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The Scalar Singlet Extension of the Standard Model: Gravitational Waves versus Baryogenesis

We study the possible gravitational wave signal and the viability of baryogenesis arising from the electroweak phase transition in an extension of the Standard Model (SM) by a scalar singlet field without a ℤ$_{2}$ symmetry. We first analyze the velocity of the expanding true-vacuum bubbles during t...

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Detalles Bibliográficos
Autores principales: Ellis, John, Lewicki, Marek, Merchand, Marco, No, José Miguel, Zych, Mateusz
Lenguaje:eng
Publicado: 2022
Materias:
Acceso en línea:https://dx.doi.org/10.1007/JHEP01(2023)093
http://cds.cern.ch/record/2841025
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author Ellis, John
Lewicki, Marek
Merchand, Marco
No, José Miguel
Zych, Mateusz
author_facet Ellis, John
Lewicki, Marek
Merchand, Marco
No, José Miguel
Zych, Mateusz
author_sort Ellis, John
collection CERN
description We study the possible gravitational wave signal and the viability of baryogenesis arising from the electroweak phase transition in an extension of the Standard Model (SM) by a scalar singlet field without a ℤ$_{2}$ symmetry. We first analyze the velocity of the expanding true-vacuum bubbles during the phase transition, confirming our previous finding in the unbroken ℤ$_{2}$ symmetry scenario, where the bubble wall velocity can be computed from first principles only for weak transitions with strength parameters α ≲ 0.05, and the Chapman-Jouguet velocity defines the maximum velocity for which the wall is stopped by the friction from the plasma. We further provide an analytical approximation to the wall velocity in the general scalar singlet scenario without ℤ$_{2}$ symmetry and test it against the results of a detailed calculation, finding good agreement. We show that in the singlet scenario with a spontaneously broken ℤ$_{2}$ symmetry, the phase transition is always weak and we see no hope for baryogenesis. In contrast, in the case with explicit ℤ$_{2}$ breaking there is a region of the parameter space producing a promising baryon yield in the presence of CP violating interactions via an effective operator involving the singlet scalar and the SM top quarks. Yet, we find that this region yields unobservable gravitational waves. Finally, we show that the promising region for baryogenesis in this model may be fully tested by direct searches for singlet-like scalars in di-boson final states at the HL-LHC, combined with present and future measurements of the electron electric dipole moment.
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institution Organización Europea para la Investigación Nuclear
language eng
publishDate 2022
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spelling cern-28410252023-09-18T02:19:46Zdoi:10.1007/JHEP01(2023)093http://cds.cern.ch/record/2841025engEllis, JohnLewicki, MarekMerchand, MarcoNo, José MiguelZych, MateuszThe Scalar Singlet Extension of the Standard Model: Gravitational Waves versus Baryogenesisastro-ph.COAstrophysics and Astronomyhep-phParticle Physics - PhenomenologyWe study the possible gravitational wave signal and the viability of baryogenesis arising from the electroweak phase transition in an extension of the Standard Model (SM) by a scalar singlet field without a ℤ$_{2}$ symmetry. We first analyze the velocity of the expanding true-vacuum bubbles during the phase transition, confirming our previous finding in the unbroken ℤ$_{2}$ symmetry scenario, where the bubble wall velocity can be computed from first principles only for weak transitions with strength parameters α ≲ 0.05, and the Chapman-Jouguet velocity defines the maximum velocity for which the wall is stopped by the friction from the plasma. We further provide an analytical approximation to the wall velocity in the general scalar singlet scenario without ℤ$_{2}$ symmetry and test it against the results of a detailed calculation, finding good agreement. We show that in the singlet scenario with a spontaneously broken ℤ$_{2}$ symmetry, the phase transition is always weak and we see no hope for baryogenesis. In contrast, in the case with explicit ℤ$_{2}$ breaking there is a region of the parameter space producing a promising baryon yield in the presence of CP violating interactions via an effective operator involving the singlet scalar and the SM top quarks. Yet, we find that this region yields unobservable gravitational waves. Finally, we show that the promising region for baryogenesis in this model may be fully tested by direct searches for singlet-like scalars in di-boson final states at the HL-LHC, combined with present and future measurements of the electron electric dipole moment.We study the possible gravitational wave signal and the viability of baryogenesis arising from the electroweak phase transition in an extension of the Standard Model (SM) by a scalar singlet field without a $\mathbb{Z}_2$ symmetry. We first analyze the velocity of the expanding true-vacuum bubbles during the phase transition, confirming our previous finding in the unbroken $\mathbb{Z}_2$ symmetry scenario, where the bubble wall velocity can be computed from first principles only for weak transitions with strength parameters $\alpha \lesssim 0.05$, and the Chapman-Jouguet velocity defines the maximum velocity for which the wall is stopped by the friction from the plasma. We further provide an analytical approximation to the wall velocity in the general scalar singlet scenario without $\mathbb{Z}_2$ symmetry and test it against the results of a detailed calculation, finding good agreement. We show that in the singlet scenario with a spontaneously broken $\mathbb{Z}_2$ symmetry, the phase transition is always weak and we see no hope for baryogenesis. In contrast, in the case with explicit $\mathbb{Z}_2$ breaking there is a region of the parameter space producing a promising baryon yield in the presence of CP violating interactions via an effective operator involving the singlet scalar and the SM top quarks. Yet, we find that this region yields unobservable gravitational waves. Finally, we show that the promising region for baryogenesis in this model may be fully tested by direct searches for singlet-like scalars in di-boson final states at the HL-LHC, combined with present and future measurements of the electron electric dipole moment.arXiv:2210.16305CERN-TH-2022-150KCL-PH-TH/2022-48IFT–UAM/CSIC–22-133oai:cds.cern.ch:28410252022-10-28
spellingShingle astro-ph.CO
Astrophysics and Astronomy
hep-ph
Particle Physics - Phenomenology
Ellis, John
Lewicki, Marek
Merchand, Marco
No, José Miguel
Zych, Mateusz
The Scalar Singlet Extension of the Standard Model: Gravitational Waves versus Baryogenesis
title The Scalar Singlet Extension of the Standard Model: Gravitational Waves versus Baryogenesis
title_full The Scalar Singlet Extension of the Standard Model: Gravitational Waves versus Baryogenesis
title_fullStr The Scalar Singlet Extension of the Standard Model: Gravitational Waves versus Baryogenesis
title_full_unstemmed The Scalar Singlet Extension of the Standard Model: Gravitational Waves versus Baryogenesis
title_short The Scalar Singlet Extension of the Standard Model: Gravitational Waves versus Baryogenesis
title_sort scalar singlet extension of the standard model: gravitational waves versus baryogenesis
topic astro-ph.CO
Astrophysics and Astronomy
hep-ph
Particle Physics - Phenomenology
url https://dx.doi.org/10.1007/JHEP01(2023)093
http://cds.cern.ch/record/2841025
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