[Paper Review] A dark force for baryons

Michael L. Graesser, Ian M. Shoemaker+1 more|arXiv (Cornell University)|Jul 13, 2011

Dark Matter and Cosmic Phenomena77 references21 citations

TL;DR

This paper proposes a unified origin for baryonic and dark matter via a spontaneously broken U(1)_B gauge symmetry that stabilizes the proton and generates a GeV-scale dark matter candidate. The Affleck-Dine mechanism in SUSY models simultaneously produces baryonic and dark matter asymmetries, with the dark matter relic abundance set by Z_B-mediated annihilation, consistent with direct detection and collider constraints for mediators down to the GeV scale.

ABSTRACT

We suggest the existence of a fundamental connection between baryonic and dark matter. This is motivated by both the stability of these two types of matter as well as the observed similarity of their present-day densities. A unified genesis of baryonic and dark matter is natural in models in which the baryon number is promoted to a spontaneously broken local gauge symmetry. This is illustrated in a specific class of SUSY models using the Affleck-Dine mechanism. The dark matter candidate in these scenarios is charged under the baryon gauge symmetry and must have a mass around the GeV scale to give the correct present-day abundance. We discuss constraints from B-factories, LEP, mono-jet searches at the Tevatron, and dark matter direct detection experiments. A baryonic dark force is shown to be consistent with all data for mediators as light as the GeV scale.

Motivation & Objective

• To explain the observed similarity in baryonic and dark matter relic abundances through a unified genesis mechanism.
• To address proton stability by promoting baryon number to a local U(1)_B gauge symmetry, ensuring its conservation at all orders.
• To identify a dark matter candidate naturally arising from the same gauge sector as baryons, with mass in the GeV range.
• To ensure consistency with cosmological, collider, and direct detection constraints across a broad parameter space.
• To demonstrate that both baryonic and dark matter asymmetries are generated simultaneously via the Affleck-Dine mechanism in SUSY models.

Proposed method

• Promote baryon number to a local U(1)_B gauge symmetry, leading to a new anomalous global symmetry and a new gauge boson Z_B.
• Introduce a SM singlet chiral superfield X as the dark matter candidate, stable due to its charge under U(1)_B.
• Utilize supersymmetric flat directions to implement the Affleck-Dine mechanism for simultaneous generation of baryonic and dark matter asymmetries.
• Ensure anomaly cancellation by introducing exotic quarks with specific U(1)_B charges, and allow their decay via a singlet superfield.
• Construct a nonanomalous accidental global symmetry U(1)_D that unifies baryonic and dark matter number conservation.
• Calculate relic abundances via Z_B-mediated annihilation and constrain couplings using B-factory, LEP, Tevatron mono-jet, and direct detection data.

Experimental results

Research questions

• RQ1 Can a unified origin for baryonic and dark matter be achieved through a spontaneously broken U(1)_B gauge symmetry?
• RQ2 How does the Affleck-Dine mechanism in SUSY models simultaneously generate baryonic and dark matter asymmetries?
• RQ3 What is the required mass range for the dark matter candidate to reproduce the observed relic abundance?
• RQ4 How do constraints from B-factories, LEP, Tevatron mono-jet searches, and direct detection experiments constrain the model?
• RQ5 Can a vectorially coupled dark matter candidate remain consistent with direct detection limits while being light (GeV scale) and stable?

Key findings

• The dark matter candidate is a GeV-scale particle charged under the U(1)_B gauge symmetry, with its mass naturally constrained to the sub-GeV to tens of GeV range to reproduce the correct relic abundance.
• The simultaneous generation of baryonic and dark matter asymmetries via the Affleck-Dine mechanism leads to a primordial asymmetry ratio η_B/η_X ≈ 1, explaining the observed similarity in relic densities.
• For vectorial coupling to the Z_B gauge boson, the dark matter candidate must be around the GeV scale to evade direct detection constraints, consistent with current experimental limits.
• The model remains consistent with all existing constraints—including B-factory, LEP, Tevatron mono-jet, and direct detection experiments—for Z_B mediator masses as light as the GeV scale.
• The solution μ_u = μ_d, μ_e = μ_ν = 0, and μ_0 = 0 at high temperature ensures lepton number washout while preserving baryon number via the nonanomalous U(1)_D symmetry.
• The sphaleron processes decouple above the electroweak phase transition, and the resulting chemical potential solution (μ_0 = 0) ensures that baryon number asymmetry is preserved while lepton number is washed out.