Picosecond time-of-flight measurement for colliders using Cherenkov light

We propose to measure the velocity of particles produced at a hadron or lepton collider by measuring the time-of-flight in a finely segmented cylindrical geometry, in which the particles produce Cherenkov light while traversing the window of one element in an array of large-area (e.g. 5 cm /spl times/ 5 cm) multi-channel-plate photomultipliers (MCP's). There has been a substantial improvement in the time resolution of MCP's, which now have achieved a 10-psec transit-time spread (FWHM) for a single photon. We have simulated the Cherenkov emission and MCP response spectra for several commercially available MCP's, and find that a TOF resolution on the order of 1 psec should be attainable. This would allow /spl pi//K separation at 1/spl sigma/ up to a transverse momentum of /spl sime/ 25 GeV/C, in a detector such as CDF at the Fermilab Tevatron. It may also be possible to associate a photon with its production vertex by conversion directly in front of the MCP. The system we are considering requires a custom large-area MCP design with an anode consisting of impedance-matched segments, directly coupled to a circuit capable of psec resolution. Possible problems we know of so far are showering in the magnet coil that is in front of the system and stray magnetic field outside the coil. One last consideration is the cost, which will be comparable to other major detector subsystems.