Elsevier

Nuclear Physics B

Volume 128, Issue 3, 3 October 1977, Pages 461-505
Nuclear Physics B

A measurement of the electromagnetic size of the pion from direct elastic pion scattering data at 50 GeV/c

https://doi.org/10.1016/0550-3213(77)90056-6Get rights and content

Abstract

We report the results of a pion-electron scattering experiment to measure the charge radius of the pion. The experiment was performed in a 50 GeV/c negative, unseparated beam at the IHEP accelerator, Serpukhov, and has been briefly reported in an earlier publication [1]. A magnetic spectrometer instrumented with wire spark chambers was used to record the incident pion trajectory and the angles and momenta of the scattered particles. Events are reconstructed by detailed trackfinding programs, and a set of kinematic and geometric cuts define the elastic sample. Electrons are identified both by kinematic criteria and pulse height information from total absorption lead glass Čerenkov counters. The final elastic sample consisted of 40 000 πe events in the region of four-momentum transfer squared 0.013 (GeV/c)2q2 ⩽ 0.036 (GeV/c)2. A full error matrix fit to the form factors of the pion gave the r.m.s. charge radius of the pion: 〈rπ212 = (0.78−0.10+0.09) fm.

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    Now at Institute of Nuclear Research, Warsaw, Poland.

    ★★

    Now at the Institute of Nuclear Physics, Krakow, Poland.

    Supported in part by the U.S. Energy Research and Development Administration.

    ǂ

    Now at Varian Associates, Hansen Way, Palo Alto, California 94306.

    Deceased.

    ǂǂ

    Now at the High Energy Physics Laboratory, Stanford University, Stanford, California 94305.

    ǂ

    Now at University of Pittsburgh, Pittsburgh, Pennsylvania 15260; Supported in part by the National Science Foundation.

    ¶¶

    Supported in part by the U.S. National Science Foundation.

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