J. Repond

Proton-antiproton annihilations at rest into π0ω, π0η, π0γ, π0π0, and π0η′☆

Proton-antiproton annihilations at rest in liquid hydrogen were investigated through the inclusive γ spectrum, related to the annihilation. The high-energy part of the spectrum was used to deduce branching ratios for the so far unobserved annihilation channels: R(pp→π0ω) = (2.38 ± 0.65)%, R(pp→ π0η) = (0.82 ± 0.10%, Rpp→π0γ) = (0.015 ± 0.007)%, and R(pp → π0π0 = (0.06 ± 0.04)%. An upper limit for the π0η′ channel was deduced to be R(pp → π0η′) < 1.1%.

New results in the search for narrow states in the p system below threshold

The γ-ray spectrum after p annihilation at rest was measured in two independent high-statistics runs. Both spectra show narrow peaks, corresponding to masses of 1210, 1638, 1694 and 1771 MeV.

Search for narrow signals in the γ-spectrum from pp̄ annihilation at rest

The [gamma]-spectrum originating from pp[combining macron] annihilations at rest in liquid hydrogen was measured with two BGO spectrometers. A total of 24 i?œ 106[gamma]’s were accumulated. No narrow peaks indicating exotic states such as baryonium were observed. The upper limit for the branching ratio with 1040 [less-than-or-equals, slant] mx [less-than-or-equals, slant] 1770 MeV/c2 and with [lambda]x [less-than-or-equals, slant] 25 MeV/c2 is less than 10-3 with more than 99.96% confidence.

Precision measurement of strong interaction isotope effects in antiprotonic 16O, 17O, and 18O atoms

Abstract The strong-interaction effects in antiprotonic 16O, 17O, and 18O atoms were measured at the CERN antiproton facility, LEAR. The shifts ϵ and the widths Γ of the 3d level were determined to be −112±20 eV ( 16 O ) , −140±46 eV ( 17 O ) , −195±20 eV ( 18 O ) , and 495±45 eV ( 16 O ) , 540±150 ( 17 O ) , 640±40 eV ( 18 O ) , respectively.

A π0 and η spectrometer of lead glass and BGO for momenta up to 1 GeV/c

Abstract A spectrometer consisting of two sets of bismuth germanium oxide (BGO) crystals and a lead-glass array has been used to measure the π 0 and η momentum spectra produced from proton-antiproton annihilations at rest. We describe the test of the BGO sets in electron beams of energies from 50 to 450 MeV. We discuss the method of construction and calibration of the lead-glass array, as well as procedures to extract the energy and position resolutions for detected photons. A momentum resolution (σ) for π 0 s and ηs of 4% and 3%, respectively has been achieved at momenta below 1 GeV/ c .

Experimental determination of the branching ratios\(p\bar p \to 2\pi ^0 ,\pi ^0 \gamma \), and 2γ at rest

AbstractThe branching ratios of

Experimental determination of the branching ratios {Mathematical expression}, and 2γ at rest

p\bar p

π0 and η spectra from\(p\bar p\) annihilations at rest

annihilations into the neutral final states 2π0, π0γ, and 2γ are measured by stopping antiprotons in liquid hydrogen. They are