Restrained dark U ( 1 ) d at low energies

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We examine theoretical features of U(1) X extensions of the Standard Model whose quantum anomalies are canceled per generation. Similarly to other versions, the theory consists of a Two-Higgs-Doublet Model plus a scalar singlet embedded into the SM ⊗ U(1) X gauge group, and introduces small modifications to the Z-boson interactions. These changes can be minimized by exclusively charging right-handed fermions under the new Abelian symmetry, and are compensated by the neutral X-boson exchange. Nonuniversality of fermion couplings can also be achieved by requiring one single X-charged family. In general, X gauge bosons can be separated into A and Z subsets, distinguished by the presence of axial-vector components in the Z exchange. A physics, in particular the dark photons case, is commonly simpler to constrain and therefore favored by experimental tests. Finally, the model can be UV completed both by stable χ fermions or by right-handed neutrinos. The prior case may provide cold WIMPs in the theory.

Section: Introductionmentioning

confidence: 99%

Light mediators in anomaly free U (1)X models. Part I. Theoretical framework

Correia

Fajfer

2019

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“…• LSND: We choose to use the search [67] for electron neutrino ν e via the inclusive charged-current reaction ν e + C → e − + X. 6 Following [21], we will consider that the outgoing e + e − pair is interpreted as a single electron event satisfying the energy cut, 60 MeV < E e + + E e − < 200 MeV and use the electron detection efficiency of around 10%. Given the uncertainties presented in [67] (see especially Fig 29 and the Tables IV and V), and the fact that the energy distribution of our process would not have been uniform, we will consider that 25 events should have been observed and draw our contours accordingly.…”

Section: Dark Higgs Boson Decay and Detectionmentioning

confidence: 99%

“…The effect it can have on BBN can be constrained using the PLANCK measured value of N eff . The definition of effective number of neutrino species assumes that the three neutrino species instantaneously decouple giving a definite neutrino-photon temperature ratio T ν /T γ = (4/11) 1/3 , so that 6) where N ν = 3 is the number of neutrino species. Since the energy injected by the S decays will lead to a reheating of the electron-photon bath with respect to the neutrinos, this decreases T ν /T γ .…”

Section: Bbn Constraintsmentioning

confidence: 99%

Light dark Higgs boson in minimal sub-GeV dark matter scenarios

Rao

Roszkowski

2018

Minimal scenarios with light (sub-GeV) dark matter whose relic density is obtained from thermal freeze-out must include new light mediators. In particular, a very wellmotivated case is that of a new "dark" massive vector gauge boson mediator. The mass term for such mediator is most naturally obtained by a "dark Higgs mechanism" which leads to the presence of an often long-lived dark Higgs boson whose mass scale is the same as that of the mediator. We study the phenomenology and experimental constraints on two minimal, self-consistent dark sectors that include such a light dark Higgs boson. In one the dark matter is a pseudo-Dirac fermion, in the other a complex scalar. We find that the constraints from BBN and CMB are considerably relaxed in the framework of such minimal dark sectors. We present detection prospects for the dark Higgs boson in existing and projected proton beam-dump experiments. We show that future searches at experiments like Xenon1T or LDMX can probe all the relevant parameter space, complementing the various upcoming indirect constraints from astrophysical observations. * a luc.darme@ncbj.gov.pl †b soumya.rao@ncbj.gov.pl ‡c leszek.roszkowski@ncbj.gov.pl

“…from its simplicity, the U(1) X SM extension is commonly found in different models as the first step of a gauge breaking scheme, like, for instance, in Grand Unified Theories E 6 , where E 6 → SO(10) ⊗ U(1) → SU(5) ⊗ U(1) ⊗ U(1) → SM ⊗ U (1). Guided by our theoretical analysis of SM⊗U(1) X theories, in this paper we describe the constraints from the existing experimental data on the dark gauge boson phenomenology at the low energies (MeV regime) [11].…”

Section: Jhep10(2019)279mentioning

confidence: 99%

“…Phenomenology of U(1) gauge bosons X µ (see e.g. [1][2][3][4][5][6][7][8][9]) is, in general, very dependent on the particle content and the X-hypercharge assignment of the fundamental theory. The canonical requirements for the formulation of an ultraviolet (UV) model, such as to be anomaly free and to recover the Standard Model (SM) fermion mass matrices, indicates the presence of new scalars and stable fermions even in minimal extensions like the Two Higgs Doublet Model (2HDM).…”

Section: Introductionmentioning

confidence: 99%

Light mediators in anomaly free U (1)X models. Part II. Constraints on dark gauge bosons

Correia¹,

Fajfer²

2019

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We consider experimental constraints in the MeV region in order to determine the parameter space for the U(1) X extension of the Standard Model, presented in the first part of our work. In particular, we focus on the model UV-completed by cold WIMPs. We conclude that the electron anomalous magnetic moment and the neutrino trident production provide the most stringent bounds to g 2 X ∼ 10 −6 in the mass interval below the di-muon threshold. By allowing the axial-vector coupling of the dark gauge boson Z , the interference effect with the SM gauge bosons may reduce the bounds coming from the neutrino trident production. At the same time, such coupling allows a region of the parameter space already favored both by the relic abundance and by the discrepancy between experimental result and theoretical prediction for the muon anomalous magnetic moment. We emphasize that light-Z interactions, non-universal for the two first lepton families, necessarily create a difference in the proton charge radius measured in the Lamb shift of the e-hydrogen and µ-hydrogen. Finally, we determine the effects of the new gauge boson on the forward-backward asymmetry in e + e − →f f , f = µ, τ , and on the leptonic decays M → jν j l + l − , where M = π, K, D, D s , B and j, l = e, µ.