C.L. Jordan

COINCIDENCE ELECTROPRODUCTION IN THE REGION OF THE rho MESON.

Cross sections for the reaction ep-+epX, measured by detecting both the scattered electron and proton, are given for missing masses mx between 0 and 1 GeV/c’. A large cross section is observed at mx=O due to radiative processes, but the resolution of the apparatus is such that the contribution of the mx=O peak is small for rnxL 0.6 GeV/c2. Enhancements rare observed in the region of the rho meson at q2=0. 1 and 0.5 (GeV/c)2. The electroproduction of all states with mx between 0.7 and 0.83 GeV/c2 varies like e -7.5t for q2=0.1 (GeV/c)2, similar to missing mass photoproduction in this region, but for q2=0. 5 (GeV/c)2 it varies like e -3.5t . (Submitted to Phys. Rev. Letters. A preliminary version of this paper was submitted to the 1971 International Symposium on Electron and Photon Interactions at High Energies, Cornell University, Ithaca, New York, August 23-27, 1971.) * Work supported by the U. S. Atomic Energy Commission t Present address: University of Washington, Seattle, Washington ItPresent address: Bonn University, Bonn, Germany This letter reports the results of an inelastic electron scattering experiment at SLAC where a final state proton was detected in coincidence with the scattered electron, ep + epX. The measured variables are Eo, the incident electron energy, E’, 0 , and @, the momentum, polar scattering angle, and azimuthal angle of the scattered electron; and P P’ BP and

Electron scattering at 4° with energies of 4.5-20 GeV

P’ the corresponding proton variables. These measurements uniquely determine mx, the mass of the unobserved state X. rnE=2G Pp cos0 I It-l y p-s2-t(l+ v/‘Mp) where q2=4EoE1sin2(0/2)= -(four momentum transfer from the electron)2, 1, =EO-E’ , &I = v, d = an t 2MpTp= -(four momentum transfer to the proton)2. Tp is the kinetic energy of the proton,Mp is its mass, and 8 is the w angle between

High-Energy Single-Arm Inelastic e − p and e − d Scattering at 6 and 10°

andq. The cross section may be written’ d6, = r, d3”ab s dQdE’dtdmxdqq dtbxd9, where rT is the flux of virtual photons and Qq-is the azimuthal angle of 5 P around qwith respect to the electron scattering plane. d%abs/dtdmxd9, then represents the absorption of photons of mass q2 and energy v with a polarization parameter which is near unity for this experiment. During the experiment, E. and E1 were fixed at 20 and 13 GeV respectively. Two values of 8 were used, 1.124’ and 2. 51°, corresponding to q2=0. 1 and 0.5 (GeV/c)2. At each angle data were taken for values of t between 0.15 and