arXiv subjects

Maya Hager

Publications and source records attributed to Maya Hager.

3 recordsLinked to original sources

arXiv2025

Characterizing LHC-Resonances in extended HEFT: information on the nature of extended scalar sectors

In theories with extended scalar sectors the lightest new scalar degree of freedom might be accessible at colliders. Going beyond simplified models, such a theory can be described in a gauge-invariant and agnostic way via an EFT with a non-linearly realized electroweak symmetry. In this extended HEFT, depending on the $SU(2)$ nature of the new scalar in the UV, operators will be suppressed by different powers of a heavy mass scale. We use dimensional analysis to systematically evaluate expected hierarchies between Wilson coefficients, leading to structural relations between potential LHC observables, such as di-boson resonances, tau pair production or the di-photon channel. Once future collider data reveals a hint of a new scalar field, it can be fitted to this extended HEFT and such a structural analysis will help interpret it with respect to possible UV models, circumventing the need to individually test each possible model on the data or to fix the $SU(2)$ representation of the new scalar beforehand. For illustration, the framework is applied to the tentative 95 GeV resonance. In addition to its usefulness for collider physics, the extended HEFT can also be beneficial for low-energy observables, allowing to describe new scalars in an agnostic way.

hep-ph↗

arXiv2024

Phasing out of Darkness: From Sterile Neutrino Dark Matter to Neutrino Masses via Time-Dependent Mixing

Sterile neutrinos are a compelling candidate for generating neutrino masses and for elucidating the nature of dark matter. Astrophysical X-ray constraints on sterile neutrino dark matter decays, however, largely exclude the active-sterile mixing required to produce simultaneously the correct left-handed neutrino spectrum and keV-scale right-handed neutrino dark matter within a type-I seesaw framework. In this study, we demonstrate how these X-ray constraints can be circumvented through a time-dependent approach, thereby reviving a broad range of active-sterile mixing scenarios. Our minimal model incorporates two right-handed neutrinos, which form a two-component dark matter candidate, and an auxiliary scalar field that experiences a very late and still ongoing phase transition, leading to the spontaneous breaking of a global $ U(1)_N $ symmetry. Prior to this phase transition, only the right-handed neutrinos are massive, while the left-handed neutrinos remain massless because of the scalar field's vanishing expectation value. As the phase transition develops, the growing expectation value of the scalar field increases the active-sterile mixing, thereby opening dark matter decay channels and inducing neutrino masses. The time dependence allows the scenario to be consistent with X-ray constraints as well as current measurements of left-handed neutrino masses. The anticipated level of active-sterile mixing today is within the detection capabilities of the forthcoming TRISTAN (KATRIN) tritium-beta decay project. Additionally, cosmological surveys such as DESI or EUCLID and supernova neutrino observations can test the prediction of massless left-handed neutrinos prior to the phase transition.

hep-ph↗

arXiv2023

Restoring Naturalness via Conjugate Fermions

We propose a novel mechanism for cancelling the leading order contribution to the potential in composite Higgs scenarios. The mechanism relies on the splitting of a real representation of the global symmetry into a complex representation and its conjugate of the unbroken group. We identify two cosets one of which includes a custodial symmetry. A numerical analysis is performed in a phenomenological three-site model and the resulting fine-tuning is analysed. The cancelling of the leading order potential results in a drastic reduction of the fine-tuning. For a symmetry breaking scale of the strong sector as high as $f=1600$ GeV, fine-tuning can be as good as $10\%$ or even better. We discuss a possible interpretation in the 5D holographic dual. Unique signatures of the model include quarks with baryon number $B=2/3$ with highly distinctive decays which can be looked for at the LHC.

hep-ph↗