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Topics in model building and phenomenology beyond the standard model by Johannes Heinonen This thesis/dissertation document has been electronically approved by the following individuals: Csaki,Csaba (Chairperson) Perelstein,Maxim (Minor Member) Wittich,Peter (Minor Member) TOPICS IN MODEL BUILDING AND PHENOMENOLOGY BEYOND THE STANDARD MODEL A Dissertation Presented to the Faculty of the Graduate School of Cornell University in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy by Johannes Heinonen August 2010 c 2010 Johannes Heinonen ALL RIGHTS RESERVED TOPICS IN MODEL BUILDING AND PHENOMENOLOGY BEYOND THE STANDARD MODEL Johannes Heinonen, Ph.D. Cornell University 2010 The origin of electroweak symmetry breaking is about to be explored by the LHC, which has started taking high-energy data this spring. In this thesis, we explore several theories proposed to extend the standard mode (SM) of particle physics and their phenomenological consequences for the LHC. First we show that there exists an anomaly-free Littlest Higgs model with an exact T-parity by explicitly constructing such a weakly coupled UV completion. We show that an extended gauge and fermion sector is needed and estimate the impact of new TeV scale particles on electroweak precision observables. We also give both a supersymmetric and a five-dimensional solution to the remaining hierarchy problem up to the Planck scale. We then examine the feasibility of distinguishing a fermionic partner of the SM gluon from a bosonic one at the LHC. We focus on the case when all allowed tree-level decays of this partner are 3-body decays into two jets and a massive, invisible particle. We show that the dijet invariant mass distributions differ sig- nificantly in the two models, as long as the decaying particle is substantially more massive than its invisible daughter. Finally we analyze the theory and phenomenology of anomalous global chi- ral symmetries in the presence of an extra dimension. We propose a simple extension of the standard model in 5D whose signatures closely resemble those of supersymmetry with gauge mediation. BIOGRAPHICAL SKETCH Johannes Heinonen was born in Hamburg, Germany, on September 8 1979 as the first child of his father Rauno, an engineer, and his mother Gudrun, a medical technical assistant and homemaker. Together with his younger brother Karl Henrik, he spent his childhood and adolescence in his hometown of Oering, Germany. He graduated at top of his class, receiving his “Abitur” degree from the Dahlmannschule in Bad Segeberg in 1998. After completing 13 month of obligatory alternative service in a hospi- tal, he enrolled at the Ruprecht-Karls University of Heidelberg and started his training as a physicist in the fall of 1999. In the academic year 2002/03 he spent an exchange year at Cornell Univer- sity. Back in Heidelberg, he specialized in theoretical physics and graduated in July 2005 with a “Diplom” thesis on the “Renormalization flow in the Hub- bard model” under the supervision of Prof. Christof Wetterich. From 2000 until the completion of his degree in 2005 he was supported by the German National Merit Foundation (“Studienstiftung des Deutschen Volkes”). In 2005, he returned to Cornell University to pursue a Ph.D. in theoretical particle physics under the supervision of Prof. Csaba Csaki.´ He worked on building models of electroweak symmetry breaking and exploring their phe- nomenology. After receiving his degree, he will join the high energy theory group at the University of Chicago as postdoctoral research associate with a McCormick fellowship. iii Rauzille. iv ACKNOWLEDGEMENTS I wish to thank my parents Gudrun and Rauno for always supporting me and encouraging me to learn about the world, and my brother Kalle and his girl- friend Anni for being there for me and being the best little brother I can imagine. I also want to thank my girlfriend Natalie for always loving me. I am very grateful to my advisor Csaba Csaki´ for being a great physicist, good teacher and even better advisor. I will miss the discussions, not only about physics (I might even miss teaching E&M). I want to show my gratitude to my collaborators Maxim Perelstein, Jay Hubisz, Yuri Shirman and Christian Speth- mann. I have learned a lot from all the discussions with each of you. I also thank my third committee member Peter Wittich. In addition, I thank my advisor and the KITP in Santa Barbara for beautiful four month in Southern California, all the students and professors who made TASI 2008 unforgettable and Seongchan Park for showing me Tokyo. I am indebted to my colleague and coworkers at