Measurements of Total Cross Sections forK20Mesons on Protons and Selected Nuclei from 168 to 343MeVcand Measurement of theK20Mean Life

Abstract

We have measured $K_2^{}{}_{}{}^0-p$ total cross sections for $K_2^{}{}_{}{}^0$ laboratory momenta between 168 and 343 $\frac{\mathrm{MeV}}{c}$. From these data we have determined the isotopic spin-1 $\overline{K}N$ $s$-wave scattering length to be $(0.00\mathrm{}\pm 0.14)\pm i(0.62\mathrm{}\pm 0.06)$ F. This is in fair agreement with previous determinations. We have also measured $K_2^{}{}_{}{}^0$-nuclear total cross sections for seven species of nuclei which span the periodic table, in the same momentum range, to statistical accuracies of typically a few percent in each of eleven momentum intervals within the range. The data at the highest momentum do not obey an $A^{\frac{2}{3}}$ law. We have also measured the $K_2^{}{}_{}{}^0$ mean life to be (5.15±0.14)×${10}^{-8\mathrm{}}$ sec. This is in agreement with previous results and represents an improvement in statistical accuracy by about a factor of 3. We have also studied $K_2^{}{}_{}{}^0$ and $\gamma$ production at 93° by 2.8-GeV protons on 1.5-in. platinum. The experiment was performed using a scintillation-counter $K_2^{}{}_{}{}^0$ detector. Kinematic identification of each $K_2^{}{}_{}{}^0$ particle was made using a time-of-flight method: The bunched time structure of the internal proton beam of the Princeton-Pennsylvani accelerator was used to determine $K_2^{}{}_{}{}^0$ production times, and an electronic chopping technique was used to eliminate unwanted proton bunches. Depending upon beam conditions, between ${10}^3$ and ${10}^4$ useful $K_2^{}{}_{}{}^0$ mesons per hour were detected with momentum resolution of a few percent. In conjunction with the timing calibration of the system, we have made a direct velocity measurement of the relativistic limiting speed for electrons. The result is $(1-{\beta }_{max})=0.005\mathrm{}\pm 0.005$.