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Collider probes of baryogenesis with maximal CP asymmetry

Debasish Borah, Kun Cheng, Arnab Dasgupta, Tao Han, Keping Xie

Abstract

We propose a novel collider probe of baryogenesis at TeV scale by measuring decay asymmetries into particle and anti-particle final states. Motivated by the idea of Dirac leptogenesis, we consider an extension of the standard model with new colored and $SU(2)_L$ singlet particles in such a way that the out-of-equilibrium decay of heavy colored fermions creates equal and opposite CP asymmetries in two sectors, prevented from equilibrating with each other. While the TeV scale viability of this mechanism requires a resonantly enhanced CP asymmetry, the latter also plays a crucial role leading to observable decay asymmetries in colliders. In addition to discussing conventional signatures of such heavy colored particles, namely, mono-jet plus missing transverse energy, displaced vertex, colored track at hadron colliders, we also show the unique possibility of measuring decay asymmetries via forward-backward and charge asymmetries at future muon colliders. In addition to being a verifiable TeV-scale baryogenesis scenario, the model also predicts a singlet scalar dark matter candidate consistent with the required thermal dark matter properties near the Higgs resonance.

Collider probes of baryogenesis with maximal CP asymmetry

Abstract

We propose a novel collider probe of baryogenesis at TeV scale by measuring decay asymmetries into particle and anti-particle final states. Motivated by the idea of Dirac leptogenesis, we consider an extension of the standard model with new colored and singlet particles in such a way that the out-of-equilibrium decay of heavy colored fermions creates equal and opposite CP asymmetries in two sectors, prevented from equilibrating with each other. While the TeV scale viability of this mechanism requires a resonantly enhanced CP asymmetry, the latter also plays a crucial role leading to observable decay asymmetries in colliders. In addition to discussing conventional signatures of such heavy colored particles, namely, mono-jet plus missing transverse energy, displaced vertex, colored track at hadron colliders, we also show the unique possibility of measuring decay asymmetries via forward-backward and charge asymmetries at future muon colliders. In addition to being a verifiable TeV-scale baryogenesis scenario, the model also predicts a singlet scalar dark matter candidate consistent with the required thermal dark matter properties near the Higgs resonance.

Paper Structure

This paper contains 20 sections, 67 equations, 22 figures, 2 tables.

Table of Contents

  1. Introduction
  2. The Model
  3. Mass spectrum and decay width
  4. Loop induced asymmetry
  5. Generation of baryon asymmetry
  6. Collider Signals
  7. Constraints from current LHC data
  8. Mono-jet signal from the prompt decay $\psi\to u\phi$
  9. The displaced vertex and colored track for $\eta$
  10. Asymmetry at muon collider
  11. Forward-backward asymmetry
  12. Charge asymmetry
  13. Summary and Conclusion
  14. Loop induced asymmetry
  15. Loop induced asymmetry
  16. ...and 5 more sections

Figures (22)

  • Figure 1: The Feynman diagrams for $\psi$ and $\eta$ decays.
  • Figure 2: Left: The tree-level decay widths and branching fractions (inner panel) for $\psi$, Right: for $\eta$ and the decay length $c\tau$ (dashed curves), with the benchmark parameter choices of Eqs. (\ref{['eq:bench1']}) and (\ref{['eq:Y']}).
  • Figure 3: Left: The dependence of the up quark asymmetry $A_u$ in the first recursive (1) and resummed (R) solutions, with respect to the zero-th order approximation $\mathcal{B}^{(0)}(\psi \to u \phi)\mathcal{B}^{(0)}(\psi \to N\eta)$. Right: The dependence of the branching fractions of $\psi$ and $\bar{\psi}$ on the mass ratio $x=M_{\eta}/M_\psi$ in the resummation calculation.
  • Figure 4: Representative washout processes, with the $\eta$ decay in Fig. \ref{['fig:decay']} (right).
  • Figure 5: Dominant processes keeping $\psi, \eta$ in equilibrium with the bath.
  • ...and 17 more figures