of 20%. The events show a typical 2-jet structure. The mean transverse momentum approaches a constant value with increasing energy implying a shrinkage of the jet opening angle.
We report on an experiment where the different contributions from the transverse and longitudinal polarization of the virtual photon are measured separately for the reaction e − p→e − π + n. The data taken above the resonance region at small ∣ t ∣ values in the q 2 range of ∣ q 2 ∣ < 0.5 GeV 2 show a clear dominance of the longitudinal part of the cross section and are well described by a generalized Born-term model. Using this model the electromagnetic form factor of the pion is determined. At q 2 = −0.35 GeV 2 one gets F π = 0.598 ± 0.021.
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AVERAGED OVER RESTRICTED PHI RANGE. THIS IS MAINLY (D(SIG(NAME=U))/DT + EPS*D(SIG(NAME=L))/DT) SINCE COMPONENTS P AND I ARE EXPECTED TO REMAIN SMALL FOR LARGER -T.
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Antineutrino interactions in BEBC are compared to look for differences between the differential cross sections per nucleon in neon and in deuterium. The identical geometries, beam spectra and muon identification criteria and acceptances allow comparison with very small systematic errors. The results are compared in detail with μ and e scattering data from EMC and SLAC. We find no rise in the ratio d σ/ d x ( ν Ne )/σ/ d x ( ν D 2 ) at low x , independent of Q 2 up to Q 2 ∼ 14 GeV 2 .
VALUES OF Q**2 IN THIS TABLE ARE :- 1.07,2.59,4.33,6.14,7.67,8.28,6.35 (FOR ALL Q**2) AND :-,7.9,9.5,11.5,13.2,13.9,11.6 (FOR Q**2 > 4.5 ).
An exposure of BEBC equipped with the hydrogen-filled TST to the v μ wide band beam at the CERN SPS has been used to study v μ interactions on free protons. About neutral induced interactions have been observed inside the hydrogen and separated into charged current, neutral current and neutral hadron interactions using a multivariate discriminant analysis based on the kinematics of the events. The neutral to charged current cross-section ratio has been determined to be R p v = 0.33 ± 0.04 . When combined with the value of R p v previously determined in the same experiment, the result is compatible with the prediction of the standard SU (2) × U (1) model for sin 2 θ W = 0.24 −0.08 +0.06 and ρ = 1.07 −0.08 +0.06 . Fixing the parameter ρ = 1 yields sin 2 θ W = 0.18 ± 0.04.
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We present the first data on photon-photon annihilation into hadrons for CM energies > 1 GeV obtained with the detector PLUTO at the e + e − storage ring PETRA. Cross sections are extracted using an inelastic eγ scattering formalism. The results are compared to expectations from Regge-like models.
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