This thesis is a presentation of an analysis of the $ZZ\rightarrow 4\ell$ ($\ell = e,\mu$) process in proton-proton collisions with centre-of-mass energy $\sqrt{s}$ = 13 TeV at the LHC during 2015 and 2016 (a total integrated luminosity of 36.1 fb$^{-1}$), using the ATLAS detector. Candidate $ZZ \rightarrow 4\ell$ events are selected in the three decay channels, $4e$, $2e2\mu$ and $4\mu$. The cross section of the $ZZ\rightarrow 4\ell$ process is measured in four fiducial regions closely matching the detector acceptance: one for each decay channel ($4e$, $2e2\mu$ and $4\mu$) and one for the combination of all decay channels. The total cross section of $pp\rightarrow ZZ$ is measured in a phase-space in which both $Z$ bosons have a mass $m_{Z}$ in the range 66 GeV $ < m_{Z} < $ 116 GeV to be 16.5 $\pm 0.5$ (stat.) $\pm 0.4$ (syst.) $\pm 0.5$ (lumi.)$\,$ pb which is consistent with a next-to-next-to-leading-order prediction of $16.9^{+0.6}_{-0.5}$ pb. Observed event yields in four bins of transverse momentum are used to set 95{\%} CL$_{\text{s}}$ limits on four neutral triple gauge couplings ($f^{V}_{i}$, $V=Z,\gamma$, $i=4,5$) which parameterise an effective $ZZV$ vertex (assuming both $Z$ bosons are on shell). The obtained limits are of the order of $|f^{V}_{i}|<0.0017$.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:744520 |
| Date | January 2018 |
| Creators | Rosten, Jonatan Hans Niclas |
| Contributors | Batley, John Richard |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.repository.cam.ac.uk/handle/1810/271838 |
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