Trapped Ions and Beam Coherent Instability

In accelerators with negatively charged beams, ions generated from the residual gas molecules may be trapped by the beam. Trapped ions may interact resonantly with the beam and cause a beam-ion coherent instability. This coherent instability bears many similarities to the resistive wall instability and can present important limitations to those machines operation. A description of this effect requires a treatment of the beam coherent instability including both the normal machine wake field and the interaction with ions. They present a linear approach incorporating contributions from the machine impedance as well as ion forces. it also includes spreads in beam and ion frequencies and thus Landau damping. The analysis results in a modified stability diagram which will be used together with physical arguments to explain experimental observations in the Fermilab antiproton accumulator

Study of the \u3c71 and \u3c72 charmonium states formed in p annihilations

We report on a study of the \u3c7 1( 3P 1) and \u3c7 2( 3P 1) states of charmonium formed in antiproton-proton annihilations. An energy scan through the resonances, performed with a very narrow momentum-band beam of antiprotons intersecting a hydrogen jet target, enables us to perform very precise measurements of the mass and the total width of the two resonances. From a sample of 513 \u3c7 1 and 585 \u3c7 2 events we find M \u3c71 = (3510.53 \ub1 0.13) MeV/c 2, M \u3c72 = (3556.15 \ub1 0.14) MeV/c 2, \u393 \u3c71 = (0.88 \ub1 0.14) MeV and \u393 \u3c72 = (1.98 \ub1 0.18) MeV. From our measurement of the quantity \u393(R \u2192 p\u304p) 7 BR(R \u2192 J/\u3c8\u3b3) 7 BR(J/\u3c8/ \u2192 e + e -), using known branching ratios, we obtain \u393(\u3c7 1 \u2192 p\u304p) = (69 \ub1 13) eV and \u393(\u3c7 2 \u2192 p\u304p) = (180 \ub1 31) eV

Measurement of the atmospheric neutrino flavor composition in Soudan-2

The atmospheric neutrino flavour ratio measured using a 1.52 kton-year exposure of Soudan 2 is found to be 0.72 +- 0.19 +0.05 -0.07 relative to the expected value from a Monte Carlo calculation. The possible background of interactions of neutrons and photons produced in muon interactions in the rock surrounding the detector has been investigated and is shown not to produce low values of the ratio.Comment: 18 pages, LaTeX, 3 ps files, and 2 style files. Submitted to Physics Letter