Discovering the Higgs with Low Mass Muon Pairs

63 citations (61 excluding self-citations).

The Problem

If the Higgs boson decays into a pair of light pseudoscalars, as occurs in many extended Higgs sectors, the standard LEP and Tevatron search channels lose sensitivity. When the pseudoscalar mass falls below about 10 GeV, the dominant decay is to tau pairs, producing a four-tau final state that is experimentally challenging due to the low tau reconstruction efficiency and large combinatoric backgrounds. This left open the question of whether any clean discovery channel existed for cascade-decaying Higgs bosons with very light pseudoscalars.

The Key Idea

Even though the pseudoscalar branching ratio to muon pairs is suppressed by a factor of (m_μ/m_τ)² relative to the tau channel, requiring one pseudoscalar to decay to muons provides a narrow mass peak that dramatically reduces backgrounds. The dimuon invariant mass gives a clean resonance that can be triggered on efficiently, and the remaining pseudoscalar decaying to taus provides additional kinematic handles. This mixed channel (2μ + 2τ) offered realistic discovery potential with the complete Tevatron dataset or early LHC running, bridging the gap left by the pure four-tau search.

Recollections

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• DOI
• arXiv:0903.1377
• INSPIRE