Multinucleon effects in muon capture onHe3at high energy transfer

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)/

Break-up channels in muon capture onHe3

“…[9] we performed the first calculations for the µ − + 3 He → ν µ + n + d reaction taking into account only nucleon-nucleon forces but including final state interactions. We analyzed some experimental data [16,17] and found large effects of final state interactions. In the present paper we calculate the total capture rate for the two-body and three-body break-up reactions and analyze more complete data sets from Refs.…”

“…In the present paper we calculate the total capture rate for the two-body and three-body break-up reactions and analyze more complete data sets from Refs. [16,17] and Ref. [15].…”

“…[17]. These data points were averaged over 5-MeV-wide energy bins and our theoretical predictions are prepared consistently.…”

“…[15]) and the older (from Refs. [16,17]) experimental data on differential capture rates for the reactions µ − + 3 He → ν µ + n + d and µ − + 3 He → ν µ + n + n + p. Finally, Sec. VI contains some concluding remarks.…”

Muon capture on deuteron andHe3

“…Finally, we remark that it would be interesting to extend these calculations to the processes µ − + 3 He → n + d + ν µ and µ − + 4 He → n + 3 H + ν µ , for which experimental data are also available [73,74].…”