We present here some results of a mass analysis of the secondary particles produced at 15.9° to the circulating beam in an aluminum target bombarded by 25-Gev protons in the CERN proton synchrotron.The apparatus (Fig. 1) essentially was a mass spectrometer where the momentum of a particle was determined in the magnet M and its velocity was measured by timing the particle between counters 1 and 3. The distance between 1 and 3 was 27 m, which corresponds to a time of flight of 90 nanoseconds for light. Counter 3 was at 61 m from the target and subtended at the target a solid angle of 1.61 xlO" 6 steradian. A time sorter, 1 preceded by zero-crossing circuits and gated by the coincidence 123, was used to display the time difference between the pulses in counters 1 and 3, with the pulses in 1 suitably delayed. The total time range displayed in the 100 channels of the time sorter was ~15 nsec.Typical spectra for positive and negative particles are shown in Fig. 2. The pion peak (which in fact contains a small contamination of muons and electrons) indicates that the time resolution of the apparatus is about 0.9 nsec. The greater width of the proton peak is caused by the spread in flight times due to the finite momentum band (Ap/p ~ 3%) accepted by the magnet.The results obtained for negative particles
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In order to test the universality of the V-A Fermi interaction and the presence of the induced pseudoscalar term in the Hamiltonian, we have measured the rate of the reaction iT-\-He 3 -» H 3 +*> M . This reaction is closely analogous to the fundamental muon-capture interaction n~-\-p -» n-j-v^. We also have measured the total muon-capture rates in He 3 and He 4 ; that is, the rates for the reactions i u""+He 3 -> all final states and /z~+He 4 -> all final states. Negative muons were brought to rest in a high-pressure helium-gas target. The capture processes all yield a charged particle, whose energy was measured by observation of scintillation in the helium gas. Captures into the H 3 channel were recognized by the unique energy (1.9 MeV) of the triton recoil. The total capture rates obtained were: A (He 3 ) = 2170_ 4 30 +17° sec -1 , and A (He 4 ) = 375_ 3 oo +3° sec -1 . The partial capture rate to the triton ground state was measured as A (He 3 -> H 3 ) = 1505±46 sec -1 . These results are in good agreement with theoretical predictions based on a universal Fermi interaction, and on a conserved vector current. They also indicate that the induced-pseudoscalar-coupling coefficient is positive. Interpretation of these results in terms of the fundamental muon-capture process is somewhat ambiguous because of the uncertainty in the structure of the helium nucleus.where the total muon-disappearance rate is AT-AB 4 A. F. Yano, Phys. Rev. Letters 12, 110 (1964). B127 B 128 AUERBACH, ESTERLING, HILL, JENKINS, LACH, AND LIP MAN 42 A. M. L. Messiah, Phys. Rev. 87, 639 (1952). 43 A. F. Yano (private communication).
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