Rise and Fall of Light Top Squarks in the LHC Top-Quark Sample

Area of Science:

• High Energy Physics
• Particle Physics
• Supersymmetry

Background:

• The Large Hadron Collider (LHC) searches for new physics beyond the Standard Model.
• Top-quark events provide a rich environment for discovering new phenomena.
• Existing kinematic distributions are well-studied but may hide subtle new physics signals.

Purpose of the Study:

• To explore the potential of the invariant mass distribution (m_bℓ) of b-jets and charged leptons in fully leptonic top-antitop (tt[over ¯]) events for discovering new physics.
• To investigate a specific supersymmetric scenario involving light supersymmetric particles (top-squark, chargino, neutralino).
• To identify general features of light new physics models that evade current LHC searches.

Main Methods:

• Analysis of the m_bℓ kinematic distribution in fully leptonic tt[over ¯] events.
• Study of a supersymmetric model with light particles, focusing on their mass spectra and resulting m_bℓ distribution features.
• Recasting public LHC data from new physics searches to identify viable candidate models.
• Derivation of expected signal yields for identified models.

Main Results:

• New physics signals can be detected in the rising portion of the m_bℓ distribution.
• A light supersymmetric scenario with specific mass differences creates a unique endpoint in the m_bℓ distribution, currently not excluded by LHC searches.
• This sharp feature in the m_bℓ distribution is a general characteristic of light new physics models that have evaded detection.
• Recasting LHC data identified candidate models with untapped discovery potential.

Conclusions:

• The m_bℓ distribution offers a powerful tool for discovering light new physics at the LHC.
• Supersymmetric models with light particles can be probed effectively using this distribution.
• Further dedicated searches exploiting the m_bℓ distribution are warranted to uncover new physics and potentially discover new particles.