Multihadron production by electron-positron colliding beams has been investigated for total centre-of-mass energies ranging from 1.2 to 2.4 GeV. The total cross-section, σtot ≡ σ(e+e−→π+π−+ + anything), is of the order of σμμ ≡ σ(e+e−→μ+μ−), with a threshold near 1 GeV. Partial cross-sections for the various channels are also derived. The cross-section of the specific channel e+e−→π+π−π+π− exhibits an energy dependence which is suggestive of a heavier vector meson, ρ' (mρ,≈ 1.6 GeV,Гρ, ≈ 350 Mev), having the same quantum numbers as the ρ-meson. An upper limit is given for the coupling constantfρ′ (fρ′/4π<18, wherefρ′=mρ′2e/gγρ′). Final states withG+ parity are found to be much more abundant than those withG− parity. The average multiplicity (charged plus neutral final-state pions) is found to be betweet 4 and 5 over all the energy range explored.
No description provided.
VALUES OF R CALCULATED FROM TOTAL CROSS SECTION.
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We have measured the cross section of four charged pion production in photon-photon interactions in the invariant mass range 1.0≦Wγγ≦3.2 GeV and up toQ2=16 GeV2. For 1.2 GeV≦Wγγ≦1.7 GeV the process is dominated by ρ0ρ0 production with a rapid rise in cross section around 1.2 GeV, well below the nominal ρ0ρ0 threshold. The observed distributions in the two particle masses and in the production and decay angles are well described by an incoherent sum of the phase-space subprocesses γγ →ρ0ρ0, →ρ0π+π−, and →π+π−π+π−. A spin-parity analysis of the ρ0ρ0 system showsJP=2+ to dominate, although 0+ is also possible forWγγ≦1.4 GeV. Negative partity states are excluded.
Fractions of subprocesses from 3-parameter fit to the no-tag data.
Fractions of subprocesses from 2-parameter fit to the no-tag data in limited energy range. The Q=1R contribution is set equal to zero.
Fractions of subprocesses from 3-parameter fit to the single-tag data.
We present results of a K − d experiment performed with the 81 cm Saclay deuterium bubble chamber which was exposed to a K − beam at 4 momenta between 680 and 840 MeV/ c at the CERN PS. Cross sections were measured for inelastic two- and three-body K − n reactions on the basis of 5200 events/mb. Resonance production in the three-body reactions is discussed. In addition, differential cross sections and polarisations are presented for inelastic two-body reactions.
CROSS SECTIONS FOR TWO-BODY REACTIONS.
CROSS SECTIONS FOR THREE-BODY REACTIONS.
CROSS SECTIONS FOR K- P REACTIONS.
This paper presents the results of a study of the dominant neutral final states from π−p interactions. The data were obtained in an experiment performed at the Brookhaven National Laboratory Alternating Gradient Synchrotron, using a set of steel-plate optical spark chambers surrounding a liquid-hydrogen target. We present differential and total cross sections for the reactions (1) π−p→n+π0 and (2) π−p→n+η0(η0→2γ) and total cross sections for the reactions (3) π−p→n+kπ0 (k=2, 3, 4, and 5) and (4) π−p→all neutrals for eighteen values of beam momentum in the interval 1.3 to 4.0 GeV/c. The angular distributions for (1) and (2) have been analyzed in terms of expansions in Legendre polynomials, the coefficients for which are also given.
No description provided.
SIG = 4*PI*LEG(L=0).
FORWARD DIFFERENTIAL CROSS SECTION CALCULATED FROM LEGENDRE POLYNOMIAL COEFFICIENTS AND ERROR MATRICES.
At the Bonn 2.5.GeV electron synchrotron the target asymmetry for the photoproduction of positive pions has been measured. Data were taken at photon energies between 0.7 and 2.2 GeV and a pion CM-angle of 65°.
Axis error includes +- 0.0/0.0 contribution (?////).
No description provided.
An extensive investigation of antiproton-proton interactions at 5.7 GeV/c without strange-particle production was carried out using a hydrogen bubble chamber. Cross-sections for different channels are given and discussed. The reliability of the analysis was checked using artificially generated events. The cross-sections for elastic scattering, for all processes involving annihilation, and for all other inelastic processes are respectively σel=(16.3±0.6)mb,σannlbil=(22.5±2.0)mb, σinel=(24.8±2.0)mb. TheN * 1:38 is present both in the single and multiple pion production channels. For the reaction MediaObjects/11539_2007_Article_BF02720569_f1.jpg a cross-section of (1.05±0.21) mb was obtained. Cross-sections forN * 1238 production in other channels are also given. Some indication of the presence ofI=1/2 isobars was found in the nucleon-pion and the nucleon-two-pion systems. The inelastic nonannihilation reactions were found to be strongly peripheral. The one-pion exchange model including either a form factor or corrections for absorption was applied to the reaction MediaObjects/11539_2007_Article_BF02720569_f2.jpg . Neither version of the model could correctly account for all features of the reaction. The average number of pions in the annihilation was found to be 7.3±0.6. The presence of an asymmetry in the angular distribution of the charged pions was confirmed at this energy; it is due mostly to high-energy pions. The production of ρ and ω mesons was observed in various annihilation channels. Rates of up to 80% for ρ production and up to 15% for ω production were obtained by fitting phase-space and Breit-Wigner curves to the effective-mass distributions of different channels.
No description provided.
'1'.
'1'.
The differential cross section for π + p elastic scattering at 895, 945, 995 and 1040 MeV/ c has been measured in a hydrogen bubble chamber. The results are in good agreement with previous measurements using counter techniques except at extreme backward angles where significantly lower cross sections are obtained.
No description provided.
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The ep -> e'pi^+n reaction was studied in the first and second nucleon resonance regions in the 0.25 GeV^2 < Q^2 < 0.65 GeV^2 range using the CLAS detector at Thomas Jefferson National Accelerator Facility. For the first time the absolute cross sections were measured covering nearly the full angular range in the hadronic center-of-mass frame. The structure functions sigma_TL, sigma_TT and the linear combination sigma_T+epsilon*sigma_L were extracted by fitting the phi-dependence of the measured cross sections, and were compared to the MAID and Sato-Lee models.
Structure functions for Q**2 = 0.30 GeV**2 and W = 1.11 GeV.
Structure functions for Q**2 = 0.30 GeV**2 and W = 1.13 GeV.
Structure functions for Q**2 = 0.30 GeV**2 and W = 1.15 GeV.
New experimental results on the reactions K L 0 p→K S 0 p, Λπ + , Σ 0 π + andΛπ + π 0 at c.m. energies between 1.54 and 1.71 GeV are presented. This experiment has a statistical accuracy comparable with or greater than corresponding K − p and K − d experiments in the same energy range and a comparison with the data from these different types of experiments has been made. A search has been made for narrow states with masses in the region of 1.58 GeV.
No description provided.
No description provided.
No description provided.
The target asymmetry for the reaction γ p → K + Λ 0 was measured at the Bonn 2.5 GeV synchroton. Data were taken at a fixed kaon c.m. angle of 90° and at photon energies between 1.1 and 1.3 GeV. The kaons were detected in a large aperture magnetic spectrometer.
5 PCT TARGET POLARIZATION UNCERTAINTY INCLUDED IN QUOTED ERRORS.
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