We report results on the differential and total cross sections for inclusive production of the charmed particles D*+, D*0, D0, D+, Ds, and Λc in e+e− annihilations at √s=10.55 GeV. Widely used quark fragmentation models are discussed and compared with the measured charmed-particle momentum distributions. This comparison, as well as that with measurements at other center-of-mass energies, shows the need to take QCD corrections into account and their importance for a correct interpretation of the model parameters. The observed rate of D0 and D+ production is compared to the expected total charm production cross section. We measure the probability of a charmed meson being produced as a vector meson and the D*+ decay branching fraction into D0π+.
No description provided.
No description provided.
No description provided.
Data from e + e − annihilations at 29 GeV have been used to measure the production cross section and fragmentation function of η mesons. The signal is observed in the η → γγ decay channel. The fragmentation for p η >1.5 GeV/ c agrees well with the prediction of the Lund model, whereas the prediction of the Webber model lies above the data. The mean multiplicity is measured to be 〈 n η 〉=0.58±0.10 η mesons per hadronic event, of which 0.51 represents the direct production of η and η ′ mesons in the fragmentation chain.
Statistical errors only.
Extrapolated to full z range using LUND model.
We report a measurement of the charged K ∗ (892) production in e + e − annihilations at 29 GeV center-of-mass energy. The 300 pb −1 data sample used for this analysis is obtained with the High Resolution Spectrometer at the SLAC storage ring PEP. The total mean multiplicity is measured to be 〈n K ∗± (892) 〉=0.62±0.045±0.04 per hadronic event. Evidence is also given for the production of a charged K 2 ∗ (1430) tensor meson.
Extrapolation to full x-range using Lund model.
Data requested from authors.
Extrapolation to full x-range usisng fragmentation friction predicted by the Webber cluster model.
We report cross sections for the process γγ→pp¯ at center-of-mass energies W from 2.0 to 2.8 GeV. These results have been extracted from measurements of e+e−→e+e−pp¯ at an overall center-of-mass energy of 29 GeV, using the TPC/Two-Gamma facility at the SLAC storage ring PEP. Cross sections for the untagged mode [both photons nearly real] are shown to lie well above QCD predictions. Results are also presented for the single-tagged mode [one photon in the range 0.16
Data read from graph in preprint. Statistical errors only.
Data read from graph. Statistical errors only.
Data read from graph. Statistical errors only.
The production of strange baryons Σ± (1385) and Ξ− has been observed in e+e− annihilations at 29 GeV center-of-mass energy, by use of data obtained with the High Resolution Spectrometer at the SLAC storage ring PEP. The total mean multiplicities are measured to be 〈nΣ±(1385)〉=0.033±0.006±0.005 and &〉=0.016±0.004 ±0.004 per hadronic event. The results are in good agreement with the Lund string model.
Lund model extrapolation to full x range.
Lund model extrapolation to full x range.
No description provided.
Two high statistics measurements of antiproton-proton small-angle elastic scattering, at p = 233 MeV/ c and p = 272 MeV/ c , are presented. The measurements were carried out at the LEAR facility at CERN. By the Coulomb-nuclear interference method, values are obtained for the real-to-imaginary ratio ρ of the p̄p forward nuclear scattering amplitude and for its exponential slope b : ρ = + 0.041 ± 0.026 and b = 71.5 ± 4.5 (GeV/ c ) −2 at 233 MeV/ c and ρ = −0.014 ± 0.027 and b = 47.7 ± 2.7 (GeV/ c ) −2 at 272 MeV/ c . The method to derive these values is discussed in detail and so are the uncertainties contributing to their systematic error. The results are compared with predictions from forward dispersion relation calculations and with predictions from p̄p potential models.
The corrected cross section is the measured divided by the average folding correction given in the paper.
The corrected cross section is the measured divided by the average folding Correction given in the paper.
Fits to data use the value of total cross sections of 263 & 296 mb for 272 & 233 Mev respectively derived from the authors total cross sections measurement. ETA is the spin dependence parameter.
Neutral D ∗ meson production in e + e − annihilation at √ s =29 GeV has been studied using the high resolution spectrometer. The decay of D ∗0 into D 0 γ, where the D 0 decays into K −π + , has been observed. The production cross section in units of the point cross section is 0.63±0.22 for fractional energy Z ⩾0.5. The fragmentation function is compared with that of the D ∗+ meson measured in the same experiment.
No description provided.
Assuming additionaly BR(D0-->K PI) of 0.56 +- 0.005.
Corresponding R value.
The production of the tensor mesons f0(1270) and K*0(1430) and the scalar meson S(975) has been observed in e+e− annihilation at 29 GeV center-of-mass energy by use of data obtained with the high-resolution spectrometer at the SLAC e+e− storage ring PEP. The mean multiplicities for meson momenta greater than 1450 MeV/c are 〈nf0〉=0.11±0.04, 〈nK*0(1430)〉=0.10±0.06, and 〈nS〉=0.05±0.02 per hadronic event. The fragmentation functions of the tensor mesons are in good agreement with the predictions of the Webber cluster model. The data are consistent with a predominant strange-quark content on the S meson.
No description provided.
No description provided.
This paper reports measurements of the differential cross sections for the reactions e+e−→e+e− (Bhabha scattering) and e+e−→γγ (γ-pair production). The reactions are studied at a center-of-mass energy of 29 GeV and in the polar-angular region ‖costheta‖<0.55. A direct cross-section comparison between these two reactions provides a sensitive test of the predictions of quantum electrodynamics (QED) to order α3. When the ratio of γ-pair to Bhabha experimental cross sections, integrated over ‖costheta‖<0.55, is divided by the same ratio predicted from α3 QED theory, the result is 1.007±0.009±0.008. The 95%-confidence limits on the QED-cutoff parameters are Λ+>154 GeV and Λ−>220 GeV for Bhabha scattering, and Λ+>59 GeV and Λ−>59 GeV for γ-pair production.
No description provided.
We report measurements of the two-photon processes e+e−→e+e−π+π− and e+e−→e+e−K+K−, at an e+e− center-of-mass energy of 29 GeV. In the π+π− data a high-statistics analysis of the f(1270) results in a γγ width Γ(γγ→f)=3.2±0.4 keV. The π+π− continuum below the f mass is well described by a QED Born approximation, whereas above the f mass it is consistent with a QCD-model calculation if a large contribution from the f is assumed. For the K+K− data we find agreement of the high-mass continuum with the QCD prediction; limits on f′(1520) and θ(1720) formation are presented.
Data read from graph. Additional overall systematic error 20% not included.
Data read from graph.. Additional overall systematic error 20% not included.
Data read from graph.. Additional overall systematic error 20% not included.. The Q**2 dependence is normalized to unity for the bin centred on Q**2 = 0.
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