A Study of the Reactions p̅p → π⁺π⁻, and p̅p → k⁺k⁻ from 0.7 to 2.4 GeV/c

Citation

Nicholson, Howard White, Jr. (1971) A Study of the Reactions p̅p → π⁺π⁻, and p̅p → k⁺k⁻ from 0.7 to 2.4 GeV/c. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/EX75-KA90. https://resolver.caltech.edu/CaltechTHESIS:06112018-112047312

Abstract

Differential cross sections for the annihilation reactions ⁻pp → π⁺π⁻, and ⁻pp → k⁺k⁻ have been measured in the angular region 0.65≾ cos θ_cm ≾ 1.0 at 14 incident antiproton moments at intervals of approximately .1 GeV/c between 0.7 and 2.4 GeV/c. In the angular region .90 ≾ cos θ_cm ≾ 1.00 the forward going particle traversed a magnet and the differential cross sections for its charge sign could be measured. In the remaining angular region only the folded cross sections [dσ/dΩ (θ_cm) + dσ/dΩ (π – θ_cm)] could be obtained. The data which, when binned in cos θ_cm bins which varied between .02 and .05 gave differential cross sections with statistical errors between 10 and 30%, were obtained in a counter experiment at the Alternating Gradient Synchrotron of the Brookhaven National Laboratory during the fall and winter of 1968.

At extreme angles the two pion annihilations show considerable structure, while the two kaon annihilations fall approximately exponentially. Between 0.7 and 1.34 GeV/c the positive meson has a larger cross section for moving in the p beam direction; between 1.34 and 2.40 GeV/c the situation reverses. The data from this experiment have been combined with the data from a previous Caltech experiment to give complete folded angular distributions and total annihilation cross sections at 12 momenta. The folded pion cross sections show dramatic energy dependence changing from a single dipped distribution at low momenta to a doubled dipped distribution at the higher momenta. The folded two kaon cross sections also show considerable energy dependence but its distribution remains predominately single dipped over the momentum range of this experiment.

The folded two pion annihilation data have been fit by a simple resonance model with two resonances. The two kaon data have been interpreted in terms of particle exchanges.

Thesis Files