Hunting wino and higgsino dark matter at the muon collider with disappearing tracks

Understand

We study the capabilities of a muon collider experiment to detect disappearing tracks originating when a heavy and electrically charged long-lived particle decays via $X^+ \to Y^+ Z^0$, where $X^+$ and $Z^0$ are two almost mass degenerate new states and $Y^+$ is a charged Standard Model particle.

• The backgrounds induced by the in-flight decays of the muon beams (BIB) can create detector hit combinations that mimic long-lived particle signatures, making the search a daunting task.
• We design a simple strategy to tame the BIB, based on a detector-hit-level selection exploiting timing information and hit-to-hit correlations, followed by simple requirements on the quality of reconstructed tracks.
• Our strategy allows us to reduce the number of tracks from BIB to an average of 0.08 per event, hence being able to design a cut-and-count analysis that shows that it is possible to cover weak doublets and triplets with masses close to $\sqrt{s}/2$ in the 0.1-10 ns range.