Prospect studies for Higgs Boson pair production to bbyy final state at the HL-LHC with the ATLAS detector

Briglin, Daniel Lawrence (2020). Prospect studies for Higgs Boson pair production to bbyy final state at the HL-LHC with the ATLAS detector. University of Birmingham. Ph.D.

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Abstract

By the end of the HL-LHC era, before 2040, the ATLAS experiment aims to increase the size of the dataset from $\sim$300fb$^{-1}$, acquired at the end of LHC running, up to $\sim$3000fb$^{-1}$. The large dataset expected after HL-LHC operation increases the likelihood of seeing rare processes such as the $H \rightarrow HH \rightarrow b\bar{b}\gamma\gamma$ decay channel. This channel is one of the most promising for measuring the Higgs boson self-coupling. To mimic the expected ATLAS detector response to various physics objects at the HL-LHC, upgrade performance functions are constantly developed and updated. A recent update to these functions included the addition of a considerably more realistic estimate of the expected material budget of the ITk, as well as dedicated functions for both the 50$\times$50$\mu$m$^2$ and 25$\times$100$\mu$m$^2$ pixel sensor geometries. A Boosted Decision Tree method was applied to the $H \rightarrow HH \rightarrow b\bar{b}\gamma\gamma$ channel to determine the effects of these changes. It was shown that the more realistic material budget and dedicated 50$\times$50$\mu$m$^2$ functions result in a significance for observing this channel of 3.10$\pm$0.13. Comparable results are obtained when using either a pixel sensor geometry of 25$\times$100$\mu$m$^2$ or reducing the radius of the innermost pixel layer.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):