Short overview of experiments with SND detector at VEPP-2M e^+e^- collider in the energy range 2E = 400 - 1400 MeV and preliminary results of data analysis are presented.
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The yields and average transverse momenta of pions, kaons, and antiprotons produced at the Fermilab p¯p collider at s=300, 540, 1000, and 1800 GeV are presented and compared with data from the energies reached at the CERN collider. We also present data on the dependence of average transverse momentum 〈pt〉 and particle ratios as a function of charged particle density dNcdη; data for particle densities as high as six times the average value, corresponding to a Bjorken energy density 6 GeV/fm3, are reported. These data are relevant to the search for quark-gluon phase of QCD.
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Measurements have been made of the π ∓ proton total cross sections over the laboratory kinetic energy range 70 to 290 MeV. The absolute accuracy of the data is generally 0.5 %, but decreases to 1 % for some points where applied corrections are large or where low particle fluxes limit the statistical accuracy.
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We present new high statistics data on hadron production in photon-photon reactions. The data are analyzed in terms of an electron-photon scattering formalism. The dependence of the total cross section of Q 2 , the four-momentum transfer squared of the scattered electron, and on the mass W of the hadronic system is investigated. The data are compared to predictions from Vector-Meson Dominance and the quark model.
DEPENDENCE ON VISIBLE HADRONIC INVARIANT MASS.
We have measured the production cross section for K s 0 in e + e − annihilation from 3.6 to 5.0 GeV center of mass energy. A substantial increase of the K s 0 yield is observed around 4 GeV in qualitative agreement with the charm hypothesis.
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Differential cross sections have been measured for π+p and π−p elastic scattering at 378, 408, 427, 471, 509, 547, 586, 625, 657, and 687 MeV/c in the angular range -0.8<cosθc.m.<0.8. The scattered pion and recoil proton were detected in coincidence using scintillation-counter hodoscopes. A liquid-hydrogen target was used except for measurements at forward angles, in which a CH2 target was used. Statistical uncertainties in the data are typically less than 1%. Systematic uncertainties in acceptance and detection efficiency are estimated to be 1%. Absolute normalization uncertainties are 2–3 % for most of the data. The measurements are compared with previous data and with the results of recent partial-wave analyses. The data are fit with Legendre expansions from which total elastic cross sections are obtained.
Normalisation uncertainty = 4.1 pct.
Normalisation uncertainty = 2.1 pct.
Normalisation uncertainty = 3.6 pct.
The analyzing power for π−p→π0n has been measured at five incident momenta from 547 to 687 MeV/c using a transversely polarized target. Data were obtained with scintillation counters at 10 angles simultaneously covering the range −0.9≤cosθc.m.π≤0.9. Our results and those of Kim et al. are used for a model-independent test of isospin invariance which is based on the triangle inequalities applied to the transversity-up as well as the transversity-down cross sections. No evidence is found of isospin violation.
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We have used the momentum spectrum of leptons produced in semileptonic B-meson decays to set a 90%-confidence-level upper limit on Γ(b→ulν)Γ(b→clν) of 4%. We also measure the semileptonic branching fractions of the B meson to be (12.0±0.7±0.5)% for electrons and (10.8±0.6±1.0)% for muons.
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The reactionγγ→π+π−π+π− has been studied with the ARGUS detector. The rate in the invariant mass region below 1.8 GeV/c2 is found to be largely due toρ0ρ0 production. A spin-parity analysis shows a dominance of the partial wave (JP,Jz)=(2+, 2) with a small admixture fromJP=0+. The contribution of negative parity states is consistent with zero. The large ratio of cross sectionsσ(γγ→ρ0ρ0)/σ(γγ→ρ+ρ−)≃4, and the dominance of theJP=2+ wave in the reactionγγ→ρ0ρ0 is a signature consistent with the production of an exotic (I=2) resonance.
Statistical errors only.. Cross-section assuming phase-space distribution, as obtained by a 7 parameter fit.
Statistical errors only.. Cross-section assuming phase-space distribution, as obtained by a 7 parameter fit.
Partial wave components for the (JP,JZ) contribution to RHO0 RHO0 cross section.