The anatomy of the multilepton anomalies at the LHC and a candidate for a singlet scalar

TL;DR

This paper investigates multi-lepton anomalies at the LHC, analyzing their potential origins and presenting a simplified model that could explain the excesses, along with a search for related narrow resonances.

Contribution

It provides a detailed analysis of multi-lepton anomalies at the LHC and proposes a simplified model framework to interpret these excesses, including a resonance search with significant results.

Findings

Multi-lepton anomalies are observed in various phase-space regions.

A simplified model can potentially explain the anomalies.

A resonance at 151.5 GeV with 5.1σ local significance was found.

Abstract

In this presentation an account of the multi-lepton (electrons and muons) anomalies at the LHC is given. These include the excess production of opposite sign leptons with and without b-quarks, including a corner of the phase-space with a full hadronic jet veto; same sign leptons with and without b-quarks; three leptons with and without b-quarks, including also the presence of a $Z$. Excesses emerge in corners of the phase space where a range of SM processes dominate, indicating that the potential mismodeling of a particular SM process is unlikely to explain them. A procedure is implemented that avoids parameter tuning or scanning the phase-space in order to nullify potential look-else-where effects or selection biases. The internal consistency of these anomalies and their interpretation in the framework of a simplified model are presented. Motivated by the multi-lepton anomalies, a search for narrow resonances with $S\rightarrow\gamma\gamma, Z\gamma$ in association with light jets, $b$-jets or missing transverse energy is performed. The maximum local (global) significance is achieved for $m_S=151.5$\,GeV with 5.1$\sigma$ (4.8$\sigma$).