Multi-muon events at CDF

TL;DR

This study investigates unusual multi-muon events at Fermilab's Tevatron, finding a significant excess of events with muons produced outside the beam pipe that standard models cannot fully explain, suggesting potential new physics or detector effects.

Contribution

The paper presents the first detailed analysis of multi-muon events with muons produced outside the beam pipe, highlighting discrepancies with standard model predictions and proposing possible new physics explanations.

Findings

Significant excess of multi-muon events with muons outside the beam pipe.

Standard model processes do not fully account for the observed events.

Known QCD processes explain events with muons inside the beam pipe.

Abstract

We report a study of multi-muon events produced at the Fermilab Tevatron collider and recorded by the CDF II detector. In a data set acquired with a dedicated dimuon trigger and corresponding to an integrated luminosity of 2100 pb$^{-1}$, we isolate a significant sample of events in which at least one of the identified muons has large impact parameter and is produced outside the beam pipe of radius 1.5 cm. We are unable to fully account for the number and properties of the events through standard model processes in conjunction with our current understanding of the CDF II detector, trigger and event reconstruction. Several topological and kinematic properties of these events are also presented. In contrast, the production cross section and kinematics of events in which both muon candidates are produced inside the beam pipe are successfully modeled by known QCD processes which include heavy flavor production. The presence of these anomalous multi-muon events offers a plausible resolution to long-standing inconsistencies related to $b\bar{b}$ production and decay.