High Multiplicity Searches at the LHC Using Jet Masses

57 citations (52 excluding self-citations).

The Problem

Many BSM scenarios, particularly R-parity violating supersymmetry, produce final states with very high jet multiplicities (10+ jets). Standard search strategies based on counting resolved jets become inefficient in this regime because jet reconstruction degrades when decay products overlap, and QCD multijet backgrounds grow rapidly with jet multiplicity. Missing energy cuts, the workhorse of most SUSY searches, are useless when R-parity is violated and no invisible particles are produced.

The Key Idea

Instead of counting individual jets, recluster the entire event into a small number of large-radius fat jets and cut on their masses. A massive fat jet signals that it contains multiple hard partons from a heavy particle decay, effectively compressing multiplicity information into a more robust observable. Requiring multiple massive fat jets in an event provides strong discrimination against QCD, which produces mostly massless jets. Applied to gluino pair production, this approach extended the estimated mass reach by 20-50% compared to existing LHC searches. The follow-up paper, “Learning How to Count,” refined the technique by using subjet counting within the fat jets for even greater sensitivity.

Recollections

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• DOI
• arXiv:1202.0558
• INSPIRE