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Unified origin of baryons and dark matter

Ryuichiro Kitano, Hitoshi Murayama, Michael Ratz

TL;DR

The authors tackle the tension between standard baryogenesis and dark matter production with gravitino/moduli constraints by proposing a late-decaying heavy scalar $oldsymbol{}$phi$$ that dominates the universe before BBN and decays to reheat the plasma. Baryogenesis is achieved by dynamically generating a $oldsymbol{q_oldsymbol{}}$phi$$-number and converting it into baryons at $oldsymbol{}$phi$$ decay, yielding the observed $n_b/s$ once the decay temperature $T_d$ is constrained to preserve BBN. Dark matter is produced non-thermally from $oldsymbol{}$phi$$ decays with Wino/Higgsino LSPs, where annihilation after production can bring $oldsymbol{}$Omega$_{CDM}$ to the observed level for $m_$ in the TeV range and $m_$-dependent cross sections, and the predicted ratio $ rac{oldsymbol{}$Omega$_{CDM}}{oldsymbol{}$Omega$_b}$ is naturally $\sim 5$ for $m_ rac{100}{ m GeV}$ and $M rac{M_P}{ }$. Overall, the framework links the origins of baryons and dark matter through a common late-time scalar decay, avoids gravitino/moduli problems, and suggests new directions for inflation-model-building where reheating is governed by $oldsymbol{}$phi$$ rather than the inflaton.

Abstract

We investigate the possibility that both the baryon asymmetry of the universe and the observed cold dark matter density are generated by decays of a heavy scalar field which dominates the universe before nucleosynthesis. Since baryons and cold dark matter have common origin, this mechanism yields a natural explanation of the similarity of the corresponding energy densities. The cosmological moduli and gravitino problems are avoided.

Unified origin of baryons and dark matter

TL;DR

The authors tackle the tension between standard baryogenesis and dark matter production with gravitino/moduli constraints by proposing a late-decaying heavy scalar phi that dominates the universe before BBN and decays to reheat the plasma. Baryogenesis is achieved by dynamically generating a phi-number and converting it into baryons at phi decay, yielding the observed once the decay temperature is constrained to preserve BBN. Dark matter is produced non-thermally from phi decays with Wino/Higgsino LSPs, where annihilation after production can bring Omega to the observed level for in the TeV range and -dependent cross sections, and the predicted ratio OmegaOmega is naturally for and . Overall, the framework links the origins of baryons and dark matter through a common late-time scalar decay, avoids gravitino/moduli problems, and suggests new directions for inflation-model-building where reheating is governed by phi rather than the inflaton.

Abstract

We investigate the possibility that both the baryon asymmetry of the universe and the observed cold dark matter density are generated by decays of a heavy scalar field which dominates the universe before nucleosynthesis. Since baryons and cold dark matter have common origin, this mechanism yields a natural explanation of the similarity of the corresponding energy densities. The cosmological moduli and gravitino problems are avoided.

Paper Structure

This paper contains 7 sections, 23 equations, 1 figure, 1 table.

Table of Contents

  1. Introduction
  2. Baryogenesis
  3. Basic idea
  4. $\boldsymbol{\phi}$ evolution
  5. Baryogenesis via $\boldsymbol{\phi}$ decay
  6. Dark matter from $\boldsymbol{\phi}$ decay
  7. Conclusions

Figures (1)

  • Figure 1: $\Omega_\chi\,h^2$ as a function of the mass $m_\phi$ for various $W$ino masses $m_\chi$. We use for the mass difference between charged and neutral $W$inos $\Delta m_\chi=165\,\mathrm{MeV}$, and fix $M=M_\mathrm{P}$. The shaded bar corresponds to the $2\sigma$ region of $\Omega_\mathrm{CDM}$ as reported by WMAP Spergel:2006hy. As usual, we fix the present energy density of the universe so that $\Omega$ can formally become larger than one ('overclosure').