The complete results of the experiments carried out with the Neutral Detector at the e + e − storage ring VEPP-2M in the energy range 2 E =0.5–1.4 GeV are reviewed. The data sample corresponds to a total integrated luminosity of 19 pb −1 .
ND results from Dolinsky et al., PL B174 (1986) 453.. Statistical errors only are shown. There is an additional systematic errorof 8%.
New ND data.. Statistical errors only are shown. There is an additional systematic errorof 8%.
Averaged ND data.. Statistical errors only are shown. There is an additional systematic errorof 8%.
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 have measured the mass of the Z boson to be 91.11±0.23 GeV/c2, and its width to be 1.61−0.43+0.60 GeV. If we constrain the visible width to its standard-model value, we find the partial width to invisible decay modes to be 0.62±0.23 GeV, corresponding to 3.8±1.4 neutrino species.
The total cross section for electron-positron annihilation into three or more hadrons has been measured for centre of mass energies between 1.4 and 2.0 GeV. The data were obtained at ADONE by the BB̄ experiment.
NOTE THAT THIS MEASUREMENT OF R EXCLUDES TWO-BODY FINAL STATE EVENTS. RADIATIVE CORRECTIONS WERE APPLIED.
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.
The cross section of W-boson pair-production is measured with the L3 detector at LEP. In a data sample corresponding to a total luminosity of 629.4/pb, collected at centre-of-mass energies ranging from 189 to 209 GeV, 9834 four-fermion events with W bosons decaying into hadrons or leptons are selected. The total cross section is measured with a precision of 1.4 % and agrees with the Standard Model expectation. Assuming charged-lepton universality, the branching fraction for hadronic W-boson decays is measured to be: Br(W-->hadrons) = 67.50 +- 0.42 (stat.) +- 0.30(syst.) %, in agreement with the Standard Model. Differential cross sections as a function of the W- production angle are also measured for the semi-leptonic channels qqev and qqmv.
Measured cross section for the process E+ E- --> LEPTON NU LEPTON NU.
Measured cross section for the process E+ E- --> QUARK QUARKBAR ELECTRON NEUTRINO.
Measured cross section for the process E+ E- --> QUARK QUARKBAR MUON NEUTRINO.
We have measured the total cross section for electron-positron annihilation into three or more hadrons, with at least two charged particles in the final state. The measurement was made at a center-of-mass energy of 4 GeV with a 2π−sr nonmagnetic detector. With 88 events detected, we obtain a model-independent lower limit on the hadron production cross section of 9.6 ± 1.4 nb; a calculation of detection efficiency based on invariant phase-space production of pions leads to a total cross section of 26 ± 6 nb. This cross section is 4.7 ± 1.1 times the theoretical total cross section for e+e−→μ+μ−. The average charged multiplicity is n¯=4.2±0.6.
No description provided.
Data were taken at the energy 2 E = 990 MeV to search for multibody events, with the same large solid angle detector which has been used for the measurement of the ϱ , ω and φ production by e + e − annilations. Assuming a π + π − π 0 π 0 production by the quasi two-body process e + e − → ϱ → ωπ 0 we give the correspondi ng cross section σ (e + e − → π + π − π 0 π 0 ) = (1.1 ± 0.5) 10 −32 cm 2 . Since no events with 3 and 4 charged pions have been observed σ (e + e − → π + π − π 0 π − ) ⩽ 1.5 × 10 −33 cm 2 .
RATIO TO MUON PAIR PRODUCTION CALCULATED FROM CROSS SECTION. INCLUDING SYSTEMATIC ERRORS.
Multihadronic production has been observed at the Adone e + e − storage ring, in the c.m. energy range 1.4 - 2.4 GeV. The cross sections for the reactions e + + e − → 2 π ± + nπ o (1 ⩽ n ⩽ 4) and e + + e − → (4 π ± + nπ ± ) (0 ⩽ n ⩽ 2) have been measured, assuming that the produced particles are only pions with a pure phase space momentum distribution.
New results on the multihadron production by electron and positron beams colliding with a total energy of up to 3 GeV are reported. Disregarding possible kaon final states, the ratio σ mh / σ μμ of the total multihadron cross-section to the point-like cross section for process e + e − → μ + μ − has an average value of 1.58 ± 0.25 in the energy interval 2.6–3.0 GeV. The average charged multiplicity over this energy range is 〈 n c 〉 = 2.9 ± 0.3.
AT A MEAN ENERGY OF 2.85 GEV, THE AVERAGE MULTIHADRON CROSS SECTION IS 16.4 +- 2.6 NB (R = 1.58 +- 0.25).
