The scalar singlet extension of the Standard Model: gravitational waves versus baryogenesis

Journal of High Energy Physics

Regular Article - Theoretical Physics

John Ellis¹  Marek Lewicki²  Marco Merchand²  Mateusz Zych²  José Miguel No³ 

[1] Department of Physics, King’s College London, Strand, WC2R 2LS, London, UK;Theoretical Physics Department, CERN, Geneva, Switzerland;National Institute of Chemical Physics & Biophysics, Rävala 10, 10143, Tallinn, Estonia;Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093, Warsaw, Poland;Instituto de Física Teórica, IFT-UAM/CSIC, Cantoblanco, 28049, Madrid, Spain;Departamento de Física Teórica, Universidad Autónoma de Madrid, 28049, Madrid, Spain;

关键词: Baryo-and Leptogenesis;    Phase Transitions in the Early Universe;   

DOI  :  10.1007/JHEP01(2023)093

 received in 2022-11-18, accepted in 2022-12-30,  发布年份 2022

来源: Springer

【 摘 要 】

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 ℤ2 symmetry. We first analyze the velocity of the expanding true-vacuum bubbles during the phase transition, confirming our previous finding in the unbroken ℤ2 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 ℤ2 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 ℤ2 symmetry, the phase transition is always weak and we see no hope for baryogenesis. In contrast, in the case with explicit ℤ2 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.

【 授权许可】

Unknown   
© The Author(s) 2023

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