Durham E-Theses

Durham E-Theses Beyond the Standard Model through the Higgs Portal RO, GUNNAR,OYVIND,ISAKSSON How to cite: RO, GUNNAR,OYVIND,ISAKSSON (2016) Beyond the Standard Model through the Higgs Portal, Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/11392/ Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in Durham E-Theses • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full Durham E-Theses policy for further details. Academic Support Oce, Durham University, University Oce, Old Elvet, Durham DH1 3HP e-mail: [email protected] Tel: +44 0191 334 6107 http://etheses.dur.ac.uk Beyond the Standard Model through the Higgs Portal Gunnar Ro A thesis presented for the degree of Doctor of Philosophy Institute for Particle Physics Phenomenology Department of Physics University of Durham England October 2015 Beyond the Standard Model through the Higgs Portal Gunnar Ro Submitted for the degree of Doctor of Philosophy October 2015 Abstract In this thesis, we will investigate the collider phenomenology and cosmological con- sequences of extensions of the Standard Model (SM) with hidden sectors coupled to the SM via a Higgs portal coupling. We will explore how models with classical scale invariance, where all mass scales are dynamically generated, can address the short- comings of the SM without destabilising the Higgs mass. The matter-antimatter asymmetry in the Universe and the tiny masses of active neutrinos are addressed in a U(1)B L extension of the SM with GeV scale right-handed neutrinos. We then − investigate a range of models with both Abelian and non-Abelian gauge groups in the hidden sector to show how we can stabilise the Higgs potential and at the same time provide phenomenologically viable dark matter candidates where all scales in the theory have a common origin. For non-Abelian gauge groups in the hidden sector, we also show that hidden magnetic monopoles can make up a significant fraction of dark matter. The dark matter in this model, which consists of both magnetic monopoles and gauge bosons, has long-range self-interactions which could explain the too-big-to-fail-problem at small scales in the standard cold dark matter scenario. We then study the collider phenomenology of hidden sector models with dark matter candidates through a simplified model framework both at the LHC and at a future 100 TeV collider. Hidden sector extensions of the SM with a Higgs portal coupling give a rich and predictive model building framework for BSM physics without introducing a large hierarchy of scales. Declaration The work in this thesis is based on research carried out at the Institute for Particle Physics Phenomenology, Department of Physics, Durham University, England. No part of this thesis has been submitted elsewhere for any other degree or qualification and it is all my own work unless referenced to the contrary in the text. Chapter2 is based on work appearing in [1,2]. Chapter3 is based on research reported in [1] and Chapter4 is based on [2]. The text of Chapter5 is based on work appearing in [3] and Chapter6 is based on [4]. All these papers were published with Valentin V Khoze, [2] was also written in collaboration with Christopher McCabe and [4] with Michael Spannowsky. Copyright c 2015 by Gunnar Ro. \The copyright of this thesis rests with the author. No quotations from it should be published without the author's prior written consent and information derived from it should be acknowledged". iii Acknowledgements I would like to thank my supervisor, Professor Valentin V Khoze, for all his support and time, without which this thesis would not have be possible. His knowledge of and passion for particle physics and his encouragement have given me a lot motiva- tion and inspiration. It has also been a privilege to work with and learn from my collaborators Christopher McCabe and Michael Spannowsky. My fellow PhD students in the IPPP have been an important source of support during my PhD. They have been good friends, and I have learned a lot from them. Together with all my friends from St John's College, they have made my PhD much more enjoyable. I would also like to thank my parents for their support not only during my PhD, but through my entire life. They have always encouraged me to read, learn and explore while letting me find my own way. Finally, I would especially like to thank Siiri for her constant support and companionship. I am very grateful for everything she has given me. I gratefully acknowledge the financial support from Durham University through the Durham Doctoral Studentship. iv Contents Abstract ii Declaration iii Acknowledgements iv 1 Introduction1 1.1 The Standard Model...........................1 1.1.1 Introduction to the Standard Model...............1 1.1.2 Overview of Experimental Successes...............7 1.2 Beyond the Standard Model.......................8 1.2.1 Dark Matter............................9 1.2.2 Matter-Antimatter Asymmetry................. 