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Beyond MSSM Baryogenesis

Kfir Blum, Yosef Nir

TL;DR

This paper investigates how beyond-MSSM, TeV-scale non-renormalizable DST operators can reshape electroweak baryogenesis in the MSSM. By modifying the Higgs quartic coupling and the finite-temperature potential, DST extend the MSSM EWBG window, allowing a strongly first-order phase transition with a Higgs mass above the LEP bound and with a lighter left-handed stop, thereby reducing fine-tuning. Moreover, DST introduce new CP-violating sources that enable dynamical bubble-wall phases and alter SUSY particle currents, offering qualitatively new mechanisms for BAU generation beyond the MSSM. Overall, BMSSM effects can be significant for both the Higgs/stop sector and CP-violation dynamics, making baryogenesis more natural and potentially testable via collider and cosmological signals.

Abstract

Taking the MSSM as an effective low-energy theory, with a cut-off scale of a few TeV, can make significant modifications to the predictions concerning the Higgs and stop sectors. We investigate the consequences of such a scenario for electroweak baryogenesis. We find that the window for MSSM baryogenesis is extended and, most important, can be made significantly more natural. Specifically, it is possible to have one stop lighter than the top and the other significantly lighter than TeV simultaneously with the Higgs mass above the LEP bound. In addition, various aspects concerning CP violation are affected. Most notably, it is possible to have dynamical phases in the bubble walls at tree level, providing CP violating sources for Standard Model fermions.

Beyond MSSM Baryogenesis

TL;DR

This paper investigates how beyond-MSSM, TeV-scale non-renormalizable DST operators can reshape electroweak baryogenesis in the MSSM. By modifying the Higgs quartic coupling and the finite-temperature potential, DST extend the MSSM EWBG window, allowing a strongly first-order phase transition with a Higgs mass above the LEP bound and with a lighter left-handed stop, thereby reducing fine-tuning. Moreover, DST introduce new CP-violating sources that enable dynamical bubble-wall phases and alter SUSY particle currents, offering qualitatively new mechanisms for BAU generation beyond the MSSM. Overall, BMSSM effects can be significant for both the Higgs/stop sector and CP-violation dynamics, making baryogenesis more natural and potentially testable via collider and cosmological signals.

Abstract

Taking the MSSM as an effective low-energy theory, with a cut-off scale of a few TeV, can make significant modifications to the predictions concerning the Higgs and stop sectors. We investigate the consequences of such a scenario for electroweak baryogenesis. We find that the window for MSSM baryogenesis is extended and, most important, can be made significantly more natural. Specifically, it is possible to have one stop lighter than the top and the other significantly lighter than TeV simultaneously with the Higgs mass above the LEP bound. In addition, various aspects concerning CP violation are affected. Most notably, it is possible to have dynamical phases in the bubble walls at tree level, providing CP violating sources for Standard Model fermions.

Paper Structure

This paper contains 10 sections, 36 equations, 2 figures.

Table of Contents

  1. Introduction
  2. The Lightest Higgs Mass in the MSSM
  3. The DST operators and the light Higgs mass
  4. The scalar potential
  5. The electroweak phase transition
  6. CP violation
  7. CP violation in bubble wall
  8. SUSY particle currents
  9. Discussion
  10. Substituting $m_1^2,m_2^2,m_{12}^2$

Figures (2)

  • Figure 1: The soft SUSY-breaking mass of $\widetilde{t}_L$, $m_Q$, versus the light Higgs mass, $m_h$, for various values of $\epsilon_1$. Other relevant parameters are fixed at $X_t=0$, $m_{\widetilde{t}_R}=150$ GeV, $m_A=300$ GeV and $\tan\beta=4$. The gray line marks the LEP lower bound, $m_h=114$ GeV.
  • Figure 2: The Higgs VEV at the lowest minimum as a function of temperature for various values of $m_h$, $\epsilon_1$ and $\epsilon_2$. Other relevant parameters are fixed at $X_t=0$, $m_{\widetilde{t}_R}=150$ GeV, $m_Q=500$ GeV, $m_A=300$ GeV and $\tan\beta=4$. The different sets of ($m_h,\epsilon_1,\epsilon_2$) all yield the same $m_h^2(v_c/T_c)$ to within about $5\%$.