Dielectron line with no IP cuts (2)

Physics case: search for dark photons in the e+ e- spectrum of promptly produced and displaced dielectrons, themselves the products of a pi0 or eta decay to e+e- gamma.

New dielectron line with no IP cuts. Very similar to displaced dielectron line but with IP cuts removed and replaced by a new cut on brem-corrected pt of the dielectron candidate. The pt threshold is set to 1 GeV and mass ranges / prompt-displaced thresholds and a new pt cut/prescale control the total rate added by these lines to ~1kHz.

See !732 (closed) for previous history.