The Doppler-shift attenuation method was used to obtain the following mean lifetimes (in psec) for the indicated nuclear levels: 10 C(3.36), r=0.155 ±0.025; 10 B(3.59), r=0.150±0.015; 10 Be(3.37), r=0.189 ±0.020; 10 B (2.15), r= 2.7_ 0 .4 +0 -8 . A limit of r <30 fsec is obtained for 10 B (1.74), which is a factor of 8 greater than, and therefore consistent with, the lifetime computed from the analog 0 decay of 10 C. Transition strengths obtained from the 10 B(2.15) and 10 B(3.59) lifetimes are in good agreement with the effectiveinteraction calculations of Cohen and Kurath, as modified by Warburton et at. The 10 C(3.36) and 10 Be(3.37) states decay by analog E2 transitions: 2 + , r=l-»0 + , T=1, with 7%=±l, whose strengths are well described by calculations of Kurath's for an effective charge €«= € p =0.5. An upper limit was obtained for the corresponding transition 5.17 ->1.74 in 10 B(r*=0) which is consistent (factor of 4 greater) with the analog strengths observed in the T e -ztl nuclei.

No abstract

Energy spectra of both protons and deuterons emitted following the capture of negative muons by He nuclei have been measured for energies above 15 MeV. A limited number of proton-neutron pairs emitted in coincidence were also observed. A simple plane wave impulse approximation (PWIA) model calculation yields fair agreement with the measured proton energy spectra, but underpredicts the measured rate of deuteron production above our energy threshold by a large factor. A more sophisticated PWIA calculation for the two-body breakup channel, based on a realistic three-body wave function for the initial state, is closer to the deuteron data at moderate energies, but still is signi6cantly lower near the kinematic end point. The proton-neutron coincidence data also point to the presence of signi6cant strength involving more than one nucleon in the capture process at high energy transfer. These results indicate that additional terms in the capture matrix element beyond the impulse approximation contribution may be required to explain the experimental data. Speci6cally, the inclusion of nucleon-nucleon correlations in the initial or 6nal state and meson exchange current contributions could bring calculations into better agreement with our data. A fully microscopic calculation would thus open the possibility for a quantitative test of multinucleon effects in the weak interaction.Present address: Stanford Linear Accelerator Center, Stanford, CA 94309.Nuclear muon capture Z+p m (Z -1)'+v"normally leads to the emission of an energetic neutrino carrying most of the rest energy of the muon, while the energy transfer to the nucleus q = m& -E"is relatively small.The transferred energy leads to low-lying excitations of the residual nucleus up to the giant resonant region [1] or to the emission of medium energy neutrons (see, e. g., Ref. [2] and references therein). These conditions can be understood in the impulse approximation (IA) picture, in 0556-2813/94/50(4)/

No abstract

We have measured pion single charge exchange differential cross sections on the proton at 27.5 MeV incident π − kinetic energy in the center of momentum angular range between 0 • and 55 • . The extracted cross sections are compared with predictions of the standard pion-nucleon partial wave analysis and found to be in excellent agreement.