The pionic beta decay in chiral perturbation theory

Within the framework of chiral perturbation theory with virtual photons and leptons, we present an updated analysis of the pionic beta decay including all electromagnetic contributions of order e**2 p**2. We discuss the extraction of the Cabibbo-Kobayashi-Maskawa matrix element |Vud| from experimental data. The method employed here is consistent with the analogous treatment of the Kl3 decays and the determination of |Vus|.Comment: 8 pages, 1 figure, latex file, uses EPJC macro

The CP-violating asymmetry in K_L -> pi+ pi- e+ e-

We update the theoretical analysis of the CP-violating asymmetry in the decay K_L -> pi+ pi- e+ e-, relying on chiral perturbation theory and on the most recent phenomenological information. With the experimentally determined magnetic amplitude and branching ratio as input, the asymmetry can be calculated with good accuracy. The theoretical interpretation of the sign of the asymmetry is discussed.Comment: 11 page

Low energy electron energy-loss spectroscopy of CF₃X (X=Cl,Br)

We report threshold electron energy-loss spectra for the fluorohalomethanes CFC₃X (X=Cl,Br). Measurements were made at incident electron energies of 30 and 100 eV in energy-loss range of 4-14 eV, and at scattering angles of 4 degrees and 15 degrees. Several new electronic transitions are observed which are ascribable to excitation of low-lying states as well as are intrinsically overlapped in the molecules themselves. Assignments of these electronic transitions are suggested. These assignments are based on present spectroscopic and cross-section measurements, high-energy scattering spectra, and ab initio molecular orbital calculations. The calculated potential curves along the C-X bond show repulsive nature, suggesting that these transitions may lead to dissociation of the C-X bond. The present results are also compared with the previous ones for CF₃H, CF₄, and CF₃I.This work was performed with the support and under the auspices of the CUP, the IAEA’s Co-ordinated Research Program, MEXT, and JAEA. One of the authors C.M. had been also thankful to the Japan Society for Promotion of Science for financial support under Grant No. P04064. One of the authors L.P. also acknowledges partial support by the Academic Frontier Program of MEXT. One of the authors H.C. acknowledges the support from the Korea Research Foundation 2006-311-C00031

Convergence of CI single center calculations of positron-atom interactions

The Configuration Interaction (CI) method using orbitals centered on the nucleus has recently been applied to calculate the interactions of positrons interacting with atoms. Computational investigations of the convergence properties of binding energy, phase shift and annihilation rate with respect to the maximum angular momentum of the orbital basis for the e^+Cu and PsH bound states, and the e^+-H scattering system were completed. The annihilation rates converge very slowly with angular momentum, and moreover the convergence with radial basis dimension appears to be slower for high angular momentum. A number of methods of completing the partial wave sum are compared, an approach based on a Delta X_J = a/(J + 1/2)^n + b/(J + 1/2)^(n+1) form (with n = 4 for phase shift (or energy) and n = 2 for the annihilation rate) seems to be preferred on considerations of utility and underlying physical justification.Comment: 23 pages preprint RevTeX, 11 figures, submitted to PR