The charged particle multiplicities of two- and three-jet events from the reaction e+e- -> Z0 -> hadrons are measured for Z0 decays to light quark (uds) flavors. Using recent theoretical expressions to account for biases from event selection, results corresponding to unbiased gluon jets are extracted over a range of jet energies from about 11 to 30 GeV. We find consistency between these results and direct measurements of unbiased gluon jet multiplicity from upsilon and Z0 decays. The unbiased gluon jet data including the direct measurements are compared to corresponding results for quark jets. We perform fits based on analytic expressions for particle multiplicity in jets to determine the ratio r = Ng/Nq of multiplicities between gluon and quark jets as a function of energy. We also determine the ratio of slopes, r(1) = (dNg/dy)/(dNq/dy), and of curvatures, r(2) = (d2Ng/dy2)/(d2Nq/dy2), where y specifies the energy scale. At 30 GeV, we find r = 1.422 +/- 0.051, r(1) = 1.761 +/- 0.071 and r(2) = 1.98 +/- 0.13, where the uncertainties are the statistical and systematic terms added in quadrature. These results are in general agreement with theoretical predictions. In addition, we use the measurements of the energy dependence of Ng and Nq to determine an effective value of the ratio of QCD color factors, CA/CF. Our result, CA/CF = 2.23 +/- 0.14 (total), is consistent with the QCD value of 2.25.
Measurements of the mean charged particle multiplicity of biased two-jet uds flavour events from Z0 decays as a function of the transverse momentum cutoff PT(C=LU) used to separate two- and three-jet events.
Measurements of the mean charged particle multiplicity of three-jet uds flavour 'Y events' from Z0 decays, as a function of the angle THETA1 between the lowest two energy jets. The results for the quark jet scale SQRT(S(C=QQBAR)) and the gluon jet scales PT(C=LU) and PT(C=LE) are also given.
Measurements of the unbiased gluon multiplicity as a function of the energy scale Q=PT(C=LU). The corresponding bins of THETA1 in 'Y events' are also indicated.
Inclusive momentum spectra and multiplicity distributions of charged particles measured with BESII detector at center of mass energies of 2.2,2.6,3.0,3.2,4.6 and 4.8 GeV are presented. Values of the second binomial moment, $R_2$, obtained from the multiplicity distributions are reported. These results are compared with both experimental data from high energy $e^+e^-$, $ep$ and $p\bar{p}$ experiments and QCD calculations.
Measured xi =-ln(2p/sqrt(s)) spectra for centre of mass energy 2.2 GeV.. Errors are statistical and systematic added in quadrature.
Measured xi =-ln(2p/sqrt(s)) spectra for centre of mass energy 2.6 GeV.. Errors are statistical and systematic added in quadrature.
Measured xi =-ln(2p/sqrt(s)) spectra for centre of mass energy 3.0 GeV.. Errors are statistical and systematic added in quadrature.
The charged particle multiplicity distributions for two-jet events ine+e− annihilation at 29 GeV have been measured using the High Resolution Spectrometer at PEP. A Poisson distribution describes the data for both the complete event and for the single jets. In addition, no correlation is observed between the multiplicities in the two jets of an event. For fixed values of the prong number of the complete event, the multiplicity sharing between the two jets is in good agreement with a binomial distribution. The rapidity gap distribution is exponential with a slope equal to the mean rapidity density. These observations, which are consistent with a picture of independent emission of single particles, are contrasted to the results from soft hadronic collisions and conclusions are drawn about the nature of clusters.
Charged Particle Multiplicity distributions for single jet and whole event from the two jet sample. The numerical values are given in the paper Derrick et al, PR D34 (86) 3304, and are coded in this database as (<a href=http://durpdg.dur.ac.uk/scripts/reacsearch.csh/TESTREAC/red+1437> RED = 1437 </a>).
Single Jet Mean Multiplicities.
Total event charged multiplicities.
We present the charged-particle multiplicity distributions for e+e− annihilation at center-of-mass energies from 50 to 61.4 GeV. The results are based on a data sample corresponding to a total integrated luminosity of 30 pb−1 obtained with the AMY detector at the KEK storage ring TRISTAN. The charged-particle multiplicity distributions deviate significantly from the modified Poisson and pair Poisson distributions, but follow Koba-Nielsen-Olesen scaling and are well reproduced by the LUND parton-shower model.
Fully corrected charged particle multiplicity distributions. Errors for n=2 and 4 are systematic only since these were derived using the LUND 6.3 Monte Carlo normalized to the observations at higher n values.
No description provided.
