Dark Matter with Density-dependent Interactions

The decay and annihilation cross sections of dark matter particles may depend on the value of a chameleonic scalar field that both evolves cosmologically and takes different values depending on the local matter density. This possibility introduces a separation between the physics relevant for freeze-out and that responsible for dynamics and detection in the late universe. We investigate how such dark sector interactions might be implemented in a particle physics Lagrangian and consider how current and upcoming observations and experiments bound such dark matter candidates. A specific simple model allows for an increase in the annihilation cross section by a factor of 106 between freeze-out and today, while more complicated models should also allow for scattering cross sections near the astrophysical bounds. Disciplines Physical Sciences and Mathematics | Physics Comments Boddy, K. K., Carroll, S. M., & Trodden, M. (2012). Dark Matter with Density-dependent Interactions. Physical Review D, 86(12), 123529. doi: 10.1103/PhysRevD.86.123529 © 2012 American Physical Society This journal article is available at ScholarlyCommons: http://repository.upenn.edu/physics_papers/272 Dark matter with density-dependent interactions Kimberly K. Boddy,* Sean M. Carroll, and Mark Trodden California Institute of Technology, Pasadena, California 91125, USA Center for Particle Cosmology, Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA (Received 31 August 2012; published 28 December 2012) The decay and annihilation cross sections of dark matter particles may depend on the value of a chameleonic scalar field that both evolves cosmologically and takes different values depending on the local matter density. This possibility introduces a separation between the physics relevant for freeze-out and that responsible for dynamics and detection in the late universe. We investigate how such dark sector interactions might be implemented in a particle physics Lagrangian and consider how current and upcoming observations and experiments bound such dark matter candidates. A specific simple model allows for an increase in the annihilation cross section by a factor of 10 between freeze-out and today, while more complicated models should also allow for scattering cross sections near the astrophysical bounds. DOI: 10.1103/PhysRevD.86.123529 PACS numbers: 95.35.+d