Muonic hydrogen and deuterium in H-D mixture and muon transfer in excited states.

The deexcitation of µp and µd atoms in hydrogen-deuterium mixtures has been studied with a new kinetics model that takes the energy dependence of the cascade processes into account. The X-ray yields, the populations of atomic states, and the muon transfer from hydrogen to deuterium during the cascade have been calculated as functions of density and isotope fractions. The evolution of the kinetic energy distribution during the cascade is shown to play an important role in the transfer kinetics. The atomic energy distribution in the ground state is significantly changed by the transfer. The calculated X-ray yields and the muon transfer probabilities are in fair agreement with experimental data provided the current theoretical transfer rates are reduced by a factor of about 2

Precise measurement of muon capture on the proton

The aim of the muCap experiment is a 1% measurement of the singlet capture rate Lambda(S) for the basic electro-weak reaction mu + p --> n + nu(mu). This observable is sensitive to the weak form-factors of the nucleon, in particular to the induced pseudoscalar coupling constant g(p). It will provide a rigorous test of theoretical predictions based on the Standard Model and effective theories of QCD. The present method is based on high precision lifetime measurements of mu(-) in hydrogen gas and the comparison with the free mu(+) lifetime. The mu(-) experiment will be performed in ultra-clean, deuterium-depleted H-2 gas at 10 bar. Low density compared to liquid H-2 is chosen to avoid uncertainties due to ppmu formation. A time projection chamber acts as a pure hydrogen active target. It defines the muon stop position in 3D and detects rare background reactions. Decay electrons are tracked in cylindrical wire-chambers and a scintillator array covering 75% of 4pi

Dispersion relation analysis of the neutral kaon regeneration amplitude in carbon

We apply a forward dispersion relation to the regeneration amplitude for kaon scattering on C-12 using all available data. The CPLEAR data at low energies allow the determination of the net contribution from the subthreshold region which turns out to be much smaller than earlier evaluations, solving a long standing puzzle

Pion correlations and resonance effects in (p)over-bar-p annihilation at rest to 2 pi(+)2 pi(-)pi(0)

We study pi pi correlations in the exclusive reaction (p) over bar p –> 2 pi(+)2 pi(-)pi(0) at rest with complete reconstruction of the kinematics for each event. Inclusive and differential distributions properly normalized show an enhancement for small invariant masses M++,M– of like-pion pairs. An even stronger enhancement is seen for the double differential distributions for low pion-pair masses. The signal is strongest when the pi(0) energy is large and much weaker when this energy is small. Dynamical models with resonances in the final state are confronted with the data. For the kinematic situation where the rho 3 pi channel is important the simulation predicts a large pion correlation for the double differential density, qualitatively explaining the observed bahaviour. The stochastic HBT mechanism is not supported by these findings for the exclusive annihilation reaction studied

Direct determination of two-pion correlations for pp -> 2 pi(+)2 pi(-) annihilation at rest

We study pi pi correlations in the exclusive reaction (p) over bar p –> 2 pi(+)2 pi(-) at rest measured by the CPLEAR experiment. Avoiding the introduction of an arbitrary reference sample, we analyse differential distributions for equal charge pion pairs removing the phase-space factor event by event. A peak at small relative momenta is most pronounced for large total momentum of the pair. The physical implications of bosonic symmetrization for the properties of the pion source, in particular its radius, are briefly discussed. The two extremes considered are the chaotic Hanbury-Brown-Twiss mechanism and the coherent Skyrmion model