An analysis of W and Z boson production at UA1, using 4.66 pb −1 of data from the 1988 and 1989 CERN p p Collider runs at s =0.63 TeV , yields R ≡ σ W Br(W→ μ v)/ σ z Br( Z → μμ )=10.4 −1.5 +1.8 stat.±0.8(syst.) We find R =9.5 −1.0 +1.1 (stat.+syst.) when combining all available UA1 data, in both the electron and muon channel, taken in the period 1983–1989. In the framework of the standard model, the value of R is used to infer the total width of the W boson, Γ W tot =2.18 −0.24 +0.26 (exp.)±0.04(theory) GeV/ c 2 .
No description provided.
We have measured the cross-section of the reaction e + e − → γγ at center of mass energies around the Z 0 mass. The results are in good agreement with QED predictions. For the QED cutoff parameters the limit of Λ + > 103 GeV and Λ − 118 GeV are found. For the decays Z 0 → γ ,Z 0 → π 0 γ , Z 0 → γγγ we find upper limits of 2.9 × 10 −4 ,2.9×10 −4 ,4.1×10 −4 and 1.2×10 −4 , respectively. All limits are at 95% CL.
No description provided.
We have measured the partial widths for the three reactions e + e − → Z 0 → e + e − , μ + μ − , τ + τ − . The results are Γ ee = 84.3±1.3 MeV, √ Γ ee Γ μμ =83.9±1.4 MeV, and √ Γ ee Γ ττ =83.9±1.4 MeV, where the errors are statistical. The systematic errors are estimated to be 1.0 MeV, 0.9 MeV, and 1.4 MeV, respectively. We perform a simultaneous fit to the cross sections for the e + e − →e + e − , μ + μ − , and τ + τ − data, the differential cross section as a function of polar angle for the electron data, and the forward- backward asymmetry for the muon data. We obtain the leptonic partial with Γ ℓℓ =84.0±0.9 (stat.) MeV. The systematic error is estimated to be 0.8 MeV. Also, we obtain the axial-vector and vector weak coupling constants of charged leptons, g A =−0.500±0.003 and g ν =−0.064 −0.013 +0.017 .
Cross section from 1990 data.
Visible cross section obtained using the cuts required by Method I (see text of paper). (1989 and 1990 data).
Visible cross section obtained using the cuts required by Method II (see text of paper). (1989 and 1990 data). RE = E+ E- --> E+ E- (GAMMA).
Overall systematic error is 2.3 pct.
Overall systematic error is 2.6 pct.
Overall systematic error is 2.8 pct.
A determination of the partial width Γ c c ̄ of the Z 0 boson into charm quark pairs is presented, based on a total sample of 36 900 Z 0 hadronic decays measured with the DELPHI detector at the LEP collider. The production rate of cc̄ events is derived from the inclusive analysis of charged pions coming from the decay of charmed meson D ∗+ → D 0 π + and D ∗− → D ̄ 0 π − where the π ± is constrained by kinematics to have a low p T with respect to the axis. The probability to produce these π ± from D ∗± decay in cc̄ events is taken to be 0.31 ±_0.05 as measured at √ s =10.55 GeV. The measured relative partial width Γ c c ̄ Γ h = 0.162± 0.030 ( stat. ) ±0.050 ( syst. ) is in good agreement with the standard moel value of 0.171. Together with our previous measurement of the total hadronic width Γ h this implies Γ c c ̄ = 282±53 ( stat. )±88( syst. ) MeV .
No description provided.
We present a study of jet multiplicities based on 37 000 hadronic Z 0 boson decays. From this data we determine the strong coupling constant α s =0.115±0.005 ( exp .) −0.010 +0.012 (theor.) to second order QCD at √ s =91.22GeV.
Errors are combined statistical and systematic uncertainties.
No description provided.
We have measured the cross section for e + e − →hadrons over the center of mass energy range of the Z 0 peak, from 88.22 to 95.03 GeV. We determine the Z 0 mass M z =91.164±0.013 (experiment) ±0.030 (LEP) GeV. Within the framework of the standard model we determine the invisible width, Γ invisible =0.502±0.018 GeV, and the number of light neutrino species, N ν =3.01±0.11. We exclude the existence of a supersymmetric scalar neutrino having a mass less than 31.4 GeV, at the 95% confidence level. We performed a model independent combined fit to the e + e − →hadrons and e + e − → μ + μ − data to determine total width, leptonic width and hadronic width of the Z 0 .
Cross sections from 1990 data. Additional systematic error 1.5 pct.
Cross sections from 1989 data. This data has been rescaled by 0.96 from original publication PL B237 (90) 136. Additional systematic error 2.0 pct.
The elastic magnetic form factor of Ca41 has been determined by 180° electron scattering in the momentum-transfer range 0.9–2.0 fm−1. An analysis of the data indicates that the amplitudes of the M3 and M5 multipoles are quenched by factors of 0.57±0.16 and 0.68±0.07 relative to the simple shell model. In contrast, the magnitude of the M7 form factor is in good accord with this model. Calculations that include multiparticle-multihole configurations in the 1f7/2 and 1d3/2 subshells, first-order core polarization to higher excited orbitals, and meson exchange currents give reasonable agreement with the data for all multipoles. The rms radius of the 1f7/2 neutron orbit was determined by means of a combined analysis of our results and previous data obtained at higher momentum transfers. After correcting for core polarization and meson exchange currents, the radius was found to be 3.96±0.05 fm, in agreement with the predictions of mean-field calculations.
No description provided.
A high-statistics experiment on the reaction π − p→ π + π − π 0 n at 8.06 GeV/ c has been performed using a spectrometer detecting both charged particles and gamma rays. A partial-wave analysis based on the isobar model has been carried out for π + π − π 0 data in the mass range between 0.86 and 1.50 GeV for four t ′ regions: 0.0–0.1, 0.1–0.25, 0.25–0.45 and 0.45–0.95 (GeV/ c 2 ). Two axial-vector resonances, a 1 (1260) and h 1 (1170), were observed in the analysis. The masses and widths of a 1 and h 1 were determined to be M (a 1 = 1121 ± 8 MeV, Λ (a 1 = 239± 11 MeV, M (h 1 = 1168±4 MeV and Λ (h 1 = 345±6 MeV, respectively, by fitting the Breit-Wigner formula to the partial wave amplitude. A fit including the Deck type background was also tried in each t ′ region. The results showed a small effect on these resonance parameters and were consistent with those obtained by the simple Breit-Wigner fitting.
Production cross section of A2(1320) from the 12+ rhoD1+ partial wave.
Production cross section of H1(1190) from the 01+ rhoS0+ partial wave.
Production cross section of A1(1270) from the 11+ rhoS1+ partial wave.
A study of the two-jet mass spectrum measured with the UA 2 calorimeter has revealed a signal from hadronic decays ofW andZ bosons above a large background. Production and decay properties of the signal have been measured. The combined production cross-section σ·B(W, Z → two jets) is 9.6±2.3 (stat.)±1.1 (syst.) nb, compared with an expectation of 5.8 nb calculated to order αs2. A limit on the production cross-section of additional heavy vector bosons decaying into two jets is given as a function of the boson mass.
No description provided.
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