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We report our investigations of X rays emitted during the muonic cascade in hydrogen employing charge coupled devices as X-ray detectors. The density dependence of the relative X-ray yields for the muonic hydrogen lines (K_alpha, K_beta, K_gamma) has been measured at densities between 0.00115 and 0.97 of liquid hydrogen density. In this density region collisional processes dominate the cascade down to low energy levels. A comparison with recent calculations is given in order to demonstrate the influence of Coulomb deexcitation., Comment: 5 pages, Tex, 4 figures, submitted to Physical Review Letters

We report the first direct observation of excited state muon transfer in hydrogen/deuterium mixtures by direct measurement of q_1s, the probability that a mu-p atom, which is initially formed in an excited state, reaches the 1s ground state. The dependence of q_1s on deuterium concentration c_d was measured for two different densities at cryogenic temperatures using charge coupled devices (CCDs) to detect the muonic X rays. First results based on the analysis of the K_alpha-lines of the two isotopes are presented., 4 figures

The pionic deuterium 3{ital P}{minus}1{ital S} x-ray transition was measured with a quartz crystal spectrometer in combination with a cyclotron trap and charge coupled device detectors. The strong interaction shift and total decay width of the 1{ital S} level are {epsilon}{sub 1{ital S}}(shift)=2.48{plus_minus}0.10 eV (repulsive), {Gamma}{sub 1{ital S}}(width)=1.02{plus_minus}0.21 eV, where the statistical and systematic errors were added linearly. They yield the total pionic deuterium {ital S}-wave scattering length: {ital a}{sub {pi}{sup {minus}}{ital d}}= {minus}0.0264({plus_minus}0.0011)+{ital i}0.0054({plus_minus}0.0011){ital m}{sub {pi}}{sup {minus}1}.

Measurements of the K X-ray transitions of muonic hydrogen (μ−p and μ−d) were performed at H2 or D2 gas pressures between 17 and 533 hPa (T ≈ 293 K). The intensity ratios K α K total and K β K total depend on the gas density because the strength of excited state collisional interactions increases at higher densities. The data are compared with the results of a cascade calculation. They are sensitive to the collisional Stark mixing rates at the main quantum levels n = 4, …,8.

The $3p\ensuremath{-}1s$ x-ray line of pionic hydrogen was measured with a reflecting bent crystal spectrometer. The strong interaction energy level shift and the total decay width of the $1s$ state, obtained from the transition energy and the linewidth, are ${\ensuremath{\varepsilon}}_{1s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}7.127\ifmmode\pm\else\textpm\fi{}0.028\left(\mathrm{stat}\right)\ifmmode\pm\else\textpm\fi{}0.036(\mathrm{syst})\phantom{\rule{0ex}{0ex}}\mathrm{eV}$ (attractive) and ${\ensuremath{\gamma}}_{1s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.97\ifmmode\pm\else\textpm\fi{}0.10\left(\mathrm{stat}\right)\ifmmode\pm\else\textpm\fi{}0.05\left(\mathrm{syst}\right)\phantom{\rule{0ex}{0ex}}\mathrm{eV}$. The corresponding hadronic $\ensuremath{\pi}N$ s-wave scattering lengths for elastic scattering and single charge exchange are ${a}_{{\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}p}^{h}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.0885\ifmmode\pm\else\textpm\fi{}{0.0009m}_{\ensuremath{\pi}}^{\ensuremath{-}1}$ and ${a}_{{\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}n}^{h}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}0.136\ifmmode\pm\else\textpm\fi{}{0.010m}_{\ensuremath{\pi}}^{\ensuremath{-}1}$.

A study of nonequilibrium phonon propagation in a low-temperature bolometric detector with a Monte Carlo code is presented. The simulation of the thermalization process allows us to predict the temperature pulse in a 1 cm3 germanium bolometer detecting 5 MeV alpha-particles.