MEASUREMENT OF NEUTRAL- AND CHARGED-PION FORM-FACTOR SLOPES

In an experiment performed at Columbia University's Nevis cyclotron, we studied the reactions (1) π0→γ+e++e- and (2) π-+p→n+e++e- for π- at rest. Using a system of counters and spark chambers, we selected pairs with an opening angle near 120°. We analyzed the invariant-mass spectrum of the pairs (1) in 2200 π0 decays and (2) in 400 radiative captures. For the π0 form-factor slope, we find a=(+0.01±0.11)mπ02. We obtain the charged-pion form-factor slope for time like momentum transfers of the order of mπ. Our result for the pion charge radius is rπ<1.9 F with a 90% confidence level. © 1969 The American Physical Society.