10 research outputs found
Muon capture by 3He nuclei followed by proton and deuteron production
The paper describes an experiment aimed at studying muon capture by
nuclei in pure and mixtures at various densities. Energy distributions of
protons and deuterons produced via and are measured for the
energy intervals MeV and MeV, respectively. Muon capture
rates, and are obtained using two different analysis methods. The
least--squares methods gives , . The Bayes theorem
gives ,
. The experimental
differential capture rates, and , are compared with theoretical
calculations performed using the plane--wave impulse approximation (PWIA) with
the realistic NN interaction Bonn B potential. Extrapolation to the full energy
range yields total proton and deuteron capture rates in good agreement with
former results.Comment: 17 pages, 13 figures, accepted for publication in PR
Nuclear muon capture by 3He: meson exchange currents for the triton channel
Exchange current corrections are calculated using currents found from the
hard-pion model and AV14+3BF wavefunctions. Results are given for the rate and
spin observables. Their sensitivity to g_P, the nucleon pseudoscalar form
factor, is reported.Comment: 35 pages, uuencoded gz-compressed tar file 42 Kbyte
Polarized photons in radiative muon capture
We discuss the measurement of polarized photons arising from radiative muon
capture. The spectrum of left circularly polarized photons or equivalently the
circular polarization of the photons emitted in radiative muon capture on
hydrogen is quite sensitive to the strength of the induced pseudoscalar
coupling constant . A measurement of either of these quantities, although
very difficult, might be sufficient to resolve the present puzzle resulting
from the disagreement between the theoretical prediction for and the
results of a recent experiment. This sensitivity results from the absence of
left-handed radiation from the muon line and from the fact that the leading
parts of the radiation from the hadronic lines, as determined from the chiral
power counting rules of heavy-baryon chiral perturbation theory, all contain
pion poles.Comment: 10 pages, 6 figure
Quenching of Weak Interactions in Nucleon Matter
We have calculated the one-body Fermi and Gamow-Teller charge-current, and
vector and axial-vector neutral-current nuclear matrix elements in nucleon
matter at densities of 0.08, 0.16 and 0.24 fm and proton fractions
ranging from 0.2 to 0.5. The correlated states for nucleon matter are obtained
by operating on Fermi-gas states by a symmetrized product of pair correlation
operators determined from variational calculations with the Argonne v18 and
Urbana IX two- and three-nucleon interactions. The squares of the charge
current matrix elements are found to be quenched by 20 to 25 % by the
short-range correlations in nucleon matter. Most of the quenching is due to
spin-isospin correlations induced by the pion exchange interactions which
change the isospins and spins of the nucleons. A large part of it can be
related to the probability for a spin up proton quasi-particle to be a bare
spin up/down proton/neutron. We also calculate the matrix elements of the
nuclear Hamiltonian in the same correlated basis. These provide relatively mild
effective interactions which give the variational energies in the Hartree-Fock
approximation. The calculated two-nucleon effective interaction describes the
spin-isospin susceptibilities of nuclear and neutron matter fairly accurately.
However 3-body terms are necessary to reproduce the compressibility. All
presented results use the simple 2-body cluster approximation to calculate the
correlated basis matrix elements.Comment: submitted to PR
Part I : a simple model of the hypertriton. Part II : muon capture by 3He
The thesis is in two parts. Part I is covered in chapters 1 and 2 and concerns a simple
model of the hypertriton developed by the author. The model is based on the fact that
the lambda particle is loosely bound and so a lambda-inert core approach should be
reasonable. The core is taken to be exactly like the free deuteron and a separable AN
potential is used to construct the binding potential for the A particle. The model is
tested in chapter 2 by calculating the ratio of two body to all pionic decay rates of the
hypertriton and the result is found to agree well with experiment.
Chapters 3 to 7 concern muon capture by 3He. Using the elementary particle model it
is shown that the spin observables for quasi-elastic muon capture by 3He are much more
sensitive to the nuclear pseudoscalar form factor ( and hence the nucleon pseudoscalar
form factor ) than is the rate. Reliable and sophisticated wavefunctions for 3He and
are then used to find the muon capture Hamiltonian in the impulse approximation.
The result differs from that found in the elementary particle model in that the magnetic
( and dominant ) part of the Hamiltonian lacks strength. In chapter 5 new theory is
developed for the muon wavefunction overlap reduction factor leading to the result C =
0.979. Chapter 6 details a calculation of muon capture by 3He leading to the deuteron
neutron break-up final state in the plane wave impulse approximation. Finally, the
processes leading to muonic atom formation are considered in chapter 7 with particular
reference to final hyperfine population densities and their dependencies on target and
beam polarization. It is shown that if only the intra-atomic processes are included, the
results for the hyperfine population densities are unreliable.Science, Faculty ofPhysics and Astronomy, Department ofGraduat