Triggering Soft Bombs at the LHC

TL;DR

This paper proposes a novel high-level trigger strategy for the LHC to efficiently detect 'soft bomb' events characterized by high multiplicity soft particles, which are difficult to distinguish from pile-up using traditional methods.

Contribution

It introduces a 'belt of fire' trigger concept that enhances detection efficiency of soft bombs by identifying a dense hit band in the tracker, enabling better separation from pile-up events.

Findings

Achieves about 10% trigger efficiency for soft bombs of several hundred GeV.

Demonstrates the feasibility of detecting Higgs-related soft bombs with marginally higher rates than traditional triggers.

Provides a proof-of-concept for a new trigger strategy to identify strongly-coupled hidden valley signatures.

Abstract

Very high multiplicity, spherically-symmetric distributions of soft particles, with $p_T$ ~ few hundred MeV, may be a signature of strongly-coupled hidden valleys that exhibit long, efficient showering windows. With traditional triggers, such "soft bomb" events closely resemble pile-up and are therefore only recorded with minimum bias triggers at a very low efficiency. We demonstrate a proof-of-concept for a high-level triggering strategy that efficiently separates soft bombs from pile-up by searching for a "belt of fire": A high density band of hits on the innermost layer of the tracker. Seeding our proposed high-level trigger with existing jet, missing transverse energy or lepton hardware-level triggers, we show that net trigger efficiencies of order 10% are possible for bombs of mass several hundred GeV. We also consider the special case that soft bombs are the result of an exotic decay of the 125 GeV Higgs. The fiducial rate for "Higgs bombs" triggered in this manner is marginally higher than the rate achievable by triggering directly on a hard muon from associated Higgs production.