Measurement of the fusion rate in mu d(3)He

Many atomic and molecular processes may occur after a muon has been stopped in a mixture of hydrogen and helium isotopes. In particular, the muonic mo lecule mu d(3)He can be formed. This molecule either decays or undergoes mu on catalyzed fusion. Theory predicts a fusion rate much lower than the deca y rate; moreover, the various theoretical predictions differ from each othe r by several orders of magnitude. With the experiment presented here we intend to measure the effective fusio n rate via the detection of the 14.7 MeV fusion proton. A new target and ga s mixing system, designed at JINR, were used in a ten-day test run at PSI. The fusion protons and products from other transfer and background reaction s were measured with several different detectors (plastic scintillators, BG O, Germanium, neutron, and Silicon detectors). The formation rate of the mu d(3)He molecule and an upper limit for the eff ective fusion rate have been measured and are presented here.