With use of the LENA detector at the DORIS e+e− storage ring, the hadronic cross section and the μ-pair decay branching ratio of the ϒ(9.46) resonance have been measured. Γee=1.23±0.10 (±0.14) keV, Bμμ=[3.5±1.4 (±0.4)]%, and Γtot=35−10+25 ({+9}{−7}) keV have been obtained. The first set of errors gives the statistical uncertainty. The numbers in parentheses represent systematic errors arising from the uncertainty in the total hadronic cross section.
Energy correlations have been measured with the MARK II detector at the PEP storage ring (Stanford Linear Accelerator Center) at c.m. energy of 29 GeV and are compared to first-order QCD predictions. Fragmentation processes are significant and limit the precision with which the first-order strong-coupling constant can be determined.
MEASUREMENT OF THE STRONG COUPLING CONSTANT.
Energy-energy-correlations (EEC) have been measured with the JADE detector at c.m. energies of 14 GeV, 22 GeV and in the region 29 GeV<Ecm<36 GeV. Corrected results are presented of EEC and their asymmetry, which can be directly compared to theoretical predictions. At 〈Ecm〉=34 GeV a comparison with second order QCD predictions yields good agreement for the string model fragmentation resulting in a value of the strong coupling constant αs=0.165±0.01 (stat.). The independent fragmentation models, which yield values of αs between 0.10 and 0.15 depending on the treatment of energy and momentum conservation and of the gluon splitting, do not provide a satisfactory description of the data over the full angular range.
TABLES GIVEN HERE CONTAIN SELF CORRELATION. THIS IS SUBTRACTED IN THE FIGURE.
VALUE OF ASSYMETRY IN CORRELATIONS.
No description provided.
The forward-backward asymmetries of$$e^ + e^ - \to Z^0 \to b\bar b and e^ + e^ - \to Z^0 \to c\bar c$$
Measurement of the asymmetry in b-quark production on the Z0 peak using a two parameter fit, neglecting the effects of B0-BBAR0 mixing.
Measurement of the asymmetry in b-quark production on the Z0 peak using a two parameter fit and correcting for B0-BBAR0 mixing. The second systematic error is due to the uncertainty of the mixing factor.
Measurement of the asymmetry in c-quark production on the Z0 peak using a two parameter fit.
We have measured the mass of the Z boson to be 91.14±0.12 GeV/c2, and its width to be 2.42−0.35+0.45 GeV. If we constrain the visible width to its standard-model value, we find the partial width to invisible decay modes to be 0.46±0.10 GeV, corresponding to 2.8±0.6 neutrino species, with a 95%-confidence-level upper limit of 3.9.
No description provided.
The contributions of the PLUTO experiment to e + e − physics at collision energies in the range of 3–32 GeV are reviewed. The review briefly sketches the storage rings DORIS and PETRA at DESY, and describes the most important features of the PLUTO detector, of data processing, and of the analysis methods. It covers the physics results in the fields of electroweak interactions, of the heavy lepton τ and the search for still heavier leptons, of hadron production with evidence for quark and gluon jets, as well as for single and multiple gluon emission, of Y decays and their relation to QCD, and presents results in high-energy photon-photon interactions, including the first measurement of the photon structure function.
SUMMARY OF MEASUREMENTS OF R (REVISED FROM EARLIER PUBLICATIONS). RADIATIVE CORRECTIONS APPLIED. TAU HEAVY LEPTON CONTRIBUTION SUBTRACTED.
Summary of measurements of the cross section around the UPSI(1S) (revised from earlier publication Phys.Lett. 76B (1978) 243) with radiative corrections a pplied and leptons contribution subtracted. Data extracted from graph by VVE.
None
CROSS SECTION EXCLUDES ANY CONTRIBUTION FROM TWO-BODY FINAL STATES (PI+ PI- AND K+ K-).
CHARGED AND NEUTRAL MULTIPLICITIES.
The production rates for 2-, 3-, 4- and 5-jet hadronic final states have been measured with the DELPHI detector at the e + e − storage ring LEP at centre of mass energies around 91.5 GeV. Fully corrected data are compared to O(α 2 s ) QCD matrix element calculations and the QCD scale parameter Λ MS is determined for different parametrizations of the renormalization scale ω 2 . Including all uncertainties our result is α s ( M 2 Z )=0.114±0.003[stat.]±0.004[syst.]±0.012[theor.].
Corrected jet rates.
Second systematic error is theoretical.
The strong interaction coupling constant α s has been measured with a new method, the planar triple energy correlation in the reaction e + e - → hadrons at center-of-mass energies ranging from 14 GeV to 46.78 GeV. A complete second-order perturbative QCD calculation was used. Λ MS = 110 ± 30 −55 +70 MeV is found.
No description provided.
No description provided.
No description provided.
