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Exploring New Physics at Low and High Energies Using the Standard Model Effective Field Theory


Wilsch, Felix. Exploring New Physics at Low and High Energies Using the Standard Model Effective Field Theory. 2023, University of Zurich, Faculty of Science.

Abstract

Contents
1 Introduction 1
1.1 The Standard Model of particle physics................................................................................ 3
1.2 Motivations and hints for new physics ................................................................................ 5
1.2.1 Muon anomalous magnetic moment ...................................................................... 6
1.2.2 Lepton-flavor-universality violation......................................................................... ?
1.3 Effective field theories.............................................................................................................. ?
1.4 The Standard Model as an effective theory......................................................................... 10
2 Standard Model effective field theory 12
2.1 Operator bases........................................................................................................................... 12
2.1.1 Redundant operators ................................................................................................. 13
2.1.2 The Warsaw basis....................................................................................................... 19
2.1.3 Further bases.............................................................................................................. 21
2.1.4 Higher-dimensional operators................................................................................... 22
2.2 The size of the Wilson coefficients....................................................................................... 22
2.2.1 Power counting and dimensional analysis............................................................... 22
2.2.2 Loop-level versus tree-level generated operators.................................................. 24
2.3 Constraints and validity.......................................................................................................... 25
2.3.1 Convergence of the 1/A expansion and the EFT validity range....................... 25
2.3.2 Unitarity violation and positivity constraints........................................................ 26
2.3.3 Gauge anomalies and reparametrization invariance............................................... 27
3 Low-energy effective field theory 28
3.1 Electroweak-symmetry breaking in the SMEFT.......................... 29
3.2 Integrating out the weak-scale particles in SMEFT............................................................ 32
4 Global symmetries 34
4.1 Baryon and lepton number ..................................................................................................... 35
4.2 Flavor symmetries.............................................. 35
4.2.1 The U(3)5 symmetry and minimal flavor violation................................................ 36
4.2.2 The U(2)5 symmetry and minimal breaking ......................................................... 40
4.2.3 Employing flavor symmetries for high-pr searches at theLHC............................ 47
4.2.4 Further symmetry options and renormalization groupeffects............................... 50
4.3 Custodial symmetry................................................................................................................ 52
5 One-loop matching of effective field theories 57
5.1 Diagrammatic matching......................................................................................................... 58
5.1.1 Off-shell and on-shell matching................................................................................. 58
5.1.2 Dimensional regularization: the method of regions and 75 in D dimensions . . 61
5.1.3 Example: leptonic dipole operators in the Si leptoquark model....................... 65
5.2 Functional matching................................................................................................................ 68
5.2.1 Supertrace evaluation with the covariant derivative expansion.......................... 70
5.2.2 Example: a toy model with a heavy vectorlike fermion........................................ 75
5.2.3 Example: the Si leptoquark model........................................................................ 78
5.2.4 Matchete: matching effective theories efficiently................................................. 80
5.3 Evanescent operators........................................................................................................... 82
5.3.1 Evanescence-free renormalization schemes........................................................... 83
5.3.2 Evanescent operators in the SMEFT..................................................................... 86
6 Beyond the Standard Model phenomenology: leptonic dipole operators in the SMEFT 92
6.1 The workflow of SMEFT analyses........................................................................................ 92
6.2 Renormalization group evolution ........................................................................................ 95
6.3 Low-energy constraints in the LEFT .................................................................................. 96
6.4 Flavor alignment of the leptonic dipole operators...................................................................100
6.4.1 Dynamical alignment mechanisms............................................................................... 103
6.4.2 Alignment through flavor symmetries......................................................................... 104
6.4.3 Alignment in an explicit new-physics model ............................................................106
7 Drell-Yan tails in the SMEFT 109
7.1 Drell-Yan tails beyond the Standard Model.............................................................................Ill
7.1.1 General form-factor decomposition.............................................................................112
7.1.2 Matching form factors to new-physics models.........................................................114
7.1.3 Cross-section calculation ............................................................................................ 120
7.1.4 Collider observables......................................................................................................122
7.1.5 HighPT: high-py tails...................................................................................................126
7.2 Phenomenological analyses......................................................................................................127
7.2.1 Single parameter fits...................................................................................................... 127
7.2.2 Lepton-flavor violation in a leptoquark model .........................................................131
7.2.3 Drell-Yan tails in light of the Rd^i anomalies.........................................................132
7.2.4 Implications of the quark-flavor alignment............................................................... 140
7.3 EFT validity and higher-dimensional operators......................................................................141
7.4 Confronting the vector leptoquark hypothesis with pp -> tt and b —> cru measurementsl50
7.4.1 Flavor structure of the Ui leptoquark model............................................................151
7.4.2 Low-energy analysis...................................................................................................... 155
7.4.3 High-energy analysis...................................................................................................... 157
8 Conclusion 165
A Matchete 168
A.l Defining a model..........................................................................................................................168
A.2 Simplification of the EFT operator basis............................................................................... 171
A.3 The vectorlike fermion toy model in Matchete......................................................................174
A. 4 Matching the Si leptoquark model to the SMEFT............................................................... 176
B HighPT 182
B. l The full flavor likelihood for the d < 8 SMEFT......................................................................183
B.2 Analyzing lepton-flavor violation in leptoquarkmodels..................... 186
B.3 Determining the EFT validity for leptoquark models....................... 187
Scientific publications 189
Acknowledgments 190
Bibliography igi

