Results are presented from a study of the annihilation interaction p―p→K+K−π+π− at 8.3 GeV/c based on data from an experiment performed with the large-aperture solenoid spectrometer (LASS) at the Stanford Linear Accelerator Center. A measurement of the reaction cross section is made, and contributions to the final state from the φ, f0A20, K*(890), K*(1430), and ρ0 resonances are studied.
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We report the final results of a search for narrow structures in the p¯p total cross section between 395 and 740 MeV/c with a rms mass resolution of 1.5 MeV around the S-resonance region. A reanalysis of the data significantly improved the statistical accuracy. No evidence is found for narrow structures and a 90%-confidence-level upper limit of 24 mb MeV is set at around 500 MeV/c for the integrated cross section of a Breit-Wigner-type resonance of width ≲4 MeV.
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η′η pair production in the charge exchange reaction π−p→η′ηn has been observed and studied in a search for glueballs with the 38 GeV/c pion beam of the 70 GeV IHEP accelerator. The γ-rays from the decay η′η→4γ were detected with the hodoscope spectrometer GAMS-2000. The η′η events in the mass range from threshold up to 1.8 GeV are decays of the scalar G(1590)-meson which has been already observed in its ηη decay mode. The measured ratio of the partial widths of the G→η′η and the G → ηη decay channels is 2.7±0.8 in agreement with the value expected for glueballs.
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We have studied antiproton elastic scattering on Al, Cu, and Pb for two incident momenta: 514 and 633 MeV/c. The angular region covered extends from the forward Coulomb region to approximately 30 deg. The differential cross sections were analyzed using a nonrelativistic optical potential of the Woods-Saxon form, with the imaginary shape taken from electron scattering data. We obtained fits for the strengths of the real and imaginary parts of the potential, (V0, W0), of (51, 116) MeV for Al, (12, 71) MeV for Cu, and (12, 278) MeV for Pb.
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A study is made of the ωπ 0 system produced near threshold in the reaction γ p→ π + π − π 0 π 0 p. A spin-parity analysis shows that the ωπ 0 enhancement is consistent with predominant 1 + B(1235) production, with ∼20% J P = 1 − background.
MEAN BEAM ENERGY IS 39 GEV.
ESTIMATE OF B(1235) PRODUCTION CROSS SECTION ASSUMING 1+ CROSS SECTION OF 0.63 +- 0.20 MUB AND THAT 20 PCT OF THIS IS DUE TO BACKGROUND S-WAVE CONTRIBUTIONS.
The EM form factor of the pion has been studied in the time-like region by measuring σ (e + e − → π + π − ) normalized to σ (e + e − → μ + μ − ). Results have been obtained for q 2 down to the physical threshold.
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DATA ARE CORRECTED FOR TWO-PHOTON AND TAU PRODUCTION EFFECTS, ACCEPTANCE AND QED RADIATIVE EFFECTS UP TO ORDER ALPHA**3. THERE IS ALSO A 6 PCT NORMALISATION ERROR NOT INCLUDED. THE OVERALL AVERAGE VALUE OF R FROM THIS DATA IS 3.88 +- 0.04 +- 0.22.
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SEE PRL 55, 665 FOR MOST RECENT VALUES OF THE MU+ MU- CROSS SECTIONS.
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.
Hadronic events obtained with the CELLO detector at PETRA are compared with second order QCD predictions using different models for the fragmentation of quarks and gluons into hadrons. We find that the model dependence in the determination of the strong coupling constant persists when going from first to second order QCD calculations.
ASYMMETRY FOR DATA CORRECTED WITH IF MODEL (ALPHA-S=0.12).
ASSYMETRY FOR DATA CORRECTED WITH SF MODEL (ALPHA-S=0.19).
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Using data obtained with EHS equipped with the Rapid Cycling Bubble Chamber (RCBC) exposed to a proton beam of 360 GeV/c, we calculate topological cross sections. We present in great detail the procedure and the techniques used to correct raw data. Finally, we give multiplicity moments and multiplicity correlations and we compare the values obtained in our experiment, together with data at other energies, with different models.
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