The inclusive production of the omega(782) vector meson in hadronic Z decays is measured and compared to model predictions. The analysis is based on 4 million hadronic Z decays recorded by the ALEPH detector between 1991 and 1995. The production rate for x_p = p_meson/p_beam > 0.05 is measured in the omega -> pi^+ pi^- pi^0 decay mode and found to be 0.585 +- 0.019_stat +- 0.033_sys per event. Inclusive eta meson production is also measured in the same decay channel for x_p > 0.10, obtaining 0.355 +- 0.011_stat +- 0.024_sys per event. The branching ratio for omega -> mu^+ mu^- is investigated. A total of 18.1 +- 5.9 events are observed, from which the muonic branching ratio is measured for the first time to be BR(omega -> mu^+ mu^-) = (9.0 +- 2.9_stat +- 1.1_sys)*10^-5.
Extrapolation using JETSET 7.4 is used to correct down to X = 0.0. The second DSYS error, where relevant, shows the estimated uncertainty on the extrapolation.
Production rate and differential cross sections for the ETA.
Production rate and differential cross sections for the OMEGA.
We report on measurements of the inclusive production rate of Sigma+ and Sigma0 baryons in hadronic Z decays collected with the L3 detector at LEP. The Sigma+ baryons are detected through the decay Sigma+ -> p pi0, while the Sigma0 baryons are detected via the decay mode Sigma0 -> Lambda gamma. The average numbers of Sigma+ and Sigma0 per hadronic Z decay are measured to be: < N_Sigma+ > + < N_Sigma+~ > = 0.114 +/- 0.011 (stat) +/- 0.009 (syst), < N_Sigma0 > + < N_Sigma0~ > = 0.095 +/- 0.015 (stat) +/- 0.013 (syst). These rates are found to be higher than the predictions from Monte Carlo hadronization models and analytical parameterizations of strange baryon production.
Inclusive production rates.
The production rates of D*+-, Ds*+-, D+-, D0 / D0bar, Ds+, and Lambda_c in Z to ccbar decays are measured using the LEP I data sample recorded by the ALEPH detector. The fractional energy spectrum of the D*+- is well described as the sum of three contributions: charm hadronisation, b hadron decays and gluon splitting into a pair of heavy quarks. The probability for a c quark to hadronise into a D*+ is found to be f(c to D*+) = 0.233 +- 0.010 (stat.) +- 0.011 (syst.). The average fraction of the beam energy carried by D*+- mesons in Z to cc events is measured to be < X_E (D*+-) >_cc = 0.4878 +- 0.0046 (stat.) +- 0.0061 (syst.). The D*+- energy and the hemisphere mass imbalance distributions are simultaneously used to measure the fraction of hadronic Z decays in which a gluon splits to a cc pair: n_{gluon to cc} = (3.23 +- 0.48 (stat.) +- 0.53 (syst.) %. The ratio of the Vector/(Vector+Pseudoscalar) production rates in charmed mesons is found to be P_V = 0.595 +- 0.045. The fractional decay width of the Z into cc pairs is determined from the sum of the production rates for various weakly decaying charmed states to be Rc = 0.1738 +- 0.0047 (stat.) +- 0.0116 (syst.).
The differential D*+- production rate. Statistical errors only.
The multiplicity of D*+- events using a MC shape to do the very small extrapolation over the entire X range.
Fraction of hadronic Z0 decays into charm quark pairs summing all the contributions of the fundamental charmed states and including a contribution from baryons not decaying to LAMBDA/C+. The second DSYS error is due to the uncertainty in the branching ratio.
The production rates and the inclusive cross sections of the isovector meson${\rm \pi^0}$, the isoscalar mesons$\eta$and
Inclusive cross section for PI0 production in hadronic events.
Inclusive cross section for ETA production in hadronic events.
Inclusive cross section for ETAPRIME production in hadronic events.
The data set collected with the ALEPH detector from 1991 to 1995 at LEP has been analysed to measure the charm forward-backward asymmetry at the Z. Out of a total of 4.1 million hadronic Z decays, about 36000 high momentum D*+, D+ and D0 decays were reconstructed, of which 80% originate from Z -> ccbar events...
No description provided.
No description provided.
An improved measurement of the forward-backward asymmetry in Z →b b ̄ decays is presented, based on a sample of 4.1 million hadronic Z decays collected by ALEPH between 1991 and 1995. Data are analysed as a function of polar angle of the event axis and b purity. The event tagging efficiency and mean b -jet hemisphere charge are measured directly from data. From the measured forward-backward jet charge asymmetry, the b quark asymmetry at s =m Z is determined to be: A b FB =0.1017±0.0038(stat.)±0.0032(syst.). In the context of the Standard Model this corresponds to a value of the effective weak mixing angle of sin 2 θ W eff =0.23109±0.00096.
Only statistical errors are given for sqrt(s) = 89.43 and 92.97 GeV.
The combination of the data on and off peak of Z-boson.
The combination of the data on and off peak of Z-boson.
The full statistics of hadronic Z decays collected with the ALEPH detector are analysed to measure, by three methods, the ratio, ${\rm R_c}$ , of the partial decay
No description provided.
An experimental investigation of the structure of identified quark and gluon jets is presented. Observables related to both the global and internal structure of jets are measured; this allows for test
The measured jet broadening distributions (B) in quark and gluon jets seperately.
Measured distributions of -LN(Y2), where Y2 is the differential one-subjet rate, that is the value of the subjet scale parameter where 2 jets appear from the single jet.
The mean subjet multiplicity (-1) for gluon jets and quark jets for different values of the subject resolution parameter Y0.
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.
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.
No description provided.
No description provided.
The second syst. errors results due to extranal branching ratios. Charge conjugated states are implied. FD is considered as a quark fragmentation fraction. Sqrt(s(E+ E-)) = 91.2 GeV.
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