Abstract
Dark matter may be hidden, with no standard model gauge interactions. At the same time,in WIMPless models (WIMP: weakly interacting massive particles) with hiddenmatter masses proportional to hidden gauge couplings squared, the hidden darkmatter’s thermal relic density may naturally be in the right range, preservingthe key quantitative virtue of WIMPs. We consider this possibility in detail. Wefirst determine model-independent constraints on hidden sectors from big bangnucleosynthesis and the cosmic microwave background. Contrary to conventionalwisdom, large hidden sectors are easily accommodated. A flavour-free version ofthe standard model is allowed if the hidden sector is just 30% colder than theobservable sector after reheating. Alternatively, if the hidden sector contains aone-generation version of the standard model with characteristic mass scale below1 MeV, even identical reheating temperatures are allowed. We then analyse hiddensector freeze-out in detail for a concrete model, solving the Boltzmann equationnumerically and explaining the results from both observable and hidden sector points ofview. We find that WIMPless dark matter does indeed obtain the correct relicdensity for masses in the range . The upper bound results from the requirement of perturbativity, and the lower boundassumes that the observable and hidden sectors reheat to the same temperature, and israised to the MeV scale if the hidden sector is ten times colder. WIMPless dark mattertherefore generalizes the WIMP paradigm to the largest mass range possible for viablethermal relics and provides a unified framework for exploring dark matter signals acrossnine orders of magnitude in dark matter mass.
Highlights
In WIMPless models, hidden sector particles X have masses and couplings that may be very different from WIMPs, but which satisfy mX gX2
We find that WIMPless dark matter may have the desired thermal relic density for the entire range of keV mX TeV, where the lower bound is set by the requirement that dark matter freeze-out is non-relativistic, and the upper bound follows from the requirement of perturbative gauge couplings
WIMPless dark matter encompasses as large a range of masses as one could expect of dark matter that has the naturally correct thermal relic density, and it provides a unified framework for addressing many diverse dark matter signals and phenomenology
Summary
We assume that the observable sector is the minimal supersymmetric standard model (MSSM), which is supplemented with a single hidden sector. Model A is a one-generation flavour-free version of the MSSM, with all Yukawa couplings of order 1 We see that it is allowed for ξRH < 0.92, that is, reheat temperatures that are almost identical to the observable sector ones. Such a hidden sector is much colder than the MSSM at BBN times, since its cooling is not slowed by the disappearance of heavy degrees of freedom, in contrast to the MSSM This cooling is critical, given the fourth power of the temperature in equation (7), and makes such a hidden sector allowed. This contrasts with the case of the SM, where CMB constraints may be viewed as consistency checks on BBN results
Sign-in/Register to view highlights & summary 
Submitted Version (
Free)
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
