Collider and dark matter searches in the inert doublet model from Peccei-Quinn symmetry

Published for SISSA by Springer Received: June 28, 2016 Revised: August 12, 2016 Accepted: September 14, 2016 Published: October 4, 2016 Collider and dark matter searches in the inert doublet model from Peccei-Quinn symmetry a Departamento de Ciências Exatas e da Terra, Universidade Federal de São Paulo, Diadema-SP, 09972-270, Brasil b Universidade Federal do ABC, Centro de Ciências Naturais e Humanas, 09210-580, Santo André-SP, Brasil c Instituto de Fı́sica, Universidad de Antioquia, Calle 70 No. 52-21, Medellı́n, Colombia d Universidade Federal do ABC, Centro de Matemática, Computação e Cognição Naturais, 09210-580, Santo André-SP, Brasil e Max-Planck-Institut fur Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany E-mail: , , , , , Abstract: Weakly Interacting Massive Particles (WIMPs) and axions are arguably the most compelling dark matter candidates in the literature. Could they coexist as dark matter particles? More importantly, can they be incorporated in a well motivated framework in agreement with experimental data? In this work, we show that this two component dark matter can be realized in the Inert Doublet Model in an elegant and natural manner by virtue of the spontaneous breaking of a Peccei-Quinn U(1)P Q symmetry into a residual Z2 symmetry. The WIMP stability is guaranteed by the Z2 symmetry and a new dark matter component, the axion, arises. There are two interesting outcomes: (i) vector-like quarks needed to implement the Peccei-Quinn symmetry in the model may act as a portal between the dark sector and the SM fields with a supersymmetry-type phenomenology at colliders; (ii) two-component Inert Doublet Model re-opens the phenomenologically interesting 100–500 GeV mass region. We show that the model can successfully realize a two component dark matter framework and at the same time avoid low and high energy physics constraints such as monojet and dijet plus missing energy, as well as indirect and direct dark matter detection bounds. Keywords: Beyond Standard Model, Cosmology of Theories beyond the SM, Discrete Symmetries ArXiv ePrint: 1606.07086 Open Access, c The Authors. Article funded by SCOAP3 . doi:10.1007/JHEP10(2016)015 JHEP10(2016)015 Alexandre Alves,a Daniel A. Camargo,b Alex G. Dias,b Robinson Longas,c Celso C. Nishid and Farinaldo S. Queiroze Contents 1 2 The model 3 3 Collider constraints 3.1 Bounds from SUSY and DM searches in jets plus missing energy and monojets 7 7 4 Dark matter phenomenology 4.1 WIMP relic density 4.2 Axion relic density 4.3 Mixed WIMP-axion dark matter in the IDM 4.4 New coannihilations with vector-like quarks 4.5 Direct detection 4.6 Indirect detection 12 12 13 13 14 16 18 5 Conclusions 18 6 Prospects 19 A Simple UV completions A.1 U(1)PQ breaking in the Higgs potential A.2 Lighter exotic quark mass 20 20 21 1 Introduction The nature of dark matter (DM) is one of the most puzzling mysteries of astroparticle physics. Dark matter which accounts for 27% of the total energy density of the Universe is often interpreted in terms of WIMPs. More precisely, only one species makes up the entire DM of the universe. Although, this minimal scenario having just one particle making up the entire DM sounds appealing, there is no observational evidence supporting this idea. In fact, both matter and radiation components of the Universe energy budget is comprised of more than one particle. Thus it is rather possible that DM is constituted by more than one particle. Albeit, having as a second WIMP merely to account for some fraction of the relic density is not so compelling, unless two solid signals are observed consistent with the two WIMPs scenario. Hence, an ideal scenario would occur if the second DM component solves a major problem in particle physics such as the Strong CP problem. This is precisely our case understudy, where the second component is the axion field. As we shall see, the addition of axions to the WIMP paradigm has two motivating outcomes: the WIMP is –1– JHEP10(2016)015 1 Introduction stability is naturally addressed; the strong CP problem in the Standard Model (SM) is solved. To put this framework into perspective we need to briefly review how this come into play. Thus, the scenario in which both WIMP and axion make up the DM of the Universe is a natural and compelling framework. With that in mind we add a new and well motivated ingredient, the axion, in one of the simplest extensions of the Standard Model with a WIMP: the Inert Doublet Model (IDM), which contains an additional SU(2)L Higgs doublet with the lightest component stabilized by an ad hoc Z2 symmetry [12–14]. In other words, we propose the axion as the DM companion to the IDM component H 0 . To this end we have developed a model based on the observation made in [15], where a U(1)P Q symmetry broken spontaneously into a Z2 symmetry was advocated to stabilize the WIMP.1 We tacitly assume that the U(1)P Q symmetry is protected against gravitational effects — which generate Planck-scale-suppressed symmetry breaking operators — by some sort of discrete symmetry (as in e.g. [23, 24]) to avoid destabilization of the solution to the strong CP problem, and also of the WIMP [25]. The use of this global symmetry to stabilize the WIMPs is safe from gravitational effects which might violate the U(1) P Q [25], since only Planck suppressed operators of dimension six are present. To complete this two component DM system, at least a scalar singlet field hosting the axion a and a vector-like quark D are necessary in addition to the inert Higgs doublet whose lightest neutral component is the heavy DM [26–28]. The vector-like quark allows a simple implementation of the U(1)P Q symmetry, as in the KSVZ axion model [7, 8], and acts as a portal connecting the SM and the dark sector. As a consequence of the residual Z2 symmetry, the heavy vector quarks decay only to new heavy scalars and SM quarks, mimicking the phenomenology of R-parity conserving supersymmetry (SUSY) at colliders, including the classic SUSY signal of jets plus large missing energy. As there is currently many experimental constraints on supersymmetry from the LHC searches, we performed, prior to the study of the multi-component DM scenario of our model, an investigation of the limits from the searches of jets plus missing energy and monojets at the LHC. After that, we focused on the main goal of the paper, which is 1 Other contexts where the WIMP is stabilized by an accidental symmetry that remains from the breaking of a more fundamental symmetry at a higher energy scale are given in [16–22]. –2– JHEP10(2016)015 WIMPs that are the most popular candidate for DM suggest a connection between DM physics and the weak scale. The stability of the WIMP is usually assumed to be due to the presence of ad hoc discrete global symmetry, such as a Z2 symmetry, which prevents its decay. Another candidate is the axion [1, 2], which is the pseudo Nambu-Goldstone of the brea (...truncated)