None
No description provided.
No description provided.
No description provided.
The cross section of the process e+e-\to\mu+\mu- was measured in the SND experiment at the VEPP-2M e+e- collider in the energy region \sqrt{s}=980, 1040 -- 1380 MeV. The event numbers of the process e+e-\to\mu+\mu- were normalized to the integrated luminosity measured using e+e-\to e+e- and e+e-\to\gamma\gamma processes. The ratio of the measured cross section to the theoretically predicted value is 1.006\pm 0.007 \pm 0.016 and 1.005 \pm 0.007 \pm 0.018 in the first and second case respectively. Using results of the measurements, the electromagnetic running coupling constant \alpha in the energy region \sqrt{s}=1040 -- 1380 MeV was obtained <1/\alpha> = 134.1\pm 0.5 \pm 1.2 and this is in agreement with theoretical expectation.
The E+ E- --> MU+ MU- cross section obtained using the (GAMMA GAMMA) luminosity measurement.
The measured E+ E- --> E+ E- cross section in the electron angle 30 to 150 degrees.
Compton scattering of quasi-real virtual photons, gamma e+- -> gamma e+-, is studied with 0.6fb-1 of data collected by the L3 detector at the LEP e+e- collider at centre-of-mass energies root(s')=189-209GeV. About 4500 events produced by the interaction of virtual photons emitted by e+- of one beam with e-+ of the opposite beam are collected for effective centre-of-mass energies of the photon-electron and photon-positron systems in the range from root(s')= 35GeV up to root(s')=175GeV, the highest energy at which Compton scattering was ever probed. The cross sections of the gamma e+- -> gamma e+- process as a function of root(s') and of the rest-frame scattering angle are measured, combined with previous L3 measurements down to root(s')~20GeV, and found to agree with the QED expectations.
Measured Compton scattering cross section as a function of the effective centre of mass of the photon-electron system. THETA(RF=CM) is the electron rest frame scattering angle.
The measured angular distribution over the photon-electron centre of mass energy range 35 to 175 GeV.
The measured Compton scattering cross section using the full data sample including the lower energy data from Acciarri et al. PL B439(1998)183. Errors are combined statistics and systematics.
During 1993 and 1995 LEP was run at 3 energies near the Z$^0$peak in order to give improved measurements of the mass and width of the resonance. During 1994, LEP o
Hadronic cross section measured with the 1993 data. Additional systematic error of 0.10 PCT (efficiencies and backgrounds) and 0.29 PCT (absolute luminosity).
Hadronic cross section measured with the 1994 data. Additional systematic error of 0.11 PCT (efficiencies and backgrounds) and 0.11 PCT (absolute luminosity).
Hadronic cross section measured with the 1995 data. Additional systematic error of 0.10 PCT (efficiencies and backgrounds) and 0.11 PCT (absolute luminosity).
We report on measurements of e + e − annihilation into hadrons and lepton pairs. The data have been taken with the L3 detector at LEP at center-of-mass energies between 161 GeV and 172 GeV. In a data sample corresponding to 21.2 pb −1 of integrated luminosity 2728 hadronic and 868 lepton-pair events are selected. The measured cross sections and leptonic forward-backward asymmetries agree well with the Standard Model predictions.
No description provided.
No description provided.
No description provided.
Neutrino-electron elastic scattering was observed with a 15-ton fine-grained tracking calorimeter exposed to electron neutrinos from muon decay at rest. The measured νee−→νee− elastic scattering rate of 236±35 events yields the total elastic scattering cross section 10.0±1.5(stat)±0.9(syst)×10−45 cm2×[Eν (MeV)], and a model-independent measurement of the strength of the destructive interference between the charged and neutral currents, I=−1.07±0.21, that agrees well with the standard model (SM) prediction I=−1.08. The agreement between the measured electroweak parameters and SM expectations is used to place limits on neutrino properties, such as neutrino flavor-changing neutral currents and neutrino electromagnetic moments. Limits are placed on the masses of new bosons that interact with leptons: for a neutral tensor boson, MT>105 GeV; for a neutral (pseudo)scalar boson, MP,S>47 GeV; for a charged Higgs boson, Mχ+>87 GeV; and for a purely left-handed charged (neutral) vector boson, Mx>239 (119) GeV.
No description provided.
No description provided.
A measurement of the reaction νe+e−→νe+e− was performed using a beam-stop source of νe. Based upon 234±35 events, we obtain a cross section of σ(νee)=[9.9±1.5(stat)±1.0(syst)]×10−42 cm2 ×[Eν (GeV)]. This reaction is mediated by the exchange of W and Z bosons and is thus sensitive to the interference between them. This interference is measured to be -1.07±0.17(stat)±0.11(syst), consistent with the destructive interference (-1.08) predicted by the standard model.
No description provided.
A total of 22 muon-neutrino-electron elastic-scattering events (νμe→νμe) have been observed in an exposure of the Fermilab 15-foot bubble chamber filled with a heavy neon-hydrogen mixture to a wide-band neutrino beam. The elastic-scattering cross section is measured to be 1.67±0.44×10−42Eν cm2 GeV−1. The value of the weak mixing angle (sin2θW) determined from this cross section, which is consistent with other measurements of this angle, is 0.20−0.05+0.06.
No description provided.
Total and differential cross sections for νμe→νμe and ν¯μe→ν¯μe are measured. Values for the model-independent neutral-current couplings of the electron are found to be gV=−0.107±0.035(stat)±0.028(syst) and gA=−0.514±0.023(stat)±0.028(syst). The electroweak mixing parameter sin2θW is determined to be 0.195±0.018(stat)±0.013(syst). Limits are set for the charge radius and magnetic moment of the neutrino as (〈r2〉)<0.24×10−32 cm2 and fμ<0.85×10−9 Bohr magnetons, respectively.
No description provided.
No description provided.
No description provided.
The weak coupling constants of the electron, gVe and gAe, are determined from measurements of the total and differential cross sections for the reaction νμe→νμe. The data also place limits of interest on the magnitudes of a neutrino charge radius and a possible neutrino magnetic dipole moment.
Neutrino beam 0 - 5 GeV.
Forum