Search for Axion-Like Particles at the LHC - LightAtLHC

Programme(s): H2020-EU.1.1. - EXCELLENT SCIENCE - European Research Council (ERC)

Topic(s): ERC-2019-COG - ERC Consolidator Grant

Call for proposal: ERC-2019-COG

Funding Scheme: ERC-COG - Consolidator Grant

Grant agreement ID: 864950

Project description:
Search for axion particles heats up
Axions and axion-like particles (ALPs) are hypothetical elementary particles that are well motivated theoretically: ALPs can solve the strong CP problem, act as a dark matter candidate and also explain the famous muon (g-2) discrepancy. The experimental efforts to search for ALPs as dark matter candidates is ongoing and has been intensified in recent years. However, none of these experiments is sensitive to ALPs that can explain low-energy anomalies such as (g-2). The EU-funded LightAtLHC will pioneer alternative search approaches to detect ALPs using data collected at the Large Hadron Collider. If successful, project researchers will either rule out the most promising ALP models in a mass range from 10 MeV to 1 TeV, or discover a new elementary particle.

Objective:
Axions and other very light axion-like particles (ALPs) appear in many extensions of the Standard Model and are well motivated theoretically: ALPs can solve the well-known strong CP problem, act as a dark matter candidate and could also explain the famous muon (g-2) discrepancy. The experimental effort to search for ALPs as dark matter candidates is ongoing and has been considerably intensified in recent years, leading to the proposal and construction of a wide range of dedicated experiments. However, none of these dedicated experiments is sensitive to those ALPs that can explain low-energy anomalies such as (g-2). I propose therefore to pioneer an alternative search strategy for axion-like particles via their decay into two photons, using data collected at the Large Hadron Collider. This approach requires fundamental innovations on the photon identification capabilities of the current detectors as well as radically new analysis strategies.

Within the LightAtLHC project, I will study proton-proton and lead-lead collisions, collected during LHC Run-3, and search for Higgs Boson decays in two ALPs as well as the direct production of ALPs via photon fusion and their subsequent decay into two low-energy photons. To achieve the required sensitivity, I will develop highly specialized photon reconstruction algorithms for the ATLAS detector.
These efforts will largely cover the relevant parameter space, leaving out only a small region. To also close this gap, I will extend the upcoming FASER experiment at the LHC by an innovative presampler detector, which allows for an unambiguous ALPs detection. By the end of the LightAtLHC project, I can either rule out the most promising ALP models in a mass range from 10 MeV to 1 TeV, or discover a new elementary particle.