A high statistics experiment was performed on Bhabha scattering at energies between 14 and 34 GeV. Good agreement with QED was observed. The combined data on Bhabha scattering and μ pair production were found to agree with the standard theory of electroweak interaction giving sin 2 θ = 0.27 −0.07 +0.06 . Assuming for the Z 0 mass a value of 90 GeV the leptonic weak coupling constants were determined to g V 2 = −0.04 ± 0.06 and g A 2 = 0.35 ± 0.09. A search for scalar leptons sets lower limits on the mass of scalar electrons of M s e > 16.6 GeV and of scalar muons of M s μ > 16.4 GeV.
No description provided.
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Measurements have been made of the differential cross section and asymmetry A on for p p elastic scattering at 15 incident momenta between 497 MeV/ c and 1550 MeV/ c . The angular range where both particles have enough energy to traverse target and setup has been covered. The results are compared with predictions of various N N potential models. None of these models fully explains the present results, although the general trend of the data is predicted correctly.
No description provided.
No description provided.
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The reactione+e−→µ+µ− has been studied at centre of mass energies between 35.0 and 46.8 GeV using the TASSO detector at PETRA. We present measurements of the forward-backward charge asymmetry (Aμμ) and cross section σμμ for this reaction at three energies. At 35.0 GeV we obtain a cross section relative to the QED prediction ofRμμ=σμμ/σo=0.932±0.018±0.044 andAμμ=(−10.6−2.3+2.2±0.5)%. At 38.3 GeV we findRμμ=0.951±0.072−0.057+0.063 andAμμ=(+1.7−8.6+8.5±0.5)%. At 43.6 GeV we measureRμμ=0.921±0.037±0.055 andAμμ=(−17.6−4.3+4.4±0.5)%. Our results are in good agreement with the predictions of the standard model. Including previous TASSO data we present improved determinations of muonic electroweak parameters. We also report on lower limits of possible contributions from contact interactions.
If only one error is given, this is the sum of the statistical and systematic errors in quadrature.
The data are corrected for 'reduced QED' radiative corrections. Statistical errors only.
The data are corrected for 'reduced QED' radiative corrections. Statistical errors only.
None
No description provided.
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The differential cross section of the reactione+e−→e+e− at a c.m. energy of 34.7 GeV has been measured. The result, together with our previously measurede+e−→α+α− data, are compared with the standard model predictions. We obtain for the weak neutral current couplings the valuesgv2=0.09×0.06,ga2=0.38×0.08. A fit of the Weinberg mixing angle gives the valuegv2=0.09×0.06,ga2=0.038×0.08. The data are also used to set limits on possible deviations from the pointlike structure of leptons. An upper limit for thee+e− coupling to a heavy spin 0 boson is also given.
Fully corrected results for Bhabha scattering.
The differential cross section for Bhabha scattering.
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Differential cross sections dσdΩ for the inclusive reaction N14 + p→Z + anything (for 3≤Z≤6) have been measured at six laboratory production angles (θ<5°) for 7.3 GeV nitrogen ions interacting in liquid hydrogen. The angular distributions for C, B, and Be fragments decrease sharply with increasing angle, as expected for this type of peripheral reaction. The corresponding transverse momentum (pt) distributions for these fragments can be represented by Gaussian functions of pt. The Li distribution appears to be non-Gaussian, suggesting one (or more) different production mechanisms. The dependence of the widths of the momentum distributions on fragment mass is not consistent with theoretical predictions, and shows some evidence for an "effective" number of nucleons which determine the fragmentation spectrum of the nitrogen nucleus. Integration of the angular distributions gives partial production cross sections which are consistent with results at higher energy. This energy-independent behavior implies that limiting fragmentation is applicable down to energies of 0.5 GeV/nucleon. NUCLEAR REACTIONS Relativistic heavy ions; fragmentation of 7.3 GeV nitrogen on protons.
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p-He4 elastic scattering has been measured at 1.05-GeV incident proton energy, close to 180° in the center of mass. The steep backward peak observed at lower energies is still present, but its slope appears to decrease.
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The angular distribution of the inclusive reaction 4 He + p → 3 He + X was measured with 6.85 GeV/ c incident alphas. At large angles, the observed kinematics corresponds to the elastic scattering on the target proton of an 3 He present in the incoming 4 He, the remaining neutron being a spectator. This shows the presence of an important component of 3 He in 4 He. The integrated cross section for 3 He production is σ 3He = 24.1 ± 1.9 mb.
No description provided.
Differential cross sections for backward π − d elastic scattering (−1 ≦ cos θ c.m ≦ −0.98) have been measured at fourteen momenta from 0.98 to 1.76 GeV/ c and at 2.45 GeV/ c . Energy dependence of the cross section exibits a new wide structure at √ s ≈ 2.9 GeV. Possible mechanisms of the reaction accounting for this structure are presented. Experimental data are compared with theoretical calculations.
BEAM ERROR D(P)/P = 0.300 PCT.
BEAM ERROR D(P)/P = 0.300 PCT.
BEAM ERROR D(P)/P = 0.300 PCT.
We present results on charged multiplicity nch=2 and nch>2 muon events produced in e+e− collisions with 〈s12〉=7.3 GeV at 90° to the beams. The background-subtracted inclusive cross section for the nch=2 events is 10.2±5.4 pb/sr, in agreement with the expected contribution from the heavy lepton τ. The cross section for the nch>2 events is 19.0±6.5 pb/sr whereas we expect only 2.9 pb/sr from the τ, indicating that we may be seeing the weak decays of charmed mesons.
No description provided.
No description provided.
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