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Early Universe Cosmology and the Matter-Antimatter Asymmetry Minerva Access is the Institutional Repository of The University of Melbourne Author/s: BALDES, IASON Title: Early universe cosmology and the matter-antimatter asymmetry Date: 2015 Persistent Link: http://hdl.handle.net/11343/55205 File Description: Early universe cosmology and the matter-antimatter asymmetry The University of Melbourne Doctoral Thesis Early Universe Cosmology and the Matter-Antimatter Asymmetry Supervisors: Author: Assoc. Prof. Nicole F. Bell Iason Baldes and Prof. Raymond R. Volkas Submitted in total fulfilment of the requirements of the degree of Doctor of Philosophy in the School of Physics The University of Melbourne July 2015 Produced on archival quality paper Early Universe Cosmology and the Matter-Antimatter Asymmetry by Iason Baldes UNIVERSITY OF MELBOURNE Faculty of Science School of Physics Doctor of Philosophy Abstract The universe is made up almost exclusively of matter and not antimatter. Having made this observation, what can we say about the conditions of the first second of the universe after the big bang? The high temperatures present in that epoch allow the copious production of massive particles. These particles can create the matter- antimatter asymmetry which is thought to arise dynamically in the early universe. We first discuss a rarely studied way of generating the matter-antimatter asymmetry using collisions. We then investigate open questions in particle physics such as neutrino masses and the identity of dark matter in light of these considerations. Observable effects in particle colliders or proton decay are also investigated. Chapter 1 provides an introduction to the baryon asymmetry of the universe. We begin by outlining the observational evidence showing that the universe has a baryon asym- metry. We then review the Sakharov conditions | the conditions required to generate a baryon asymmetry dynamically. We discuss various baryogenesis mechanisms, proposed in the literature, for generating the baryon asymmetry of the universe. We also intro- duce the Boltzmann equations which are used for calculating the asymmetry produced in standard model extensions. Possible related issues of the neutrino masses and dark matter density are also touched upon. In Chapter 2 we consider the principles behind generating particle-antiparticle asym- metries using annihilations. This mechanism has not been extensively studied in the literature. In providing a general framework for generating asymmetries with annihila- tions we hope to point out the challenges and possibilities for further research in this area. In Chapter 3 we apply what we have learned about asymmetry generation from anni- hilations to study a neutron portal baryogenesis scenario. We include the charge parity violating annihilations in our calculations. We discuss the formulation of the Boltzmann ii equations and solve these equations numerically. We show the annihilations play the dominant role over the decays in generating the baryon asymmetry in this scenario. In Chapter 4 we change tack slightly and study the cosmological implications of two radiative inverse seesaw models. These models can explain the neutrino masses inferred from neutrino oscillations. They violate lepton number and can interfere with | or perhaps generate | the baryon asymmetry in the early universe. These models contain dark matter candidates and we discuss the phenomenology thereof. We discuss limits from colliders and other experiments. In Chapter 5 we study extensions of the standard model involving exotic scalars. These scalars violate the baryon number and can therefore change the baryon asymmetry. We discuss limits from nucleon stability and cosmology. We also discuss the LHC phe- nomenology of such particles. We then briefly conclude. Declaration of Authorship This is to certify that: i. the thesis comprises only my original work towards the PhD except where indicated in the Preface, ii. due acknowledgement has been made in the text to all other material used, iii. the thesis is fewer than 100 000 words in length, exclusive of tables, maps, bibli- ographies and appendices. Signed: Date: iii Preface This thesis comprises six main chapters. Chapter 1 is an original literature review. Chapter 2 is based on publication 1. Chapter 3 is based on publication 2. Chapter 4 is based on publication 3. Chapter 5 is based on publication 4. Chapter 6 is the conclusion. These publications were done in collaboration with Nicole F. Bell (publications 1{4), Alexander Millar (Publication 2), Kalliopi Petraki (publications 1{3) and Raymond R. Volkas (publications 1{4). While Nicole F. Bell, Kalliopi Petraki and Raymond R. Volkas are responsible for the original inspiration for these projetcs, all calculations, results and analyses presented within this thesis are my own work unless stated otherwise. Chapter 5, based on publication 4, deals with baryon number violating scalar particles. Such particles were also the topic of my MSc thesis. The following substantial additions and improvements have been made: (i) inclusion of an estimate of the loop integrals in the nucleon stability bounds, (ii) inclusion of the Boltzmann suppressed inverse decay rate which can have a substantial effect on the washout bound, (iii) corrected and updated calculation of the resonant production of diquarks at the LHC. Publications 1. I. Baldes, N. F. Bell, K. Petraki, R. R. Volkas, \Particle-antiparticle asymmetries from annihilations," Phys. Rev. Lett. 113 (2014) 181601, arXiv:1407.4566. 