Mass and transverse momentum dependence of the dielectron yield inp-Be collisions at 4.9 GeV

We present the invariant mass and transverse momentum dependence of direct electron-positron pair production in p-Be collisions at a beam kinetic energy of 4.9 GeV. The acceptance of our apparatus is shown to have no significant effect for masses above 0.15 GeV. After a correction is made for the available phase space, the transverse momentum dependence of the data is found to be comparable to hadron-hadron observations. A phenomenological calculation involving ${\pi }^{+}$ ${\pi }^{\mathrm{-}}$ annihilation into $e^{+}$ $e^{\mathrm{-}}$ is shown to be in good agreement with our measurements.