We have studied hadronic events from e+e- annihilation data at centre-of-mass energies of sqrt{s}=172, 183 and 189 GeV. The total integrated luminosity of the three samples, measured with the OPAL detector, corresponds to 250 pb^-1. We present distributions of event shape variables, charged particle multiplicity and momentum, measured separately in the three data samples. From these we extract measurements of the strong coupling alpha_s, the mean charged particle multiplicity <nch> and the peak position xi_0 in the xi_p=ln(1/x_p) distribution. In general the data are described well by analytic QCD calculations and Monte Carlo models. Our measured values of alpha_s, <nch> and xi_0 are consistent with previous determinations at sqrt{s}=MZ.
Distribution of Thrust.
Distribution of Thrust Major.
Distribution of Thrust Minor.
The results of the first experiment performed at DCI in e + e − annihilations in the c.m. energy range 1.350–2.125 GeV region are presented. The cross sections of various multipion channels are extracted. Significant structure appears in some specific channels. A relatively narrow resonance around 1.660 GeV decaying into 3 π 's is found. Charged and neutral multiplicities, and also the ratio R are given.
PEAK CROSS SECTION FROM FIT WITH BREIT-WIGNER RESONANCE PLUS CONSTANT BACKGROUND TO ISOSCALAR JPC = 1-- STRUCTURE OF MASS 1652 +- 17 MEV AND WIDTH OF 42 +- 17 MEV.
R VALUE SEEMS CONSTANT OVER THIS ENERGY RANGE.
We present the general properties of jets produced bye+e− annihilation. Their production and fragmentation characteristics have been studied with charged particles for c.m. energies between 12 and 43 GeV. In this energy rangee+e− annihilation into hadrons is dominated by pair production of the five quarksu, d, s, c andb. In addition, hard gluon bremsstrahlung effects which are invisible at low energies become prominent at the high energies. The observed multiplicity distributions deviate from a Poisson distribution. The multiplicity distributions for the overall event as well as for each event hemisphere satisfy KNO scaling to within ∼20%. The distributions ofxp=2p/W are presented; scale breaking is observed at the level of 25%. The quantityxpdδ/dxp is compared with multigluon emission calculations which predict a Gaussian distribution in terms of ln(1/x). The observed energy dependence of the maximum of the distributions is in qualitative agreement with the calculations. Particle production is analysed with respect to the jet axis and longitudinal and transverse momentum spectra are presented. The angular distribution of the jet axis strongly supports the idea of predominant spin 1/2 quark pair production. The particle distributions with respect to the event plane show clearly the growing importance of planar events with increasing c.m. energies. They also exclude the presence of heavy quark production,e+e−→Q\(\bar Q\) for quark masses up to 5<mQ<20.3 GeV (|eQ|=2/3) and 7<mQ<19 GeV (|eQ|=1/3). The comparison of 1/σtotdδ/dpT measured at 14, 22 and 34 GeV suggests that hard gluon bremsstrahlung contributes mainly to transverse momenta larger than 0.5 GeV/c. The rapidity distribution forW≧22 GeV shows an enhancement away fromy=0 which corresponds to an increase in yield of 10–15% compared to the centre region (y=0). The enhancement probably results from heavy quark production and gluon bremsstrahlung. The particle flux around the jet axis shows with increasing c.m. energy a rapidly growing number of particles collimated around the jet axis, while at large angles to the jet axis almost noW dependence is observed. For fixed longitudinal momentump‖ approximate “fan invariance” is seen: The shape of the angular distribution around the jet axis is almost independent ofW. The collimation depends strongly onp‖. For smallp‖,p‖<0.2 GeV/c, isotropy is observed. With increasingp‖ the particles tend to be emitted closer and closer to the jet axis.
R VALUES BELOW 32.5 GEV ARE IDENTICAL TO THOSE GIVEN IN BRANDELIK ET AL., PL 113B, 499 (1982).
No description provided.
CHARGED PARTICLE MULTIPLICITY DISTRIBUTIONS.
The branching fraction for the decay of the ϒ(1S) into τ paris has been measured to be (3.4±0.4±0.4)%. This result agrees with the previously measured branching ratio of the decay into muon pairs.
VISIBLE CROSS SECTIONS IN THE PEAK.
No description provided.
None
Data from Run 1. There is an additional overall systematic uncertainty of 5.2 pct.
Data from Run 2. There is an additional overall systematic uncertainty of 5.2 pct.
Average R value.
We have searched the mass region 3.2 to 5.9 GeV for evidence of narrow resonances in e+e−→hadrons. We find no evidence for any such resonances other than the ψ(3695) in this region with a sensitivity ranging from about 12 to 45% of the integrated cross section of the ψ(3695). The more stringent bounds apply to resonances of a few MeV width, while the looser bounds apply to resonances of up to 20 MeV width.
EXTREAMLY GOOD DATA, MUST BE ASCED FROM AUTHORS.
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