Dielectron measurements in p+p and p+d collisions from 1.0 to 5.0 GeV kinetic beam energy

The first measurements of dielectron production in p+p and p+d interactions at incident kinetic energies from 1.0-4.9 GeV are summarized. The beam energy and invariant mass dependence of the dielectron yield in p+d interactions relative to the yield in p+p interactions are presented. The ratio of the yield in p+d to that in p+p interactions decreases from nearly 9 at 1.0 GeV to {approx} 2 at 4.9 GeV. The large ratio at 1.0 GeV suggests that dielectron production in the p+d system is dominated by a p+n process. The beam energy dependence of the ratio indicates that this p+n contribution decreases with respect to the other dielectron sources as the incident energy is increased.