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Cosmological implications of a QCD-like composite Higgs model

Hristova, Hristina Georgieva LU (2021) FYTM03 20211
Theoretical Particle Physics
Department of Astronomy and Theoretical Physics
Abstract
Some of the shortcomings of the Standard Model of particle physics are the 'unnatural' value of the mass of the Higgs boson and the fact that the model cannot account for the process of baryogenesis - a mechanism which generates the observed asymmetry between matter and anti-matter in the Universe. The former is related to the fundamental scalar nature of the Higgs boson, connected to quadratic divergences in the mass corrections. The latter is related to the fact that the Standard Model does not accommodate all three Sakharov conditions necessary for baryogenesis to occur. We present an effective UV-complete composite Higgs model built in analogy to Quantum Chromodynamics and confined at higher energy scales of O(TeV). The parameter-space... (More)
Some of the shortcomings of the Standard Model of particle physics are the 'unnatural' value of the mass of the Higgs boson and the fact that the model cannot account for the process of baryogenesis - a mechanism which generates the observed asymmetry between matter and anti-matter in the Universe. The former is related to the fundamental scalar nature of the Higgs boson, connected to quadratic divergences in the mass corrections. The latter is related to the fact that the Standard Model does not accommodate all three Sakharov conditions necessary for baryogenesis to occur. We present an effective UV-complete composite Higgs model built in analogy to Quantum Chromodynamics and confined at higher energy scales of O(TeV). The parameter-space of the model and the particle spectra have been explored and first-order phase transitions are sought for. The purpose is to study whether the gravitational waves produced by such events could be detected by the LISA interferometer as well as other proposed projects such as BBO and DECIGO. Albeit not many, such parameter-space points that feature strong first-order phase transitions did indeed cross the sensitivity curves of all three interferometers. A couple of benchmark points produced a very high signal-to-noise ratio value and one of them is within LISA's sensitivity domain. The thesis demonstrates that such strongly confined theories, going by the name of technicolor, may indeed provide potentially observable cosmological consequences worth further exploration. (Less)
Popular Abstract
In a wonderful talk given at the The Royal Institution of Great Britain, professor David Tong expresses his indignation on the following matter. The model that particle physicists have been working on for more than half a century now, carries this rather unfortunate adjective in front: 'standard'. There is really nothing standard in the model. It is, in fact, quite extraordinary. It successfully describes the quantum world in just 28 independent parameters and is the most accurately tested theoretical model up to date.

Fortunately for us, this model is not at all complete. It is indeed fortunate as it means that there are still theories to be developed and discoveries to be made. What could be classified as unfortunate is that theory... (More)
In a wonderful talk given at the The Royal Institution of Great Britain, professor David Tong expresses his indignation on the following matter. The model that particle physicists have been working on for more than half a century now, carries this rather unfortunate adjective in front: 'standard'. There is really nothing standard in the model. It is, in fact, quite extraordinary. It successfully describes the quantum world in just 28 independent parameters and is the most accurately tested theoretical model up to date.

Fortunately for us, this model is not at all complete. It is indeed fortunate as it means that there are still theories to be developed and discoveries to be made. What could be classified as unfortunate is that theory advances over experiments and the validity of some very well-established models cannot be tested since the technology to do so is yet to be explored.

One can make a list of topics which the Standard Model does not accommodate very well. Now, however, we shall concentrate on only a few. One topic that bothers some physicists is the definition of the Higgs boson in the Standard Model. Being introduced as a fundamental scalar, we are forced to very (very!) delicately 'tweak' the parameters of the Standard Model in such a way that the Higgs boson restores its experimentally observed mass of 125 GeV. It might be that scientists are worrying a bit too much about it but nevertheless such behaviour is indeed quite peculiar and it makes people wonder.

Another issue with the Standard Model is that it cannot account for the observed matter-antimatter asymmetry in the Universe, as one of the three so-called Sakharov conditions are not realized, namely the early Universe should have experienced a thermal inequilibrium with respect to baryon-number-violating reactions. Such a thermal inequilibrium implies a very abrupt transitions from 1) a Universe filled with zero Higgs vacuum expectation value to 2) a Universe filled with non-zero Higgs vacuum expectation value. However, in the Standard Model, such transitions happen very smoothly and do not provide conditions for an asymmetric Universe.

Scientists have introduced various ideas that could both reproduce the values of the conventional and experimentally tested Standard Model and also make it possible for phenomena such as the one described above to occur. One such bright idea is technicolor. In the present thesis, we both redefine the Higgs sector and introduce a mechanism that generates such abrupt transitions. How would we know if the theory we consider points in the right direction? Earlier, it was mentioned that technology has not yet advanced to probe certain models. Nevertheless, it has advanced tremendously and just enough for us to be able to probe something quite amazing, namely gravitational wave signals from such possible transitions. State-of-the-art interferometers such as LISA and the proposed BBO and DECIGO are designed to do just that. Hopefully, some ten years from now we would have a new and exciting story to tell. (Less)
Please use this url to cite or link to this publication:
author
Hristova, Hristina Georgieva LU
supervisor
organization
course
FYTM03 20211
year
type
H2 - Master's Degree (Two Years)
subject
keywords
composite Higgs, technicolor, gravitational waves, LISA, phase transition
report number
LU-TP 21-33
language
English
id
9061904
date added to LUP
2021-08-03 14:40:15
date last changed
2021-08-03 14:40:27
@misc{9061904,
  abstract     = {{Some of the shortcomings of the Standard Model of particle physics are the 'unnatural' value of the mass of the Higgs boson and the fact that the model cannot account for the process of baryogenesis - a mechanism which generates the observed asymmetry between matter and anti-matter in the Universe. The former is related to the fundamental scalar nature of the Higgs boson, connected to quadratic divergences in the mass corrections. The latter is related to the fact that the Standard Model does not accommodate all three Sakharov conditions necessary for baryogenesis to occur. We present an effective UV-complete composite Higgs model built in analogy to Quantum Chromodynamics and confined at higher energy scales of O(TeV). The parameter-space of the model and the particle spectra have been explored and first-order phase transitions are sought for. The purpose is to study whether the gravitational waves produced by such events could be detected by the LISA interferometer as well as other proposed projects such as BBO and DECIGO. Albeit not many, such parameter-space points that feature strong first-order phase transitions did indeed cross the sensitivity curves of all three interferometers. A couple of benchmark points produced a very high signal-to-noise ratio value and one of them is within LISA's sensitivity domain. The thesis demonstrates that such strongly confined theories, going by the name of technicolor, may indeed provide potentially observable cosmological consequences worth further exploration.}},
  author       = {{Hristova, Hristina Georgieva}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Cosmological implications of a QCD-like composite Higgs model}},
  year         = {{2021}},
}