Electroweak Baryogenesis in Two Higgs Doublet Models and B meson anomalies (1107.3559v3)

Abstract: Motivated by 3.9 sigma evidence of a CP-violating phase beyond the standard model in the like-sign dimuon asymmetry reported by DO, we examine the potential for two Higgs doublet models (2HDMs) to achieve successful electroweak baryogenesis (EWBG) while explaining the dimuon anomaly. Our emphasis is on the minimal flavour violating 2HDM, but our numerical scans of model parameter space include type I and type II models as special cases. We incorporate relevant particle physics constraints, including electroweak precision data, b to s gamma, the neutron electric dipole moment, R_b, and perturbative coupling bounds to constrain the model. Surprisingly, we find that a large enough baryon asymmetry is only consistently achieved in a small subset of parameter space in 2HDMs, regardless of trying to simultaneously account for any B physics anomaly. There is some tension between simultaneous explanation of the dimuon anomaly and baryogenesis, but using a Markov chain Monte Carlo we find several models within 1 sigma of the central values. We point out shortcomings with previous studies that reached different conclusions. The restricted parameter space that allows for EWBG makes this scenario highly predictive for collider searches. We discuss the most promising signatures to pursue at the LHC for EWBG-compatible models.

Overview of Electroweak Baryogenesis in Two Higgs Doublet Models and $B$ Meson Anomalies

The paper under analysis explores the intersection of electroweak baryogenesis (EWBG) and observed anomalies in $B$ meson decays, within the framework of Two Higgs Doublet Models (2HDMs). Specifically, it examines how 2HDMs might accommodate new CP-violating phases required for EWBG, while simultaneously offering explanations for the CP violations hinted at by like-sign dimuon asymmetry in semi-leptonic $B$ decays, which deviate from the Standard Model (SM) at a statistical significance of 3.9σ.

Key Aspects and Methodology

Authors focus primarily on the minimal flavor-violating (MFV) version of 2HDMs, which mitigates core issues like flavor-changing neutral currents (FCNCs) without reliance on discrete symmetries that characterize Type I and II 2HDMs. Through numerical parameter scans and a Markov Chain Monte Carlo approach, the paper investigates whether 2HDMs can accommodate a first-order electroweak phase transition—sufficiently strong for successful baryogenesis—and the observed asymmetry in $B$ decays.

The paper rigorously constrains the model by incorporating electron-weak precision data, $b \to s \gamma$ transitions, neutron electric dipole moments, $R_b$, and perturbative coupling bounds. The paper highlights an interesting tension: a large enough baryon asymmetry is achievable only within narrow parameter subsets, complicating the simultaneity of baryogenesis and full alignment with $B$ physics anomalies.

Numerical Findings and Theoretical Constraints

The analysis reveals that a strong electroweak phase transition, crucial for viable baryogenesis, occurs across a limited parameter space, emphasizing typically low SM-like Higgs masses and heavy neutral scalars above 300 GeV. The paper provides explicit examples where the baryon density produced aligns closely with the value observed in our universe, albeit with the uncertainty tied to theoretical approximations.

Significantly, the findings suggest potential collider signatures. The restricted parameter space offers specific predictions, such as distinct collider signatures that could be explored at the Large Hadron Collider (LHC). However, the challenges lie in resonance detection of predicted heavy scalars, particularly above the $t\bar{t}$ threshold.

Broader Implications

The results carry implications for both particle physics and cosmology. From a theoretical standpoint, the paper accentuates the constrained nature of 2HDMs in addressing both baryogenesis and $B$ meson anomalies, pushing for a refined focus on collider validations as future work.

Conclusion and Future Outlook

This paper maps out a stringent landscape where 2HDMs can serve as potential links between cosmological phenomena and particle physics anomalies. In the evolving domain of AI and collider physics, the research underscores the importance of precise parameter scanning techniques, which might benefit from future advancements in computational models. As experiments like those at the LHC continue to probe the energy scales predicted by 2HDMs, this paper sets a foundational understanding of the necessary conditions for a successful intersection between electroweak baryogenesis and $B$ meson physics, carving out pathways for theoretical developments and empirical validations.