Dark Matter and Collider Physics
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Beyond the Standard Model: Dark Matter and Collider Physics DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Russell Colburn, B.S. Graduate Program in Physics The Ohio State University 2017 Dissertation Committee: Linda Carpenter, Advisor Chris Hill Annika Peter Stuart Raby c Copyright by Russell Colburn 2017 Abstract In this work we analyze dark matter annihilation in dwarf galaxies as well as scenarios of new physics relevant to current and future runs at the LHC. Our work with dark matter focuses on the implications for dark matter models from observations from the Fermi-LAT telescope while our work on LHC physics offers an explanation for the 750 GeV diphoton excess as well as a new possible decay channels of a scalar color octet. Using gamma-ray observations of dwarf spheroidal galaxies from the pass-7 Fermi-LAT experiment, we discuss the implications on dark matter models where dark matter annihi- lates to multiple final state configurations: where dark matter annihilates to third generation fermions and Standard Model vector bosons. We present limits in various slices of model pa- rameter space both as limits on dark matter mass and in the context of effective operators. We visualize our bounds for models with multiple final state annihilations by projecting parameter space constraints onto triangles, a technique familiar from collider physics; and we compare our bounds to collider limits on equivalent models. We extend this analysis to the pass-8 Fermi-LAT observations of dwarfs by using a more robust \stacked" analysis using a joint-likelihood analysis to combine multiple dwarf galaxies. We once again look at dark matter annihilations to multiple final-state fermions and interpret these results in the context of the most popular simplified models, including those with s- and t-channel dark matter annihilation through scalar and vector mediators. Additionally, we compare our simplified model results to those of effective field theory contact interactions in the high-mass limit. We propose that the sbino, the scalar partner of a Dirac bino can explain the 750 GeV diphoton excess observed by the ATLAS and CMS collaborations. We analyze the minimal completion of the effective operator model in which the sbino couples to pairs of gauge bosons through loops of heavy sfermions, with the sfermion-bino coupling originating from scalar potential D-terms. We find that the sbino model may be fit the 750 GeV excess by considering gluon fusion processes with decay to diphotons. Finally, we explore the phenomenology of scalar fields in the adjoint representation of SM gauge groups at the LHC. We write a general set of dimension 5 effective operators in which SM adjoint scalars couple to pairs of standard model bosons. Using these effective ii operators, we explore new possible decay channels of a scalar color octet into a gluon and a Z boson, another gluon, or a photon. We recast several analyses from Run I of the LHC to find constraints on an a scalar octet decaying into these channels, and we project the discovery potential of color octets in our gluon+photon channel for the 14 TeV run of LHC. iii Acknowledgments There are many people to whom I owe sincere gratitude for their contributions to my work and education. I would first like to thank my advisor, Linda Carpenter, for her patience, mentorship, and guidance throughout my graduate career. I would also like to thank to Stuart Raby for providing opportunities to enrich my knowledge of particle physics by leading multiple reading courses in his spare time as well as teaching many courses on the subject. During the course of my research, I had the privilege of collaborating with Jesi Goodman and Tim Linden on various projects. Over the years, Jesi has also provided advice and knowledge making her akin to a second advisor in my mind. I have been lucky to have Chris Svoboda, Brian Daintan, Sushant More, Khalida Hen- dricks, and Humberto Gilmer as my office mates over the years. They have provided much assistance over the years from discussing physics to helping finding bugs in codes to helping maintain sanity. I would like to thank members of the OSU high energy and nuclear physics groups who have been more than willing to discuss physics and willing to assist with various issues over the years: Archana Anandakrishnan, Chuck Bryant, Zijie Poh, Shaun Hampton, Hong Zhang, Bowen Shi, Alex Dyhdalo, Dennis Bazow, Sarah Wesolowski, Heiko Hergert, Sebastion Kronig, Gojko Vujanovic, Mauricio Martinez Guerrero, Kenny Ng, Shirley Li, Hudson Smith, Abhishek Mohapatra, and Evan Johnson. Finally I would like to thank my family and friends who have provided support and encouragement over the course