Measurements of the reactions e++e−→e++e−, μ++μ−, and τ++τ− at PETRA energies (s12=13,17,27.4,30 and 31.6 GeV) are reported. The results show that these reactions agree well with the predictions of quantum electrodynamics thus determining that all the known charged leptons are pointlike particles to a distance < × 10−16 cm.
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Hadron jets produced in e + e − annihilation between 13 GeV and 31.6 GeV in c.m. at PETRA are analyzed. The transverse momentum of the jets is found to increase strongly with c.m. energy. The broadening of the jets is not uniform in azimuthal angle around the quark direction but tends to yield planar events with large and growing transverse momenta in the plane and smaller transverse momenta normal to the plane. The simple q q collinear jet picture is ruled out. The observation of planar events shows that there are three basic particles in the final state. Indeed, several events with three well-separated jets of hadrons are observed at the highest energies. This occurs naturally when the outgoing quark radiates a hard noncollinear gluon, i.e., e + e − → q q g with the quarks and the gluons fragmenting into hadrons with limited transverse momenta.
NORMALIZED TRANSVERSE MOMENTUM DISTRIBUTION WITH RESPECT TO THE SPHERICITY AXIS AT 13, 17, AND 27.4 TO 31.6 GEV.
Two (Δ(1238)ππ) enhancements at 1.93 and 2.12 GeV have been observed in an analysis of the invariant-mass spectra of Δ++(1238)π-π0 and Δ++(1238)π-π- from π-p→π-pπ+π-π0 events in 4.5 GeV/c π-p interactions. An enhancement at 2.2 GeV is also seen with a dominant branching to the Δ(1238)ρ system. The 1.93 and 2.12 enhancements seem to be produced mainly through a ρ-meson exchange process. The 2.2 GeV enhancement seems to be produced diffractively and is considered to correspond to theG17(2190) state.
No description provided.
EXPONENTIAL FITS TO T-DISTRIBUTIONS.
This paper reports on the first results of the study of e+e− collisions at s=27.4 GeV and s=27.7 GeV at PETRA, using the 4π-sr electromagnetic and calorimetric detector MARK-J. We obtain an average R=σ(e+e−→hadrons)σ(e+e−→μ+μ−)=3.8±0.3 (statistical)±0.6 (systematic) and a relative R=1.0±0.2 between the two energies. The R values, the measured thrust distribution, and average spherocity show no evidence for the production of new quark flavors.
THE RELATIVE VALUE OF R BETWEEN THESE TWO ENERGIES IS 1.0 +- 0.2.
THRUST DISTRIBUTION (1/N)*DN/DTHRUST AT 13, 17 AND 27 GEV. THESE DATA ARE RATHER DETECTOR DEPENDENT.
We report on the results of the study of e + e − collisions at the highest PETRA energy of √ s = 31.57 GeV, using the 4π sr, electromagnetic and calorimetric detector Mark J. Based on 88 hadron events, and an integrated luminosity of 243 nb −1 we obtain R = σ (e + e − → hadrons)/ σ (e + e − → μ + μ − ) = 4.0 ± 0.5 (statistical) ± 6 (systematic). The R value, the measured thrust distribution and average spherocity show no evidence for the production of new quark flavors.
CORRECTIONS FOR TWO-PHOTON PROCESSES, TAU HEAVY LEPTON PRODUCTION AND INITIAL STATE RADIATIVE CORRECTIONS HAVE BEEN APPLIED.
THRUST DISTRIBUTION (1/N)*DN/DTHRUST AT 31.57 GEV. THESE DATA ARE RATHER DETECTOR DEPENDENT.
We have measured the polarization of the Λ hyperon produced in the reaction π−p→K0Λ at 3 and 5 GeV/c, for four-momentum transfers t′ out to 1.6 GeV2, by observing the parity-violating decay Λ→pπ−. With an increase in statistical power by a factor of 3 to 4 over the best previous experiments in this energy range, we confirm earlier observations that the polarization is small and positive below t′=0.4 GeV2, becoming large and positive for larger values of t′. In particular, at 5 GeV/c for all t′ between 0.8 and 1.6 GeV2 the polarization is consistent with a value of - 1.
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Backward production of ω (1670) is observed in the reactions K − p→ φ + φ − ω 0 Λ 0 and K − p→ φ + φ − φ 0 φ 0 for | U ' Λ |<1.0 GeV 2 . The cross section for the ω (1670) → φ + φ − ω 0 decay mode is 1.90±0.35 μ b for 8.25 GeV/ c incident K − . Evidence is presented for the importance of the sequential decay, ω (1670) → B φ → ωφφ with a branching ratio ω (1670) → B φ /all ω (1670) → ωφφ =1.0± 0.25 0.00 .
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Cross sections and charged multiplicity distributions forK+p interactions at 70 GeV/c are presented and compared withK+p data at other energies. Comparisons are also made with available π+p,pp, andK−p data.
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DATA OBTAINED IN ASSUMPTION THAT RHO(MM=00,P=3,XYZ=SH)=1-2*RHO(MM=1-1,P=3,XYZ=SH).
INTEGRATED CROSS SECTION, INCLUDING SYSTEMATIC UNCERTAINTY IN ERRORS Axis error includes +- 15/15 contribution (DECAY-BR(BRN=OMEGA --> PI0 GAMMA,BR=0.088 +- 0.005)).
THESE TABULATED VALUES OF THE TOTAL CROSS SECTION RATIO R ARE INCLUDED IN THE RECORD OF P. A. RAPIDIS ET AL., PRL 39, 526 (1977) AND PRL 39, 974 (1977) (ERRATUM).
THE D MESON INCLUSIVE PRODUCTION CROSS SECTIONS AND DECAY BRANCHING FRACTIONS AT THE PSI(3772)0 RESONANCE ARE PUBLISHED IN I. PERUZZI ET AL., PRL 39, 1301 (1977).
THESE D AND K MESON INCLUSIVE PRODUCTION CROSS SECTIONS ARE PUBLISHED IN M. PICCOLO ET AL., PL 86B, 220 (1979).