Using the CLEO-c detector at the Cornell Electron Storage Ring, we have measured inclusive and exclusive cross sections for the production of D+, D0 and Ds+ mesons in e+e- annihilations at thirteen center-of-mass energies between 3.97 and 4.26 GeV. Exclusive cross sections are presented for final states consisting of two charm mesons (DD, D*D, D*D*, Ds+Ds-, Ds*+Ds-, and Ds*+Ds*-) and for processes in which the charm-meson pair is accompanied by a pion. No enhancement in any final state is observed at the energy of the Y(4260).
Exclusive cross section for two body neutral non-strange charm mesons.
Exclusive cross section for two body charged non-strange charm mesons.
Exclusive cross section for two body strange charm mesons.
Using the CLEO III detector, we measure absolute cross sections for e+e- --> hadrons at seven center-of-mass energies between 6.964 and 10.538 GeV. The values of R, the ratio of hadronic and muon pair production cross sections, are determined within 2% total r.m.s. uncertainty.
Measured values of R as a function of CM energy. The first DSYS error is the correlated uncertainty and the second is the uncorrelated.
We have updated our measurement of the cross section for e^+e^- -> psi(3770) -> hadrons, our publication "Measurement of sigma(e^+e^- -> psi(3770) -> hadrons) at E_{c.m.} = 3773 MeV", arXiv:hep-ex/0512038, Phys.Rev.Lett.96, 092002 (2006). Simultaneous with this arXiv update, we have published an erratum in Phys.Rev.Lett.104, 159901 (2010). There, and in this update, we have corrected a mistake in the computation of the error on the difference of the cross sections for e^+e^- -> psi(3770) -> hadrons and e^+e^- -> psi(3770) -> DDbar. We have also used a more recent CLEO measurement of cross section for e^+e^- -> psi(3770) -> DDbar. From this, we obtain an upper limit on the branching fraction for psi(3770) -> non-DDbar of 9% at 90% confidence level.
Measured cross section for the process E+ E- --> PSI(3770) --> hadrons.
Inclusive production of the f_0(980), f_2(1270) and \phi(1020) resonances has been studied in a sample of 4.3 million hadronic Z^0 decays from the OPAL experiment at LEP. A coupled channel analysis has been used for the f_0 in simultaneous fits to the resonances in inclusive \pi+\pi- and K+K- mass spectra. Fragmentation functions are reported for the three states. Total inclusive rates are measured to be 0.141 +/- 0.007 +/- 0.011 f_0, 0.155 +/- 0.011 +/- 0.018 f_2, and 0.091 +/- 0.002 +/- 0.003 \phi mesons per hadronic Z^0 decay. The production properties of the f_0, including those in three-jet events, are compared with those of the f_2 and \phi, and with the Lund string model of hadron production. All measurements are consistent with the hypothesis that the f_0 is a conventional qq(bar) scalar meson.
Total inclusive production rates.
Fragmentation functions. Additional systematic errors of 7.6 PCT for F0, 11.6 PCT for F2 and 3.5 PCT for PHI. The uncorrelated systematic errors for F0 and F2 are negligible in comparison to the other errors.
Using the CLEO detector at the Cornell Electron Storage Ring, we have made a measurement of R=sigma(e+e- ->hadrons)/sigma(e+e- ->mu+mu-) =3.56+/-0.01+/-0.07 at ECM=10.52 GeV. This implies a value for the strong coupling constant of alpha_s(10.52 GeV)=0.20+/-0.01+/-0.06, or alpha_s(M_Z)=0.13+/-0.005+/-0.03.
Corrected for background and radiactive effects.
Value of ALPHAS, the strong coupling constant, from the measurement of R. CT,= ALPHAS also given evolved to the Z0 mass.
We have studied hadronic events produced at LEP at a centre-of-mass energy of 161 GeV. We present distributions of event shape variables, jet rates, charged particle momentum spectra and multiplicities. We determine the strong coupling strength to be αs(161 GeV) = 0.101±0.005(stat.)±0.007(syst.), the mean charged particle multiplicity to be 〈nch〉(161 GeV) = 24.46 ± 0.45(stat.) ± 0.44(syst.) and the position of the peak in the ξp = ln(1/xp) distribution to be ξ0(161 GeV) = 4.00 ±0.03(stat.)±0.04(syst.). These results are compared to data taken at lower centre-of-mass energies and to analytic QCD or Monte Carlo predictions. Our measured value of αs(161 GeV) is consistent with other measurements of αs. Within the current statistical and systematic uncertainties, the PYTHIA, HERWIG and ARIADNE QCD Monte Carlo models and analytic calculations are in overall agreement with our measurements. The COJETS QCD Monte Carlo is in general agreement with the data for momentum weighted distributions like Thrust, but predicts a significantly larger charged particle multiplicity than is observed experimentally.
