Novel approach to measure the leptonic eta(')->mu+mu- decays via charmed meson decays

TL;DR

This paper proposes a new method to measure the rare leptonic decays of eta and eta' mesons through charmed meson decays, leveraging LHCb data to improve precision and potentially observe eta' decays.

Contribution

It introduces a novel approach using charmed meson decays to measure eta(')->mu+mu- branching ratios, with estimates of improved accuracy from existing and future LHCb data.

Findings

Existing LHCb data can yield competitive measurements of Br(eta->mu+mu-)

Projected data from 2015-2018 can reduce uncertainties to about 10%

First observation of Br(eta'->mu+mu-) may be possible with LHCb upgrade

Abstract

In this article, we propose a novel approach to measure the branching ratios of the leptonic eta(')-> mu+mu- decays by using charmed meson decays, namely, D+(s)->pi+ eta(')(->mu+mu-) and D0->K-pi+eta(')(->mu+mu-). We advocate that the data available at LHCb can already yield a new measurement of Br(eta->mu+mu-) with accuracy competitive with the current world average. We also estimate that using the data collected by LHCb between 2015 and 2018 in proton-proton collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.0/fb, the relative uncertainties to this branching ratio can be reduced down to ~10%. We also show that the first observation of Br(eta'->mu+mu-) may be possible with the Upgrade of the LHCb experiment.