This paper presents the charged-particle multiplicity distributions for e+e− annihilation at √s =29 GeV measured in the High Resolution Spectrometer. The data, which correspond to an integrated luminosity of 185 pb−1, were obtained at the SLAC e+e− storage ring PEP. The techniques used to correct the observed prong numbers are discussed. The multiplicity distribution of the charged particles has a mean value 〈n〉=12.87±0.03±0.30, a dispersion D2=3.67±0.02±0.18, and an f2 moment of 0.60±0.02±0.18. Results are also presented for a two-jet sample selected with low sphericity and aplanarity. The charged-particle distributions are almost Poissonian and narrower than have been reported by other e+e− experiments in this energy range. The mean multiplicity increases with the event sphericity, and for the sample of threefold-symmetric three-jet events, a value of 〈n〉=16.3±0.3±0.7 is found. No correlation is observed between the multiplicities in the two hemispheres when the events are divided into two jets by a plane perpendicular to the thrust axis. This result is in contrast with the situation in soft hadronic collisions, where a strong forward-backward correlation is measured. For the single jets, a mean multiplicity of 6.43±0.02±0.15 and a dispersion value of D2=2.55±0.02±0.13 are found. These values give further support to the idea of independent jet fragmentation. The multiplicity distributions are well fit by the negative-binomial distribution. The semi-inclusive rapidity distributions are presented. Comparisons are made to the measurements of charged-particle multiplicities in hadron-hadron and lepton-nucleon collisions.
Charged particle multiplicity distribution for the Inclusive Data Sample.
Charged particle multiplicity distribution for the Two Jet Data Sample.
Properties of multiplicity distributions for Inclusive Data Sample.
In this paper, results are presented from a study of the hadronic final states in e+e− annihilation at 29 GeV. The data were obtained with the High Resolution Spectrometer (HRS) at the SLAC PEP e+e− colliding-beam facility. The results are based on 6342 selected events corresponding to an integrated luminosity of 19.6 pb−1. The distributions of the events in sphericity (S), thrust (T), and aplanarity (A) are given and compared to other e+e− data in the same energy range. We measure 〈S〉=0.130±0.003±0.010 and 〈1-T〉=0.100±0.002. The sphericity distribution is compared to sphericity measurements made for beam jets in hadronic collisions as well as jets studied in neutrino scattering. The data sample is further reduced to 4371 events with the two-jet selections, S≤0.25 and A≤0.1. The single-particle distributions in the longitudinal and transverse directions are given. For low values of the momentum fraction (z=2p/W), the invariant distribution shows a maximum at z∼0.06, consistent with a QCD expectation. The data at high Feynman x (xF) show distribution consistent with being dominated by a (1-xf)2 variation for the leading quark-meson transition. The rapidity distribution shows a shallow central minimum with a height (1/NevdNh/dY‖Y=0=2.3±0.02±0.07. The mean charged multiplicity is measured to be 〈nch〉=13.1±0.05±0.6. The mean transverse momentum relative to the thrust axis 〈pT〉 rises as a function of z to a value of 0.70±0.02 GeV/c for z≳0.3. The distributions are compared to those measured in other reactions.
New values supplied 6.7.87 by M.Derrick.
No description provided.
New values supplied 6.7.87 by M. Derrick.
Charged-particle multiplicity was studied in e + e − annihilation at s = 57.8 GeV using the TOPAZ detector at TRISTAN. The average multiplicity was 〈 n ch 〉 = 17.64± 0.05(stat.) ± 0.41(syst.). It was found that the multiplicity depends on the thrust ( T ) of an event. From extrapolating this relation to T = 2 3 , the multiplicity for three-fold symmetric events was estimated to be 〈n ch 〉 T = 2 3 = 23.50 −1.45 +1.25 . From this, the multiplicity ratio between gluon- and quark-jet was estimated to be r g q = 1.46 −0.13 +0.09 without any possible bias from jet clustering.
No description provided.
Multiplicity measured for events with a Thrust of 2/3. These are three-foldsymmetric events.
Mean charged particle multiplicity as function of -log(1-THRUST).
Inclusive momentum spectra are measured for all charged particles and for each of $\pi~{\pm}$, $K~{\pm}$, $K~0/\overline{K~0}$, and $p/\overline{p}$ in hadronic events produced via $e~+e~-$ annihilation at $\sqrt{s}$=58GeV . The measured spectra are compared with QCD predictions based on the modified leading log approximation(MLLA). The MLLA model reproduces the measured spectra well. The energy dependence of the peak positions of the spectra is studied by comparing the measurements with those at other energies. The energy dependence is also well described by the MLLA model.
Errors include both statistical and systematic errors.
Errors include both statistical and systematic errors.
Statistical errors only.
We present the general properties of multihadron final states produced by e+e− annihilation at center-of-mass energies from 52 to 57 GeV in the AMY detector at the KEK collider TRISTAN. Global shape, inclusive charged-particle, and particle-flow distributions are presented. Our measurements are compared with QCD+fragmentation models that use either leading-logarithmic parton-shower evolution or QCD matrix elements at the parton level, and either string or cluster fragmentation for hadronization.
Rapidity distribution with respect to the Thrust axis.
Charged particle X distribution.
Charged particle PL distribution.
Separate samples of charm quark and light quark (u, d, s) jets have been isolated in an experiment studying e + e − annihilations at s = 29 GeV . The results come from data corresponding to an integrated luminosity of 111 pb −1 collected by the High Resolution Spectrometer. Differences were observed in charged multiplicities, momentum distributions, and rapidity of the size expected from the different fragmentation functions and leading particle decay properties of the two samples.
Charm Quark Jet Trigger. Characteristics of Jet Opposite the Trigger Jet.
Light Quark Jet Trigger. Characteristics of Jet Opposite the Trigger Jet.
No description provided.
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