Probing Baryogenesis with Displaced Vertices at the LHC
  The generation of the asymmetric cosmic baryon abundance requires a departure
from thermal equilibrium in the early universe. In a large class of
baryogenesis models, the baryon asymmetry results from the out-of-equilibrium
decay of a new, massive particle. We highlight that in the interesting scenario
where this particle has a weak scale mass, this out-of-equilibrium condition
requires a proper decay length larger than O(1) mm. Such new fields are within
reach of the LHC, at which they can be pair produced leaving a distinctive,
displaced-vertex signature. This scenario is realized in the recently proposed
mechanism of baryogenesis where the baryon asymmetry is produced through the
freeze-out and subsequent decay of a meta-stable weakly interacting massive
particle ("WIMP baryogenesis"). In analogy to missing energy searches for WIMP
dark matter, the LHC is an excellent probe of these new long-lived particles
responsible for baryogenesis via the low-background displaced vertex channel.
In our paper, we estimate the limits on simplified models inspired by WIMP
baryogenesis from two of the most sensitive collider searches by CMS and ATLAS
with 8 TeV LHC data. We also estimate the LHC reach at 13 TeV using current
strategies, and demonstrate that O(10) improvements in cross-section limits can
be achieved by requiring two displaced vertices while lowering kinematic
thresholds. For meta-stable WIMPs produced through electroweak interactions,
the high luminosity LHC is sensitive to masses up to 2.5 TeV for lifetimes
around 1 cm, while for singlets pair-produced through the off-shell-Higgs
portal, the LHC is sensitive to production cross sections of O(50) ab for
benchmark masses around 150 GeV. Our analysis and proposals also generally
apply to displaced vertex signatures from other new physics such as hidden
valley models, twin Higgs models and displaced supersymmetry.
