We present measurements of the total production rates and momentum distributions of the charmed baryon $\Lambda_c^+$ in $e^+e^- \to$ hadrons at a center-of-mass energy of 10.54 GeV and in $\Upsilon(4S)$ decays. In hadronic events at 10.54 GeV, charmed hadrons are almost exclusively leading particles in $e^+e^- \to c\bar{c}$ events, allowing direct studies of $c$-quark fragmentation. We measure a momentum distribution for $\Lambda_c^+$ baryons that differs significantly from those measured previously for charmed mesons. Comparing with a number of models, we find none that can describe the distribution completely. We measure an average scaled momentum of $\left< x_p \right> = 0.574\pm$0.009 and a total rate of $N_{\Lambda c}^{q\bar{q}} = 0.057\pm$0.002(exp.)$\pm$0.015(BF) $\Lambda_c^+$ per hadronic event, where the experimental error is much smaller than that due to the branching fraction into the reconstructed decay mode, $pK^-\pi^+$. In $\Upsilon (4S)$ decays we measure a total rate of $N_{\Lambda c}^{\Upsilon} = 0.091\pm$0.006(exp.)$\pm$0.024(BF) per $\Upsilon(4S)$ decay, and find a much softer momentum distribution than expected from B decays into a $\Lambda_c^+$ plus an antinucleon and one to three pions.
LAMBDA/C+ differential production rate per hadronic event for the continuum at cm energy 10.54 GeV.
The integrated number of LAMBDA/C+'s per hadronic event for the continuum at cm energy 10.54 GeV.
LAMBDA/C+ differential production rate per UPSILON(4S) decay at cm energy 10.58 GeV.
Using data collected in the region of the Upsilon(4S) resonance with the CLEO II detector operating at the Cornell Electron Storage Ring CESR, we present the first observation of B mesons decaying into the charmed strange baryons Xi_c0 and Xi_c+. We find 79 +/- 27 Xi_c0 and 125 +/- 28 Xi_c+ candidates from B decays, leading to product branching fractions of BR(Bbar -> Xi_c0 X)BR(Xi_c0 -> Xi- pi+) = (0.144 +/- 0.048 +/- 0.021) x 10~-3 and BR(Bbar -> Xi_c+ X)BR(Xi_c+ -> Xi- pi+ pi+) = (0.453 +/- 0.096 +0.085-0.065) x 10~-3.
Charge conjugated states are included. P(P=4,C=MAX) equals sqrt(Ebeam**2 - m(XI/C)**2). The kinematic limit is : (P(XI/C) / P(P=4,C=MAX)) < 0.5.
Charge conjugated states are included. P(P=4,C=MAX) equals sqrt(Ebeam**2 - m(XI/C)**2). The kinematic limit is : (P(XI/C) / P(P=4,C=MAX)) < 0.5.
Previously published and as yet unpublished QCD results obtained with the ALEPH detector at LEP1 are presented. The unprecedented statistics allows detailed studies of both perturbative and non-perturbative aspects of strong interactions to be carried out using hadronic Z and tau decays. The studies presented include precise determinations of the strong coupling constant, tests of its flavour independence, tests of the SU(3) gauge structure of QCD, study of coherence effects, and measurements of single-particle inclusive distributions and two-particle correlations for many identified baryons and mesons.
Charged particle sphericity distribution.
Charged particle aplanarity distribution.
Charged particle Thrust distribution.
Quark and gluon jets with the same energy, 24 GeV, are compared in symmetric three-jet configurations from hadronic Z decays observed by the ALEPH detector. Jets are defined using the Durham algorithm. Gluon jets are identified using an anti-tag on b jets, based on a track impact parameter method. The comparison of gluon and mixed flavour quark jets shows that gluon jets have a softer fragmentation function, a larger angular width and a higher particle multiplicity, Evidence is presented which shows that the corresponding differences between gluon and b jets are significantly smaller. In a statistically limited comparison the multiplicity in c jets was found to be comparable with that observed for the jets of mixed quark flavour.
B-jets are identified with the lepton-tag analysis.
The same kinematics as in the table 1.
We have studied the production of D*± mesons in a sample of 1.25 million multihadronic decays of the Z0, in which 1969 candidates have been identified. We have determined the total multiplicity of charged D* mesons in multihadronic Z0 decays to be
No description provided.
Multiplicity data uncorrected for decay branching ratios.
No description provided.
The production of charmed mesons$$\mathop {D^0 }\limits^{( - )} $$,D
No description provided.
The DSYS error is due to the error in the branching ratio.
The DSYS error is due to the error in the branching ratio.
Distributions are presented of event shape variables, jet roduction rates and charged particle momenta obtained from 53 000 hadronicZ decays. They are compared to the predictions of the QCD+hadronization models JETSET, ARIADNE and HERWIG, and are used to optimize several model parameters. The JETSET and ARIADNE coherent parton shower (PS) models with running αs and string fragmentation yield the best description of the data. The HERWIG parton shower model with cluster fragmentation fits the data less well. The data are in better agreement with JETSET PS than with JETSETO(αS2) matrix elements (ME) even when the renormalization scale is optimized.
Sphericity distribution.
Sphericity distribution.
Aplanarity distribution.
Using the ARGUS detector at DORIS II, we have studied the production of the charmed baryon Λ c in e + e − annihilation at centre-of-mass energies near 10 GeV. The Λ c + was seen in the three decay modes pK − π + , Λπ + π − π + and K̄ 0 p, with products of normalized cross section times branching ratio [ R ·Br] of (10.8±1.4±1.2)×10 −3 , 6.6±1.5±0.9)×10 −3 and (6.7±1.4±0.8)×10 −3 respectively. The measured mass for the Λ c was (2283.1±1.7±2.0) MeV/ c 2 . A limit on the decay rates to Λπ + is reported. The fragmentation function of the Λ c was measured.
Data requested from authors.
No description provided.
Using the ARGUS detector at the DORIS II e+e− storage ring at DESY, we have obtained evidence for a new charmed resonance which decays into D*±(2010)π∓. The observed mass and width are 2420±6 MeV/c2 and 70±21 MeV/c2, respectively. The fragmentation function is found to be hard, as expected for a state containing a leading charm quark produced by nonresonant e+e− annihilation.
No description provided.
Estimated production cross section obtained by comparison with observed D*(2010) production rate.
Using the ARGUS detector at DORIS, we have observed the production of F ± mesons in e + e − annihilation at a centre of mass energy of 10 GeV through their subsequent decays into φπ ± and φπ + π − π ± . The values obtained for [ R (e + e − →FX). Branching Ratio] are (1.47 ± 0.32 ± 0.20)% and (1.63 ± 0.42 ± 0.41)% respectively. The observed mass is (1973.6 ± 2.6 ± 3.0) MeV c 2 . The F momentum spectrum is as expected for the fragmentation of c quarks into charmed mesons, but is somewhat softer than for fragmentation into D ∗ mesons. The relevant angular distributions are consistent with a spin-zero assignment of the F meson.
RESULTS OF FITS FOR SPECIFIED DECAY CHANNELS.
ACCEPTANCE CORRECTED FRAGMENTATION FUNCTION FOR THE TWO DECAY CHANNELS COMBINED. X IS PF/PMAX. DATA HAVE BEEN READ FROM THE GRAPH.
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