Rare and forbidden kaon decays at NA62

Monica Pepe

doi:10.1051/epjconf/20159503029

Abstract

A precision lepton universality test by measurement of the helicity suppressed ratio of leptonic decay rates of the charged kaon with ∼ 150000 K ± → e ± ν decays collected by the NA62 experiment in 2007-08 is presented. The record accuracy of 0.4% constrains the parameter space of new physics models with extended Higgs sector, a fourth generation of quarks and leptons or sterile neutrinos.An improved upper limit on the rate of the lepton number violating decay K ± → π ∓ μ ± μ ± , which probes the resonant enhancement of the rate in the presence of heavy Majorana neutrinos in the ∼ 100 MeV range, is presented.The rare decays K + → π + νν are excellent processes to make tests of new physics at the highest scale complementary to LHC thanks to their theoretically cleaness. The NA62 experiment at CERN SPS aims to collect of the order of 100 events in two years of data taking, keeping the background at the level of 10%.

Highlights

Kaon physics offers several opportunities for a deep study of the Standard Model (SM) investigating the flavour sector of fundamental interactions and being sensitive to possible effects of New Physics
NA62 and the NA48/2, NA48/1, NA48, NA31 series of experiments represent the long term CERN program in kaon physics: they are fixed target experiments at the CERN SPS dedicated to the study of CP violation and rare decays in the kaon sector with different beam configurations
The ratio Rk = Γ(Ke2)/Γ(Kμ2) of kaon leptonic decay rates is computed with very high accuracy in the SM thanks to cancellation of hadronic effects: the SM prediction inclusive of Internal Bremsstrahlung (IB) radiation is [1]: RSKM

Summary

Introduction

Kaon physics offers several opportunities for a deep study of the Standard Model (SM) investigating the flavour sector of fundamental interactions and being sensitive to possible effects of New Physics. NA62 and the NA48/2, NA48/1, NA48, NA31 series of experiments represent the long term CERN program in kaon physics: they are fixed target experiments at the CERN SPS dedicated to the study of CP violation and rare decays in the kaon sector with different beam configurations. While the NA48 experimental set-up has been upgraded in the course of operations, NA62 is a new experiment dedicated to the measurement of the ultra-rare K+ → π+νν decay. Within extensions of the SM involving two Higgs doublets, RK is sensitive to lepton flavour violating effects induced by loop processes with the charged Higgs boson (H±) exchange [2, 3]. In this paper the improved NA62 [7] result based on data collected in 2007 and 2008 is presented

Beam and Detector

The measurement of RK

Findings

The NA62 experiment