Role of Scalar Fields in Particle Physics and Cosmology
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Role of Scalar Fields in Particle Physics and Cosmology Abhijit Kumar Saha A thesis submitted for the degree of Doctor of Philosophy Department of Physics Indian Institute of Technology Guwahati Guwahati - 781039, Assam, India TH-2013_126121001 TH-2013_126121001 Role of Scalar Fields in Particle Physics and Cosmology A thesis submitted by Abhijit Kumar Saha to Indian Institute of Technology Guwahati in partial fulfillment of the requirements for the award of the degree of Doctor of Philosophy in Physics Supervisor Dr. Arunansu Sil Department of Physics Indian Institute of Technology Guwahati Guwahati - 781039, Assam, India TH-2013_126121001 TH-2013_126121001 Declaration The work in this thesis is based on research carried out at the Department of Physics, Indian Institute of Technology Guwahati, India under the supervision of Dr. Arunansu Sil. No part of this thesis has been submitted elsewhere for award of any other degree or qualification. Works presented in the thesis are entirely my own unless referenced to the contrary in the text. Signed: Date: TH-2013_126121001 TH-2013_126121001 Certificate Dr. Arunansu Sil Associate Professor Department of Physics, IIT Guwahati Email: [email protected] It is certified that the work contained in the thesis entitled \Role of Scalar Fields in Particle Physics and Cosmology" by Mr. Abhijit Kumar Saha, a PhD student of the Department of Physics, IIT Guwahati was carried out under my supervision and has not been submitted elsewhere for award of any degree. Dr. Arunansu Sil TH-2013_126121001 TH-2013_126121001 Acknowledgements I would like to express my greatest appreciation to Dr. Arunansu Sil for his constant support and guidance throughout my PhD tenure. Being my supervisor, he has taught me to remain focused, dedicated and calm in achieving the goal. His observations and comments helped me to think everything in depth. Along with the academic support, he was always there for me to serve regarding anything, anytime. Words are not enough to describe his backing to overcome those hard times. My journey would never be complete without his immense care. I would like to acknowledge my DC committee members: Prof. Bipul Bhuyan, Dr. Soumitra Nandi and Dr. K.V. Srikanth. I also convey my gratitude to Dr. Subhaditya Bhattacharya and Prof. Jose Wudka who were very kind to collaborate with me. In particular I am grateful to Subhoda for introducing me into the field of dark matter. I also thank Prof. Palash Baran Pal for having several closed door interesting discussion sessions during his visit to IIT Guwahati. He was very kind to provide me the opportunity to work with him. I also thank Prof. Subhendra Mohanty for his wonderful lectures on Particle Physics and Cosmology during SARC school at BITS, Pilani and his visit to IIT Guwahati. I enjoyed the personal interaction sessions with him. It is the best time to convey gratefulness to my well wishers including my group members, friends, family members and few other people. I would like to express my deepest respect and gratitude to Bishuda (Dr. Biswajit Karmakar). Very few people come with such golden fate to get senior like him. I also thank Sujoyda (Sujay Shil) for introducing and teaching me the fundamentals of particle physics during my early days of PhD. I thank Rishav and Dr. Amit Dutta Banik for providing me countless academic and non-academic helps. Here at IITG, I have spent many beautiful, mesmerizing and emotional moments. I thank few of my close local friends Ramiz, Kallol, Sourav, Ashis, Koushik, Sudin, Rahul, Shibananda, Atanu. Their love, care and encouragement helped me to survive in the difficult situations. I am also grateful to Srikrishna, Pankaj, Srimoy, Pulak, Anabilda for playing several important parts during this long journey. I would also like to thank my dear friend cum collaborator Purusottam Ghosh for having many meaningful academic and non-academic discussions. My special thank to Luxmi Machahari from Gauhati University for giving me company during few academic and non-academic trips. I owe my deepest gratitude to Pranoy for being there always since college days. I convey my heartiest gratitude to Samiran Roy from HRI for his constant inspiration. I am also grateful ix TH-2013_126121001 x Acknowledgements to Sushmita Gogoi for providing me motivation and immense mental support during PhD days. I thank Mita Pramanick for tolerating me during the early years of my PhD. Before I end, I would like to express that I am nothing without my family. I dedicate every seconds of my life to my parents, Ma: Shipra Saha and Baba: Monojit Kumar Saha, my brother: Chandrajit Kumar Saha, my sister: Ruma Das and my loving niece: Mani. Finally I convey my heartiest gratitude to Alolika Mandal for her selfless affection and