Search for the production of Higgs-portal scalar bosons in the NuMI beam using the MicroBooNE detector

TL;DR

This paper reports the most stringent experimental limits to date on a Higgs-portal scalar particle's mixing angle in the 110-155 MeV mass range, using the MicroBooNE detector and NuMI beam data.

Contribution

It provides new experimental constraints on Higgs-portal scalar particles in a specific mass range using a novel detection method with the MicroBooNE detector.

Findings

Set upper limits on the mixing angle at 95% confidence level for masses 125 and 150 MeV.

Utilized a large dataset of NuMI beam protons on target to search for scalar decays.

Analyzed kaon decays in flight and at rest as sources of scalar particles.

Abstract

We present the strongest experimental limits to date on the mixing angle, $\theta$, with which a new scalar particle, $S$, mixes with the Higgs field in the mass range $110\text{ MeV}<m_S<155\text{ MeV}$. This result uses the MicroBooNE liquid argon time projection chamber to search for decays of these Higgs-portal scalar particles through the $S\rightarrow e^+e^-$ channel with the decays of kaons in the NuMI neutrino beam acting as the source of the scalar particles. The analysis uses an exposure of $2.01\times 10^{21}$ protons on target of NuMI beam data including periods when the beam focusing system was configured to focus positively charged hadrons and separate periods when negatively charged hadrons were focused. The analysis searches for scalar particles produced from kaons decaying in flight in the beam's decay volume and at rest in the target and absorber. At $m_S=125\text{ MeV}$ ($m_S=150\text{ MeV})$ we set a limit of $\theta<3.19\times 10^{-4}$ ($\theta<2.79\times 10^{-4}$) at the 95% confidence level.