Average charged multiplicities have been measured separately in $b$, $c$ and light quark ($u,d,s$) events from $Z~0$ decays measured in the SLD experiment. Impact parameters of charged tracks were used to select enriched samples of $b$ and light quark events, and reconstructed charmed mesons were used to select $c$ quark events. We measured the charged multiplicities: $\bar{n}_{uds} = 20.21 \pm 0.10 (\rm{stat.})\pm 0.22(\rm{syst.})$, $\bar{n}_{c} = 21.28 \pm 0.46(\rm{stat.}) ~{+0.41}_{-0.36}(\rm{syst.})$ $\bar{n}_{b} = 23.14 \pm 0.10(\rm{stat.}) ~{+0.38}_{-0.37}(\rm{syst.})$, from which we derived the differences between the total average charged multiplicities of $c$ or $b$ quark events and light quark events: $\Delta \bar{n}_c = 1.07 \pm 0.47(\rm{stat.})~{+0.36}_{-0.30}(\rm{syst.})$ and $\Delta \bar{n}_b = 2.93 \pm 0.14(\rm{stat.})~{+0.30}_{-0.29}(\rm{syst.})$. We compared these measurements with those at lower center-of-mass energies and with perturbative QCD predictions. These combined results are in agreement with the QCD expectations and disfavor the hypothesis of flavor-independent fragmentation.
Average charge multiplicity in B-tagged events.
Average charge multiplicity in C-tagged events.
Average charge multiplicity in light quark (uds) events.
Four-fermion events have been selected in a data sample of 5.8 pb −1 collected with the aleph detector at centre-of-mass energies of 130 and 136 GeV. The final states ℓ + ℓ − q q , ℓ + ℓ − ℓ + ℓ − , ν ν q q , and ν ν ℓ + ℓ − have been examined. Five events are observed in the data, in agreement with the Standard Model predictions of 6.67±0.38 events from four-fermion processes and 0.14 −0.05 +0.19 from background processes.
The statistical and systematic uncertainties have been combined in quadrature in the background expectations.
A measurement of theτ lepton polarization and its forward-backward asymmetry at the Z0 resonance using the OPAL detector is described. The measurement is based on analyses of τ→ρντ, ττπ(K)ντ,\(\tau\to e\bar \nu _e \nu _\tau\),\(\tau\to \mu \bar \nu _\mu\nu _\tau\) andτ→a1ντ decays from a sample of 89075 e+e−→τ+τ− candidates corresponding to an integrated luminosity of 117 pb−1. Assuming that theτ lepton decays according to V-A theory, we measure the averageτ polarization at √s=MZ to be 〈P〉=(−13.0±0.9±0.9)% and theτ polarization forward-backward asymmetry to be ApolFB=(−9.4±1.0±0.4)%, where the first error is statistical and the second systematic. These results are consistent with the hypothesis of lepton universality and, when combined, can be expressed as a measurement of sin2θefflept=0.2334±0.0012 within the context of the Standard Model.
No description provided.
The highest-energy measurement of ΔσL(pp) and the first ever measurement of ΔσL(p¯p), the differences between proton-proton and antiproton-proton total cross sections for pure longitudinal spin states, are described. Data were taken using 200-GeV/c polarized beams incident on a polarized-proton target. The results are measured to be ΔσL(pp)=−42±48(stat)±53(syst) μb and ΔσL(p¯p)=−256±124(stat)±109(syst) μb. Many tests of systematic effects were investigated and are described, and a comparison to theoretical predictions is also given. Measurements of parity nonconservation at 200 GeV/c in proton scattering and the first ever of antiproton scattering have also been derived from these data. The values are consistent with zero at the 10−5 level.
No description provided.
No description provided.
The analyzing power AN in inclusive π− and π+ production has been measured with a 200 GeV/c transversely polarized antiproton beam over a wide xF range (0.2≤xF≤0.9) and at moderate pT (0.2≤pT≤1.5GeV/c). The asymmetry AN increases with increasing xF from zero to large positive values for π−'s, and decreases from zero to large negative values for π+'s. A threshold for the onset of the asymmetry is observed about pT∼0.5GeV/c, below which AN is essentially zero and above which AN increases (decreases) with pT for π−'s ( π+'s) in the covered pT range.
No description provided.
No description provided.
No description provided.