18 1.2.3 Stability of the Higgs Potential................. 22 1.2.4 Hierarchy Problem........................ 24 1.3 Outline of the Thesis........................... 30 2 Classical Scale Invariance 33 2.1 Classical Scale Invariance......................... 33 2.2 Coleman-Weinberg Mechanism...................... 35 2.2.1 Effective Action and Potential.................. 36 2.2.2 One Loop Effective Potential for Classically Massless U(1).. 37 2.2.3 Coleman-Weinberg Mechanism and Renormalisation Group Running.............................. 40 2.3 BSM Models with Classical Scale Invariance.............. 41 v Contents vi 2.3.1 Hierarchy Problem in Classically Scale-Invariant Models...................... 41 2.3.2 U(1) CSI Extension of the SM.................. 43 2.3.3 CSI Extensions of the SM.................... 47 2.3.4 Classically Scale-Invariant BSM Physics............ 50 2.3.5 Phenomenology of CSI Models.................. 52 3 Leptogenesis and Neutrino Oscillations in the Classically Scale- Invariant Standard Model with the Higgs Portal 54 3.1 Brief Review of Thermal Field Theory................. 55 3.1.1 Phase Transitions......................... 57 3.2 The B L Coleman-Weinberg Extension of the Standard Model... 58 − 3.3 Neutrino Oscillations and Leptogenesis................. 60 3.3.1 Leptogenesis Triggered by Oscillations of Majorana Neutrinos 60 3.3.2 Leptogenesis in Classically Massless Models.......... 66 3.4 Baryon Asymmetry and Phenomenology................ 70 3.5 Conclusions................................ 79 4 Higgs Vacuum Stability from the Dark Matter Portal 81 4.1 CSI ESM Building and Generation of the EW Scale.......... 82 4.1.1 CSI U(1)CW SM......................... 82 × 4.1.2 CSI U(1)B−L SM........................ 86 × 4.1.3 CSI SU(2)CW SM........................ 87 × 4.1.4 CSI ESM Singlet........................ 88 ⊕ 4.2 RG Evolution............................... 89 4.2.1 Standard Model U(1)CW .................... 89 × 4.2.2 Standard Model U(1)B−L ................... 90 × 4.2.3 Standard Model U(1)B−L Singlet.............. 91 × ⊕ 4.2.4 Standard Model SU(2)CW .................... 92 × 4.2.5 Standard Model SU(2)CW singlet.............. 93 × ⊕ 4.2.6 Initial Conditions and Stability Bounds............. 94 4.3 Higgs Physics: Stability and Phenomenology.............. 95 Contents vii 4.3.1 CSI U(1)CW SM......................... 98 × 4.3.2 CSI U(1)B−L SM........................ 100 × 4.3.3 CSI U(1)B−L SM singlet................... 102 × ⊕ 4.3.4 CSI SU(2)CW SM........................ 102 × 4.3.5 CSI SU(2)CW SM singlet................... 102 × ⊕ 4.4 Dark Matter Physics: Relic Abundance and Constraints....... 104 4.4.1 Vector Dark Matter........................ 105 4.4.2 Singlet Scalar Dark Matter.................... 108 4.4.3 Scalar and Vector Dark Matter................. 111 4.5 Conclusions................................ 114 5 Dark Matter Monopoles, Vectors and Photons 116 5.1 The Model................................. 117 5.1.1 Monopoles............................. 118 5.1.2 Mass-Scale Generation...................... 120 5.1.3 Coleman-Weinberg Mechanism with an Adjoint Scalar.... 121 5.2 Dark Radiation and Neff ......................... 122 5.3 Dark Matter Relic Density........................ 125 5.3.1 Dark Gauge Bosons: Sommerfeld Enhancement and Relic Den- sity................................. 126 5.3.2 Dark Monopoles.......................... 128 5.4 Self-Interacting Dark Matter....................... 138 5.5 Conclusions................................ 142 6 Spectroscopy of Scalar Mediators to Dark Matter at the LHC and at 100 TeV 144 6.1 Introduction................................ 144 6.2 Models................................... 146 6.2.1 The Singlet Mixing Model.................... 147 6.2.2 Generic Higgs-like Scalar Mediator Model........... 150 6.3 Relic Density and Direct Detection Constraints............ 150 Contents viii 6.4 Collider Limits on Scalar Mediators with two Jets and MET at the LHC.................................... 152 6.4.1 Width Effect on Differential Distributions........... 154 6.4.2 Exclusion Limit Reach at the LHC............... 154 6.4.3 Distinguishing Between Models with Different

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