Neutrino dark matter and the Higgs portal: improved freeze-in analysis
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Springer
Received: April 3, Revised: August 31, Accepted: September 20, Published: October 21,
2020 2020 2020 2020
Valentina De Romeri,a Dimitrios Karamitros,b Oleg Lebedevc and Takashi Tomad,e a
Institut de F´ısica Corpuscular CSIC/Universitat de Val`encia, Parc Cient´ıfic de Paterna, C/ Catedr´ atico Jos´e Beltr´ an, 2 E-46980 Paterna (Valencia), Spain b National Centre for Nuclear Research, ul. Pasteura 7, 02-093 Warsaw, Poland c Department of Physics, University of Helsinki, Gustaf H¨ allstr¨ omin katu 2a, Helsinki, Finland d Department of Physics, McGill University, 3600 Rue University, Montr´eal, Qu´ebec H3A 2T8, Canada e Institute of Liberal Arts and Science, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
E-mail: [email protected], [email protected], [email protected], [email protected] Abstract: Sterile neutrinos are one of the leading dark matter candidates. Their masses may originate from a vacuum expectation value of a scalar field. If the sterile neutrino couplings are very small and their direct coupling to the inflaton is forbidden by the lepton number symmetry, the leading dark matter production mechanism is the freeze-in scenario. We study this possibility in the neutrino mass range up to 1 GeV, taking into account relativistic production rates based on the Bose-Einstein statistics, thermal masses and phase transition effects. The specifics of the production mechanism and the dominant mode depend on the relation between the scalar and sterile neutrino masses as well as on whether or not the scalar is thermalized. We find that the observed dark matter abundance can be produced in all of the cases considered. We also revisit the freeze-in production of a Higgs portal scalar, pointing out the importance of a fusion mode, as well as the thermalization constraints. Keywords: Beyond Standard Model, Cosmology of Theories beyond the SM ArXiv ePrint: 2003.12606
c The Authors. Open Access, Article funded by SCOAP3 .
https://doi.org/10.1007/JHEP10(2020)137
JHEP10(2020)137
Neutrino dark matter and the Higgs portal: improved freeze-in analysis
Contents 1
2 The model 2.1 The scalar sector 2.1.1 Thermal corrections 2.2 Constraints on sterile neutrino dark matter
3 4 5 6
3 Relativistic rates for asymmetric reactions
8
4 Thermalization constraints 4.1 Sterile neutrino thermalization 4.2 Thermalization of s 4.2.1 Self-thermalization due to λs
11 11 13 14
5 Sterile neutrino production I: thermalized s 5.1 Reaction rates 5.1.1 hh → νν 5.1.2 hs → νν 5.1.3 ss → νν 5.1.4 s → νν 5.2 Dark matter abundance: ms > 2M 5.2.1 Qualitative behaviour of the Boltzmann equation solution 5.2.2 Results 5.3 Light s: ms < 2M
16 16 17 17 17 18 18 19 19 22
6 Sterile neutrino production II: non-thermal s 6.1 Heavy s 6.2 Small couplings: freeze-in production of s 6.2.1 hh → s rate 6.2.2 h → ss and hh → ss rates 6.2.3 Results 6.2.4 On electroweak phase transition effects
24 24 25 25 26 26 28
7 Conclusion
29
A Leading thermal corrections
31
B s decay partial widths
32
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