Improved Limits on Lepton-Flavor-Violating Decays of Light Pseudoscalars via Spin-Dependent μ→e Conversion in Nuclei.

Lepton-flavor-violating decays of light pseudoscalars, P=π^{0},η,η^{'}→μe, are stringently suppressed in the standard model up to tiny contributions from neutrino oscillations, so that their observation would be a clear indication for physics beyond the standard model. However, in effective field theory such decays proceed via axial-vector, pseudoscalar, or gluonic operators, which are, at the same time, probed in spin-dependent μ→e conversion in nuclei. We derive master formulas that connect both processes in a model-independent way in terms of Wilson coefficients and study the implications of current μ→e limits in titanium for the P→μe decays.

The relation between sensory processing sensitivity and telomere length in adolescents.

Background: In the present study, we investigated the association between sensory processing sensitivity (SPS) and telomere length (TL), which is considered a biomarker of cellular aging. SPS is an individual characteristic describing increased perception and procession of inner or outer stimuli, and is positively related to self-perceived stress.

Methods: We recruited 82 healthy adolescents aged 13-16 from secondary schools in Germany.

On the scalar form factor beyond the elastic region.

Pion-kaon ( ) pairs occur frequently as final states in heavy-particle decays. A consistent treatment of scattering and production amplitudes over a wide energy range is therefore mandatory for multiple applications: in Standard Model tests; to describe crossed channels in the quest for exotic hadronic states; and for an improved spectroscopy of excited kaon resonances. In the elastic region, the phase shifts of scattering in a given partial wave are related to the phases of the respective form factors by Watson's theorem.

Toward Complete Leading-Order Predictions for Neutrinoless Double β Decay.

The amplitude for the neutrinoless double β (0νββ) decay of the two-neutron system nn→ppe^{-}e^{-} constitutes a key building block for nuclear-structure calculations of heavy nuclei employed in large-scale 0νββ searches. Assuming that the 0νββ process is mediated by a light-Majorana-neutrino exchange, a systematic analysis in chiral effective field theory shows that already at leading order a contact operator is required to ensure renormalizability. In this Letter, we develop a method to estimate the numerical value of its coefficient (in analogy to the Cottingham formula for electromagnetic contributions to hadron masses) and validate the result by reproducing the charge-independence-breaking contribution to the nucleon-nucleon scattering lengths.

Two-Loop Analysis of the Pion Mass Dependence of the ρ Meson.

Analyzing the pion mass dependence of ππ scattering phase shifts beyond the low-energy region requires the unitarization of the amplitudes from chiral perturbation theory. In the two-flavor theory, unitarization via the inverse-amplitude method (IAM) can be justified from dispersion relations, which is therefore expected to provide reliable predictions for the pion mass dependence of results from lattice QCD calculations. In this work, we provide compact analytic expression for the two-loop partial-wave amplitudes for J=0, 1, 2 required for the IAM at subleading order.