First measurements of the W -> lnu and Z/gamma* -> ll (l = e, mu) production cross sections in proton-proton collisions at sqrt(s) = 7 TeV are presented using data recorded by the ATLAS experiment at the LHC. The results are based on 2250 W -> lnu and 179 Z/gamma* -> ll candidate events selected from a data set corresponding to an integrated luminosity of approximately 320 nb-1. The measured total W and Z/gamma*-boson production cross sections times the respective leptonic branching ratios for the combined electron and muon channels are $\stotW$ * BR(W -> lnu) = 9.96 +- 0.23(stat) +- 0.50(syst) +- 1.10(lumi) nb and $\stotZg$ * BR(Z/gamma* -> ll) = 0.82 +- 0.06(stat) +- 0.05(syst) +- 0.09(lumi) nb (within the invariant mass window 66 < m_ll < 116 GeV). The W/Z cross-section ratio is measured to be 11.7 +- 0.9(stat) +- 0.4(syst). In addition, measurements of the W+ and W- production cross sections and of the lepton charge asymmetry are reported. Theoretical predictions based on NNLO QCD calculations are found to agree with the measurements.
Measured fiducial cross section times leptonic branching ratio for W+ production in the W+ -> e+ nu final state.
Measured fiducial cross section times leptonic branching ratio for W- production in the W- -> e- nubar final state.
Measured fiducial cross section times leptonic branching ratio for W+/- production in the combined W+ -> e+ nu and W- -> e- nubar final state.
The cross section of the process e+e- -> pi+pi- has been measured at the CMD-2 detector in the 370-520 MeV center-of-mass (c.m.) energy range. A systematic uncertainty of the measurement is 0.7 %. Using all CMD-2 data on the pion form factor, the pion electromagnetic radius was calculated. The cross section of muon pair production was also determined.
The measured Born muon pair production cross section. Errors are statistical only.
The measured pion form factor. The errors are statistical only.
The measured bare PI+ PI- production cross section. This is corrected for radiative effects but excludes a correction for vacuum polarization effects. The errors are statistical only.
A search for phi radiative decays has been performed using a data sample of about 2.0 million phi decays collected by the CMD-2 detector at VEPP-2M collider in Novosibirsk. From the selected e+ e- -> pi+ pi- gamma events the following results were obtained: B(phi -> f0(980) gamma) < 1x10-4 for destructive and B(phi -> f0(980) gamma) < 7x10-4 for constructive interference with the Bremsstrahlung process respectively, B(phi -> gamma -> pi+ pi- gamma) < 3x10-5 for E of gamma > 20 MeV, B(phi -> rho gamma) < 7x10-4. From the selected e+ e- -> mu+ mu- gamma events B(phi -> mu+ mu- gamma) = (2.3+-1.0)x10-5 has been obtained for E of gamma> 20 MeV. The upper limit on the P,CP-violating decay eta -> pi+ pi- has also been placed: B(eta -> pi+ pi-) < 9x10-4 . All upper limits are at 90 % C.L.
Only statistical errors are shown in the table.
Cross-sections for hadronic and leptonic two-fermion events, and leptonic forward-backward asymmetries, have been measured in e + e − collisions at a centre-of-mass energy of 161 GeV, using the OPAL detector at LEP. Results are presented both including and excluding the dominant production of radiative γZ 0 events. We have measured R b , the ratio of the number of b b to all multihadronic events at 161 GeV, and compared it to the result obtained at 130–136 GeV. All results agree well with the Standard Model expectations. In a model-independent fit to the Z 0 lineshape, the data presented here give an improved precision on the γZ 0 -interference term. The data have also been used to obtain new limits on extensions of the Standard Model described by effective four-fermion contact interactions.
No description provided.
No description provided.
THETA(P=4 5) is an acollinearity angle between electron and positron.
The results of total cross section measurements for theνμ,\(\bar \nu _\mu\) interactions with isoscalar target in the 3 – 30 GeV energy range have been presented. The data were obtained with the IHEP-JINR Neutrino Detector in the “natural” neutrino beams of the U-70 accelerator. Neutrino fluxes were obtained by averaging the spectra, based on the calculations with the use of the experimental data on secondary particle yields from the target and muon fluxes measurements in 9 gaps of the muon filter, as well as the spectra determined from quasi-elastic events and spectra defined by extrapolating differential distributiondσ/dy in the regiony=0. The significant deviation from the linear dependence forσtot versus neutrino energy is determined in the energy range less than 15 GeV.
No description provided.
No description provided.
The CLEO II detector is used to search for the production of χc2 states in two-photon interactions. We use the signature χc2→γJ/ψ→γl+l− with l=e,μ. Using 1.49 fb−1 of data taken with beam energies near 5.29 GeV, the two-photon width of the χc2 is determined to be Γ(χc2→γγ)=1.08±0.30(stat)±0.26(syst) keV, in agreement with predictions from perturbative QCD.
Results below were obtained usign J/psi from-factors in the two photon propogators, and assumes that only transversely polarized photons are significant inthe production of the CHI/C2(1P) state.
No description provided.
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CHARGED PARTICLES HAVE LARGE ESCAPE ANGLE. DIFRACTIVE SCATTERED PION.
CHARGED PARTICLES HAVE LARGE ESCAPE ANGLE. DIFRACTIVE SCATTERED PION.
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The cross section per nucleon is evaluated with assumption of the linear atomic number dependence. SIG(C=NEUTRINO) and SIG(C=ANTINEUTRINO) are corresponded to the NUMU and NUMUBAR data, respectevly. CLOOP-OVER.
Measurements are presented of the cross section ratios R ℓ = σ ℓ ( e + e − →ℓ + ℓ − ) σ h ( e + e − →hadrons) for ℓ=e, μ and τ using data taken from a scan around the Z 0 . The results are R e =(5.09± o .32±0.18)%, R μ =(0.46±0.35±0.17)% and R τ =(4.72±0.38±0.29)% where, for the ratio R e , the t -channel contribution has been subtracted. These results are consistent with the hypothesis of lepton universality and test this hypothesis at the energy scale s ∼8300 GeV 2 . The absolute cross sections σ ℓ (e + e − →ℓ + ℓ − ) have also been measured. From the cross sections the leptonic partial widths Γ e =(83.2±3.0±2.4) MeV, (Γ e Γ μ ) 1 2 =(84.6±3.0±2.4) MeV and (Γ e Γ τ ) 1 2 =(82.6±3.3±3.2) MeV have been extracted. Assuming lepton universality the ratio Γ ℓ Γ h =(4.89±0.20±0.12) × 10 −2 w was obtained, together with Γ ℓ =(83.6±1.8±2.2) MeV. The number of light neutrino species is determined to be N v =3.12±0.24±0.25. Al the data are consistent with the predictions of the standard model.
E+ E- final state is t-channel subtracted.
No t-channel subtraction. Statistical errors only.
Statistical errors only.
None
No description provided.
No description provided.
No description provided.
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