The scalar sector of the Randall–Sundrum model

Abstract

We consider the scalar sector of the Randall-Sundrum model. We derive the effective potential for the Standard Model Higgs-boson sector interacting with Kaluza-Klein excitations of the graviton (h ν n µ ) and the radion (φ) and show that only the Standard Model vacuum solution of ∂V (h)/∂h = 0 (h is the Higgs field) is allowed. We then turn to our main focus: the consequences of the curvaturescalar mixing ξ R H † H (where H is a Higgs doublet field on the visible brane), which causes the physical mass eigenstates h and φ to be mixtures of the original Higgs and radion fields. First, we discuss the theoretical constraints on the allowed parameter space. Next, we give precise procedures for computing the h and φ couplings given the physical eigenstate masses, m h and m φ , ξ and the new physics scales of the model. Relations among these new-physics scales are discussed and a set of values not far above the smallest values required by precision electroweak constraints and RunI data is chosen. A simple result for the sum of the ZZh and ZZφ squared couplings relative to the ZZh SM squared coupling is derived. We demonstrate that this sum rule in combination with LEP/LEP2 data implies that a) not both the h and φ can be light. We present explicit results for the still allowed region in the (m h , m φ ) plane that remains after imposing the appropriate LEP/LEP2 upper limits coming from the Higgs-strahlung channel. In the remaining allowed region of parameter space, we examine numerically the couplings and branching ratios of the h and φ for several cases with m h = 120 GeV and m φ ≤ 300 GeV.The resulting prospects for detection of the h and φ at the LHC, a future LC and a γγ collider are reviewed. For moderate |ξ|, both the anomalous h → gg coupling and (when m h > 2m φ ) the non-standard decay channel h → φφ can substantially impact h discovery. Presence of the latter is a direct signature for non-zero ξ. We find that BR(h → φφ) as large as 30 ÷ 40 % is possible when |ξ| is large. Conversely, if m φ > 2m h then BR(φ → hh) is generally large. Detection of a light φ might require the LC. Detection of a heavy φ might need to take into account the φ → hh channel. The feasibility of experimentally measuring the anomalous gg and γγ couplings of the h and φ is examined. PACS: 04.50.+h, 12.60.Fr Keywords: extra dimensions, Higgs-boson sector, Randall-Sundrum model 2 In other words we consider here contributions from the massless zero Kaluza-Klein mode, see Eq. (11).3 We note that our ǫ 2 is related to the κ 2 of [2] by ǫ 2 = 2κ 2 .

Radion/dilaton-Higgs mixing phenomenology in light of the LHC

“…We show how in this way one can arrive at an effective Lagrangian that describes the different mixing possibilities encountered in these kinds of models. We also show that moving the Higgs from the brane into the bulk of the extra dimension can already have important consequences on how the radion couples to SM particles, leading to a different radion phenomenology compared to the brane Higgs case [9][10][11][12][13]16]. In particular we show that due to the geometry/conformal symmetry of the radion in the bulk, its couplings to 4D scalar kinetic terms vanish, and therefore the radion coupling to massive gauge bosons is suppressed.…”

“…3 Radion-Higgs mixing Light radion/dilaton phenomenology and mixing with an IR-brane localized Higgs has been studied extensively in the literature [10][11][12][13][14][15]. It has been found that current LHC measurements, in particular of the Higgs mass and signal strengths, already put significant constraints on the parameter space of these models [18][19][20].…”

Astrophysical implications of a visible dark matter sector from a custodially warped GUT

“…Various studies on radion phenomenology have been performed in the past [35,36,101,37,38,102,103,104,105], including recent works where radion dynamics was considered within realistic models of electroweak breaking with bulk SM fields [105,106,107]. For example in the case of radion mass lighter than 2M W , r → γγ is a promising channel [106], which can be also dramatically enhanced in the presence of Higgs-radion mixing [107].…”

Randall–Sundrum reality at the LHC

“…Similar analyses were done in ref. [5,28,29,30,31,32,33,34]. We refine the calculations appropriate to the LHC experiments at 7 TeV (LHC7), and consider the possibility of finding φ in the ongoing LHC Higgs searches.…”