Dark matter could be a thermal relic comprised of strongly interacting massive particles (SIMPs), where 3→2 interactions set the relic abundance. Such interactions generically arise in theories of chiral symmetry breaking via the Wess-Zumino-Witten term. In this work, we show that an axionlike particle can successfully maintain kinetic equilibrium between the dark matter and the visible sector, allowing the requisite entropy transfer that is crucial for SIMPs to be a cold dark matter candidate. Constraints on this scenario arise from beam dump and collider experiments, from the cosmic microwave background, and from supernovae. We find a viable parameter space when the axionlike particle is close in mass to the SIMP dark matter, with strong-scale masses of order a few hundred MeV. Many planned experiments are set to probe the parameter space in the near future.
Bibliographical noteFunding Information:
We thank Babette Dobrich, Eder Izaguirre, Tongyan Lin and Tracy R. Slatyer for useful conversations and correspondence pertaining to this work. Y. H., E. K. and H. M. also thank Tomer Volansky and Jay Wacker for early collaboration on this project. We acknowledge the importance of equity and inclusion in this work and are committed to advancing such principles in our scientific communities. Y. H. is supported by the Israel Science Foundation (Grant No. 1112/17), Binational Science Foundation (Grant No. 2016155), I-CORE Program of the Planning Budgeting Committee (Grant No. 1937/12), German Israel Foundation (Grant No. I-2487-303.7/2017), and Azrieli Foundation. E. K. is supported by the Israel Science Foundation (Grant No. 1111/17), Binational Science Foundation (Grant No. 2016153) and I-CORE Program of the Planning Budgeting Committee (Grant No. 1937/12). H. M. is supported by the U.S. DOE under Contract No. DE-AC02-05CH11231, and by the National Science Foundation under Grants No. PHY-1316783 and No. PHY-1638509. H. M. is also supported by the JSPS Grant-in-Aid for Scientific Research (C) (No. 26400241 and No. 17K05409), MEXT Grant-in-Aid for Scientific Research on Innovative Areas (No. 15H05887 and No. 15K21733), WPI, MEXT, Japan the Binational Science Foundation (No. 2016155), and the Alexander von Humboldt Foundation. R. M. and K. S. are supported by the National Science Foundation Graduate Research Fellowship Program. K. S. is also supported by a Hertz Foundation Fellowship.
© 2018 authors. Published by the American Physical Society.