arXiv subjects

H. Schneuwly

Publications and source records attributed to H. Schneuwly.

3 recordsLinked to original sources

arXiv2003

Experimental study of $μ$--atomic and $μ$--molecular processes in pure helium and deuterium--helium mixtures

We present experimental results of $μ$--atomic and $μ$--molecular processes induced by negative muons in pure helium and helium--deuterium mixtures. The experiment was performed at the Paul Scherrer Institute (Switzerland). We measured muonic x--ray $K$ series transitions relative intensities in $(μ^{3,4}\mathrm{He})^*$ atoms in pure helium as well as in helium--deuterium mixture. The muon stopping powers ratio between helium and deuterium atoms and the $d μ^3 \mathrm{He}$ radiative decay probability of for two different helium densities in $\mathrm{D}_2 + {}^3\mathrm{He}$ mixture were also determined. Finally, the $\mathrm{q}_{1s}^{\mathrm{He}}$ probability for a $dμ$ atom formed in an excited state to reach the ground state was measured and compared with theoretical calculations using a simple cascade model.

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arXiv2003

Muon capture by 3He nuclei followed by proton and deuteron production

The paper describes an experiment aimed at studying muon capture by ${}^{3}\mathrm{He}$ nuclei in pure ${}^{3}\mathrm{He}$ and $\mathrm{D}_2 + {}^{3}\mathrm{He}$ mixtures at various densities. Energy distributions of protons and deuterons produced via $μ^-+{}^{3}\mathrm{He}\to p+n+n + ν_{μ}$ and $μ^-+{}^{3} \mathrm{He} \to d+n + ν_μ$ are measured for the energy intervals $10 - 49$ MeV and $13 - 31$ MeV, respectively. Muon capture rates, $λ_\mathrm{cap}^p (ΔE_p)$ and $λ_\mathrm{cap}^d (ΔE_d)$ are obtained using two different analysis methods. The least--squares methods gives $λ_\mathrm{cap}^p = (36.7\pm 1.2) {s}^{- 1}$, $λ_\mathrm{cap}^d = (21.3 \pm 1.6) {s}^{- 1}$. The Bayes theorem gives $λ_\mathrm{cap}^p = (36.8 \pm 0.8) {s}^{- 1}$, $λ_\mathrm{cap}^d = (21.9 \pm 0.6) {s}^{- 1}$. The experimental differential capture rates, $dλ_\mathrm{cap}^p (E_p) / dE_p $ and $ dλ_\mathrm{cap}^d (E_d) / dE_d$, 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.

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arXiv2003

Muon transfer from deuterium to helium

We report on an experiment at the Paul Scherrer Institute, Villigen, Switzerland measuring x rays from muon transfer from deuterium to helium. Both the ground state transfer via the exotic dmu3,4He* molecules and the excited state transfer from mud* were measured. The use of CCD detectors allowed x rays from 1.5 keV to 11 keV to be detected with sufficient energy resolution to separate the transitions to different final states in both deuterium and helium. The x-ray peaks of the dmu3He* and dmu4He* molecules were measured with good statistics. For the D2+3He mixture, the peak has its maximum at E_dmu3He = 6768 +- 12 eV with FWHM Gamma_dmu3He = 863 +- 10 eV. Furthermore the radiative branching ratio was found to be kappa_dmu3He = 0.301 +- 0.061. For the D_2+4He mixture, the maximum of the peak lies at E_dmu4He = 6831 +- 8 eV and the FWHM is Gamma_dmu4He = 856 +- 10 eV. The radiative branching ratio is kappa_dmu4He = 0.636 +- 0.097. The excited state transfer is limited by the probability to reach the deuterium ground state, q_1s. This coefficient was determined for both mixtures: q^3He_1s = 68.9 +- 2.7% and q^4He_1s = 90.1 +- 1.5.

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