Abstract

Contents
1 Introduction 1
1.1 The Standard Model of particle physics................................................................................ 3
1.2 Motivations and hints for new physics ................................................................................ 5
1.2.1 Muon anomalous magnetic moment ...................................................................... 6
1.2.2 Lepton-flavor-universality violation......................................................................... ?
1.3 Effective field theories.............................................................................................................. ?
1.4 The Standard Model as an effective theory......................................................................... 10
2 Standard Model effective field theory 12
2.1 Operator bases........................................................................................................................... 12
2.1.1 Redundant operators ................................................................................................. 13
2.1.2 The Warsaw basis....................................................................................................... 19
2.1.3 Further bases.............................................................................................................. 21
2.1.4 Higher-dimensional operators................................................................................... 22
2.2 The size of the Wilson coefficients....................................................................................... 22
2.2.1 Power counting and dimensional analysis............................................................... 22
2.2.2 Loop-level versus tree-level generated operators.................................................. 24
2.3 Constraints and validity.......................................................................................................... 25
2.3.1 Convergence of the 1/A expansion and the EFT validity range....................... 25
2.3.2 Unitarity violation and positivity constraints........................................................ 26
2.3.3 Gauge anomalies and reparametrization invariance............................................... 27
3 Low-energy effective field theory 28
3.1 Electroweak-symmetry breaking in the SMEFT.......................... 29
3.2 Integrating out the weak-scale particles in SMEFT............................................................ 32
4 Global symmetries 34
4.1 Baryon and lepton number ..................................................................................................... 35
4.2 Flavor symmetries.............................................. 35
4.2.1 The U(3)5 symmetry and minimal flavor violation................................................ 36
4.2.2 The U(2)5 symmetry and minimal breaking ......................................................... 40
4.2.3 Employing flavor symmetries for high-pr searches at theLHC............................ 47
4.2.4 Further symmetry options and renormalization groupeffects............................... 50
4.3 Custodial symmetry................................................................................................................ 52
5 One-loop matching of effective field theories 57
5.1 Diagrammatic matching......................................................................................................... 58
5.1.1 Off-shell and on-shell matching................................................................................. 58
5.1.2 Dimensional regularization: the method of regions and 75 in D dimensions . . 61
5.1.3 Example: leptonic dipole operators in the Si leptoquark model....................... 65
5.2 Functional matching................................................................................................................ 68
5.2.1 Supertrace evaluation with the covariant derivative expansion.......................... 70
5.2.2 Example: a toy model with a heavy vectorlike fermion........................................ 75
5.2.3 Example: the Si leptoquark model........................................................................ 78
5.2.4 Matchete: matching effective theories efficiently................................................. 80
5.3 Evanescent operators........................................................................................................... 82
5.3.1 Evanescence-free renormalization schemes........................................................... 83
5.3.2 Evanescent operators in the SMEFT..................................................................... 86
6 Beyond the Standard Model phenomenology: leptonic dipole operators in the SMEFT 92
6.1 The workflow of SMEFT analyses........................................................................................ 92
6.2 Renormalization group evolution ........................................................................................ 95
6.3 Low-energy constraints in the LEFT .................................................................................. 96
6.4 Flavor alignment of the leptonic dipole operators...................................................................100
6.4.1 Dynamical alignment mechanisms............................................................................... 103
6.4.2 Alignment through flavor symmetries......................................................................... 104
6.4.3 Alignment in an explicit new-physics model ............................................................106
7 Drell-Yan tails in the SMEFT 109
7.1 Drell-Yan tails beyond the Standard Model.............................................................................Ill
7.1.1 General form-factor decomposition.............................................................................112
7.1.2 Matching form factors to new-physics models.........................................................114
7.1.3 Cross-section calculation ............................................................................................ 120
7.1.4 Collider observables......................................................................................................122
7.1.5 HighPT: high-py tails...................................................................................................126
7.2 Phenomenological analyses......................................................................................................127
7.2.1 Single parameter fits...................................................................................................... 127
7.2.2 Lepton-flavor violation in a leptoquark model .........................................................131
7.2.3 Drell-Yan tails in light of the Rd^i anomalies.........................................................132
7.2.4 Implications of the quark-flavor alignment............................................................... 140
7.3 EFT validity and higher-dimensional operators......................................................................141
7.4 Confronting the vector leptoquark hypothesis with pp -> tt and b —> cru measurementsl50
7.4.1 Flavor structure of the Ui leptoquark model............................................................151
7.4.2 Low-energy analysis...................................................................................................... 155
7.4.3 High-energy analysis...................................................................................................... 157
8 Conclusion 165
A Matchete 168
A.l Defining a model..........................................................................................................................168
A.2 Simplification of the EFT operator basis............................................................................... 171
A.3 The vectorlike fermion toy model in Matchete......................................................................174
A. 4 Matching the Si leptoquark model to the SMEFT............................................................... 176
B HighPT 182
B. l The full flavor likelihood for the d < 8 SMEFT......................................................................183
B.2 Analyzing lepton-flavor violation in leptoquarkmodels..................... 186
B.3 Determining the EFT validity for leptoquark models....................... 187
Scientific publications 189
Acknowledgments 190
Bibliography igi

Statistics

Additional indexing

Item Type:Dissertation (monographical)
Referees:Isidori G, Grazzini Massimiliano, Pozzorini S
Communities & Collections:07 Faculty of Science > Physics Institute
UZH Dissertations
Dewey Decimal Classification:530 Physics
Language:English
Date:2023
Deposited On:19 Jan 2024 14:10
Last Modified:19 Jan 2024 14:10
Number of Pages:214
OA Status:Closed
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