Sterile neutrinos and RKR_K

Peer reviewe

ChPT tests at the NA48 and NA62 experiments at CERN

The NA48/2 Collaboration at CERN has accumulated unprecedented statistics of rare kaon decays in the Ke4 modes: Ke4(+-) ($K^\pm \to \pi^+ \pi^- e^\pm \nu$) and Ke4(00) ($K^\pm \to \pi^0 \pi^0 e^\pm \nu$) with nearly one percent background contamination. The detailed study of form factors and branching rates, based on these data, has been completed recently. The results brings new inputs to low energy strong interactions description and tests of Chiral Perturbation Theory (ChPT) and lattice QCD calculations. In particular, new data support the ChPT prediction for a cusp in the $\pi^0\pi^0$ invariant mass spectrum at the two charged pions threshold for Ke4(00) decay. New final results from an analysis of about 400 $K^\pm \to \pi^\pm \gamma \gamma$ rare decay candidates collected by the NA48/2 and NA62 experiments at CERN during low intensity runs with minimum bias trigger configurations are presented. The results include a model-independent decay rate measurement and fits to ChPT description.Comment: XIIth International Conference on Heavy Quarks and Leptons 2014, Mainz, German

First observation and study of the K±→π0π0μ±νK^{\pm} \rightarrow \pi^{0} \pi^{0} \mu^{\pm} \nu decay

The NA48/2 experiment at CERN reports the first observation of the $K^{\pm} \rightarrow \pi^{0} \pi^{0} \mu^{\pm} \nu$ decay based on a sample of 2437 candidates with 15% background contamination collected in 2003--2004. The decay branching ratio in the kinematic region of the squared dilepton mass above $0.03$~GeV$^2/c^4$ is measured to be $(0.65 \pm 0.03) \times 10^{-6}$. The extrapolation to the full kinematic space, using a specific model, is found to be $(3.45 \pm 0.16) \times 10^{-6}$, in agreement with chiral perturbation theory predictions.Comment: 16 pages, 9 figure

Causality between the minimum wage and other wages

The paper analyzes the effects of the minimum wage over the other wages in Brazil using a bargaining framework. The key result is that the minimum wage precedes the market wage in the period 1980-85 while there is simultaneous determination in the period 1986-93.

Measurement of the form factors of charged kaon semileptonic decays

A measurement of the form factors of charged kaon semileptonic decays is presented, based on 4.4 × 106K± → π0e±νe (K e3 ± ) and 2.3 × 106K± → π0μ±νμ (K μ3 ± ) decays collected in 2004 by the NA48/2 experiment. The results are obtained with improved precision as compared to earlier measurements. The combination of measurements in the K e3 ± and K μ3 ± modes is also presented

Search for heavy neutrinos at the NA48/2 and NA62 experiments at CERN

The NA48/2 experiment at CERN has collected large samples of charged kaons decaying into a pion and two muons for the search of heavy nuetrinos. In addition, its successor NA62 has set new limits on the rate of charged kaon decay into a heavy neutral lepton (HNL) and a lepton, with = e, µ, using the data collected in 2007 and 2015. New limits on heavy neutrinos from kaon decays into pions, muons and positrons are presented in this report

Kl3 FORM FACTORS WITH NA48/2 AND NA62 STATUS

The NA48/2 experiment at CERN collected a very large sample of charged kaon decays into multiple final states. These data allow measurements related to QCD. We obtained our final measurement of the charged kaon semileptonic decays form factors based on 4.28 million Ke3 and 2.91 million Kμ3 selected decays, with the smallest uncertainty for Ke3 and a competitive result for Kμ3 and leading to the most precise combined Kl3 result coming from the kaon sector that reduces the form factor uncertainty of/Vus/. The NA62 experiment at CERN SPS is designed to measure the branching ratio of the K+ → π+νν decay with 10% precision. K → πνν is one of the theoretically cleanest meson decay where to look for indirect effects of new physics complementary to LHC searches. NA62 took data in 2015-2017; the analysis of a partial data set allows to reach the Standard Model sensitivity. The status of the experiments will be presented