Filling the Gap: Hunting for Vector Bosons at the MUonE Experiment with Displaced Decay Signature

TL;DR

The paper explores MUonE's potential to detect long-lived vector bosons through displaced decay signatures, offering new sensitivity to parameter space up to 100 MeV mass, beyond current collider capabilities.

Contribution

It provides a comprehensive analysis of MUonE's ability to search for long-lived vector bosons via displaced vertices, highlighting its unique sensitivity in a previously unexplored parameter space.

Findings

MUonE can detect vector bosons with masses up to 100 MeV.

Displaced vertex detection enhances sensitivity to long-lived particles.

MUonE fills a gap in vector boson parameter space not accessible by other experiments.

Abstract

The upcoming MUonE experiment aims to precisely measure the running of the fine structure constant via elastic muon-electron scattering, to shed light on the current tension in the muon's anomalous magnetic moment. In addition to its primary function as a precision experiment, MUonE also offers a unique testing ground to probe long-lived vector bosons. Such vector bosons can be produced via $\mu e \to \mu e V$ or $\mu N \to \mu N V$ scattering and decay into an electron/positron pair a few centimeters away from the interaction point. With its high-resolution tracking system and unique geometric design, MUonE is well-suited to reconstruct displaced vertices close to the target, allowing it to probe parameter space previously unattainable at colliders and longer-baseline beam dump experiments. We present a comprehensive study of the discovery potential of BSM vector boson mediators at the MUonE experiment. We show that MUonE can fill the long-standing gap in the parameter space of vector boson mediators with masses up to around 100 MeV.