care. TH-2013_126121001 Abstract In this thesis we investigate the different kind of roles, scalar fields can serve in the Universe. First we analyze the scalar field’s role in guiding successful inflation in the early Universe. For this purpose, we focus on the sneutrino chaotic inflation model (within supesymmetric framework) which is disfavored from recent experimental observations by Planck. We deform the model minimally by coupling the inflation sector with a supersymmetry breaking sector. We find that such a coupling can provide correct magnitude of inflationary observables, consistent with Planck results. At the end of inflation dynamical supersymmetry breaking can be also realized. We also comment on some of the neutrino mass parameters. Next we study the Higgs vacuum stability in presence of chaotic inflation in early Universe. We find that extension of the inflation sector by an additional scalar field is sufficient to achieve successful inflation and absolute stability of the electroweak vacuum. After that, we explore the role of scalar field as a potential dark matter candidate. As low mass range (< 500 GeV) of a scalar dark matter is ruled out from experimental data, we extend the minimal scalar DM model further by an additional scalar field. We find that a mere interaction of this additional scalar field with the dark matter is sufficient in order to revive the scalar DM model in the low mass range. In addition, the extra scalar also helps to establish absolute stability of the EW vacuum in presence of large neutrino Yukawa coupling to generate light neutrino mass in type-I seesaw framework. Then we propose a common origin of primordial inflation and scalar DM in the Universe. In the scenario, it turns out that after the end of inflation, associated global symmetry breaks down, and corresponding Nambu Goldstone bosons can be identified with viable dark matter candidates. Finally we revisit the well known singlet doublet fermionic dark matter model extended by a scalar field. The scalar field serves instrumental role in stabilizing the electroweak vacuum as well as provides interesting features of dark matter phenomenology in view of recent experiments. xi TH-2013_126121001 TH-2013_126121001 xiii List of Publications included in the Thesis: 1. Abhijit Kumar Saha and Arunansu Sil, \A Dynamic modification to Sneutrino Chaotic Inflation", JHEP 1511 (2015) 118 [arXiv:1509.00218 [hep-ph]]. 2. Abhijit Kunar Saha and Arunansu Sil, \Higgs Vacuum Stability and Modified Chaotic Inflation” Phys. Lett. B765 (2017) 244-250 [arXiv:1608.04919 [hep-ph]]. 3. Purusottam Ghosh, Abhijit Kumar Saha and Arunansu Sil, \Electroweak Vacuum Sta- bility in an Extended Framework of Dark Matter and Neutrinos", Phys. Rev. D97 (2018) no.7, 075034 [arXiv:1706.04931 [hep-ph]]. 4. Subhaditya Bhattacharya, Abhijit Kumar Saha, Arunansu Sil and Jose Wudka, \Dark Matter as a remnant of SQCD Inflation", Preprint - arXiv:1805.03621 [hep-ph]. 5. Amit Dutta Banik, Abhijit Kumar Saha and Arunansu Sil, \A scalar assisted singlet doublet fermion dark matter model and electroweak vacuum stability ", Preprint - arXiv: 1806.08080 [hep-ph], accepted for publication in Phys. Rev. D. TH-2013_126121001 TH-2013_126121001 Contents Abstract xi 1 Introduction 1 1.1 Standard Model of Particle Physics . .3 1.1.1 Basic set up . .3 1.1.2 Success and drawbacks of the SM of particle physics . .6 1.2 Salient features of Big Bang Cosmology . .7 1.2.1 Success and shortcomings of the Big Bang Cosmology . 10 1.3 Possible resolutions of drawbacks of the Big bang cosmology and the SM of par- ticle physics . 11 1.3.1 Inflation . 11 1.3.2 Dark Matter . 15 1.3.2.1 Evidence of DM . 15 1.3.2.2 Feasible DM candidates . 17 1.3.2.3 Boltzman equation . 18 1.3.2.4 Detection of DM . 24 1.3.2.5 Real scalar singlet dark matter . 25 1.3.3 Neutrino Mass . 27 1.3.4 Higgs Vacuum Stability . 30 1.3.4.1 Higgs Vacuum Stability in Standard Model . 31 1.4 Role of scalar fields in the Universe . 34 1.5 Outline of the thesis . 34 2 Modified sneutrino chaotic inflation and dynamical Supersymmetry breaking 37 2.1 Introduction . 37 2.1.1 A brief introduction to Supersymmetry . 38 2.1.2 Preface of the work . 42 2.2 Standard sneutrino chaotic inflation in supergravity . 44 2.3 SQCD sector and supersymmetry breaking in a metastable vacuum . 46 2.4 Interaction between neutrino and SQCD sectors . 47 2.5 Modified chaotic potential and its implications to inflationary dynamics . 49 2.6 Results . 51 2.7 Dynamics after inflation . 53 xv TH-2013_126121001 xvi Contents 2.8 Dynamical breaking of U(1)R ............................. 54 2.9 Neutrino masses and mixing . 56 2.10 Reheating . 58 2.11 Chapter Summary . 59 3 EW vacuum stability and chaotic Inflation 61 3.1 Introduction . 61 3.2 Inflation Model . 63 3.3 Inflationary Predictions . 65 3.4 Study of EW Vacuum Stability . 67 3.5 Reheating after Inflation .