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| Book/Dissertation / PhD Thesis | PUBDB-2024-00440 |
; ;
2024
Verlag Deutsches Elektronen-Synchrotron DESY
Hamburg
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Please use a persistent id in citations: doi:10.3204/PUBDB-2024-00440
Report No.: DESY-THESIS-2024-001
Abstract: In this thesis, we study two $Z$ boson production mechanisms: the Drell-Yan process andreal electroweak corrections.The transverse momentum spectrum of the Drell-Yan lepton pair is of general interest asit is sensitive to the hadron structure. Moreover, the small transverse momentum region, $q{\tiny T}$ $<$ m$_{ll}$, is sensitive to the 3D structure of the hadron. To describe the $q{\tiny T}$ $<$ m$_{ll}$ region,resummation to all orders is needed. However, the $q{\tiny T}$ m$_{ll}$ region is non-perturbativeand has to be modelled. This region is modelled via a Gaussian distribution of the intrinsictransverse momentum of the incoming partons. Nonetheless, this is insufficient, and verysoftgluon radiation is needed. We investigate the effect of very-soft gluon radiations in the $q{\tiny T}$ $≪\ $m$_{ll}$ region within the Parton Branching framework, and how it relates to the Collins-Soper kernel of the $TMD$ factorisation. The very-soft gluon radiation is removed throughthe soft-gluon resolution scale in the parton showers of Monte-Carlo event generators, such as ${P}$${\small YTHIA}$$8$ and ${H}$${\small ERWIG}$$7$. We demonstrate that this leads to a centre-of-mass energydependent intrinsic transverse momentum, by tuning the intrinsic tranerse momentum. At high partonic centre-of-mass energies, electroweak corrections become large, and the $Z$ boson might be produced as a real electroweak correction. In $QCD$ processes, at highjet transverse momentum, virtual electroweak corrections become large, and at the $TeV$ scale, their contribution to the cross-section is of the order of 10 $\%$. We measure the contributionof real electroweak corrections to $QCD$ events as a function of the jet transversemomentum. We analyse proton-proton collisions at a centre-of-mass energy of 13 $TeV$ atthe $LHC$, recorded by the $CMS$ experiment during 2016, corresponding to an integratedluminosity of 36.3 fb$^{−1}$. We measure the contribution of the real electroweak correctionto a 1 $TeV$ jet transverse momentum to be 1-2 $\%$. Moreover, we investigate differentobservables sensitive to real electroweak corrections to test their modelling in differenttheoretical scenarios.
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