CERN Accelerating science

Signal box result of the search. A scale factor on the $\uCCCoh$ background is obtained from a fit region shown in the inset. A bump hunt search in the data against the scaled background prediction obtains an insignificant excess with a global significance of $0.19\sigma$, in the range $0.24 < M_{\mu\mu} < $~\SI{0.31}{GeV}. The reconstructed mass of each selected data event is shown with a caret on the bottom of the figure. Spectra of two example model points excluded at the 90\% CL (see Fig.~\ref{fig:ModelLim}) are shown.

Limits on the Higgs Portal scalar (top) and heavy axion (bottom) models. Exclusions are computed with the CL$_\text{s}$ method at the 90\% CL. The HPS limit is compared to direct searches~\cite{NA62HPS, MicroBooNEHPS, LHCbHPS1, LHCbHPS2, E949} and reinterpreted limits on the model~\cite{CHARMInterp, CHARMResult, PS191Interp, PS191Result, LSNDInterp, LSNDResult}. The ALP limit is compared to other limits on the particle~\cite{KALP, NA62HPS, MicroBooNEHPS, ALPINIST, CHARMResult}.

Limits on the Higgs Portal scalar (top) and heavy axion (bottom) models. Exclusions are computed with the CL$_\text{s}$ method at the 90\% CL. The HPS limit is compared to direct searches~\cite{NA62HPS, MicroBooNEHPS, LHCbHPS1, LHCbHPS2, E949} and reinterpreted limits on the model~\cite{CHARMInterp, CHARMResult, PS191Interp, PS191Result, LSNDInterp, LSNDResult}. The ALP limit is compared to other limits on the particle~\cite{KALP, NA62HPS, MicroBooNEHPS, ALPINIST, CHARMResult}.

Model independent limits (at the 90\% CL) on the process $K\to \pi + S(\to\mu\mu)$, for a long lived particle $S$. Contours are shown as a function of the branching ratio of the process and the particle mass, for a few example values of the particle lifetime. Limits in the full three-dimensional space are available in the supplementary material.

$\uCCCoh$ differential cross section as a function of pion energy predicted by GENIE v3.00.06 and this tune, compared to the MINERvA measurement.

$\uCCCoh$ differential cross section as a function of pion energy predicted by GENIE v3.00.06 and this tune, compared to the MINERvA measurement.