the Cornell physics de- partment and the particle physics group at Newman Lab, professors, postdocs, fellow students, secretaries and staff alike, for creating a very friendly and pro- ductive work environment. In particular, I want to thank Andi Weiler and Flip Tanedo for enjoyable chats and discussions. Finally, I want to thank my many friends in Ithaca for the fun times, good (and bad) soccer games and the distraction they provided when needed. You made it a joy to live here. Especially, I want to mention Kaden Hazzerd, At- tila Bergou, Dan Goldbaum, David Bernat and Stefan Baur for being the best friends. Lastly, my apologies to everybody I forgot. You all would have been de- served to be in here. I thank you for everything. v TABLE OF CONTENTS Biographical Sketch . iii Dedication . iv Acknowledgements . .v Table of Contents . vi List of Tables . viii List of Figures . ix 1 Introduction 1 1.1 History and the big picture . .1 1.2 The Standard Model of Particle Physics and Electroweak Symme- try Breaking . .2 1.3 The Hierarchy Problem . .6 1.4 Little Higgs models and collective symmetry breaking . 11 1.5 Distinguishing theories at the LHC: Determining the spin of stan- dard model partners . 13 1.6 Mimicking characteristic gauge-mediated SUSY breaking with a flat extra dimension . 15 2 A Weakly Coupled Ultraviolet Completion of the Littlest Higgs with T-parity 17 2.1 Motivation . 17 2.2 Introduction . 17 2.3 The Scalar/Gauge Sector for SU(5) × SU(2) × U(1) ........ 21 2.4 The Fermion Sector . 30 2.4.1 The SM fermions . 30 2.4.2 The Yukawa couplings . 33 2.4.3 A non SU(5) invariant theory . 36 2.5 Anomaly Cancellation . 36 2.5.1 Gauge anomalies . 37 2.5.2 T-parity anomalies . 40 2.6 Solutions to the Large Hierarchy Problem . 42 2.6.1 A supersymmetric version . 42 2.6.2 A five-dimensional version . 46 2.7 Constraints from the Weinberg Angle, Precision Electroweak Fits, and Dark Matter . 52 2.8 Little Higgs Mechanism in the Linear Sigma Model . 56 2.9 Conclusions and Outlook . 59 3 Testing Gluino Spin with Three-Body Decays 62 3.1 Motivation . 62 3.2 Introduction . 62 3.3 The Setup and Kinematics . 66 vi 3.4 Chiral Structure in Three-Body Decays: a Toy Model . 69 3.5 Model Discrimination: SUSY Versus UED . 70 3.5.1 Gluino decay in the MSSM . 71 3.5.2 Decay of the gluon KK mode in the UED model . 73 3.5.3 Model Discrimination: a Simplified Analysis . 75 3.5.4 Model Discrimination: a Test-Case Monte Carlo Study . 80 3.6 Conclusions . 84 4 Odd Decays from Even Anomalies: Gauge Mediation Signatures With- out SUSY 86 4.1 Motivation . 86 4.2 Introduction . 86 4.3 Basic Setup . 90 4.4 The Gauged Peccei-Quinn Symmetry . 92 4.4.1 Residual Gauge Transformations . 93 4.4.2 Tree level interactions of the B5 zero mode . 95 4.4.3 Spontaneous Breaking in the Bulk . 97 4.4.4 U(1)PQ Anomalies . 102 4.5 B5 Phenomenology . 108 4.5.1 Decays of the NLKP . 109 4.5.2 B5 Dark Matter . 111 4.5.3 Electroweak precision and direct collider constraints . 116 4.6 Conclusions . 117 A Testing Gluino Spin with Three-Body Decays 119 A.1 Polarization Analysis of the UED case . 119 A.2 The Kullback-Leibler distance . 121 B Odd Decays from Even Anomalies: Gauge Mediation Signatures With- out SUSY 123 B.1 The Goldstone Wave Functions with a Bulk Higgs VEV . 123 Bibliography 125 vii LIST OF TABLES 1.1 SM gauge charge assignments . .4 2.1 Scalar fields and their gauge charge assignments . 25 2.2 Fermion fields required to incorporate one generation of SM quarks, and their gauge charge assignments . 31 2.3 The complete fermion sector and gauge charge assignments . 38 2.4 The chiral matter content of the anomaly-free model. 39 viii LIST OF FIGURES 1.1 Loop diagrams contributing to the Higgs mass . .7 1.2 ∆χ global fit of the Higgs mass to precision data (from the GFit- ter group) . .8 2.1 Low-energy gauge symmetries and field content . 28 2.2 Complete setup of the five-dimensional model . 47 2.3 Contributions to the effective gauge coupling at low energies . 57 2.4 Contributions to the effective top coupling at low energies. 59 3.1 Dijet invariant mass distributions for two toy models . 68 3.2 Helicity considrations in a three-body decay . 70 3.3 The Feynman diagrams for gluino three-body decay in the MSSM 71 3.4 The Feynman diagrams for the KK gluon three-body decay in UED 73 3.5 Dijet invariant mass distribution for UED and MSSM, compared to pure phase space . 75 3.6 Number of events required to distinguish MSSM and UED, as a function of mL and mR ......................... 78 3.7 Number of events required to distinguish MSSM and UED, as a function of mB=mA ..........................
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