Measurements of the magnetic form-factor of the proton in the timelike region at large momentum transfer

The cross section for the reaction {bar p}p{r_arrow}e{sup +}e{sup {minus}} has been measured at s=8.8, 10.8, 12.4, 13.1, and 14.4 GeV{sup 2} by Fermilab experiment E835. A non-magnetic spectrometer is used to identify the e{sup +}e{sup {minus}} final states generated by the antiproton beam intersecting an internal hydrogen gas jet target. From the analysis of the 144 observed events, new high-precision measurements of the proton magnetic form factor for timelike momentum transfers are obtained. {copyright} {ital 1999} {ital The American Physical Society}