The differential cross sections of the reactions e + e − → e + e − and e + e − → λλ are measured at energies between 33.0 and 36.7 GeV. The results agree with the predictions of quantum electrodynamics. A comparison with the standard model of electroweak interaction yields sin 2 θ W = 0.25 ± 0.13.
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Polarization and differential cross-section data are presented for elastic scattering of antiprotons on polarized protons at eight momenta between 0.9 and 2.5 GeV/ c . The data are fitted with a diffraction model.
COMBINED 0.88 AND 0.95 GEV/C DATA.
COMBINED 1.00 AND 1.04 GEV/C DATA.
COMBINED 1.01 AND 1.055 GEV/C DATA.
The π+ photoproduction cross section in hydrogen has been measured at 180° for photon energies from 0.22 to 3.1 GeV by detecting the pion in the backward direction. The statistical accuracy of the measurements varies typically from 3 to 10% depending on the energy. The data are compared with other recent experimental results and predictions of phenomenological theories.
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Beam asymmetry and differential cross section for the reaction gamma+p->eta+p were measured from production threshold to 1500 MeV photon laboratory energy. The two dominant neutral decay modes of the eta meson, eta->2g and eta->3pi0, were analyzed. The full set of measurements is in good agreement with previously published results. Our data were compared with three models. They all fit satisfactorily the results but their respective resonance contributions are quite different. The possible photoexcitation of a narrow state N(1670) was investigated and no evidence was found.
Measured beam asymmetry at photon energy 724 MeV as a function of the ETA centre of mass angle.
Measured beam asymmetry at photon energy 761 MeV as a function of the ETA centre of mass angle.
Measured beam asymmetry at photon energy 810 MeV as a function of the ETA centre of mass angle.
The angular distributions of the reactione+e−→μ+μ− ande+e+→τ+τ− have been measured between\(\sqrt s= 50\) and 60.8 GeV with the VENUS detector at TRISTAN. The average total cross section and the forward-backward charge asymmetry for μ-pair production are observed to be 28.3±1.4±0.8 pb and (−29.0−4.8+5.0±0.5)%, and those for τ-pair production are 27.6±1.7±1.0 pb and (−32.8−6.2+6.4±1.5)% at\(\langle \sqrt s \rangle \). These values are consistent with the predictions of the standard model of electroweak interactions.
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A high-precision measurement of the differential cross section for Bhabha scattering (e+e−→e+e−) is presented. The measurement was performed with the MAC detector at the PEP storage ring of the Stanford Linear Accelerator Center, at a center-of-mass energy of 29 GeV. Effects due to electroweak interference are observed and agree well with the predictions of the Glashow-Salam-Weinberg model. The agreement between the data and the electroweak prediction rules out substructure of the electron up to mass scales of 1 TeV.
Error contains both statistics and systematics.
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Total and differential cross sections for π−p elastic scattering are presented at 35 energies between 1400 and 2000 MeV.
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Results on the channels K − p → Λ 0 η 0 , Λ 0 π 0 , Σ 0 π 0 , Λ 0 π 0 π 0 and Σ 0 π 0 π 0 are obtained in a K − p formation experiment using 1 million photographs taken in a heavy liquid bubble chamber filled with a CF 3 BrC 3 H 8 mixture. The results are compared with hydrogen bubble chamber (HBC) experiments and with experiments having full or partial gamma-ray detection. Our Λ 0 π 0 and Λ 0 + neutral cross section agree with HBC results. Our Σ 0 π 0 cross section does not exhibit a bump at 1670 MeV as previously seen in HBC experiments. Our Λ 0 π 0 π 0 data are dominated by a Σ (1385) π 0 production. Our Σ 0 π 0 π 0 data is consistent with the presence of some Σ (1405) π 0 production.
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Elastic scattering of p¯ on p has been studied for cosθc.m. between -0.88 and -1.0 and Plab(p¯) between 0.70 and 2.16 GeV/c. The momentum dependence of the cross section shows a sharp dip at 0.9 GeV/c and a broad peaking around 1.4 GeV/c. The possibility of the peak resulting from direct formation of boson resonances has been studied. Alternatively, a diffraction model agrees qualitatively with our data and other elastic data at different angles.
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The π0 photoproduction cross section has been measured at 180° for photon energies from 220 to 380 MeV, in steps of 20 MeV, by detecting the recoil proton at 0°. The statistical accuracy of the measurements varies between 3 and 7%, depending on the energy. Absolute cross sections have been deduced from a comparison of the measurements with electron-proton scattering. The experimental data are compared with theoretical results calculated from fixed-momentum-transfer dispersion relations. Special attention is paid to the prediction of the multipoles at the first resonance, namely, E1+32, M1+32, and E0+π0 to obtain agreement with experiment.
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