The B<sup loc="post">0</sup> - B̄<sup loc="post">0</sup> average mixing parameter <math altimg="si1.gif"><rm><ovl type="bar" style="s">χ</ovl></rm></math> and b forward-backward asymmetry AFB<sup loc="post">0</sup>(b) are measured from a sample of about 4 200 000 Z → qq̄ events recorded with the ALEPH detector at LEP in the years 1990–1995. High transverse momentum electrons and muons produced in b semileptonic decays provide the tag of the quark flavour and of its charge. The average mixing parameter and the pole b asymmetry are measured to be <math altimg="si1.gif"><rm><ovl type="bar" style="s">χ</ovl></rm></math> = 0.1246 ± 0.0051stat ± 0.0052syst, AFB<sup loc="post">0</sup>(b) = 0.1008 ± 0.0043stat ± 0.0028syst. The value of sin<sup loc="post">2</sup>θw<sup loc="post">eff</sup> = 0.23198 ± 0.00092 is extracted from the asymmetry measurement.
ASYM(N=FB,C=OBSERVED) is observed asymmetry including BQ, CQ and backround.
No description provided.
The properties of high-mass multijet events produced at the Fermilab proton-antiproton collider are compared with leading order QCD matrix element predictions, QCD parton shower Monte Carlo predictions, and the predictions from a model in which events are distributed uniformly over the available multibody phase-space. Multijet distributions corresponding to (4N-4) variables that span the N-body parameter space are found to be well described by the QCD calculations for inclusive three-jet, four-jet, and five-jet events. The agreement between data, QCD Matrix Element calculations, and QCD parton shower Monte Carlo predictions suggests that 2 -> 2 scattering plus gluon radiation provides a good first approximation to the full LO QCD matrix element for events with three, four, or even five jets in the final state.
3-jet mass distribution.
Inclusive 3-jet Dalitz X3 distribution.
Inclusive 3-jet Dalitz X4 distribution.
An analysis of theA-dependence of the target-diffractive cross-section is presented. Data on thet-dependence of the cross section are fitted in the usual exponential form. The mean multiplicity of negative particles produced diffractively is found not to be sensitive to the nuclear mass. TheA-dependence of the emitted proton multiplicity and the angular distributions of the produced charged particles suggest re-scattering of the emitted particles on other nucleons of the nucleus. All these facts are compared with results obtained by Monte-Carlo simulation according to a two-component Dual Parton Model.
For target-diffractive cross-section.
For target-diffractive cross-section.
Multiplicities for the diffractive system.
>From a sample of $2722 \pm 78$ $\Lambda_c~+$ decaying to the $pK~-\pi~+$ final state, we have observed, in the hadroproduction experiment E791 at Fermilab, $143 \pm 20$ $\Sigma_c~0$ and $122 \pm 18$ $\Sigma_c~{++}$ through their decays to $\Lambda_c~+ \pi~{\pm}$. The mass difference $M(\Sigma_c~0) - M(\Lambda_c~+$) is measured to be $(167.38\pm 0.29\pm 0.15)\,\mbox{MeV}$; for $M(\Sigma_c~{++}) - M(\Lambda_c~+)$, we find $(167.76\pm 0.29\pm0.15)\,\mbox{MeV}$. The rate of $\Lambda_c~+$ production from decays of the $\Sigma_c$ triplet is $(22\pm 2\pm 3)\,\mbox{\%}$ of the total $\Lambda_c~+$ production assuming equal rate of production from all three, as measured for $\Sigma_c~0$ and $\Sigma_c~{++}$. We do not observe a statistically significant $\Sigma_c$ baryon-antibaryon production asymmetry. The $x_F$ and $p_t~2$ spectra of $\Lambda_c~+$ from $\Sigma_c$ decays are observed to be similar to those for all $\Lambda_c~+$'s produced.
No description provided.
We present a study of events with Z bosons and hadronic jets produced in $\overline{p}p$ collisions at a center-of-mass energy of 1.8 TeV. The data consist of 6708 $Z \rightarrow e~+e~-$ decays from 106 pb$~{-1}$ of integrated luminosity collected using the CDF detector at the Tevatron Collider. The Z $+ \ge n$ jet cross sections and jet production properties have been measured for n = 1 to 4. The data compare well to predictions of leading order QCD matrix element calculations with added gluon radiation and simulated parton fragmentation.
The notation (N)JET(S) means greater than or equal to N jets. Cross sections include the branching ratio to E+ E-.
Transverse energy distribution of the first highest ET jet in >= 1jet events.. Data read from plots.
Transverse energy distribution of the second highest ET jet in >= 2jet events.. Data read from plots.
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