Neutrino masses from low scale partial compositeness

Abstract

We consider a class of models in which the neutrinos acquire Majorana masses through mixing with singlet neutrinos that emerge as composite states of a strongly coupled hidden sector. In this framework, the light neutrinos are partially composite particles that obtain their masses through the inverse seesaw mechanism. We focus on the scenario in which the strong dynamics is approximately conformal in the ultraviolet, and the compositeness scale lies at or below the weak scale. The small parameters in the Lagrangian necessary to realize the observed neutrino masses can naturally arise as a consequence of the scaling dimensions of operators in the conformal field theory. We show that this class of models has interesting implications for a wide variety of experiments, including colliders and beam dumps, searches for lepton flavor violation and neutrinoless double beta decay, and cosmological observations. At colliders and beam dumps, this scenario can give rise to striking signals involving multiple displaced vertices. The exchange of hidden sector states can lead to observable rates for flavor violating processes such as μ → eγ and μ → e conversion. If the compositeness scale lies at or below a hundred MeV, the rate for neutrinoless double beta decay is suppressed by form factors and may be reduced by an order of magnitude or more. The late decays of relic singlet neutrinos can give rise to spectral distortions in the cosmic microwave background that are large enough to be observed in future experiments.

Holographic models of composite Higgs in the Veneziano limit. Part I. Bosonic sector

“…Finally, note that a composite fermion may be arbitrarily light when it is a SM singlet, i.e. a sterile neutrino, with various, associated phenomenological implications [49][50][51]. Our holographic analysis of the spectrum of composite fermions may be of interest in all these contexts.…”

Probing Higgs exotic decay at the LHC with machine learning

“…Moreover, such a semi-inclusive approach particularly balances the broadness of the signal space and the usage of kinematics to suppress the background, which will complement the traditional exclusive searches and possible more modelagnostic searches. This strategy can be followed in many different channels, such as W/Z/h-decay to multiple sterile neutrinos [52], continium dark sector [53][54][55], and generally hidden strong dynamics. It is also useful to extend the study of off-shell heavy standard model particle decays, as well as the search of BSM particle decays such as W , Z , top partners and heavy Higgs.…”

Perturbative benchmark models for a dark shower search program

“…Attractive choices for the massive mediator are a new vector boson [1,8,10,16,19,20,22,24,26,33,[35][36][37], a new scalar boson [8,18,23,25,35,44,46], the SM Higgs [1,4,6,14,15,17,35,40,57,58] or the SM W/Z bosons [1,12,51]. In this class of models, the mediator mass sets the overall energy scale of the event.…”

“…The possible collider signatures of confining dark sectors were first considered in the context of hidden valley models [1], where it was noted that the resulting spectacular phenomenologies could prove to be well-motivated "stress tests" for the existing analysis strategies at the LHC. A growing body of work has further developed hidden valleys as ingredients in models that address longstanding mysteries of particle physics, such as the stability of the electroweak hierarchy [2][3][4], the matterantimatter asymmetry [5], dark matter [6][7][8][9][10], and the origin of neutrino masses [11,12]. More generally, the collider phenomenology of light, strongly-coupled hidden sectors is extremely rich and the subject of a substantial amount of work, which includes studies focusing on displaced signatures [13][14][15][16][17][18][19][20], event or jet shape variables [21][22][23][24][25][26][27][28][29][30] and machine learning techniques [31,32], as well as more general explorations and model-building efforts [33][34][35][36][37][38][39][40][41][42]…”