Phenomenology of the minimal B − L extension of the standard model: The Higgs sector

Self Cite

We study a class of non-exotic minimal U(1) extensions of the Standard Model, which includes all scenarios that are anomaly-free with the ordinary fermion content augmented by one Right-Handed neutrino per generation, wherein the new Abelian gauge group is spontaneously broken by the non-zero Vacuum Expectation Value of an additional Higgs singlet field, in turn providing mass to a Z state. By adopting the B − L example, whose results can be recast into those pertaining to the whole aforementioned class, and allowing for both scalar and gauge mixing, we first extract the surviving parameter space in presence of up-to-date theoretical and experimental constraints. Over the corresponding parameter configurations, we then delineate the high energy behaviour of such constructs in terms of their stability and perturbativity. Finally, we highlight key production and decay channels of the new states entering the spectra of this class of models, i.e., heavy neutrinos, a second Higgs state and the Z , which are amenable to experimental investigation at the Large Hadron Collider. We therefore set the stage to establish a direct link between measurements obtainable at the Electro-Weak scale and the dynamics of the underlying model up to those where a Grand Unification Theory embedding a U(1) can be realised.

Section: Jhep07(2016)086mentioning

confidence: 81%

Section: Jhep07(2016)086mentioning

confidence: 99%

Z ′, Higgses and heavy neutrinos in U(1)′ models: from the LHC to the GUT scale

Accomando

Corianò

Rose

et al. 2016

Self Cite

“…While the signatures connected to the Z ′ and an additional Higgs boson have repeatedly been studied in the literature [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21], the signatures emerging from the heavy neutrino sector have seen less investigation. From the diagonalisation of the neutrino mass matrix one obtains three very light, mostly Left-Handed (LH), neutrinos (ν l ), which are identified as the SM ones, and three heavy, mostly Right-Handed (RH), neutrinos (ν h ), with very small mixing with the light ν l 's, thereby obtaining very small yet non-vanishing couplings to the gauge bosons.…”

Section: Introductionmentioning

confidence: 99%

Extra Higgs boson and Z′ as portals to signatures of heavy neutrinos at the LHC

Accomando

Rose

Moretti

et al. 2018

Self Cite

In this paper, we discuss the potential of observing heavy neutrino (ν h ) signatures of a U(1) B−L enlarged Standard Model (SM) encompassing three heavy Majorana neutrinos alongside the known light neutrino states at the Large Hadron Collider (LHC). We exploit the theoretical decay via a heavy (non-SM-like) Higgs boson and Z ′ production followed by ν h → l ± W ∓( * ) and ν h → ν l Z ( * ) decays, ultimately yielding a 3l + 2j + E miss T signature and, depending upon how boosted the final state objects are, we define different possible selections aimed at improving the signal to background ratio in LHC Run 2 data for a wide range of heavy neutrino masses.

“…Complex singlet extensions with global U(1) symmetry yield rich phenomenological properties, such as a second Higgs particle mixed with the ordinary Higgs particle along with WIMP dark matter candidates [9][10][11]. The global U(1) symmetry also provides a foundation for further model-building [12][13][14], in particular interactions with an extra vector-like fermion [15][16][17] that may explain the LHC diphoton excesses [18,19].…”

Section: Introductionmentioning

confidence: 99%

Conformal complex singlet extension of the Standard Model: scenario for dark matter and a second Higgs boson

Wang

Steele

Hanif

et al. 2016

We consider a conformal complex singlet extension of the Standard Model with a Higgs portal interaction. The global U(1) symmetry of the complex singlet can be either broken or unbroken and we study each scenario. In the unbroken case, the global U(1) symmetry protects the complex singlet from decaying, leading to an ideal cold dark matter candidate with approximately 100 GeV mass along with a significant proportion of thermal relic dark matter abundance. In the broken case, we have developed a renormalization-scale optimization technique to significantly narrow the parameter space and in some situations, provide unique predictions for all the model's couplings and masses. We have found there exists a second Higgs boson with a mass of approximately 550 GeV that mixes with the known 125 GeV Higgs with a large mixing angle sin θ ≈ 0.47 consistent with current experimental limits. The imaginary part of the complex singlet in the broken case could provide axion dark matter for a wide range of models. Upon including interactions of the complex scalar with an additional vector-like fermion, we explore the possibility of a diphoton excess in both the unbroken and the broken cases. In the unbroken case, the model can provide a natural explanation for diphoton excess if extra terms are introduced providing extra contributions to the singlet mass. In the broken case, we find a set of coupling solutions that yield a second Higgs boson of mass 720 GeV and an 830 GeV extra vector-like fermion F , which is able to address the 750 GeV LHC diphoton excess. We 1 Corresponding author.Open Access, c The Authors. Article funded by SCOAP 3 .doi:10.1007/JHEP08(2016)065 JHEP08(2016)065also provide criteria to determine the symmetry breaking pattern in both the Higgs and hidden sectors.