Recent experiments with the C. E. R. N. synchro-cyclotron

Abstract

The C.E.R.N. synchro-cyclotron is capable of accelerating protons up to an energy of 600 MeV, and when they strike a solid target they produce intense beams of π ± -mesons. The particles produced are relatively slow, and an absorber a few centimetres thick is sufficient to bring them to rest. A large number of mesons can therefore be confined to a small volume for a relatively long time, until they decay or interact with the surrounding matter. μ ± -mesons may also be produced by allowing the π ± -mesons to decay in flight. A very important feature of the μ -meson beams so produced is that they are almost 100% longitudinally polarized; i. e. their spins are alined about the direction of motion and in a given sense. Accurate determinations can thus be made of the way features of the decay process, and of interactions with matter, depend on the spin direction. Further, by making the μ -mesons precess in a strong magnetic field, one can determine quantities like their magnetic and electric dipole moments with high precision. I shall describe experiments recently performed with the C. E. R. N. synchro-cyclotron which give new information about the weak and electromagnetic properties of the π - and μ - mesons.