An analysis is presented of inclusive π0 production in Z0 decays measured with the DELPHI detector. At low energies, π0 decays are reconstructed by using pairs of converted photons and combinations of converted photons and photons reconstructed in the barrel electromagnetic calorimeter (HPC). At high energies (up to $x_p={2cdot p≪/{sqrt s}=0.75}$) the excellent granularity of the HPC is exploited to search for two-photon substructures in single showers. The inclusive differential cross section is measured as a function of energy for qq̅ and bb̅ events. The number of π0’s per hadronic Z0 event is $N(≪^0)/Z_{had} ^0=9.2pm 0.2({⤪ stat})pm 1.0 ({⤪ syst})$ and for bb̅ events the number of π0’s is ${⤪ N}(≪^0)/{⤪ b⋏r b}=10.1pm 0.4({⤪ stat})pm 1.1 ({⤪ syst})$. The ratio of the number of π0’s in bb̅ events to hadronic Z0 events is less affected by the systematic errors and is found to be 1.09 ±0.05 ±0.01. The measured π0 cross sections are compared with the predictions of different parton shower models. For hadronic events, the peak position in the $xi_{⤪ p}={⤪ ln}(1/{⤪ x_p})$ distribution is $xi_p^{⋆ar}=3.90_{-0.14}^{+0.24}.$ The average number of π0’s from the decay of primary B hadrons is found to be N(B → π0X)/B hadron = 2.78 ± 0.15(stat) ± 0.60(syst).
Differential cross section for all events.
Mean PI0 multiplicity extrapolated below 0.011 with JETSET 7.3.
Differential cross section for the enriched (b bbar) data set.
Using 773 muons found in hadronic events from 142 pb−1 of data at a c.m. energy of 57.8 GeV, we extract the cross section and forward-backward charge asymmetry for the e+e−→bb¯ process, and the heavy quark fragmentation function parameters for the Peterson model. For the analysis of the e+e−→bb¯ process, we use a method in which the behavior of the c quark and lighter quarks is assumed, with only that of the b quark left indeterminate. The cross section and asymmetry for e+e−→bb¯ are found to be Rb = 0.57 ± 0.06(stat) ± 0.08(syst) and Ab = −0.59 ± 0.09 ± 0.09, respectively. They are consistent with the standard model predictions. For the study of the fragmentation function we use the variable 〈xE〉, the fraction of the beam energy carried by the heavy hadrons. We obtain 〈xE〉c=0.56−0.05−0.03+0.04+0.03 and 〈xE〉b=0.65−0.04−0.06+0.06+0.05, respectively. These are in good agreement with previously measured values.
No description provided.
No description provided.
Here X=E(hadron)/E(beam).
We have studied c (charm) and b (bottom) quark production at the TRISTAN energy region by tagging prompt electrons from the semileptonic decays. Electrons were identified over a wide momentum range between 1 and 29 GeV/ c by a transition-radiation-detector in addition to a lead-glass calorimeter. The production cross sections of c and b quarks and the mean values of the fragmentation functions for c and b quarks were obtained as σ c = 55.9±8.8(stat.)±7.9(syst.) pb, σ b = 13.1±2.9(stat.)±1.0(syst.) pb, 〈 x c 〉 = 0.44±0.08(stat.)±0.04(syst.) and 〈 x b 〉 = 0.72±0.12(stat.)±0.08(syst.), respectively. The forward-backward asymmetries of the c and b quarks were also measured to be −0.57±0.16(stat.)±0.06(syst.) and −0.64±0.26(stat.)± 0.07(syst.), respectively. Both the cross sections and the forward-backward asymmetries of the c and b quarks are consistent with the standard model.
No description provided.
No description provided.
Using the CLEO II detector at the Cornell Electron Storage Ring, we have determined the inclusive B* cross section above the Υ(4S) resonance in the energy range from 10.61 to 10.70 GeV. We also report a new measurement of the energy of the B*→Bγ transition photon of 46.2±0.3±0.8 MeV.
Hadronic cross section above the continuum. The final state is an unknown mixture of B BBAR + B* BBAR + B B*BAR (+ B* B*BAR only at the highest energy).
Inclusive B* cross section.
Differential cross section data of the CELLO experiment on pair production of muons, taus, and heavy quarks ine+e−-annihilation are presented and analysed, together with our data on Bhabha scattering, in terms of compositeness effects characterized by the mass scale Λ. We discuss difficulties in the combination of limits Λ from different experiments. The appropriate parameter to combine different results turns out to be ɛ=±1/Λ2, which is in contrast to Λ Gaussian distributed.
Errors are combined statistics and systematics.
Errors are combined statistics and systematics.
Errors are combined statistics and systematics.
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