Measurement of direct electron-positron pair production from hadronic bremsstrahlung

We have made a measurement of very-low-energy $e^{+}{e}^{-}$ pair production from ${\pi }^{\pm }p$ collisions at 18 GeV/c. Using the SLAC 1-m bubble chamber to study a sample of 178×${10}^3$ interactions, we find a signal of centrally produced direct $e^{+}{e}^{-}$ pairs which accounts for (48±13)% of all $e^{+}{e}^{-}$ pairs detected with $\mathrm{}\left|x\right|<0.02\mathrm{}$ and $P_T<10\mathrm{}$ MeV/c. This measurement agrees with a calculation of $e^{+}{e}^{-}$ pair production from the internal conversion of hadronic bremsstrahlung.