Cosmological implications of Standard Model criticality and Higgs inflation

• Published in: Nuclear physics. B Vol. 953; p. 114946
• Main Authors: Hamada, Yuta, Kawai, Hikaru, Nakanishi, Yukari, Oda, Kin-ya
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2020; Elsevier
• ISSN: 0550-3213; 1873-1562
• DOI: 10.1016/j.nuclphysb.2020.114946

The observed Higgs mass indicates that the Standard Model can be valid up to near the Planck scale MP. Within this framework, it is important to examine how little modification is necessary to fit the recent experimental results in particle physics and cosmology. As a minimal extension, we consider the possibility that the Higgs field plays the role of inflaton and that the dark matter is the Higgs-portal scalar field. We assume that the extended Standard Model is valid up to the string scale 1017GeV. (This translates to the assumption that all the non-minimal couplings are not particularly large, ξ≲102, as in the critical Higgs inflation, since MP/102∼1017GeV.) We find a correlated theoretical bound on the tensor-to-scalar ratio r and the dark matter mass mDM. As a result, the Planck bound r<0.09 implies that the dark-matter mass must be smaller than 1.1 TeV, while the PandaX-II bound on the dark-matter mass mDM>0.7±0.2TeV leads to r≳2×10−3. Both are within the range of near-future detection. When we include the right-handed neutrinos of mass MR∼1014 GeV, the allowed region becomes wider, but we still predict r≳10−3 in the most of the parameter space. The most conservative bound becomes r>10−5 if we allow three-parameter tuning of mDM, MR, and the top-quark mass.