Florida State University Libraries Electronic Theses, Treatises and Dissertations The Graduate School 2013 Topics in Physics Beyond the Standard Model Karoline Köpp Follow this and additional works at the FSU Digital Library. For more information, please contact [email protected] THE FLORIDA STATE UNIVERSITY COLLEGE OF ARTS AND SCIENCES TOPICS IN PHYSICS BEYOND THE STANDARD MODEL By KAROLINE KOPP¨ A Dissertation submitted to the Department of Physics in partial fulfillment of the requirements for the degree of Doctor of Philosophy Degree Awarded: Spring Semester, 2013 Karoline K¨opp defended this dissertation on March 6, 2013. The members of the supervisory committee were: Takemichi Okui Professor Directing Thesis Ettore Aldrovandi University Representative Laura Reina Committee Member Todd Adams Committee Member Christopher Gerardy Committee Member The Graduate School has verified and approved the above-named committee members, and certifies that the dissertation has been approved in accordance with the university requirements. ii To Dominik. iii ACKNOWLEDGMENTS Many readers will likely end their reading of this thesis after the preface. While this should call for particular care and effort in writing this section, I have joined the tradition of delaying it to the very last moment. So I apologize to anybody who I might fail to acknowledge and blame it on sleep deprivation. Working on my Ph.D. thesis has been a rollercoaster of fun, frustration, concentration and challenge. And now, it is (almost) done. This work would not have been possible without my advisor Takemichi Okui. His guidance and insights and many long discussion sessions were indispensable along the way. His determination to cut to the core questions of a problem have hopefully permanently influenced my own approach to do research. I am thankful to the members of my committee Laura Reina, Todd Adams, Christopher Gerardy and Ettore Aldrovandi for their input and encouragement. Thanks to the PhD students and Postdocs at FSU for many discussions about physics and beyond and for providing a friendly and helpful environment. And to Kathy for always having a friendly word and for her untiring support in navigating the university bureaucracy. I want to thank Seth, Joe, Chris, Prerit, Nathalie and Nobuo for their friendship and for providing many fun distractions from work. I would not want to imagine these past three years without them and deeply appreciate all the help I received from them along the way, ranging from reviving my computer to emergency ice cream. My gratitude also goes to the friends I met at TASI. Also, I thank Beate for her loyal friendship and for making me look forward to Mondays. The support of my parents is deeply appreciated. They always were on my side, even from a continent away. Thanks also to Fidi, Basti and Tine for their encouragement and patience. I feel blessed beyond words for Tom’s unwaivering support and love throughout every minute of every day and thank him in particular for his help in finishing and proofreading this dissertation. iv TABLE OF CONTENTS ListofTables....................................... vii ListofFigures ...................................... viii Abstract........................................... xi 1 Introduction 1 2 Effective field theories 5 2.1 Effective field theories are everywhere . 5 2.2 Basics of effective field theory . 7 2.2.1 Relevant, marginal and irrelevant operators . 7 2.2.2 Matching of effective field theories . 8 2.3 Example: heavy quark effective theory . 9 2.3.1 TheHQETlagrangian.......................... 10 2.3.2 Reparameterization Invariance . 11 2.3.3 ApplicationsofHQET.......................... 12 3 Effective theory for a heavy Majorana fermion 15 3.1 Introduction.................................... 15 3.2 Degreesoffreedom ................................ 16 3.3 Symmetries .................................... 18 3.3.1 Reparameterization Invariance . 18 3.3.2 Emergent U(1)D inMajoranaHQET.................. 19 3.3.3 Emergent Z2 SymmetryinMajoranaHQET . 19 3.4 Conclusion&applications . 21 4 LHC implications of WIMP dark matter and Grand Unification 22 4.1 Darkmatter.................................... 23 4.1.1 WIMPdarkmatter ........................... 23 4.1.2 Direct detection searches for WIMPs . 24 4.2 GrandUnification ................................ 26 4.3 Combininig the concepts of WIMP dark matter and gauge coupling unification 28 4.4 Extensions of the SM featuring WIMP DM and unification . 30 4.5 Thebenchmarkmodel .............................. 33 4.5.1 Effects of higher-dimensional operators . 34 4.6 Flavor/CP and electroweak constraints . 35 4.7 Colliderphenomenology . 38 v 4.7.1 R-hadronSignalsattheLHC . 38 4.7.2 TheLHCasaHiggsfactory. 42 4.8 Concludingremarks ............................... 