LHC phenomenology of the type II seesaw mechanism: Nondegenerate case

Abstract

In this paper, we thoroughly investigate the LHC phenomenology of the type II seesaw mechanism for neutrino masses in the nondegenerate case where the triplet scalars of various charge (H ±± , H ± , H 0 , A 0 ) have different masses. Compared with the degenerate case, the cascade decays of scalars lead to many new, interesting signal channels. In the positive scenario where M H ±± < M H ± < M H 0 /A 0 , the four-lepton signal is still the most promising discovery channel for the doubly-charged scalars H ±± . The five-lepton signal is crucial to probe the mass spectrum of the scalars, for which, for example, a 5σ reach at 14 TeV LHC for M H ± = 430 GeV with M H ±± = 400 GeV requires an integrated luminosity of 76 fb −1 . And the six-lepton signal can be used to probe the neutral scalars H 0 /A 0 , which are usually hard to detect in the degenerate case. In the negative scenario where M H ±± > M H ± > M H 0 /A 0 , the detection of H ±± is more challenging, when the cascade decay H ±± → H ± W ± * is dominant. The most important channel is the associated H ± H 0 /A 0 production in the final state ± E T b bb b, which requires a luminosity of 109 fb −1 for a 5σ discovery, while the final state ± E T b bτ + τ − is less promising. Moreover, the associated H 0 A 0 production can give same signals as the standard model Higgs pair production. With a much larger cross section, the H 0 A 0 production in the final state b bτ + τ − could reach 3σ significance at 14 TeV LHC with a luminosity of 300 fb −1 . In summary, with an integrated luminosity ∼ O(500 fb −1 ), the triplet scalars can be fully reconstructed at 14 TeV LHC in the negative scenario.

Neutrinos and Collider Physics

“…[246, [254][255][256][257][258][259][260][261][262][263][264].The doubly charged scalar boson has the following possible decay channels: ℓ ℓ ± ± , W W ± ± , W Δ ± ± and Δ Δ ± ± , if kinematically allowed. For the triplet VEV v 0.1 MeV ≲ Δ , the doubly charged Higgs couplings to W ± is suppressed and for a nearly degenerate triplet mass spectrum, the dominant decay mode of Δ ±± is same-sign dileptons [260,265].…”

Revisiting the high-scale validity of the type II seesaw model with novel LHC signature

“…As a result, the lower bounds on these scalars are very relaxed. Some collider analyses for this case have been done before [32][33][34][35][36] and after [37][38][39][40][41][42][43][44] the Higgs discovery but our analysis goes beyond what has been reported so far. In our analysis, we demonstrate the complete picture of a high-scale valid type II seesaw potential and analyze the signal significance at the LHC in the allowed parameter space.…”

Naturally small Dirac neutrino mass with intermediate SU(2) L multiplet fields

“…[18,19], we firstly discuss the tree-level realization of Dirac seesaw with at most two extra scalars S 1,2 and a heavy intermediated Dirac fermion F 1 (figure 1). Here, the global lepton number symmetry U(1) is proposed to forbid the unwanted Majorana mass term (m N /2)ν C R ν R , meanwhile the discrete Z 3 [55,58], Z 4 [48,60,61] and ∆ (27) [62] symmetry are also optional.…”

“…[20][21][22][23][24][25][26] for classic examples). In these models, new physics may arise at TeV scale and thus be detectable at LHC or other planned collider machine [27][28][29][30][31][32][33]. In ref.…”