Hi, I’m Rachel and I’m a 2nd year physics PhD student at the University of Warwick, supervised by Prof. Bill Murray. My research focuses on searches for beyond the Standard Model Higgs bosons at the ATLAS experiment.

ATLAS is a general-purpose particle physics experiment at the Large Hadron Collider (LHC) at CERN - the largest detector ever constructed for a particle collider (46m long and 25m diameter!) It records the high-energy particle collisions of the LHC taking place in the centre of the detector, which are then analysed by ATLAS scientists.

Learn more about ATLAS here: https://atlas.cern/

Research Interests

Analysis Work

The Standard Model of particle physics is our best understanding of how fundamental particles and (three of four) fundamental forces are related. In the SM, fundamental particles acquire mass via the Brout-Englert-Higgs mechanism, of which the Higgs boson is the simplest physical manifestation. A particle with mass, spin and couplings all matching the SM predictions was observed in 2012 by the ATLAS and CMS experiments at the LHC.

My research concerns the predictions of Two-Higgs-Doublet-Models (2HDMs) - theoretical extensions of the standard model that can account for some of its unanswered questions. 2HDMs predict 4 additional Higgs bosons: the A and H, H+ and H- , alongside the standard model higgs boson.

In some types of 2HDM, the A or H can decay to a charged Higgs H± and a W∓ boson. The H ± is predicted to decay to a top and bottom quark, with the top quark then decaying to another bottom quark and W ∓ boson. This decay chain:
is the signal I am searching for with the ATLAS experiment.

This search involves a variety of techniques, such as using theory and ATLAS software to simulate what the signal would look like in the ATLAS detector. Machine learning tools such as multi-variate analysis are used to find the best way to separate this signal from the background processes in the detector.

Qualification Task

The ATLAS Inner Tracker (ITk) is the proposed upgrade of the ATLAS Inner Detector (ID) for the High-Luminosity Large Hadron Collider (HL-LHC). The change in conditions with the HL-LHC, as well as radiation damage to the current ID mean it will no longer be suitable, and so will be replaced with the all-silicon ITk as part of the Phase-II upgrade of the ATLAS detector.

To test the robustness of the silicon ‘strip’ modules through temperature changes, a standard thermal cycling procedure betwen -35C and +20C is required before the modules are installed. I worked on implementing this thermal cycling in hardware and software, using the ‘coldbox’ at the lab in Warwick.

Work at CERN

I have been on long term attachment (LTA) at the CERN site throughout 2024, during which time I have contributed towards detector operations, working on run control and trigger shifts in the ATLAS control room.

I have also enjoyed working at CERN's Science Gateway, helping to explain the LHC and particle physics to the public.

Undergraduate Studies

I received my Masters in Physics and Philosophy from Balliol College, Oxford in 2022. My Master's project was with Prof. Alan Barr, and concerned Bell Inequality violation and entanglement in H → WW∗ decays at the LHC. Find out more here: https://link.springer.com/article/10.1007/JHEP05(2023)020

Teaching

In my 1st and 2nd year, I ran seminars for the first year course PX161 , covering subjects such as Classical Mechanics, Special Relativity, Electromagnetism, and Quantum phenomena. I marked students work weekly, and gave feedback during seminars.

Visiting the ATLAS detector :)

Contact Details

Office: P448A

Email:  rachel.ashby-pickering@warwick.ac.uk

Supervisor: Prof. Bill Murray