of my entire educational career. iv Vita October 29, 1988 . .Born|Danville, IL May, 2012 . B.S., Michigan State University, East Lansing, MI Publications Indirect Detection Constraints on s- and t-channel Simplified Models of Dark Matter. Linda M. Carpenter, Russell Colburn, Jessica Goodman, and Tim Linden. Phys. Rev. D94 (2016) 5, 055027, arXiv:1606.04138. Supersoft SUSY Models and the 750 GeV Diphoton Excess, Beyond Effective Operators. Linda M. Carpenter, Russell Colburn, Jessica Goodman. Phys. Rev. D94 (2016) 1, 015016, arXiv:1512.06107. Searching for Standard Model Adjoint Scalars with Diboson Resonance Signatures. Linda M. Carpenter, Russell Colburn, JHEP 1512 (2015) 151, arXiv:1509.07869. Indirect Detection Constraints on the Model Space of Dark Matter Effective Theories. Linda M. Carpenter, Russell Colburn, Jessica Goodman. Phys. Rev. D92 (2015) 9, 095011, arXiv:1506.08841. Fields of Study Major Field: Physics v Table of Contents Page Abstract........................................... ii Acknowledgments..................................... iv Vita.............................................v List of Figures ...................................... viii List of Tables ....................................... xii 1 Introduction ..................................... 1 1.1 The Standard Model............................... 2 1.2 Problems with the Standard Model....................... 6 1.2.1 Dark Matter ............................... 6 1.2.2 Hierarchy Problem............................ 10 1.3 SUSY ....................................... 10 1.3.1 Dirac Gaugino SUSY Breaking..................... 14 1.4 Effective Field Theories ............................. 15 1.4.1 Example: Fermi Theory of Weak Interactions............. 17 1.4.2 EFTs in the Search for Dark Matter.................. 18 1.5 Synopsis...................................... 19 Chapters 2 Indirect Detection Constraints on the Model Space of Dark Matter Effective Theories .................................. 21 2.1 Introduction.................................... 21 2.2 Indirect Detection from Dwarf Spheroidal Galaxies.............. 22 2.3 Models with Independent Annihilation Channels ............... 24 2.3.1 Fixed Annihilation Rate......................... 25 2.3.2 Constraints for 4 Independent Channels................ 32 2.4 Constraints in Models with Interfering Channels ............... 34 2.4.1 Limits of the EFT and Collider Constraints.............. 40 2.5 Conclusions.................................... 42 3 Indirect Detection Constraints on s- and t-Channel Simplified Models of Dark Matter .................................... 44 3.1 Introduction.................................... 44 3.2 Indirect Detection from Dwarf Spheroidal Galaxies.............. 46 vi 3.2.1 γ-ray Analyses of the Population of Dwarf Spheroidal Galaxies . 47 3.3 Generic DM Mass Bounds............................ 50 3.4 EFT completions................................. 53 3.5 Simplified Models................................. 55 3.5.1 Vector mediator ............................. 56 3.5.2 T-channel mediator ........................... 61 3.6 Conclusions.................................... 66 4 Supersoft SUSY Models and the 750 GeV Diphoton Excess, Beyond Effective Operators ................................. 68 4.1 Introduction.................................... 68 4.2 Operators in Dirac Gauginos Models...................... 70 4.3 UV completions.................................. 71 4.4 Tree Level Singlet Decays and Collider Bounds................ 73 4.5 Production and Loop Level Decays....................... 75 4.6 Stability and Electroweak Constraints ..................... 81 4.7 Conclusions.................................... 83 5 Searching for Standard Model Adjoint Scalars with Diboson Resonance Signatures ....................................... 86 5.1 Introduction.................................... 86 5.2 Effective Operators................................ 87 5.3 High Energy Models............................... 89 5.4 Production and Decay of Scalar Adjoints ................... 91 5.5 Current Limits .................................. 94 5.5.1 The Jet + γ Channel .......................... 95 5.5.2 Dijet Channel............................... 96 5.5.3 The Monojet Channel.......................... 97 5.5.4 Heavy Boson plus Jet Channel ..................... 99 5.5.5 Combined Results ............................ 102 5.6 Projection for LHC 14.............................. 105 5.7 Biadjoint Operators ............................... 107 5.8 Conclusions.................................... 108 6 Conclusion ...................................... 110 Bibliography ....................................... 112 vii List of Figures Figure Page 1.1 The comoving number density, Y , and the resulting