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.
Results are presented from a study of the structure of high energy hadronic events recorded by the L3 detector at sqrt(s)>192 GeV. The distributions of several event shape variables are compared to resummed O(alphaS^2) QCD calculations. We determine the strong coupling constant at three average centre-of-mass energies: 194.4, 200.2 and 206.2 GeV. These measurements, combined with previous L3 measurements at lower energies, demonstrate the running of alphaS as expected in QCD and yield alphaS(mZ) = 0.1227 +- 0.0012 +- 0.0058, where the first uncertainty is experimental and the second is theoretical.
The measured ALPHA_S at three centre-of-mass energies from fits to the individual event shape distributions. The first error is statistcal, the first DSYS error is the experimental systematic uncertainty, and the second DSYS error is the theoryuncertainty.
Updated ALPHA_S measurements from the BT, BW and C-Parameter distributions,from earlier L3 data at lower centre-of-mass energies.. The first error is the total experimental error (stat+sys in quadrature) and the DSYS error is the theory uncertainty.
Combined ALPHA_S values from the five event shape variables. The first error is statistical, the first DSYS error is the experimental systematic uncertainity, the second DSYS error is the uncertainty from the hadronisdation models, andthethird DSYS errpr is the uncertainty due to uncalculated higher orders in the QCDpredictions.
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EVENTS WITH IDENTIFIED PROTONS.
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CS FOR GIVEN REACTIONS BASED ON THE SAME STATISTICS FROM THE SAME EXPERIMENT ARE ALSO PRESENTED IN THE PAPER A.GIVERNAUD ET AL.,NP B160, 445, 1979, BUT NUMBERS ARE DIFFERENT DUE TO DIFFERENT CORRECTIONS FOR SLOW PROTONS.
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Results are presented on vector meson production in the hypercharge exchange reactions: π + p → K ∗+ (890) Y + and K − p→ ρ − Y + where Y + is either Σ + or Y ∗+ (1385). These reactions have been studied at 7 GeV/ c and 11.5 GeV/ c using the SLAC Hybrid Facility. Total and differential cross sections, hyperon polarization, and vector meson decay angular distributions are presented. We find that reactions with Σ + production are dominated by natural parity exchange. The Y ∗ (1385) reactions are consistent with substantial natural parity exchange contributions but also show significant unnatural parity exchange. The differential cross sections and polarization measurements for the vector meson production are compared to the pseudoscalar production reactions.
Axis error includes +- 20/20 contribution.
Axis error includes +- 20/20 contribution.
Axis error includes +- 20/20 contribution.
We have measured in a single experimental setup, the differential cross sections and decay angular distributions of the Y ∗ (1385) produced in the two line-reversed reactions: π + p → K + Y ∗+ (1385) (279 events/ω b ) and K − p → π − Y ∗+ (1385) (190 events/ωb) at 11.5 GeV/ c . The data have been derived from a triggered bubble-chamber experiment using the SLAC Hybrid Facility. We find the differential cross sections and Y ∗ polarizations for the two reactions to be in agreement with exchange-degeneracy predictions, if kinematic differences are taken into account. The Stodolsky-Sakurai and additive quark model predictions are in agreement with the main features of the decay angular distributions of the Y ∗ (1385), except for small violations at low momentum transfer, which can be associated with a finite helicity non-flip contribution in the forward direction.
Axis error includes +- 10/10 contribution.
THESE FINAL DIFFERENTIAL CROSS SECTIONS ARE INCLUDED IN THE RECORD OF J. BALLAM ET AL., PRL 41, 676 (1978).
TRANSVERSITY AMPLITUDES FOR SIG(1385P13)+ PRODUCTION. THE IMAGINARY PARTS OF T(11) AND T(-1-1) WERE ARBITRARILY FIXED AT ZERO.
Differential cross sections and density-matrix elements in ρ− decay have been measured at 6 GeV/c for p¯p→π+ρ− and its line-reversed partner π−p→pρ− in the range tmin>t>−1.5 (GeV/c)2. The reactions satisfy line-reversal symmetry and the ρ− decay is consistent with isotropy for −t≲0.5 (GeV/c)2. For −t≳0.5 (GeV/c)2, the differential cross sections show a weaker t dependence, and the decays become anisotropic.
No description provided.
FROM ROUGHLY EQUAL NUMBERS OF RHO- EVENTS AND BACKGROUND (CONSISTENT WITH ISOTROPY FOR BOTH REACTIONS).
We report measurements of inelastic photoproduction of ω and ρ± mesons from hydrogen and deuterium at incident photon energies in the range 7.5-10.5 GeV. For ωΔ and ρ−Δ++ production, differential cross sections dσdt′ and spin density matrices are presented. For higher missing masses the cross sections dσdMX2 and invariant structure functions F(x) are also given. The data are compared to a one-pion-exchange model. We conclude that pion exchange is dominant for inelastic ω photoproduction, but unimportant for ρ±.
CROSS SECTION PER NUCLEON FOR COMBINED HYDROGEN AND DEUTERIUM DATA ALLOWING FOR A GLAUBER CORRECTION FACTOR OF 0.88 FOR THE DEUTERIUM CROSS SECTIONS.
HYDROGEN AND DEUTERIUM DATA COMBINED BY AVERAGING.
OBTAINED BY EXTRAPOLATING A FIT TO D(SIG)/DT OVER -T = 0 TO 0.52 GEV**2.
The reaction K − p → K − π − π + p has been measured at 25 and 40 GeV/ c at the Serpukhov Proton Accelerator. The production cross section at 25 and 40 GeV/ c as a function of momentum transfer and K ππ mass is presented, and results of the partial-wave analysis of the K ππ system yielding information about Q(1300), K ∗ (1400) and L(1770) mesons are discussed.
No description provided.
K** DEFINED BY 1.30 < M(K PI PI) < 1.54 GEV.
L IS DEFINED AS THE 2- STATE WITH 1.6 < M(K PI PI) < 1.9 GEV.
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