Dark Matter, Baryogenesis and Neutrino Oscillations from Right Handed Neutrinos

Abstract

We show that, leaving aside accelerated cosmic expansion, all experimental data in high energy physics that are commonly agreed to require physics beyond the Standard Model can be explained when completing it by three right handed neutrinos that can be searched for using current day experimental techniques. The model that realises this scenario is known as Neutrino Minimal Standard Model (νMSM). In this article we give a comprehensive summary of all known constraints in the νMSM, along with a pedagogical introduction to the model. We present the first complete quantitative study of the parameter space of the model where no physics beyond the νMSM is needed to simultaneously explain neutrino oscillations, dark matter and the baryon asymmetry of the universe. This requires to track the time evolution of left and right handed neutrino abundances from hot big bang initial conditions down to temperatures below the QCD scale. We find that the interplay of resonant amplifications, CP-violating flavour oscillations, scatterings and decays leads to a number of previously unknown constraints on the sterile neutrino properties. We furthermore re-analyse bounds from past collider experiments and big bang nucleosynthesis in the face of recent evidence for a non-zero neutrino mixing angle θ_{13}. We combine all our results with existing constraints on dark matter properties from astrophysics and cosmology. Our results provide a guideline for future experimental searches for sterile neutrinos. A summary of the constraints on sterile neutrino masses and mixings has appeared in arXiv:1204.3902 [hep-ph]. In this article we provide all details of our calculations and give constraints on other model parameters.

Figures (17)

• Figure 1: The thermal history of the universe in the $\nu$MSM.
• Figure 2: Different constraints on $N_1$ mass and mixing. The blue region is excluded by X-ray observations, the dark gray region $M_1< 1$ keV by the Tremaine-Gunn bound Tremaine:1979weBoyarsky:2008juGorbunov:2008ka. The points on the upper solid black line correspond to observed $\Omega_{DM}$ produced in scenario I in the absence of lepton asymmetries (for $\mu_{\alpha}=0$) Laine:2008pg; points on the lower solid black line give the correct $\Omega_{DM}$ for $|\mu_{\alpha}|=1.24\cdot10^{-4}$, the maximal asymmetry we found. The region between these lines is accessible for $0\leq |\mu_\alpha|\leq 1.24\cdot10^{-4}$. We do not display bounds derived from Ly$_\alpha$ forest observations because it depends on $\mu_\alpha$ in a complicated way and the calculation currently includes considerable uncertainties Boyarsky:2008mt.
• Figure 3: Number of effective relativistic degrees of freedom $g_*$ as a function of temperature Laine:2006cp.
• Figure 4: Contributions to the $N_I$ self energies. Diagram $a)$ dominates for $T<v$, diagram $b)$ for $T>v$. $\Gamma_N$ is obtained from the discontinuity of the diagrams Weldon:1983jn, which can be computed by cutting it in various ways Bedaque:1996af. The gray self energy blobs indicate that dressed lepton and Higgs propagators have to be used. Cuts through them reveal a large number of processes, which are summarized in Asaka:2006nqAsaka:2006rw and appendix A of Shaposhnikov:2008pf. Recently it has been pointed out that current estimates suffer from an error $\mathcal{O}(1)$ due to infrared and collinear enhancements at high temperature. Systematic approaches to include these effects can be found in Anisimov:2010gyBesak:2012qm for $T> M$ (relevant for baryogenesis) and Laine:2011xmLaine:2011pqSalvio:2011sf for $M>T$ (relevant for late time asymmetries). We ignore this effect in our current study as it is comparable to other uncertainties in the kinetic equations and would only slightly change the results for the relevant regions in the $\nu$MSM parameter space.
• Figure 5: The functions $R^{(S)}(T,M)$ and $R_M^{(S)}(T,M)$ for $M=1.2$ GeV (darkest curve), $M=1.6$ GeV, $M=2$ GeV, $M=2.5$ GeV, $M=3$ GeV, $M=3.5$ GeV, $M=4$ GeV (lightest curve). We would like to thank Mikko Laine for providing us numerical data.