An experiment has been performed at the Brookhaven Cosmotron to study K + -»ir°l + v. A spark-chambermagnet system was triggered on any charged particle leaving the target after a K + had stopped. Separation between ir + and ju + was performed using momentum and range. Positrons were identified by shower production. On the basis of 300 K eZ and 350 K^ events in the momentum range 100 to 220 MeV/c, we found ratios iW (all Z + )=0.044±0.004, K^/fall #+)= 0.035 ±0.0030. The positron spectrum was consistent with a constant form factor. The ratio of constant form factors £ = /_//+ determined from the K^/K^ branching ratio was £ = +1.0±0.3.
Phys. Rev. D 4, 1937. 4~h e Compton subtraction was performed in the following manner. Since the IT' and Compton data of Anderson3) were obtained using the same proton spectrometers, we assumed that the relative normalization of these experiments was correct. By comparing our raw (ff + Compton) data with those of Anderson et a l . (Ref. 3), we found that our results had to be renormalized upwards by 20% so as to agree with their measurements. We have been unable to find the source of this discrepancy. After this renormalization we performed the subtraction using the measured points by Anderson et al., or by extrapolating their data both on t and photon energy (for the 18-GeV points). As stated in the text, no points where the subtraction was larger than 20% were presented. In the region where this experiment makes a new contribution 1-t >1.4 (~e~/ d~l , the subtraction never amounted to more than a few percent. 5~. S. Ball, G. Marchesini, and F. Zachariasen, Phys. Lett. m, 583 (1970).The reaction cross sections for K + and K -mesons in carbon and copper have been measured, at a momentum of 2.95 GeV/c, with an optical spark-chamber apparatus. In order to minimize instrumental biases, every incoming kaon triggered the system, regardless of whether o r not an interaction occurred.
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