The results of an experiment performed at Adone, the 2×1.5-GeV e+e− Frascati storage ring, are presented. During ∼ 1500 hours of running time a total of 5164 electron-positron elastic scattering events (integrated luminosity L=3.5×1035 cm−2) and 605 noncoplanar events from the reaction e+e−→a±+b±+anything (effective integrated luminosity L=2.5×1035 cm−2) have been collected at c.m. energies ranging from 1.4 to 2.4 GeV. Over the energy range explored (1.4-2.4 GeV), corresponding to an average q2 ranging from 0.8 to 2.4 (GeV/c)2, the yield of wide-angle (60°<θ<120°) electron-positron elastic scattering events is found to be in good agreement with the predictions of quantum electrodynamics (QED) (R=σexpσQED=1.05±0.04). The noncoplanar events appear to be of a hadronic nature and are produced with a much higher cross section than predicted on the basis of ρ, ω, φ dominance at these energies. The total cross section for the reaction e+e−→a±b±+anything shows a rapid increase to ∼ 90 nb between 1.0 and 1.5 GeV and falls off slowly to ∼ 50 nb at 2.4 GeV. Cross sections for some of the channels contributing to this multihadron process (e+e−→π+π−π+π−, e+e−→π+π−π+π−+neutrals, e+e−→3π+3π−) have been determined and are reported.
DATA VALUES MEASURED FROM GRAPH IN JOURNAL.
VALUES OF R CALCULATED FROM TOTAL CROSS SECTION.
Measurements of multiple particle production at ADONE, the Frascati e + e − storage ring, have been carried out at C.M. energies 1.4 GeV to 2.4 GeV. The hadronic nature of the observed particles is discussed and a lower limit of 30 nbarn set for the total multiparticle cross section.
LOWER LIMIT FOR PRODUCTION OF AT LEAST TWO CHARGED HADRONS.
We employ data taken by the JADE and OPAL experiments for an integrated QCD study in hadronic e+e- annihilations at c.m.s. energies ranging from 35 GeV through 189 GeV. The study is based on jet-multiplicity related observables. The observables are obtained to high jet resolution scales with the JADE, Durham, Cambridge and cone jet finders, and compared with the predictions of various QCD and Monte Carlo models. The strong coupling strength, alpha_s, is determined at each energy by fits of O(alpha_s^2) calculations, as well as matched O(alpha_s^2) and NLLA predictions, to the data. Matching schemes are compared, and the dependence of the results on the choice of the renormalization scale is investigated. The combination of the results using matched predictions gives alpha_s(MZ)=0.1187+{0.0034}-{0.0019}. The strong coupling is also obtained, at lower precision, from O(alpha_s^2) fits of the c.m.s. energy evolution of some of the observables. A qualitative comparison is made between the data and a recent MLLA prediction for mean jet multiplicities.
Overall result for ALPHAS at the Z0 mass from the combination of the ln R-matching results from the observables evolved using a three-loop running expression. The errors shown are total errors and contain all the statistics and systematics.
Weighted mean for ALPHAS at the Z0 mass determined from the energy evolutions of the mean values of the 2-jet cross sections obtained with the JADE and DURHAMschemes and the 3-jet fraction for the JADE, DURHAM and CAMBRIDGE schemes evaluted at a fixed YCUT.. The errors shown are total errors and contain all the statistics and systematics.
Combined results for ALPHA_S from fits of matched predicitions. The first systematic (DSYS) error is the experimental systematic, the second DSYS error isthe hadronization systematic and the third is the QCD scale error. The values of ALPHAS evolved to the Z0 mass using a three-loop evolution are also given.
The strong coupling constant, αs, has been determined in hadronic decays of theZ0 resonance, using measurements of seven observables relating to global event shapes, energy correlatio
Data corrected for finite acceptance and resolution of the detector and for intial state photon radiation. No corrections for hadronic effects are applied.. Errors include statistical and systematic uncertainties, added in quadrature.
Data corrected for finite acceptance and resolution of the detector and for intial state photon radiation. No corrections for hadronic effects are applied.. Errors include statistical and systematic uncertainties, added in quadrature.
Data corrected for finite acceptance and resolution of the detector and for intial state photon radiation. No corrections for hadronic effects are applied.. Errors include statistical and systematic uncertainties, added in quadrature.
Evidence is presented for the occurrence in e + e − annihilation of a new vector meson of mass 1821 ± 16 MeV and Γ = 31 ± 15 MeV.
MULTIHADRON EVENTS (AT LEAST THREE CHARGED TRACKS WITH ZERO OR MORE PHOTONS) PER UNIT LUMINOSITY.
None
SINGLE CHARGED PARTICLE MOMENTUM DISTRIBUTION.
No description provided.
No description provided.
Multiple particle production in electron-positron interactions has been observed in an experiment performed at Adone, the Frascati 2×1.5 GeV e+e− storage ring. A total number of 239 events collected at several energies of the incident electron and positron beams between 0.8 and 1.0 GeV were analysed. The distribution of the multiplicity of charged particles produced in the final state is discussed and some upper limits on these multiplicities are reported. The observed lower limit to the total cross-section for multiple particle production in e+e− interactions, averaged over the energy range explored, is 3·10−32 cm2 with a statistical error of ±10% and a systematic uncertainty of ±25%.
LOWER BOUND FROM OBSERVED CHARGED PARTICLES.
The strong coupling alpha_s(M_Z^2) has been measured using hadronic decays of Z^0 bosons collected by the SLD experiment at SLAC. The data were compared with QCD predictions both at fixed order, O(alpha_s^2), and including resummed analytic formulae based on the next-to-leading logarithm approximation. In this comprehensive analysis we studied event shapes, jet rates, particle correlations, and angular energy flow, and checked the consistency between alpha_s(M_Z^2) values extracted from these different measures. Combining all results we obtain alpha_s(M_Z^2) = 0.1200 \pm 0.0025(exp.) \pm 0.0078(theor.), where the dominant uncertainty is from uncalculated higher order contributions.
Final average value of alpha_s. The second (DSYS) error is from the uncertainty on the theoretical part of the calculation.
TAU is 1-THRUST.
RHO is the normalized heavy jet mass MH**2/EVIS**2.
A search for narrow resonances in the reaction e + e − → hadrons in the mass regions 1915–2345 MeV and 2970–3090 MeV has been perforned at ADONE, the Frascati storage ring. With 90% confidence level our data exclude the production of narrow resonances with integrated cross section larger than 20% of the integrated cross section for production of the J/Ψ (3100 MeV).
No description provided.
In this Report, QCD results obtained from a study of hadronic event structure in high energy e^+e^- interactions with the L3 detector are presented. The operation of the LEP collider at many different collision energies from 91 GeV to 209 GeV offers a unique opportunity to test QCD by measuring the energy dependence of different observables. The main results concern the measurement of the strong coupling constant, \alpha_s, from hadronic event shapes and the study of effects of soft gluon coherence through charged particle multiplicity and momentum distributions.
Jet fractions using the JADE algorithm as a function of the jet resolution parameter YCUT at c.m. energy 130.1 GeV.
Jet fractions using the JADE algorithm as a function of the jet resolution parameter YCUT at c.m. energy 136.1 GeV.
Jet fractions using the JADE algorithm as a function of the jet resolution parameter YCUT at c.m. energy 161.3 GeV.
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