Measurement of the very rare K⁺→π⁺νν decay

2021/03/29 by NA62 Collaboration · 1 voice
Physics and Astronomy · #hep-ex

paper · pdf · doi:10.1007/jhep06(2021)093

arxiv published 2021/03/29 · arxiv created 2021/07/05 · arxiv updated 2021/07/07

Abstract

The NA62 experiment reports the branching ratio measurement BR(K⁺ → π⁺ νν) = (10.6^+4.0_-3.4 |_{\rm stat} ± 0.9_{\rm syst}) × 10 ^-11 at 68% CL, based on the observation of 20 signal candidates with an expected background of 7.0 events from the total data sample collected at the CERN SPS during 2016-2018. This provides evidence for the very rare K⁺ → π⁺ νν decay, observed with a significance of 3.4σ. The experiment achieves a single event sensitivity of (0.839± 0.054)× 10^-11, corresponding to 10.0 events assuming the Standard Model branching ratio of (8.4±1.0)×10^-11. This measurement is also used to set limits on BR(K⁺ → π⁺ X), where X is a scalar or pseudo-scalar particle. Details are given of the analysis of the 2018 data sample, which corresponds to about 80% of the total data sample.

Discussions

• Yesterday the NA62 experiment at @CERN posted a #preprint with their measurement of the K⁺→π⁺νν̅ decay rate. https://arxiv.org/abs/2103.15389. I'll write a few words on how this is connected to the # [bsky, 0 points, 1 comments]

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