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Axis error includes +- 0.0/0.0 contribution (?////NOT GIVEN).
Axis error includes +- 0.0/0.0 contribution (?////NOT GIVEN).
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The results of the study of the π + p→K + ∑ + (1) and π + p→K + ∑ + (1385) (2) reactions at 12 GeV/ c are presented. The differential cross sections d σ /d t in| t min |<| t |<0.8 (GeV/ c ) 2 momentum transfer range are measured. The ∑ + polarisation for | t |<0.5 (GeV/ c ) 2 for reaction (1) is defined. Binary reactions (1) and (2) were selected by analyzing the missing mass spectra for the forward emitted fast K + meson. The total cross sections in the studied momentum transfer range are 20.2±2.4 μ b and 7.3±1.1 μ b for the reactions (1) and (2) respectively. The experimental results are compared with the predictions of the Regge models which take into account rescattering and secondary singularities.
SYSTEMATIC ERRORS INCLUDED.
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Using data from the TPC/Two-Gamma experiment at the SLAC e+e− storage ring PEP, a C=+1 resonance has been observed in the π+π−π0γ final state resulting from the fusion of one nearly real and one quite virtual photon. The actual decay channel is probably π+π−π0π0, where one final-state photon is not detected, and the mass of the fully reconstructed state would be approximately 1525 MeV. A four-pion decay mode in turn implies that the resonance has even isospin. The nonobservation of this R(1525) when both initial-state photons are nearly real suggests a spin-1 assignment. Since the large measured value of the product of the branching ratio into π+π−π0π0 and the γγ coupling makes it unlikely that this state is the mostly s¯s f1(1510), its interpretation may lie outside of conventional meson spectroscopy. There is a second, less-significant enhancement observed in the same reaction at a four-pion mass centered around 2020 MeV.
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Coupling parameter times the effective form factor.
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We present a measurement of the top quark pair (ttbar) production cross section in ppbar collisions at a center-of-mass energy of 1.96 TeV using 230 pb-1 of data collected by the DO detector at the Fermilab Tevatron Collider. We select events in the dilepton final states ee, emu and mumu based on kinematical properties consistent with ttbar events. For a top quark mass of 175 GeV, we measure a top pair production cross section sigma(ttbar) = 8.6 +3.2-2.7 (stat) +/-1.1 (syst) +/-0.6 (lumi) pb, in good agreement with the standard model prediction.
TTBAR production cross section.
The results of a study of strange particle production in charged current $\bar{\nu}_{\mu} N$ interactions in the Fermilab 15 ft bubble chamber filled with a heavy $Ne-H_2$ mixture are presented. Production rates and average multiplicities of $K^0$'s and Λ's as functions of W 2 and Q 2 are given. The experimental data agree well with the quark-parton model predictions if a yield of 0.06 ± 0.02 of $K^0$'s and Λ's from charm production is included. Upper limits for D-meson production are given and the shape of the charmed quark fragmentation function is discussed. Inclusive production of the K ∗ (890) and Σ(1385) resonances is measured and it is shown that only about 5% of the K 0 mesons and Λ hyperons results from resonance decays. Relative production rates of neutral strange particles on proton and neutron targets are studied.
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Quasiexclusive neutral meson production in pN-interactions is studied in experiments with the SPHINX facility operating in a proton beam from the IHEP accelerator (Ep=70 GeV). The cross sections and the parameters of the differential distributions for πo, ω, η and Ko production in the deep fragmentation region (xF > 0.79 ÷ 0.86) are presented. The results show that such proton quasiexclusive reactions with baryon exchange may be promising in searches for exotic mesons.
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The dsig/dpt**2 distribution was approximated by the expression: dsig /dpt**2 = CONST(C=1)*SLOPE(C=1)*EXP(-SLOPE(C1)*PT**2) + CONST(C=2)*SLOPE(C=2)* EXP(-SLOPE(C2)*PT**2).
We have measured the total and differential cross sections of the reaction e + e − → γγ ( γ ) at center-of-mass energies around 91 GeV, with an integrated luminosity of 14.2 pb −1 . The results are in good agreement with QED predictions. We set lower limits, at 95% confidence level, on the QED cutoff parameters of Λ + > 139 GeV, Λ − > 108 GeV and on the mass of an excited electron of m e∗ > 127 GeV . We searched for Z 0 rare decays with photonic signitures in the final state. Upper limits, at 95% confidence level, for branching ratio of Z 0 decaying into π 0 γ / γγ , νγ and γγγ are 1.2 × 10 −4 , 1.8 × 10 −4 , 3.3 × 10 −5 respectively.
Measured cross section for the 1991 data.
Measured cross section for the 1990 data.
Measured differential cross sections of combined 1990 and 1991 data.
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