Physics Data Analysis

The longer title of my analysis project is: Search for third generation leptoquarks in \(pp \to \tau\tau\) final states.

While an extensive description of the underlying motivation and theory behind the search can be found in my thesis, Ch.1 and 3 [1], the following shall give a quick introduction to also non-physicists:

What is labelled as “search” is predominantly a Standard Model [2] measurement of the fiducial differential cross section of two leptons (a family of elementary particles that also includes the electron) with at least one \(\tau\)-lepton. A theorised third generation leptoquark could negatively interfere with Standard Model \(\tau\tau\) final states through the high mass tail of the \(bb \to \tau\tau\) process as postulated by effective field theories:

The Feynman diagrams describing the generation and resonance with leptoquarks, denoted as U1. A possible interference signal is the right-most diagram, with two taus in the final state. The *b* and anti-*b* quarks are coming from the energy of proton proton collisions inside the ATLAS detector.

In simplified term “negatively interfere” means that less \(\tau\) leptons appeared (e.g. are counted) in the dataset as was expected from the Standard Model prediction.

There is a lot going into simply counting particles that would be beyond the scope of this project description. All details of the full analysis are in Ch. 3 of [1] and the paper is sheduled for publication in 2025.

My involvement

I developed a \(\texttt{Python}\) framework for fitting the maximum likelihood estimator of the leptoquark signal strength with the statistical framework \(\texttt{cabinetry}\) [3] and determining the sensitivity to leptoquarks in absence of unblinded data. I carried out my work during 2022-2023 and the fitting framework is still (with some modifications of course) used today.

My contribution had a direct input to the background event generation, so events without leptoquark interference, and application of the kinematic cuts of possible signal events. The framework also provided a way to efficiently produce statistical results and provide them to the analysis group for rapid development of the analysis strategy.