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.
We have measured the polarization of D*, the energy dependence of the polarization, and the spin-density matrix of D* in e+e− annihilation at a center-of-mass energy of 29 GeV using the Time Projection Chamber detector at the SLAC storage ring PEP. In 147 pb−1 of data we see no strong evidence for polarization, alignment, or final-state interactions in this fragmentation process.
Polarization is the factor alpha(z) in the expression d width (D*-->D pi)/domega = C(1+alpha(z)cos(theta)**2).
Spin density matrices for D* --> D0 pi+.
The TPC/Two-Gamma Collaboration has measured the inclusive cross section for production of charmed D ∗± mesons in photon-photon collisions. The reaction utilized was e + e - →e + e - D ∗± X, with D ∗± →D O π +- , D O →K -+ π ± , and either zero or one outgoing e ± detected. The result, σ(e + e - → e + e - D ∗± X) = 74±26±19 pb , is in agreement with the quark parton mo del prediction for e + e - → e + e - c c , combined with a Lund model for the hadronization of the charmed quarks.
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We report on a study of inclusive production ofD*± mesons ine+e− annihilation at c.m. energies between 28 and 46.8 GeV using the TASSO detector at the PETRA storage ring. A hardD*± energy spectrum is measured with a maximum nearED*±≃0.6Ebeam. The measured cross section ratio\((\sigma _{D^{* + } }+ \sigma _{D^{* - } } )/\sigma _{\mu \mu }= 1.28 \pm 0.09 \pm 0.18\) indicates thatD* production accounts for a large fraction of the observed charm production. Two complementary methods have been used to determine the forward-backward asymmetry of charm pair production due to electroweak interference. Combining both measurements the product of the axial vector couplings of the electron and the charm quark to the weak neutral current was determined to begAegAc=−(0.276±0.073), in agreement with the standard model prediction of −0.25. Using a sample of reconstructedD*± mesons, the relative strength of the strong interaction coupling of thec quark compared to that of an average of all flavours is measured as αs(c)/αs(all)=0.91±0.38±0.15, consistent with the coupling constant being flavour independent. An update of ourD0 lifetime measurement is presented, based on a considerable increase in statistics, the final result being\(\tau _{D^0= } (4.8 \pm _{0.9 - 0.7}^{1.0 + 0.5} )10^{ - 13} s\).
Cross sections using D0 --> K- PI+ channel.
Cross sections using D0 --> K- PI+ PI- PI+ channel.
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.
The production of charmed D* mesons in e+e− annihilations at a center-of-mass energy of 29 GeV has been studied using the time-projection-chamber (TPC) detector at the SLAC storage ring PEP. The production cross section, fragmentation function, and forward-backward asymmetry due to electroweak effects are measured, and a limit on D0-D¯0 mixing is determined.
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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.
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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.
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.
DATA PEAKS AT X=0.6 TO 0.8.
ASYMMETRY MEASUREMENT. THETA IS THE ANGLE BETWEEN THE E- AND THE D*.
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