Abstract
We propose soft breaking mechanism for dark matter (DM) shift symmetry in a class of composite dark matter models, where both DM and the Higgs boson arise as pseudo Nambu-Goldstone bosons from novel strong dynamics. Our mechanism is utilized to suppress the non-derivative portal coupling between the Higgs boson and DM particle, which can evade the stringent bound of current DM direct detection experiments. Otherwise this non-derivative portal coupling would naturally be at the same order of the Higgs quartic, rendering this class of models under severe crisis. For realizing soft breaking mechanism, we introduce vector-like top partners, dubbed as "softons", to restore the shift symmetry of DM in top Yukawa sector, which however is only broken by the softon masses. The portal coupling would automatically vanish as the shift-symmetry-breaking softon masses approach zero. Specifically we present a proof-of-concept model of soft breaking, based on the coset $O(6)/O(5)$ and the simplest fermion embedding, and study its DM phenomenology, where we show a large amount of novel parameter space is opened up by using the soft breaking mechanism.
Highlights
One plausible resolution to the hierarchy problem is to consider the Higgs boson as a pseudo Nambu-Goldstone boson (PNGB) emerging from spontaneous global symmetry breaking of a new strongly interacting sector
We propose a mechanism for softly breaking the dark matter (DM) shift symmetry in the top sector, leading to a suppressed portal coupling λ while DM still lives in the weak scale
We propose a soft-breaking mechanism for the shift symmetry of PNGB DM, which is still at the EW scale, whereas the stringent bounds from current direct detection are evaded
Summary
One plausible resolution to the hierarchy problem is to consider the Higgs boson as a pseudo Nambu-Goldstone boson (PNGB) emerging from spontaneous global symmetry breaking of a new strongly interacting sector In this scenario, the Higgs boson is protected by an approximate shift symmetry and naturally lighter than the typical scale of the strong sector. 0.065 if the top sector breaks both the shift symmetry of the Higgs boson and DM This value of λ is in tension with current direct detection bounds [24,25,26]. We propose a mechanism for softly breaking the DM shift symmetry in the top sector, leading to a suppressed portal coupling λ while DM still lives in the weak scale. We will discuss the soft-breaking mechanism in a more general framework, and demonstrate the idea in the top sector of a more minimal model
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
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.