Determination of alpha_s.
Multiplicity and higher moments.
Thrust distribution.
We have studied hadronic events produced at LEP at centre-of-mass energies of 130 and 136 GeV. Distributions of event shape observables, jet rates, momentum spectra and multiplicities are presented and compared to the predictions of several Monte Carlo models and analytic QCD calculations. From fits of event shape and jet rate distributions to\({\mathcal{O}}(\alpha _s^2 ) + NLLA\) QCD calculations, we determineαs(133 GeV)=0.110±0.005(stat.)±0.009(syst.). We measure the mean charged particle multiplicity 〈nch〉=23.40±0.45(stat.) ±0.47(syst.) and the position ζ0 of the peak in the ζp = ln(1/xp) distribution ζ0=3.94±0.05(stat.)±0.11(syst.). These results are compared to lower energy data and to analytic QCD or Monte Carlo predictions for their energy evolution.
Determination of alpha_s.
Multiplicity and high moments.
Tmajor distribution.
The production of neutral kaons in e+e− annihilation at centre-of-mass energies in the region of the Z0 mass and their Bose-Einstein correlations are investigated with the OPAL detector at LEP. A total of about 1.26×106 Z0 hadronic decay events are used in the analysis. The production rate of K0 mesons is found to be 1.99±0.01±0.04 per hadronic event, where the first error is statistical and the second systematic. Both the rate and the differential cross section for K0 production are compared to the predictions of Monte Carlo generators. This comparison indicates that the fragmentation is too soft in bothJetset andHerwig. Bose-Einstein correlations in Ks0Ks0 pairs are measured through the quantityQ, the four momentum difference of the pair. A threshold enhancement is observed in Ks0Ks0 pairs originating from a mixed sample of\(K^0 \bar K^0\) and K0K0 (\(\bar K^0 \bar K^0\)) pairs. For the strength of the effect and for the radius of the emitting source we find values of λ=1.14±0.23±0.32 andR0=(0.76±0.10±0.11) fm respectively. The first error is statistical and the second systematic.
No description provided.
The mean x is computed using the method of Lafferty and Wyatt NIM A355(1995)541.
The mean x is computed using the method of Lafferty and Wyatt NIM A355(1995)541.
Measurements have been made in the OPAL experiment at LEP of the inclusive production of strange vector φ(1020) and K*(892)0 mesons, and the tensor meson K2*(1430)0. The overall production rates per hadronic Z0 decay have been determined to be 0.100±0.004stat.±0.007syst. φ(1020) mesons, 0.74±0.03stat.±0.03syst. K*(892)0 mesons and (forxE<0.3) 0.19±0.04stat.±0.06syst. K2*(1430)0 mesons. The measurements for the vector states update previously published results based on lower statistics, while the K2*(1430)0 rate represents the first direct measurement of a strange tensor state in Z0 decay. For the vector states, both the overall production rates and normalised differential cross sections, with respect to the scaled energy variablexE, have been compared to JETSET and HERWIG predictions. The peak positions in the ζ=ln(1/xp) distributions have been measured and compared to measurements of other hadron states.
No description provided.
No description provided.
Extrapolated to full x region.
The inclusive production rates of π±,K± andp\(\bar p\) inZ0 decays have been measured with the OPAL detector at LEP. Using the energy loss measurement in the jet chamber, the momentum range up to the beam energy (45.6 GeV/c) has been covered. Differential cross sections and total particle yields are given. Comparisons of the inclusive momentum spectra and the total rates with predictions of the JETSET and the HERWIG Monte Carlo model are presented. The total single rates are found to be 17.05±0.43 π±, 2.42±0.13K± and 0.92±0.11p\(\bar p\) per hadronic event. Predictions of JETSET for cross sections and total rates agree very well for π±; however, for momenta greater than 4 GeV/c,K± rates are underestimated and\(\bar p\) rates are overestimated. Combined with data of other particle species there is evidence that the peak positions in the ξ=ln(1/xp) distributions show a different mass dependence for mesons and baryons. However, both JETSET and HERWIG Monte Carlo predictions agree with the observed data.
Normalised momentum distribution for charged pion production.
Normalised momentum distribution for charged kaon production.
Normalised momentum distribution for proton / antiproton production.
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