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
R VALUES BELOW 32.5 GEV ARE IDENTICAL TO THOSE GIVEN IN BRANDELIK ET AL., PL 113B, 499 (1982).
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CHARGED PARTICLE MULTIPLICITY DISTRIBUTIONS.
Results are presented on the inclusive photoproduction of λ and λ for incident photon energies between 25 and 70 GeV. The slope parameter of the p T 2 distribution is found to be 2.83±0.1 GeV −2 for λ and 3.28±0.25 GeV −2 for λ . The x F distributions, measured in the range −0.2 to 0.7, show that while λ are produced centrally, λ production extends to more negative values of x F ; the shapes show no energy dependence and are similar to those in pion-induced reactions. The polarization of the produced λ is less than 10%. The results are discussed in terms of vector dominance and quark fusion models.
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Prompt dimuon production has been measured. Events with mass up to 25 GeV/c2 are observed, as well as the J and ϒ resonances. Cross sections are given for J and ϒ production. For the continuum, the scaling function F(τ) is measured at very small values of τ=ms covering the range 0.05<τ<0.20.
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HERE UPSILON = ALL USILON FAMILY. ANGULAR DISTBN. IS SEEN TO BE ISOTROPIC.
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Inclusive ϱ 0 production has been investigated in p p reactions at 22.4 GeV/ c . The total cross section for ϱ 0 production is 8.1 ± 2.0 mb. The average ϱ 0 's per event is 0.17 ± 0.03. The average transverse momentum, as obtained by extrapolation of a fitted simple exponential to the p T 2 distribution, is 0.52 ± 0.12 GeV/ c . The Feynman x and c.m. rapidity distributions show ϱ 0 to be “centrally” produced.
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Inclusive K ∗0 production is studied in π − p interactions at 16 GeV/ c with x ϝ > 0.2. The K ∗0 is found to be pre-dominantly centrally produced with cross section σ( K ∗0 ) = (72 ± 12) μb for x ϝ > 0.2 and compares closely to data on K ∗0 production in π + p interactions at the same energy.
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Inclusive φ production is studied in π − p collisions at 16 GeV/ c . The φ cross section for Feynman variable x φ > 0.2 is found to be (15.5 ± 3.6) μb. This leads to an extrapolated cross section of (29.9 ± 7.0) μb for x φ > 0.0. Fitting the momentum transfer squared distribution of the φ to the form e −bp 2 T gives an average slope of b = (2.4 ± 0.3) (GeV/ c −2 for x φ > 0.5.
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DATA OBTAINED FROM FIGURE BY A.A. LEBEDEV.
We have observed an azimuthal asymmetry in inclusive hadron production by e+e− annihilation at the center-of-mass energy s=7.4 GeV. The asymmetry is caused by the polarization of the circulating beams in the storage ring and allows separate determination of the transverse and longitudinal structure functions. We find that transverse production dominates for x>0.2 where x is the scaling variable 2ps.
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Inclusive cross sections and longitudinal momentum distributions are presented for γ rays produced in K − p and K + p interactions at 32 GeV/c in the 4.5 m Mirabelle hydrogen bubble chamber at the Serpukhov accelerator. The average longitudinal and transverse momentum of neutral pions and the average π 0 multiplicity ▪ 〈 n π 0〉 are estimated. It is found that 〈 n π 0〉 is an increasing function of the number of charged prongs.
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