PHYSICAL REVIEW LETTERS

We present a new high-statistics measurement of the cross section for the process e+e~e+e m. +m at a center-of-mass energy of 29 GeV for invariant pion-pair masses M(m+m ) between 350 MeV/c' and 1.6 GeV/c2. We observe the f~( 1270) and measure its radiative width to be 3. 15+0.0420. 39 keV. We also observe an enhancement in the~+~spectrum near 1 GeV. General agreement is found with unitarized models of the yy~m m. reaction that include finalstate interactions.

= 3 GeV. The Stanford Linear Accelerator Laboratory results of e+e -l+l +missing energy can be explained as e', e' production followed by decays to ev, , JU, v&, or their antiparticles. The v, ' would be absolutely stable and escape detection. The decay of the v"' requires a mixing of either v&' or p. ' with lighter leptons.The charmed quark c will decay preferably to the p quark through the enhanced J'J'" interaction. Leptonic decays of the cn can then account for the dileptonic events seen at FNAL. The heavy pseudoscalars A. 'n, c'c, etc. , will decay via the enhanced O'J to other heavy mesons. The P'n, , n,'n, etc. , decay via the weaker interactions such as O'J', J Js or O'K', J'I . The model also in general predicts CP nonconservation by virture of the fact that J', J' are CP even while J is CP odd, so that terms linear in J' do not conserve CP. This point will be discussed in a longer paper under preparation.

The effect of the beam-generated transverse deflecting fields on the emittance of an intense bunch of particles in a high-energy linear accelerator is analyzed in this paper. The equation of motion is solved by a perturbation method for cases of a coasting beam and a uniformly accelerated beam. The results are applied to obtain some design tolerance specifications for the recently proposed SLAC Single Pass Collider.