Frédéric Alexandre DREYER Precision Physics at the Large Hadron Collider

205 Pages·2016·4.65 MB·English

THÈSE DE DOCTORAT
DE L’UNIVERSITÉ PIERRE ET MARIE CURIE
Spécialité : Physique Théorique
réalisée
au Laboratoire de Physique Théorique et Hautes Énergies
présentée par
Frédéric Alexandre DREYER
pour obtenir le grade de :
DOCTEUR DE L’UNIVERSITÉ PIERRE ET MARIE CURIE
Sujet de la thèse :
Precision Physics at the Large Hadron Collider
soutenue le 17 mai 2016
devant le jury composé de :
M. Jean-Philippe GUILLET Rapporteur
M. Fabio MALTONI Rapporteur
M. Benjamin FUKS Président
M. Keith HAMILTON Examinateur
M. Abdelhak DJOUADI Examinateur
M. José OCARIZ Examinateur
M. Gavin SALAM Directeur de thèse
M. Matteo CACCIARI Directeur de thèse

L’absurde naît de cette confrontation entre l’appel
humain et le silence déraisonnable du monde.
— Albert Camus

Acknowledgements
There are many people I need to thank for their contributions in various forms, and
whose help has been essential in completing the present work while making these almost
three years an enriching experience.
First and foremost, I would like to thank my two PhD advisors, Gavin Salam and Matteo
Cacciari, for being a role model of intellectual curiosity and scientific rigor I have aspired
to over these years. I thank Matteo for always making sure I continued asking myself
the important questions, and for his always insightful comments and ideas throughout
my thesis. I thank Gavin for his open door and warm welcome during my many visits at
CERN, for his encouragements and insights and for sharing with me his knowledge and
passion for particle physics. None of this work would have been possible without them.
I thank Mrinal Dasgupta, Grégory Soyez, and Giulia Zanderighi for their many inputs
and for discussions throughout our collaboration. Their expertise has greatly helped
me in understanding different aspects of QCD. I also thank Alexander Karlberg with
whom I collaborated closely on the VBF part of this thesis, and Pier Monni for useful
suggestions.
I thank the members of the jury, particularly Fabio Maltoni and Jean-Philippe Guillet for
their careful reading of the manuscript, and Benjamin Fuks for several useful comments.
I thank Matthijs, Jesper, Matthias, Elina, Noppadol, Jean-Claude, Rob, Stefan, Denis,
Michele, Bernardo & Stephen for all our interesting discussions at CERN over lunch and
coffee.
I thank Luc, Pierre, Hugo, Tianhan, Oscar, Johannes, Thomas & Matthieu for our
numerous lunches and coffee breaks at LPTHE, and the many discussions that came
with them.
I’m very grateful to my friends Elliott, Artem, Luiz, Praxitelis, Edouard, Adriaan, and
manyothers,fortheirfriendship,andforalwaysbeingpresentwhenIneededadistraction
from physics.
FinallyIamalsogratefultomyparents,fortheircontinuoussupportandencouragements,
and to Sophie, for always being understanding of my long evenings and travels.
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Abstract
With the advent of the LHC, particle physics has entered an era where high precision
is required. In this thesis, we tackle two of the key processes at hadron colliders using
innovative tools: inclusive jet production and Higgs production through vector-boson
fusion (VBF).
In the first part of this thesis, we show how to resum leading logarithmic terms of
the jet radius R, and apply this formalism to a detailed study of the inclusive jet
spectrum. We study subleading R-dependent terms at next-to-next-to-leading order
(NNLO), and incorporate them into our calculation. We investigate cancellations in the
scale dependence, leading to new prescriptions for evaluating uncertainties, and examine
the impact of non-perturbative effects.
In the second part of the thesis, we study QCD corrections in VBF-induced Higgs
production. Using the structure function approach, we compute the next-to-next-to-next-
to-leading order (N3LO) corrections to the inclusive cross section. We then calculate
the fully differential NNLO corrections to VBF Higgs production. We show that these
contributions are substantial after VBF cuts, lying outside the NLO scale uncertainty
bands.
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Résumé
L’avènement du LHC marque le début d’une ère de haute précision en physique des
particules. Dans cette thèse de doctorat, nous abordons avec des outils innovants deux
processus clés des collisionneurs de hadrons : la production inclusive de jets, et la
production du boson de Higgs par fusion de bosons vecteurs (VBF).
Dans la première partie de cette thèse, nous montrons comment resommer les premiers
ordres logarithmiques de rayon de jet R, et appliquons ce formalisme à une étude
approfondie du spectre inclusif des jets. Nous étudions les termes dépendant de R au
troisième ordre non-nul (next-to-next-to-leading-order, NNLO), et les intégrons dans
notre calcul. Nous examinons les éliminations dans la dépendance d’échelle, conduisant à
une nouvelle prescription pour l’évaluation des incertitudes, et vérifions l’impact d’effets
non-perturbatifs.
Dansladeuxièmepartiedecettethèse,nousétudionslescorrectionsdechromodynamique
quantique dans la production de Higgs par VBF. En utilisant l’approche des fonctions de
structure, nous calculons les corrections de quatrième ordre non-nul (N3LO) à la section
efficace inclusive. Nous calculons ensuite les corrections NNLO entièrement différentielles
àlaproductiondeHiggsparVBF.Nousmontronsquecescontributionssontsignificatives
après coupures VBF, se trouvant en dehors des bandes d’incertitude d’échelle NLO.
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