46 5 Supersymmetry and naturalness of electroweak symmetry breaking 48 5.1 Thehierarchyproblem. .. .. .. .. .. .. .. .. 48 5.2 Basicsofsupersymmetry. 49 5.2.1 The minimal supersymmetric standard model (MSSM) . 50 5.2.2 TheHiggssectoroftheMSSM . 54 5.2.3 Supersymmetrybreaking . 57 5.3 Searchesforsupersymmetry . 61 5.4 Thenaturalness problem of supersymmetry . 63 5.4.1 Howtomeasurefine-tuning . 64 5.4.2 The natural supersymmetry paradigm ................. 66 6 Reducing fine-tuning in the MSSM via stable near-criticality 67 6.1 An alternative view of the SUSY naturalness problem . 68 6.2 The concept of stable near-criticality . 70 6.3 SNCingaugemediatedMSSMmodels . 72 6.3.1 Model I: messengers in incomplete GUT multiplets . 74 6.3.2 Model II: SUSY breaking spurion in the adjoint representation . 78 6.4 Stabilizing near-criticality with respect to gauge and Yukawa couplings . 81 6.4.1 Achieving small reweighting factors r[ga,gU ] .............. 84 6.4.2 Achieving small reweighting factors r[yt,i] ............... 85 6.5 A Solution to the µ-Bµ Problem in gauge mediation compatible with SNC . 85 6.6 Proof of principle: A complete MSSM model with stable near-criticality . 87 6.6.1 Superpotential .............................. 87 6.6.2 Fine-tuning analysis at a benchmark point . 89 6.6.3 Discussion................................. 92 6.7 Conclusion: a strategy towards minimally tuned gauge mediated MSSM models 93 7 Conclusions 95 Appendix A Forbidding proton decay 97 Bibliography ....................................... 99 BiographicalSketch ................................. 114 vi LIST OF TABLES 2.1 Operator classification in effective field theories. ........... 7 2.2 Overview of D-meson cq¯ states, for the light antiquark in s- or p-wave. The parity assignments of the respective states are given in parenthesis. 13 4.1 Possible combinations of new fermions that, together with the DM V , could lead to unification. It is understood that the new fermions are vectorlike, so in writing X, U, , the presence of their charge conjugates Xc, U c, is ··· ··· also implied, except for the Majorana fermions V and G. ........... 32 5.1 The field content and nomenclature of the minimal supersymmetric standard model......................................... 50 6.1 Potential messenger particles in simple SU(5) multiplets, with their respective gauge quantum number and corresponding Dynkin-invariants. ........ 75 6.2 Benchmark choices for models with a single SUSY breaking spurion X and gauge messengers in incomplete GUT multiplets that fulfill requirement (A) of SNC. The choice of gauge messengers corresponding to a triple N ,N ,N { 1 2 3} isnotnecessarilyunique. 75 vii LIST OF FIGURES 4.1 Exclusion limits / claims of signal regions for WIMPs, in the plane of spin- independent cross section (normalized to nucleon mass) versus WIMP mass. The shaded regions correspond to SUSY predictions for LSP WIMP cross sec- tions. The cross-shaded regions correspond to LHC exclusion bounds obtained for the cMSSM. Figure taken from Ref. [1]. 25 4.2 Direct detection limits are not yet sensitive to minimal dark matter WIMP candidates as defined in [2] and [3]. Fermionic (scalar) n-tuplets of SU(2)L are denoted by nF (nS). The scenario will be probed by the upcoming XENON-1T and SuperCDMS experiments. Figure taken from Ref. [3]. 26 4.3 Contributions to K0 K¯ 0 generated by X. Left: Feynman diagram leading − to the tree-level operator (4.15). Right: Feynman diagram leading to the four fermionoperator(4.17). 36 4.4 One of the Feynman diagrams leading to the dipole operator (4.20). 37 4.5 Contribution to the ρ-parameter generated by X ................ 37 4.6 The cross section for R-hadron production at the Tevatron after all selection cuts. The bound from the CHAMP search is included for comparison. 39 4.7 The rapidity distribution of the R-hadrons at the LHC (7 TeV) for the three masspoints. .................................... 40 4.8 Time-lag distribution of the R-hadrons to arrive in the muon system at the LHC (7 TeV). Left: Time-lag distribution of the first R-hadron. Right: Time- lag distribution of the second R-hadron...................... 41 4.9 Total production cross section of R-hadron production and effective cross sec- tion after selection cuts at the LHC (7 TeV) for the three mass points. 42 4.10 Effective R-hadron production cross section after selection cuts at the LHC (14TeV). ...................................... 43 4.11 Distribution of the average Z+jet pair mass for signal and background in −1 10 fb of LHC data (14 TeV). Left: Signal for mX = 300 GeV. Right: Signal for mX =500GeV.................................. 45 viii 4.12 Distribution of MT,W W for signal (assuming mh = 200 GeV) and background −1 with a luminosity of 10 fb . Left: Signal for mX = 300