4 - From the Psi to Charmed Mesons: Three Years with the SLAC–LBL Detector at SPEAR

Summary

As I look back at the first three years or so at SPEAR, I consider this one of the most revolutionary, or perhaps the most revolutionary, experiment in the history of particle physics. It was certainly the most exciting time – in a laboratory, that is – that I have ever experienced. In this chapter I discuss the period 1973–76, which saw the discoveries of the ψ and ψ′ resonances, the χ states and most of the psion spectroscopy, the D⁰, D⁺ charmed meson doublet, and the D^*0 and D^*+ doublet. I will also refer briefly to some more recent results.

Most of these discoveries were made with the SLAC-LBL Magnetic Detector – or, as it later became known, the MARK I – that we operated at SPEAR from 1973 to 1976. The groups involved in this work were led by Burton Richter and Martin Perl of SLAC and by William Chinowsky, Gerson Goldhaber, and George Trilling of LBL.

The discovery of the ψ

Some of my personal reminiscences regarding the weekend of the ψ discovery have already been published and I will only allude to them briefly here.

Our first task was to learn how our detector behaved in the SPEAR environment. For this purpose we developed two independent analysis systems, one at LBL and the other at SLAC. The overall data acquisition was due to Martin Breidenbach.