New Detectors to Explore the Lifetime Frontier

TL;DR

The paper introduces new detector concepts, MATHUSLA and a future 100 TeV collider detector, designed to discover ultra-long-lived particles with lifetimes near BBN limits, which are undetectable by current methods.

Contribution

It proposes practical detector designs capable of observing ultra-long-lived particles with extremely long lifetimes, extending the search capabilities beyond existing strategies.

Findings

MATHUSLA can detect non-hadronic neutral LLPs with lifetimes up to 10^8 m.

A 100 TeV collider detector can discover LLPs from exotic Higgs decays at the BBN lifetime limit.

The proposed detectors are feasible with current technology and can be implemented during upcoming collider upgrades.

Abstract

Long-lived particles (LLPs) are a common feature in many beyond the Standard Model theories, including supersymmetry, and are generically produced in exotic Higgs decays. Unfortunately, no existing or proposed search strategy will be able to observe the decay of non-hadronic electrically neutral LLPs with masses above $\sim$ GeV and lifetimes near the limit set by Big Bang Nucleosynthesis (BBN), $c \tau \lesssim 10^7 - 10^8$~m. We propose the MATHUSLA surface detector concept (MAssive Timing Hodoscope for Ultra Stable neutraL pArticles), which can be implemented with existing technology and in time for the high luminosity LHC upgrade to find such ultra-long-lived particles (ULLPs), whether produced in exotic Higgs decays or more general production modes. We also advocate for a dedicated LLP detector at a future 100 TeV collider, where a modestly sized underground design can discover ULLPs with lifetimes at the BBN limit produced in sub-percent level exotic Higgs decays.