The production rates of D^*+/- mesons in charm and bottom events at centre-of-mass energies of about 91 GeV and the partial width of primary cc(bar) pairs in hadronic Z^0 decays have been measured at LEP using almost 4.4 million hadronic Z^0 decays collected with the OPAL detector between 1990 and 1995. Using a combination of several charm quark tagging methods based on fully and partially reconstructed D^*+/- mesons, and a bottom tag based on identified muons and electrons, the hadronisation fractions of charm and bottom quarks into D^*+/- mesons have been found to be: f(b -> D^*+ X) = 0.173 +/- 0.016 +/- 0.012 and f(c -> D^*+ X) = 0.222 +/- 0.014 +/- 0.014 The fraction of cc(bar) events in hadronic Z^0 decays, Gamma_cc(bar)/Gamma_had = Gamma(Z^0 -> cc(bar))/Gamma(Z^0 -> hadrons), is determined to be Gamma_cc(bar)/Gamma_had = 0.180 +/- 0.011 +/- 0.012 +/- 0.006 In all cases the first error is statistical, and the second one systematic. The last error quoted for Gamma_cc(bar)/Gamma_had is due to external branching ratios.
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Measurements of helicity density matrix elements have been made for the φ(1020), D*± and B* vector mesons in multihadronic Z0 decays in the OPAL experiment at LEP. Results for inclusive φ produced with high energy show evidence for production preferentially in the helicity zero state, with ρ00 = 0.54 ± 0.08, compared to the value of 1/3 expected for no spin alignment. The corresponding element for the D*± has a value of 0.40 ± 0.02, also suggesting a deviation from 1/3. The B* result, with ρ00 = 0.36 ± 0.09, is consistent with no spin alignment. Off-diagonal elements have been measured for the f and D* mesons; for the D* the element Re ρ1−1 is non-zero, indicating non-independent fragmentation of the primary quarks.
Helicity density matrices elements. Helicity beam frame is used.
Charge conjugated states are understood.
Helicity density matrices elements. Charge conjugated states are understood.
In this paper an investigation of the production of D ∗ ± mesons produced in e + e − collisions at energies around the Z 0 pole is presented. Based on 115 D ∗ ± mesons with x D∗ 2E D ∗ /E cm > 0.2 the properties of D ∗ mesons produced in the reaction Z 0 → c c are studied. Fixing the yield and the fragmentation function of bottom quarks to the values obtained at LEP using lepton tags, and average energy fraction of the D ∗ ± mesons from primary charmed quarks of 〈x c → D ∗ 〉 = 0.52 ± 0.03 +- 0.01 is found and Γ z 0 →c c = (323 ± 61 ± 35) MeV is determined. The first error is the combined statistical and systematic error from this experiment, and the second the total error from other sources.
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The production of D * and D mesons has been studied in e + e − annihilations at √s = 29GeV. The data, corresponding to an integrated luminosity of 300 pb −1 , were obtained using the HRS detector at PEP. The cross section is measured to be R (D 0 + D + ) = 2.40±0.35 and we determine the electroweak asymmetry to be −9.9 ± 2.7%, which corresponds to an axial vector coupling constant product g e g c = 0.26 ± 0.07.
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Reconstruction of charged D ∗ 's produced inclusively in e + e −. annihilation at CM energies near 34.4 GeV is accomplished in the decay modes D ∗ + → D 0 π + → K − gp + π 0 π + and D ∗ + → D 0 π + → K − gp + π − π + π + and their charge conjugates. Using these and previously reported D ∗ + → D 0 π + → K − gp + π + and D ∗ + → D 0 π + → K − gp + π + + missing π 0 channels we present evidence for hard gluon bremsstrahlung from charm quarks and show that the ratio of the quark-gluon coupling constant of charm quarks to the coupling constant obtained in the average hadronic event, α s c α rms = 100 ± 0.20 ± 1.20 . Our result provides evidence that the quark-gluon coupling constant is independent of flavor.
No description provided.
No description provided.
D ∗± production via e + e − →D ∗± X has been measured at an average CM energy of 34.4 GeV. The D ∗± energy spectrum is hard, with a maximum near χ = 0.6. The size of the D ∗ cross section, R D ∗ = σ( e + e − → D ∗ X ) σ μμ = 2.50 ± 0.64 ± 0.88 (assuming R D ∗0 = R D ∗+ ) indicates that a large fraction of charm quark production yields D ∗ mesons. The D ∗± angular distribution exhibits a forward—backward asymmetry, A = −0.28 ± 0.13. This is consistent with that expected in the standard theory for weak neutral currents and leads to | g A c | = 0.89 ± 0.44 for the axial vector coupling of the charm quark.
ASSUMES EQUAL RATES FOR CHARGED AND NEUTRAL D*'S. ONLY CHARGED ARE DETECTED.
ASYMMETRY MEASUREMENT. THETA IS THE ANGLE BETWEEN THE E- AND THE D*.
D ∗± production via e + e − → D ∗± X was studied at CM energies near 34 GeV. The charged particles produced in the hemisphere opposite to that of the D ∗ were used to investigate the fragmentation of charm jets. All spectra studied show a close similarity between the charm jet and the average jet obtained by summing over all quark flavours. The spectra of particles produced in the D ∗ hemisphere were used to study separately first rank and higher rank fragmentation.
THE C-JET IS THE JET IN THE HEMISPHERE OPPOSITE TO THAT CONTAINING THE D* MESON. DIVISION IS MADE BY A PLANE PERPENDICULAR TO THE THRUST AXIS.
Measurements of the forward-backward asymmetry of e + e − → cc events were carried out at a mean √s energy of 57.95 GeV at TRISTAN, KEK. The cc events were tagged either by the full-reconstruction of D ∗± or the inclusive P T spectrum of π s ± from D ∗± → D 0 ( D 0 )π s ± . The forward-backward asymmetry was measured to be A FB c = −0.49 −0.13 +0.14 (stat.) ± 0.06 (syst.), consistent with the standard model.
No description provided.
Vector mesons produced in the reaction e + e − →V+X at √ s =29 GeV were isolated by observing D ∗ mesons through the D ∗+ → D 0 π + decay. The D 0 decay modes used are D 0 →K3 π , K π , K π , and K π ( π 0 ). The data, which correspond to an integrated luminosity of 300 pb −1 , were collected by the High Resolution Spectrometer at PEP. Spin density matrix elements for the D ∗ meson are measured as a function of the energy sharing variable Z D ∗ . There is no evidence for alignment of D ∗ mesons produced in e + e − annihilation at our energy.
Spin density matrix for D0 --> K PI decay mode.
Spin density matrix for D0 --> K 3PI decay mode.
Spin density matrix for D0 --> K PI (PI0) decay mode.
Using the CLEO detector at the Cornell Electron-positron Storage Ring, we have measured the scaled momentum spectra, dsigma/dx_p, and the inclusive production cross sections of the charm mesons D+, D0, D*+, and D*0 in e+e- annihilation at about 10.5 GeV center of mass energy, excluding the decay products of B mesons. The statistical accuracy and momentum resolution are superior to previous measurements at this energy.
Total cross sections for D production from the various decay modes. The data are fully corrected for detection efficiency and decay branching ratios. The second DSYS error is the error due to the uncertainty in the branching ratio.
Differential cross sections for D+ production from the (K- PI+ PI+) decay mode.
Differential cross sections for D0 production from the (K- PI+) decay mode.
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