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Abstract

The authors propose an experiment to measure elastic kaon scattering from electrons at a beam energy of 250 GeV. This measurement provides the first experimental value for the charge radius of the kaon. The anticipated error on the determination of the radius is 0.03 Fermi. The experiment can be performed by the present E216 spectrometer in the M1 beam line. A drift chamber system will be added to improve the spectrometer resolution and minor modifications of the trigger hodoscope and shower counter geometry will be required. The experimental design incorporates their experience in performing {pi}-e elastic scattering at 50 GeV/c at Serpukhov and at 100 GeV/c in E216 at Fermilab (data taking completed on October 1, 1975). The analysis of the E216 results is well underway and they anticipate that a definitive value for the pion radius will soon be obtained (anticipated error {+-} 0.03 F). All apparatus is designed with the goal of measuring a 1% absolute cross section. To cleanly identify elastic events and reject background, the angles and momenta of both the scattered K and e are measured. Proportional chambers and drift chambers upstream and downstream of the hydrogen target measure angles to high accuracy. Two 8-24-72 analysis magnets are used, followed by a set of six 0.5 x 1.5 m{sup 2} spark chambers, to determine momenta. A lead glass shower counter hodoscope provides electron shower identification. In the trigger there is only one veto counter used which is sensitive to target interactions. It helps to suppress non K-e background and its effect on K-e elastic events is small and well understood. A time request for 200 hours of testing and 600 hours for data taking is made in the proposal. Their continued interest in pion form factor measurements at energies much higher than 100 GeV is indicated in an Appendix.

Measurement of the Kaon Form Factor

Abstract

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