Lydia Beresford

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Lydia Beresford


I am a Junior Research Fellow at St John’s College and a member of the ATLAS collaboration at CERN.

I am an experimental particle physicist searching for evidence of new particles or interactions by analysing data from the Large Hadron Collider (LHC). The LHC is famous for being the highest energy hadron collider in the world. However, in my current research I use the LHC in a different way - as the world’s highest energy photon collider.

Proton beams at the LHC occasionally narrowly miss one another resulting in an interaction between their surrounding electromagnetic fields. This can produce high energy photon collisions and new undiscovered particles could be created. Importantly, the protons can remain intact and only experience a deflection. The intact protons can be measured using the ATLAS Forward Proton (AFP) detectors sitting 200 meters away. The production of new, undiscovered particles would modify the deflection angle – thus AFP may enable us to ‘see’ invisible dark matter particles, or other new particles.

I currently lead the first analysis to use the new AFP detectors to observe and measure forward proton scattering in association with the photo-production of a pair of leptons. This measurement lays the foundations for using LHC photon collisions in conjunction with AFP to gain new sensitivity to well-motivated, unexplored phase space for dark matter models. Photon collisions also show promise to improve the measurement of the tau anomalous magnetic moment, as demonstrated in my recent phenomenology paper.

In addition to my photon collision work I have performed several searches for Z’ dark matter mediators in jet final states from 70 GeV to nearly 7 TeV in mass.