2. I. Baldes, N. F. Bell, A. Millar, K. Petraki, R. R. Volkas, \The role of CP violating scatterings in baryogenesis | case study of the neutron portal," JCAP 1411 (2014) 041, arXiv:1410.0108. 3. I. Baldes, N. F. Bell, K. Petraki, R. R. Volkas, \Two radiative inverse seesaw mod- els, dark matter, and baryogenesis," JCAP 1307 (2013) 029, arXiv:1304.6162. 4. I. Baldes, N. F. Bell, R. R. Volkas, \Baryon Number Violating Scalar Diquarks at the LHC," Phys. Rev. D 84 (2011) 115019, arXiv:1110.4450. Acknowledgements First of all, I thank my supervisors, Nicole Bell and Ray Volkas, for their support over many years during my MSc and PhD. Without their patience, belief in me and generosity with their time, I could not have completed this work. I thank Kalliopi Petraki for her patience and help during our collaboration. I also thank my parents for their ongoing support and instilling in me a curiousity for intellectual pursuits. I thank Vesna for her support, patience, encouragement and unwavering enthusiasm for physics and science. I should also mention the engaging and friendly atmosphere in CoEPP. Discussion with other students and postdocs helped me a great deal. In particular I would like to acknowledge Ahmad Galea, Benjamin Callen, Peter Cox, Stephen Lonsdale, Timothy Trott and Rebecca Leane for our discussions. Finally I especially thank Alex Millar for teaching me the Cutkosky rules. v Contents Abstract i Declaration of Authorship iii Preface iv Publications iv Acknowledgements v Contents vi List of Figures ix Abbreviations xi 1 Introduction to the baryon asymmetry 1 1.1 Evidence for the baryon asymmetry . 1 1.1.1 The discovery of antimatter . 1 1.1.2 Problems with a baryon symmetric universe . 2 1.1.3 Big bang nucleosynthesis . 4 1.1.4 Cosmic microwave background . 4 1.2 Baryogenesis mechanisms . 6 1.2.1 Initial conditions . 6 1.2.2 Sakharov conditions . 6 1.2.3 Electroweak baryogenesis . 7 1.2.4 Leptogenesis . 9 1.2.5 Affleck-Dine baryogenesis . 13 1.2.6 Spontaneous baryogenesis . 13 1.2.7 Asymmetric Dark Matter . 14 1.2.8 Leptogenesis via collisions . 15 1.2.9 Baryogenesis from dark matter annihilation . 18 1.3 Boltzmann equations . 21 1.3.1 Thermodynamics and the collision integral . 21 vi Contents vii 1.3.2 S Matrix Unitarity and Time Reversal . 25 − 1.4 Conclusion . 28 2 Particle-antiparticle asymmetries from annihilations 30 2.1 Introduction . 30 2.2 Toy model . 31 2.3 Boltzmann equations . 38 2.4 Conclusion . 42 3 The role of CP violating scatterings in baryogenesis | case study of the neutron portal 44 3.1 Introduction . 44 3.2 Neutron portal . 46 3.2.1 Lagrangian . 46 3.2.2 Decays . 47 3.2.3 Scatterings . 49 3.3 Boltzmann equations . 51 3.3.1 Differential equations . 51 3.3.2 Chemical potentials . 52 3.3.3 Numerical solutions . 55 3.4 Constraints . 59 3.5 Conclusion . 60 4 The baryon asymmetry and dark matter in radiative inverse seesaw models 62 4.1 Introduction . 62 4.2 The inverse seesaw mechanism . 63 4.2.1 The generic mass matrix . 63 4.2.2 ISS and baryogenesis . 65 4.3 Law/McDonald radiative inverse seesaw . 67 4.3.1 Review of the model . 67 4.3.2 Constraints from BAU washout . 69 4.3.3 Dark Matter . 73 4.3.4 Concluding remarks on the Law/McDonald model . 82 4.4 Ma radiative inverse seesaw model . 83 4.4.1 Review of the model . 83 4.4.2 Constraints from BAU washout . 86 4.4.3 Resonant leptogenesis . 89 4.4.4 The ρ parameter . 90 4.4.5 LHC searches . 92 4.4.6 Dark matter . 94 4.4.7 Concluding remarks on the Ma model . 96 4.5 Conclusion . 97 5 The baryon asymmetry, nucleon stability and LHC searches for scalar diquarks 98 5.1 Introduction . 98 5.2 Baryon number violating scalars . 99 Contents viii 5.2.1 A catalogue of models . 99 5.2.2 The particular model: σ3:3σ3:3σ7:2 . 104 5.3 Washout of baryogenesis . 107 5.3.1 High Temperature Baryogenesis . 107 5.3.2 Low temperature baryogenesis . 108 5.4 Collider searches . 110 5.4.1 Approximately B conserving regime . 111 5.4.2 B violating regime . 112 5.5 Discussion . 114 5.6 Conclusion . 115 6 Conclusion 116 A Toy model cross sections and CP violation 119 A.1 Toy model cross sections and CP violation . 119 A.2 Thermally averaged decay rate . 123 B Neutron portal unitarity, cross sections, decay rates and CP violation124 B.1 Unitarity constraint for multiple quark generations .
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