The cross section of the quasi-elastic reactions\(\bar v_\mup \to \mu ^ +\Lambda (\Sigma ^0 )\) in the energy range 5–100 GeV is determined from Fermilab 15′ bubble chamber antineutrino data. TheQ2 analysis of quasi-elastic Λ events yieldsMA=1.0±0.3 GeV/c2 for the axial mass value. With zero µΛK0 events observed, the 90% confidence level upper limit\(\sigma (\bar v_\mup \to \mu ^ +\Lambda {\rm K}^0 )< 2.0 \cdot 10^{ - 40} cm^2 \) is obtained. At the same time, we found that the cross section of reaction\(\bar v_\mup \to \mu ^ +\Lambda {\rm K}^0+ m\pi ^0 \) is equal to\(\left( {3.9\begin{array}{*{20}c}{ + 1.6}\\{ - 1.3}\\ \end{array} } \right) \cdot 10^{ - 40} cm^2 \).
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We have made a detailed comparison of the charged-particle flow in three-jet events (e+e−→qq¯g) and radiative two-jet events (e+e−→qq¯γ) from e+e− annihilation at Ec.m.=29 GeV. Accurate comparisons can be made because these two event types have similar topologies. In the angular region between the quark and antiquark jets, we observe substantially fewer charged tracks in the two-jet events than in the radiative three-jet events.
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Inclusive Ξ− production in e+e− annihilation at 29 GeV has been measured with the Mark II detector. From an integrated luminosity of 207 pb−1, we determine a production rate of 0.017±0.004±0.004 Ξ−+Ξ¯+ per hadronic event. A search for Ξ*0(1530)→Ξ−π+ leads to an upper limit of N(Ξ*0)/N(Ξ−)<0.35 at a 90% confidence level.
Numerical values supplied by S. Klein.
Extrapolation over full x range using LUND Monte Carlo.
We have searched for the lepton-flavor-violating decay D0→e±μ∓ in 204 pb−1 of e+e− annihilation data at Ec.m.=29 GeV from the Mark II detector. No candidates were found; we estimate an upper limit on the cross section times branching ratio of σ(e+e−→D0,D¯0; inclusive)B(D0→e±μ∓)<0.35 pb at the 90% confidence level. Simple assumptions yield the rough limit B(D0→e±μ∓)<2.1×10−3. AE.
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NUCLEUS IS THE NUCLEUS OF EMULSION.
NUCLEUS IS THE NUCLEUS OF EMULSION.
NUCLEUS IS THE NUCLEUS OF EMULSION.
Total and annihilation n¯p cross sections from 100 to 500 MeV/c are reported, the first such measurements with good statistics in this momentum range. These cross sections are well represented by A+B/p, where p is the incident antineutron momentum, and are in agreement with previous n¯p and p¯n measurements. A comparison of these cross sections with phenomenological potential model calculations is good overall. However, the microscopic quark model gives unsatisfactory predictions. The agreement between previous p¯p annihilation cross sections and n¯p cross sections above 300 MeV/c is excellent. The total n¯p cross section is lower than the total p¯p cross section in this momentum range. Both of these types of behavior are predicted by potential models. The anticipated availability of future p¯p data below 300 MeV/c should indicate whether these trends continue at lower momenta.
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