Search for Production of Invisible Final States in Single-Photon Decays of Upsilon(1S)

TL;DR

This study searches for invisible final states in Upsilon(1S) decays via single-photon events, aiming to detect potential light dark matter particles or light Higgs bosons, but finds no evidence and sets limits on new physics models.

Contribution

First search for single-photon decays of Upsilon(1S) into invisible states, constraining light dark matter and light Higgs models using BaBar data.

Findings

No evidence for invisible decays within the studied mass ranges.

Set upper limits on branching fractions for Upsilon(1S) to invisible states.

Constraints on models with light dark matter and light Higgs bosons.

Abstract

We search for single-photon decays of the Upsilon(1S) resonance, Upsilon->gamma+invisible, where the invisible state is either a particle of definite mass, such as a light Higgs boson A0, or a pair of dark matter particles, chi chi-bar. Both A0 and chi are assumed to have zero spin. We tag Upsilon(1S) decays with a dipion transition Upsilon(2S)->pi+pi-Upsilon(1S) and look for events with a single energetic photon and significant missing energy. We find no evidence for such processes in the mass range m_A0<=9.2 GeV and m_chi<=4.5 GeV in the sample of 98e6 Upsilon(2S) decays collected with the BaBar detector and set stringent limits on new physics models that contain light dark matter states.