Browsing by Author "Morais, António P."
Now showing 1 - 7 of 7
Results Per Page
Sort Options
- Anomalies in B-meson decays and the muon g-2 from dark loopsPublication . Huang, Da; Morais, António P.; Santos, RuiWe explore a class of models which can provide a common origin for the recently observed evidence for lepton flavor universality violation in b -> sl(+)l(-) decays, the dark matter (DM) problem, and the long-standing muon (g - 2) anomaly. In particular, both anomalies in the B meson decays and the muon (g - 2) can be explained by the additional one-loop diagrams with DM candidates. We first classify several simple models according to the new fields' quantum numbers. We then focus on a specific promising model and perform a detailed study of both DM and flavor physics. A random scan over the relevant parameter space reveals that there is indeed a large parameter space which can explain the three new physics phenomena simultaneously, while satisfying all other flavor and DM constraints. Finally, we discuss some of the possible new physics signatures at the Large Hadron Collider.
- CP violating hW(+)W(-) coupling in the Standard Model and beyondPublication . Huang, Da; Morais, António P.; Santos, RuiInspired by the recent development in determining the property of the observed Higgs boson, we explore the CP-violating (CPV) -cCPVhW+mu nu Wmu nu-/upsilon coupling in the Standard Model (SM) and beyond, where W-+/- mu nu and W+/- mu nu denote the W-boson field strength and its dual. To begin with, we show that the leading-order SM contribution to this CPV vertex appears at two-loop level. By summing over the quark flavor indices in the two loop integrals analytically, we can estimate the order of the corresponding Wilson coefficient to be cCPVSMsimilar to O10-23, which is obviously too small to be probed at the LHC and planned future colliders. Then we investigate this CPV hW(+)W(-) interaction in two Beyond the Standard Model benchmark models: the left-right model and the complex 2-Higgs doublet model (C2HDM). Unlike what happens for the SM, the dominant contributions in both models arise at the one-loop level, and the corresponding Wilson coefficient can be as large as of O(10(-9)) in the former model and of O(10(-3)) for the latter. In light of such a large CPV effect in the hW(+)W(-) coupling, we also give the formulae for the leading one-loop contribution to the related CPV hZZ effective operator in the complex 2-Higgs doublet model. The order of magnitude of the Wilson coefficients in the C2HDM may be within reach of the high-luminosity LHC or planned future colliders.
- Deep learning searches for vector-like leptons at the LHC and electron/muon collidersPublication . Morais, António P.; Onofre, António; Freitas, Felipe F.; Gonçalves, João; Pasechnik, Roman; Santos, Ruihe discovery potential of both singlet and doublet vector-like leptons (VLLs) at the Large Hadron Collider (LHC) as well as at the not-so-far future muon and electron machines is explored. The focus is on a single production channel for LHC direct searches while double production signatures are proposed for the leptonic colliders. A Deep Learning algorithm to determine the discovery (or exclusion) statistical significance at the LHC is employed. While doublet VLLs can be probed up to masses of 1 TeV, their singlet counterparts have very low cross sections and can hardly be tested beyond a few hundreds of GeV at the LHC. This motivates a physics-case analysis in the context of leptonic colliders where one obtains larger cross sections in VLL double production channels, allowing to probe higher mass regimes otherwise inaccessible even to the LHC high-luminosity upgrade.
- Impact of SM parameters and of the vacua of the Higgs potential in gravitational waves detectionPublication . Freitas, Felipe F.; Lourenço, Gabriel; Morais, António P.; Nunes, André; Olívia, João; Pasechnik, Roman; Santos, Rui; Viana, JoãoIn this work we discuss two different phases of a complex singlet extension of the Standard Model (SM) together with an extension that also includes new fermion fields, in particular, a Majoron model equipped with an inverse seesaw mechanism. All considered scenarios contain a global U(1) symmetry and allow for first-order phase transitions while only two of them are strong enough to favour the detection of primordial gravitational waves (GWs) in planned experiments such as LISA. In particular, this is shown to be possible in the singlet extension with a non vanishing real VEV at zero temperature and also in the model with extra fermions. In the singlet extension with no additional fermions, the detection of GWs strongly depends on the U(1) symmetry breaking pattern of the scalar potential at zero temperature. We study for the first time the impact of the precision in the determination of the SM parameters on the strength of the GWs spectrum. It turns out that the variation of the SM parameters such as the Higgs boson mass and top quark Yukawa coupling in their allowed experimental ranges has a notable impact on GWs detectability prospect
- Phenomenology of a flavored multiscalar Branco-Grimus-Lavoura-like model with three generations of massive neutrinosPublication . Ferreira, Pedro Miguel; Freitas, Felipe F.; Pino Gonçalves, João; Morais, António P.; Pasechnik, Roman; Vatellis, VasileiosIn this paper, we present several possible anomaly free implementations of the Branco-Grimus-Lavoura (BGL) model with two Higgs doublets and one singlet scalar. The model also includes three generations of massive neutrinos that get their mass via a type-I seesaw mechanism. A particular anomaly free realization, which we dub νBGL-1 scenario, is subjected to an extensive phenomenological analysis, from the perspective of flavor physics and collider phenomenology.
- A three Higgs doublet model with symmetry-suppressed flavour changing neutral currentsPublication . Das, Dipankar; Ferreira, Pedro Miguel; Morais, António P.; Padilla-Gay, Ian; Pasechnik, Roman; Rodrigues, J. PedroWe construct a three-Higgs doublet model with a flavour non-universal U(1) x DOUBLE-STRUCK CAPITAL Z(2) symmetry. That symmetry induces suppressed flavour-changing interactions mediated by neutral scalars. New scalars with masses below the TeV scale can still successfully negotiate the constraints arising from flavour data. Such a model can thus encourage direct searches for extra Higgs bosons in the future collider experiments, and includes a non-trivial flavour structure.
- Ultralight bosons for strong gravity applications from simple Standard Model extensionsPublication . Freitas, Felipe F.; Herdeiro, Carlos A. R.; Morais, António P.; Onofre, Antonio; Pasechnik, Roman; Radu, Eugen; Sanchis-Gual, Nicolas; Santos, RuiWe construct families, and concrete examples, of simple extensions of the Standard Model that can yield ultralight real or complex vectors or scalars with potential astrophysical relevance. Specifically, the mass range for these putative fundamental bosons (∼ 10−10 − 10−20 eV) would lead dynamically to both new non-black hole compact objects (bosonic stars) and new non-Kerr black holes, with masses of ∼ M to ∼ 1010M, corresponding to the mass range of astrophysical black hole candidates (from stellar mass to supermassive). For each model, we study the properties of the mass spectrum and interactions after spontaneous symmetry breaking, discuss its theoretical viability and caveats, as well as some of its potential and most relevant phenomenological implications linking them to the physics of compact objects.