Search for a Hidden Sector Scalar from Kaon Decay in the Di-Muon Final State at ICARUS

TL;DR

This paper reports a search for long-lived particles from kaon decay into muons at ICARUS, setting new limits on hidden sector models and demonstrating the detector's potential for future long-lived particle searches.

Contribution

First search for new physics with ICARUS at Fermilab, providing world-leading limits on hidden sector scalars and establishing a new experimental approach.

Findings

No new physics signal observed.

Set world-leading limits on heavy QCD axions and Higgs portal scalars.

Presented model-independent constraints on long-lived particles.

Abstract

We present a search for long-lived particles (LLPs) produced from kaon decay that decay to two muons inside the ICARUS neutrino detector. This channel would be a signal of hidden sector models that can address outstanding issues in particle physics such as the strong CP problem and the microphysical origin of dark matter. The search is performed with data collected in the Neutrinos at the Main Injector (NuMI) beam at Fermilab corresponding to $2.41\times 10^{20}$ protons-on-target. No new physics signal is observed, and we set world-leading limits on heavy QCD axions, as well as for the Higgs portal scalar among dedicated searches. Limits are also presented in a model-independent way applicable to any new physics model predicting the process $K\to \pi+S(\to\mu\mu)$, for a long-lived particle S. This result is the first search for new physics performed with the ICARUS detector at Fermilab. It paves the way for the future program of long-lived particle searches at ICARUS.