We report new measurements of the production cross section for the reaction e+e−→τ+τ− at s=29 GeV, as well as the topological decay branching fractions of the τ lepton. The data were taken with the High Resolution Spectrometer at the SLAC e+e− colliding-beam facility PEP. The measured cross section yields Rττ=1.044±0.014±0.030 [where the first (second) error is statistical (systematic)], consistent with QED and corresponding to QED cutoff parameters of Λ+>129 GeV and Λ−>284 GeV at the 95% C.L. The fractions of τ decays into one and three charged particles are B1=0.864±0.003±0.003 and B3=0.135±0.003±0.003.
No description provided.
Measurements of inclusive transverse-momentum spectra for KS0 mesons produced in proton-antiproton collisions at s of 630 and 1800 GeV are presented and compared with data taken at lower energies. The ratio, as a function of pT, of the cross section for KS0 to that for charged hadrons is very similar to what is observed at lower energies. At 1800 GeV, we calculate the strangeness-suppression factor λ=0.40±0.05.
Estimated effective cross sections for events which pass the trigger and selection criteria. The uncertainties in these represent the principal source of error in the overall normalisation of the results.
Statistical errors only.
Statistical errors only.
This paper reports cross-section measurements for the ρ0 and K*(890) vector mesons produced in e+e− annihilation at s=29 GeV. The data, which were taken with the High Resolution Spectrometer operating at the SLAC colliding-beam facility PEP, correspond to an integrated luminosity of 291 pb−1. The measured multiplicities for fractional momentum x>0.05 are Nρ0=0.79±0.04 and NK*0(890)=0.53±0.04. The measured fragmentation functions agree well with the predictions of the Lund model and when extrapolated to threshold, the corresponding total multiplicities are Nρ0=0.90±0.05 and NK*0(890)=0.59±0.05.
No description provided.
No description provided.
No description provided.
We have measured dijet angular distributions at √s =1.8 TeV with the Collider Detector at Fermilab and the Tevatron p¯p Collider and find agreement with leading-order QCD. By comparing the distribution for the highest dijet invariant masses with the prediction of a model of quark compositeness, we set a lower limit on the associated scale parameter Λc at 330 GeV (95% C.L.).
Numerical values read from figure in preprint.
We report a measurement of the e+e−→e+e−pp¯π+π− process with the TPC/Two-Gamma facility at the PEP e+e− storage ring at SLAC. Forty-five pp¯π+π− events were identified in data corresponding to an integrated e+e− luminosity of 142 pb−1. The cross section for γγ→pp¯π+π− is given both as a function of the γγ center-of-mass energy Wγγ, with Wγγ between 2.5 and 5.5 GeV, and as a function of the in variant mass squared q2 of one of the photons, with −q2<7 GeV2. This cross section falls much less rapidly with Wγγ than does the cross section for a similar process, γγ→pp¯. No Δ0Δ¯0 production is observed, and only a small fraction of the events at low Wγγ is consistent with γγ→Δ++Δ¯−−, Δ++p¯π−, or Δ¯−−pπ+. In an expanded search through the same data, four events compatible with either ΛΛ¯(Λ→pπ−) or Σ0Λ¯(Σ0→Λγ) production were found.
Statistical errors only.
Data read from graph.
We have observed Σc++ and Σc0 baryons in nonresonant e+e− interactions through their decays to Λc+π± using the CLEO detector. The mass difference M(Σc++)-M(Λc+) is measured to be 167.8±0.4±0.3 MeV; for M(Σc0)-M(Λc+) we find 167.9±0.5±0.3 MeV. Σc decay accounts for (18±3±5)% of Λc+ production.
The cross section ratio is multiplied by a factor of 1.5 to account for theunobserved SIGMA/C(2455)+.
No description provided.
In order to improve existing I=0 phase shift solutions, the spin correlation parameter ANN and the analyzing powers A0N and AN0 have been measured in n-p elastic scattering over an angular range of 50°–150° (c.m.) at three neutron energies (220, 325, and 425 MeV) to an absolute accuracy of ±0.03. The data have a profound effect on various phase parameters, particularly the P11, D23, and ε1 phase parameters which in some cases change by almost a degree. With the exception of the highest energy, the data support the predictions of the latest version of the Bonn potential. Also, the analyzing power data (A0N and AN0) measured at 477 MeV in a different experiment over a limited angular range [60°–80° (c.m.)] are reported here.
The beam analysing power at incident kinetic energy 220 MeV. Additional systematic uncertainty of +- 0.015 and a scalar error of 3.5 PCT.
The beam analysing power at incident kinetic energy 325 MeV. Additional systematic uncertainty of +- 0.018 and a scalar error of 3.1 PCT.
The beam analysing power at incident kinetic energy 425 MeV. Additional systematic uncertainty of +- 0.022 and a scalar error of 3.3 PCT.
We have measured np→dπ0 cross sections at eleven beam energies within 16 MeV of threshold. Total cross sections are only 0.67±0.10 of the value which has been generally accepted for s-wave pion production strength near threshold. The differential cross sections are anisotropic at only 1 MeV (c.m.) above threshold. Our results are compared to π+d→pp data and to predictions of two models.
Error quoted contains 2 PCT statistical uncertainty in acceptance measurement.
The analyzing power A N of proton-proton, proton-hydrocarbon, and antiproton-hydrocarbon, scattering in the Coulomb-nuclear interference region has been measured using thhe 185 GeV/ c Fermilab polarized-proton and -antiproton beams. The results are found to be consistent with theoretical predictions within statistical uncertainties.
No description provided.
Data from hydrocarbon target.
Data from hydrocarbon target.
Total and differential K0 corss sections are presented from e+e− collisions at s=29 GeV in the High Resolution Spectrometer detector. K0 and charged-particle distributions are compared in a study of the hadronization of quarks of known flavor. Ecents of the reaction e+e−→cc¯ are tagged by identifying D*'s while uu¯, dd¯, or ss¯ events are tagged through the identification of a charged particle with fractional momentum near 1. Parton-shower models with cluster and string fragmentation are compared with these data. Also, certain particle scaling tests are performed using the quark-flavor tags. In addition, K0 production in two- and three-jet events is compared to these models.
Corrected Cross Sections (Lund MC used to extrapolate).
R value for K0 production.
K0 differential cross section as function of the fractional energy.
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