Jose Miguel No

Science with the space-based interferometer eLISA. II: Gravitational waves from cosmological phase transitions

We investigate the potential for the eLISA space-based interferometer to detect the stochastic gravitational wave background produced by strong first-order cosmological phase transitions. We discuss the resulting contributions from bubble collisions, magnetohydrodynamic turbulence, and sound waves to the stochastic background, and estimate the total corresponding signal predicted in gravitational waves. The projected sensitivity of eLISA to cosmological phase transitions is computed in a model-independent way for various detector designs and configurations. By applying these results to several specific models, we demonstrate that eLISA is able to probe many well-motivated scenarios beyond the Standard Model of particle physics predicting strong first-order cosmological phase transitions in the early Universe.

Predictive model for radiatively induced neutrino masses and mixings with dark matter.

A minimal extension of the standard model to naturally generate small neutrino masses and provide a dark matter candidate is proposed. The dark matter particle is part of a new scalar doublet field that plays a crucial role in radiatively generating neutrino masses. The symmetry that stabilizes the dark matter also suppresses neutrino masses to appear first at three-loop level. Without the need of right-handed neutrinos or other very heavy new fields, this offers an attractive explanation of the hierarchy between the electroweak and neutrino mass scales. The model has distinct verifiable predictions for the neutrino masses, flavor mixing angles, colliders, and dark matter signals.

See-saw composite Higgs model at the LHC: Linking naturalness to the 750 GeV diphoton resonance

We explore the possibility of explaining the recent ∼750 GeV excesses observed by ATLAS and CMS in the γγ spectrum in the context of a compelling theory of naturalness. The potential spin-zero resonance responsible for the excesses also requires the existence of new heavy charged states. We show that both such features are naturally realized in a see-saw composite Higgs model for electroweak symmetry breaking, where the new pseudo-Goldstone bosons are expected to be comparatively heavier than the Standard Model Higgs, and the new fermions have masses in the TeV range. If confirmed, the existence of this new resonance could be the first stone in the construction of a new theory of naturalness.

Probing the Higgs Portal at the LHC Through Resonant di-Higgs Production

We investigate resonant di-Higgs production as a means of probing extended scalar sectors that include a 125 GeV Standard Model-like Higgs boson. For concreteness, we consider a gauge singlet Higgs portal scenario leading to two mixed doublet-singlet states, h_(1,2). For m(_h_2)>2m(_h_1), the resonant di-Higgs production process pp→h_(2)→h_(1)h_(1) will lead to final states associated with the decaying pair of Standard Model-like Higgs scalars. We focus on h_(2) production via gluon fusion and on the bb^¯τ^(+)τ^(−) final state. We find that discovery of the h_(2) at the LHC may be achieved with ≲100  fb^(−1) of integrated luminosity for benchmark parameter choices relevant to cosmology. Our analysis directly maps onto the decoupling limit of the next-to-minimal supersymmetric Standard Model and more generically onto extensions of the Standard Model Higgs sector in which a heavy scalar produced through gluon-fusion decays to a pair of Standard Model-like Higgs bosons.

Energy budget of cosmological first-order phase transitions

The study of the hydrodynamics of bubble growth in first-order phase transitions is very relevant for electroweak baryogenesis, as the baryon asymmetry depends sensitively on the bubble wall velocity, and also for predicting the size of the gravity wave signal resulting from bubble collisions, which depends on both the bubble wall velocity and the plasma fluid velocity. We perform such study in different bubble expansion regimes, namely deflagrations, detonations, hybrids (steady states) and runaway solutions (accelerating wall), without relying on a specific particle physics model. We compute the efficiency of the transfer of vacuum energy to the bubble wall and the plasma in all regimes. We clarify the condition determining the runaway regime and stress that in most models of strong first-order phase transitions this will modify expectations for the gravity wave signal. Indeed, in this case, most of the kinetic energy is concentrated in the wall and almost no turbulent fluid motions are expected since the surrounding fluid is kept mostly at rest.

A strong electroweak phase transition in the 2HDM after LHC8

A bstractThe nature of the electroweak phase transition in two-Higgs-doublet models is revisited in light of the recent LHC results. A scan over an extensive region of their parameter space is performed, showing that a strongly first-order phase transition favours a light neutral scalar with SM-like properties, together with a heavy pseudo-scalar (

Benchmarks for Higgs effective theory: extended Higgs sectors

{m_{{{A^0}}}}

A second Higgs doublet in the early universe: baryogenesis and gravitational waves

≳ 400 GeV) and a mass hierarchy in the scalar sector,

Singlet-catalyzed electroweak phase transitions in the 100 TeV frontier

{m_{{{H^{\pm }}}}}\lesssim {m_{{{H^0}}}}<{m_{{{A^0}}}}

Hierarchical versus degenerate 2HDM: The LHC run 1 legacy at the onset of run 2

. We also investigate the h0 → γγ decay channel and find that an enhancement in the branching ratio is allowed, and in some cases even preferred, when a strongly first-order phase transition is required.