Relative cross sections have been measured for p¯p annihilation by a new technique in the invariant-mass range 1920-1960 MeV. The 90%-confidence upper limit on simple Breit-Wigner enhancements in the S region (between 1930 and 1942 MeV) of width 4 MeV or narrower is 12 mb MeV, assuming a simple dependence with momentum of the nonresonant cross section.
No description provided.
The reactions K − p → Ξ 0 − (1320) K 0 + , Ξ − (1320) K + (890), Ξ 0 − (1530) K 0 − and Ξ 0 − (1530) K 0 + (890) are studied at 4.2 GeV/ c incident momentum. The data come from a high-statistics bubble chamber experiment with a sensitivity of ∼ 133 events/ μ b. Total anddifferential cross sections are presented. The results are compared to the SU(3)-related processes K + p → pK + and K + p → pK + (890) in the backward hemisphere. In the forward hemisphere “forbidden” peaks are observed and current ideas about them are discussed.
FULLY CORRECTED FOR ALL CUTS AND UNSEEN DECAY MODES.
TOTAL, FORWARD AND BACKWARD CROSS SECTIONS. FULLY CORRECTED FOR CUTS, K0 AND LAMBDA UNSEEN DECAY MODES AND OTHER K*(892) AND XI(1530P13) DECAYS. IN 3-BODY FINAL STATES, THETA REFERS TO THE PI-K SYSTEM.
No description provided.
In a sample of 670 000 charged-current neutrino events, 101 μ−μ− events have been observed, with 30 GeV<Eν<600 GeV and Pμ>9 GeV/c for both muons. After background subtraction, 18.5±13.9 events remain, yielding a prompt rate of (5.5±4.1)×10−5 per charged-current event. A sample of 124 000 antineutrino events yields 15 μ+μ+ events, giving 6.4±4.2 events after background subtraction and a prompt rate of (1.0±0.7)×10−4 per charged-current event. The numbers and kinematic distributions of these events are consistent with standard model sources.
No description provided.
We have measured the strange-quark content of the nucleon, ηs=−0.08+0.012, and the Kobayashi-Maskawa matrix element ‖Vcd‖=0.220−0.018+0.015 using a sample of 1797 νμ- and ν¯μ-induced μ−μ+ events with Pμ≥9 GeV/c and 30≤Eν≤600 GeV. The data are consistent with the slow-rescaling hypothesis of charm production in ν-N scattering and within this formalism yield a value of the charm-quark mass parameter mc=1.31−0.48+0.64 GeV/c2. .AE
No description provided.
No description provided.
A measurement of the cross section for e + e - → hadrons using 11 000 hadronic decays of the Z boson at ten different center-of-mass energies is presented. A three-parameter fit gives the following values for the Z mass M z , the total width Γ z , the product of the electronic and hadronic partial widths Γ e Γ h , and the unfolded pole cross section σ 0 : M Z =91.171±0.030(stat)±0.030 (beam) GeV, Γ Z =2.511±0.065 GeV, Γ e Γ h =0.148±0.006 (stat.)±0.004 (syst.) GeV 2 , σ 0 =41.6±0.7(stat.)±1.1 (syst.) nb,
No description provided.
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.
In a photoproduction experiment using a mean photon energy of 100 GeV we have observed 29±8 Λ c ( Λ c ) charmed-baryon and antibaryon decays in the pK − π + ( p K + π − ) final state. Quasi two-body final states do not contribite significantly to this channel. The mass of the Λ c was measured to be 2281.7±2.7±2.6 MeV/ c 2 and its lifetime 0.18±0.03±0.03 ps. The ratio of Λ c D production, measured in this experiment, is significantly greater than that predicted by photon-gluon fusion and using a Lund model to describe the hadronization. This excess cannot be completely accounted for in this model, even using a Λ c branching fraction in pK π as high as 5%.
Result extrapolated to all lambda/c energies has large model dependent uncertainties.
We report an improved measurement of the inverse muon decay process, ν μ +e→ μ − + ν e , at the Fermilab Tevatron. The rate of this reaction with respect to the ν μ -N charged current interaction is measured to be (0.1245±0.0057(stat.)±0.0031 (sys.)) × 10 −2 . The measurement confirms the standard model predictions for the Lorentz structure of the weak current, the helicity of the neutrino, and the energy dependence of the cross section.
Data from the Quadruple Triplet Neutrino beam (QTB).
Data from the Narrow Band Beam(NBB).
Weighted average of the QTB and NBB data.
The production rates for 2-, 3-, 4- and 5-jet hadronic final states have been measured with the DELPHI detector at the e + e − storage ring LEP at centre of mass energies around 91.5 GeV. Fully corrected data are compared to O(α 2 s ) QCD matrix element calculations and the QCD scale parameter Λ MS is determined for different parametrizations of the renormalization scale ω 2 . Including all uncertainties our result is α s ( M 2 Z )=0.114±0.003[stat.]±0.004[syst.]±0.012[theor.].
Corrected jet rates.
Second systematic error is theoretical.
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.
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