Meson factories

A different method became available with modern meson factories, where the characteristic X-radiation from exotic atoms can be studied under optimized conditions and with reasonable count rates. Such experiments require the use of high-intensity external beam lines together with a particle concentrator like the cyclotron trap and a high-resolution low-energy crystal spectrometer. 

All the particles in O Table 28.1 are produced in collisions of high-energy protons with nuclei. The protons must have a kinetic energy much higher than the mass of the particle. The meson factories (Paul Scherrer Institute, TRIUMF) use proton energies of 500-1,000 MeV to produce charged pions (w,t = 139.9MeV). The pious are then directly used for studies, or they are allowed to decay to muons via reaction ... 

On the experimental side it may come as a surprise to learn that despite 20 million J/ decays it is believed that only some 25% of all hadronic decay channels have been identified. Similarly, for the radiative decays, some 50% of the modes may still be unidentified. The situation should improve dramatically with the high luminosity (5 x 10 cm s ) and small energy spread HE 0.6 MeV) e" "e colhder BEPC in Beijing. A similar situation is envisaged for the T when the B-meson factories now under discussion are built. 

Currently, rather intense pion and muon beams can be obtained from the so-called meson factories, namely TRIUMF in Canada, LAMPF in USA, and PSI in Switzerland. Here, these particles are produced by 500-800 MeV p" (or H") beams of high current (0.1-1 mA). Pion and muon beams can also be obtained at medium-energy accelerators such as the AGS at BNL, the PS at KEK and SATURNE at Saclay, and from high-energy proton accelerators such as the PS at FNAL and the SPS at CERN (Bradamante [3.34]). 

Feasibility Study for a B Meson Factory in the CERN ISR Tunnel, T. Nakada, ed., CERN 90-02 (1990). 

P.R. Burchat Physics at an Asymmetric-Energy B Meson Factory Jun 28.1991... 

In such B-factories, the separation of pions from kaons is vital for the identification of B- or anti-B-meson and the selection of rare decays. It is important to measure the decay time from the appearance of B-mesons to the final state. 

The heart of any asymmetric B Factory detector aimed at the study of CP violation is the vertex detector. Primary emphasis is on resolution along the flight path of the B mesons, that is, the beam (z) direction, and not on resolution in the transverse plane, as in current silicon vertex systems. 

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