The ChiralityFlow Formalism and Optimising Scattering Amplitudes
(2023) Abstract
 This thesis is composed of five papers, which all attempt to optimise calculations of scattering amplitudes in highenergyphysics collisions. These scattering amplitudes are a key part of theoretical predictions for particlephysics experiments like the Large Hadron Collider at CERN. The first four papers are the main topic of the thesis, and describe a novel method called chirality flow. Chirality flow simplifies Feynmandiagram calculations and makes them more intuitive. Papers I, II, and IV describe chirality flow in detail at both treelevel and oneloop level, while paper III shows a first implementation of it in the event generator MadGraph5_aMC@NLO. The final paper instead explores the speed, accuracy, and precision of an... (More)
 This thesis is composed of five papers, which all attempt to optimise calculations of scattering amplitudes in highenergyphysics collisions. These scattering amplitudes are a key part of theoretical predictions for particlephysics experiments like the Large Hadron Collider at CERN. The first four papers are the main topic of the thesis, and describe a novel method called chirality flow. Chirality flow simplifies Feynmandiagram calculations and makes them more intuitive. Papers I, II, and IV describe chirality flow in detail at both treelevel and oneloop level, while paper III shows a first implementation of it in the event generator MadGraph5_aMC@NLO. The final paper instead explores the speed, accuracy, and precision of an approximation of the colour part of a scattering amplitude.
Paper I introduces the chiralityflow formalism, a new pictorial method used to calculate treelevel helicity amplitudes by drawing lines and connecting them to find spinor inner products, instead of doing algebraic manipulations. This method makes calculations more transparent, and often allows one to go from Feynman diagram to spinor inner products in a single line. Massless QED and QCD are treated in full.
Paper II extends the chiralityflow formalism of paper I to deal with massive particles, and therefore allows chirality flow to be used for any treelevel Standard Model calculation.
Paper III describes our implementation of chirality flow in massless QED in MadGraph5_aMC@NLO. A speed comparison is made showing up to a factor of 10 increase in evaluation speed.
Paper IV extends the chiralityflow formalism to the oneloop level for any Standard Model calculation, showing the simplifications in the numerator algebra and the tensor reduction.
Paper V describes an extension to the MadGraph5_aMC@NLO event generator in which the kinematics are calculated using BerendsGiele recursions instead of Feynman diagrams, and the colour matrix can be expanded in the number of colours Nc. The speed of the extension, and the accuracy and precision of the colour expansion are explored. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/6a796a110c934dbe9e0889255ec3ccfe
 author
 Lifson, Andrew ^{LU}
 supervisor

 Malin Sjödahl ^{LU}
 Rikkert Frederix ^{LU}
 Stefan Prestel ^{LU}
 opponent

 Professor Zeppenfeld, Dieter, Karlsruhe Institute of Technology, Germany.
 organization
 publishing date
 20230327
 type
 Thesis
 publication status
 published
 subject
 keywords
 Spinorhelicity formalism, Chiralityflow formalism, Helicity amplitudes, Standard Model, QED, QCD, Optimisations, Colour expansion, Phenomenology, Fysicumarkivet A:2023:Lifson
 pages
 268 pages
 publisher
 MediaTryck Lund
 defense location
 Lundmarksalen, Astronomihuset, Sölvegatan 27, Lund.
 defense date
 20230426 10:00:00
 ISBN
 9789180395892
 9789180395885
 project
 The ChiralityFlow Formalism and Optimising Scattering Amplitudes
 language
 English
 LU publication?
 yes
 id
 6a796a110c934dbe9e0889255ec3ccfe
 date added to LUP
 20230215 11:20:18
 date last changed
 20230531 10:16:58
@phdthesis{6a796a110c934dbe9e0889255ec3ccfe, abstract = {{This thesis is composed of five papers, which all attempt to optimise calculations of scattering amplitudes in highenergyphysics collisions. These scattering amplitudes are a key part of theoretical predictions for particlephysics experiments like the Large Hadron Collider at CERN. The first four papers are the main topic of the thesis, and describe a novel method called chirality flow. Chirality flow simplifies Feynmandiagram calculations and makes them more intuitive. Papers I, II, and IV describe chirality flow in detail at both treelevel and oneloop level, while paper III shows a first implementation of it in the event generator MadGraph5_aMC@NLO. The final paper instead explores the speed, accuracy, and precision of an approximation of the colour part of a scattering amplitude.<br/><br/>Paper I introduces the chiralityflow formalism, a new pictorial method used to calculate treelevel helicity amplitudes by drawing lines and connecting them to find spinor inner products, instead of doing algebraic manipulations. This method makes calculations more transparent, and often allows one to go from Feynman diagram to spinor inner products in a single line. Massless QED and QCD are treated in full. <br/> <br/>Paper II extends the chiralityflow formalism of paper I to deal with massive particles, and therefore allows chirality flow to be used for any treelevel Standard Model calculation. <br/><br/>Paper III describes our implementation of chirality flow in massless QED in MadGraph5_aMC@NLO. A speed comparison is made showing up to a factor of 10 increase in evaluation speed. <br/><br/>Paper IV extends the chiralityflow formalism to the oneloop level for any Standard Model calculation, showing the simplifications in the numerator algebra and the tensor reduction.<br/> <br/>Paper V describes an extension to the MadGraph5_aMC@NLO event generator in which the kinematics are calculated using BerendsGiele recursions instead of Feynman diagrams, and the colour matrix can be expanded in the number of colours Nc. The speed of the extension, and the accuracy and precision of the colour expansion are explored.}}, author = {{Lifson, Andrew}}, isbn = {{9789180395892}}, keywords = {{Spinorhelicity formalism; Chiralityflow formalism; Helicity amplitudes; Standard Model; QED; QCD; Optimisations; Colour expansion; Phenomenology; Fysicumarkivet A:2023:Lifson}}, language = {{eng}}, month = {{03}}, publisher = {{MediaTryck Lund}}, school = {{Lund University}}, title = {{The ChiralityFlow Formalism and Optimising Scattering Amplitudes}}, url = {{https://lup.lub.lu.se/search/files/140516910/e_nailingNoSignature_ex_Andrew_without_papers.pdf}}, year = {{2023}}, }