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Phase Transitions and Gravitational Waves in the Conformal Two Higgs Doublet Model

Pu, Hanxiao LU (2024) FYSM34 20241
Particle and nuclear physics
Department of Physics
Abstract
This thesis conducts an in-depth investigation of the conformal two Higgs doublet model (C2HDM) in its most general form, integrating complex couplings λ5, λ6, λ7 and a CPviolating phase e−iδ. This setup enables a detailed exploration of $\mathcal{CP}$-violation and its impact on electroweak phase transitions (EWPT) and gravitational wave (GW) signatures.

Using the Higgs basis simplifies tree-level calculations, and the Coleman-Weinberg potential within the MS scheme handles loop-level dynamics. A counterterm setup ensures the Standard Model (SM) Higgs reaches its verified mass of 125 GeV without impacting other scalars. Thermal corrections, given by a 3D effective field theory (EFT) derived from dimensional reduction approach, enhance... (More)
This thesis conducts an in-depth investigation of the conformal two Higgs doublet model (C2HDM) in its most general form, integrating complex couplings λ5, λ6, λ7 and a CPviolating phase e−iδ. This setup enables a detailed exploration of $\mathcal{CP}$-violation and its impact on electroweak phase transitions (EWPT) and gravitational wave (GW) signatures.

Using the Higgs basis simplifies tree-level calculations, and the Coleman-Weinberg potential within the MS scheme handles loop-level dynamics. A counterterm setup ensures the Standard Model (SM) Higgs reaches its verified mass of 125 GeV without impacting other scalars. Thermal corrections, given by a 3D effective field theory (EFT) derived from dimensional reduction approach, enhance the assessment of thermal effects.

Our results reveal that, although there are no direct correlations between the Higgs masses and the characteristics of phase transitions (PT), a weak correlation does suggest that strong first-order phase transitions (SFOPT) tend to favor heavier Higgs masses ($>300$ GeV). Many SFOPTs also exhibit supercooling. Additionally, specific parameter configurations, including larger absolute values of the mutual mixing angle γ and distinct CP-violation phases $\delta$, appear conducive to PTs. We have identified benchmark PT points that lie within the sensitivity curves, indicating that such PTs are likely to produce GWs detectable by observatories such as LISA, DECIGO, and BBO. (Less)
Popular Abstract
Imagine a universe where the rules of physics as we know them are just one part of a larger, more complex framework. In the field of high energy theory, researchers explore these possibilities by studying various extensions of the Standard Model, which is the current best explanation for how fundamental particles interact. One such extension is the Conformal Two Higgs Doublet Model, a theory that proposes not one, but two Higgs fields, unlike the single Higgs field of the Standard Model.

The discovery of the Higgs boson at CERN in 2012 confirmed the existence of the Higgs field, providing a crucial piece to the puzzle of how particles acquire mass. However, this discovery also opened the door to new questions and the possibility of... (More)
Imagine a universe where the rules of physics as we know them are just one part of a larger, more complex framework. In the field of high energy theory, researchers explore these possibilities by studying various extensions of the Standard Model, which is the current best explanation for how fundamental particles interact. One such extension is the Conformal Two Higgs Doublet Model, a theory that proposes not one, but two Higgs fields, unlike the single Higgs field of the Standard Model.

The discovery of the Higgs boson at CERN in 2012 confirmed the existence of the Higgs field, providing a crucial piece to the puzzle of how particles acquire mass. However, this discovery also opened the door to new questions and the possibility of unknown aspects of the universe that are yet to be discovered. The Conformal Two Higgs Doublet Model is exciting because it introduces an additional Higgs field, which could explain certain phenomena that the Standard Model cannot, and might be key to understanding the early universe’s rapid expansion, known as inflation.

Moreover, this model allows for the exploration of CP-violation—a discrepancy between the behavior of particles and their antiparticles, which is not fully explained by the Standard Model but is essential for understanding why the universe is predominantly composed of matter, not antimatter. This model, with its complex couplings and additional CP-violating elements, provides a fertile ground for studying how these asymmetries arose.

This thesis investigates the most general form of the Conformal Two Higgs Doublet Model, focusing on its implications for the universe’s metamorphosis from a symmetric state in its infancy to a state where the symmetries are broken as it cooled down. These transitions are more than just theoretical constructs; they have tangible signatures in the form of gravitational waves—ripples in the fabric of spacetime. Detecting such waves from these transitions would open a new window into understanding the universe’s formative moments.

The research presented in this thesis simulates how these transitions occur and predicts the signals they would generate. This involves advanced mathematics and computational techniques that examine the behavior of the extended Higgs sector under extreme conditions, similar to those just after the Big Bang.

The findings of this study are not only vital for high energy theory but also for cosmology, as they help bridge the gap between theoretical predictions and observable phenomena, providing a coherent picture that could one day be tested by gravitational wave detectors like LISA, DECIGO, and BBO. This research thus stands at the crossroads of high energy theory and observational cosmology, striving to answer some of the most profound questions about the universe’s origin and its fundamental nature. (Less)
Please use this url to cite or link to this publication:
author
Pu, Hanxiao LU
supervisor
organization
course
FYSM34 20241
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
9165871
date added to LUP
2024-06-20 08:47:52
date last changed
2024-06-20 08:47:52
@misc{9165871,
  abstract     = {{This thesis conducts an in-depth investigation of the conformal two Higgs doublet model (C2HDM) in its most general form, integrating complex couplings λ5, λ6, λ7 and a CPviolating phase e−iδ. This setup enables a detailed exploration of $\mathcal{CP}$-violation and its impact on electroweak phase transitions (EWPT) and gravitational wave (GW) signatures. 

Using the Higgs basis simplifies tree-level calculations, and the Coleman-Weinberg potential within the MS scheme handles loop-level dynamics. A counterterm setup ensures the Standard Model (SM) Higgs reaches its verified mass of 125 GeV without impacting other scalars. Thermal corrections, given by a 3D effective field theory (EFT) derived from dimensional reduction approach, enhance the assessment of thermal effects.

Our results reveal that, although there are no direct correlations between the Higgs masses and the characteristics of phase transitions (PT), a weak correlation does suggest that strong first-order phase transitions (SFOPT) tend to favor heavier Higgs masses ($>300$ GeV). Many SFOPTs also exhibit supercooling. Additionally, specific parameter configurations, including larger absolute values of the mutual mixing angle γ and distinct CP-violation phases $\delta$, appear conducive to PTs. We have identified benchmark PT points that lie within the sensitivity curves, indicating that such PTs are likely to produce GWs detectable by observatories such as LISA, DECIGO, and BBO.}},
  author       = {{Pu, Hanxiao}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Phase Transitions and Gravitational Waves in the Conformal Two Higgs Doublet Model}},
  year         = {{2024}},
}