Rui Santos

Rui Santos
Instituto Politécnico de Lisboa | ISEL · Department of Physics

PhD

About

152
Publications
7,068
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3,073
Citations
Additional affiliations
August 2010 - present
University of Lisbon
Position
  • Researcher

Publications

Publications (152)
Preprint
Full-text available
We use the associated production of top-quark pairs with a generic scalar boson at the LHC to explore the sensitivity of a large set of observables to the sign of the CP mixing angle, present in the coupling between the scalar boson and the top quarks. The mass of the scalar boson is set to $m_{\phi}=125$ GeV and its coupling to top-quarks is varie...
Preprint
Full-text available
We calculate the leading radiative corrections to the dark-matter-nucleon scattering in the pseudo-Nambu-Goldstone dark matter model augmented with a second Higgs doublet (S2HDM). In this model, the cross sections for the scattering of the dark-matter on nuclei vanishes at tree-level in the limit of zero momentum-transfer due to a U(1) symmetry. Ho...
Article
Direct detection experiments are the only way to obtain indisputable evidence of the existence of dark matter (DM) in the form of a particle. These experiments have been used to probe many extensions of the Standard Model (SM) that provide DM candidates. Experimental results like the latest ones from XENON1T lead to severe constraints in the parame...
Preprint
Current gravitational wave (GW) detections rely on the existence of libraries of theoretical waveforms. Consequently, finding new physics with GWs requires libraries of non-standard models, which are computationally demanding. We discuss how deep learning frameworks can be used to generate new waveforms "learned" from a simulation dataset obtained,...
Article
We present the public code that performs parameter scans and checks parameter points in theories beyond the Standard Model (BSM) with extended scalar sectors. incorporates theoretical and experimental constraints from many different sources in order to judge whether a parameter point is allowed or excluded at approximately $${95}{\%}~\text {{CL}}$$...
Preprint
Full-text available
The search for dark matter (DM) at colliders is founded on the idea of looking for something invisible. There are searches based on production and decay processes where DM may reveal itself as missing energy. If nothing is found, our best tool to constrain the parameter space of many extensions of the Standard Model (SM) with a DM candidate is the...
Preprint
Full-text available
We present a comprehensive study on Higgs pair production in various archetypical extended Higgs sectors such as the real and the complex 2-Higgs-Doublet Model, the 2-Higgs-Doublet Model augmented by a real singlet field and the Next-to-Minimal Supersymmetric extension of the Standard Model. Taking into account all relevant theoretical and experime...
Article
We 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 (boso...
Article
Full-text available
A bstract The Higgs invisible decay width may soon become a powerful tool to probe extensions of the Standard Model with dark matter candidates at the Large Hadron Collider. In this work, we calculate the next-to-leading order (NLO) electroweak corrections to the 125 GeV Higgs decay width into two dark matter particles. The model is the next-to-min...
Preprint
Full-text available
In 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. All models allow for a strong first-order electroweak phase transition and the detection of primordial gravitational waves (GWs) in planned experiments such as LISA is shown to be p...
Preprint
Full-text available
The 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. Implications for...
Preprint
Full-text available
We 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 ($\sim 10^{-10}-10^{-20}$ eV) would lead dynamically to both new non-black hole compact obj...
Preprint
The Higgs invisible decay width may soon become a powerful tool to probe extensions of the Standard Model with dark matter candidates at the Large Hadron Collider. In this work, we calculate the next-to-leading order (NLO) electroweak corrections to the 125 GeV Higgs decay width into two dark matter particles. The model is the next-to-minimal 2-Hig...
Article
Full-text available
A bstract We discuss the vacuum structure of a version of the Georgi-Machecek model with an exact ℤ 2 symmetry acting on the triplet fields. Besides the usual custodial-symmetric model, with ρ = 1 at tree-level, a model with a dark matter candidate is also viable. The other phases of the model lead to electric charge breaking, a wrong pattern of el...
Article
Full-text available
A bstract Inspired by the recent development in determining the property of the observed Higgs boson, we explore the CP -violating (CPV) $$ -{c}_{\mathrm{CPV}}{hW}^{+\mu \nu}{\tilde{W}}_{\mu \nu}^{-}/\upsilon $$ − c CPV hW + μν W ˜ μν − / υ coupling in the Standard Model (SM) and beyond, where W ± μν and $$ {\tilde{W}}^{\pm \mu \nu} $$ W ˜ ± μν den...
Preprint
Full-text available
In this paper we propose a new reconstruction method to explore the low mass region in the associated production of top-quark pairs ($t\bar{t}$) with a generic scalar boson ($\phi$) at the LHC. The new method of mass reconstruction shows an improved resolution of at least a factor of two in the low mass region when compared to previous methods, wit...
Preprint
Full-text available
We discuss the vacuum structure of a version of the Georgi-Machecek model with an exact $\mathbb{Z}_2$ symmetry acting on the triplet fields. Besides the usual custodial-symmetric model, with $\rho=1$ at tree-level, a model with a dark matter candidate is also viable. The other phases of the model lead to electric charge breaking, a wrong pattern o...
Article
Full-text available
A bstract Having so far only indirect evidence for the existence of Dark Matter a plethora of experiments aims at direct detection of Dark Matter through the scattering of Dark Matter particles off atomic nuclei. For the correct interpretation and identification of the underlying nature of the Dark Matter constituents higher-order corrections to th...
Article
Full-text available
We 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 diagr...
Article
Full-text available
A bstract In this paper, we investigate sizeable interference effects between a heavy charged Higgs boson signal produced dominantly via $$ gg\to t\overline{b}{H}^{-} $$ gg → t b ¯ H − (+ c.c.) followed by the decay $$ {H}^{-}\to b\overline{t} $$ H − → b t ¯ (+ c.c.) and the irreducible background given by $$ pp\to t\overline{t}b\overline{b} $$ pp...
Preprint
Inspired by the recent development in determining the property of the observed Higgs boson, we explore the $CP$-violating (CPV) $- c_{\rm CPV} h W^{+\, \mu\nu}\tilde{W}^{-}_{\mu\nu}/v$ coupling in the Standard Model (SM) and beyond, where $W^{\pm \, \mu \nu}$ and $\tilde{W}^{\pm\,\mu\nu}$ denote the $W$-boson field strength and its dual. To begin w...
Preprint
Having so far only indirect evidence for the existence of Dark Matter a plethora of experiments aims at direct detection of Dark Matter through the scattering of Dark Matter particles off atomic nuclei. For the correct interpretation and identification of the underlying nature of the Dark Matter constituents higher-order corrections to the cross se...
Article
Full-text available
A bstract We discuss the dark phases of the Next-to-2-Higgs Doublet model. The model is an extension of the Standard Model with an extra doublet and an extra singlet that has four distinct CP-conserving phases, three of which provide dark matter candidates. We discuss in detail the vacuum structure of the different phases and the issue of stability...
Preprint
We present the public code ScannerS-2 that performs parameter scans and checks parameter points in theories beyond the Standard Model (BSM) with extended scalar sectors. ScannerS incorporates theoretical and experimental constraints from many different sources in order to judge whether a parameter point is allowed or excluded at approximately 95% C...
Preprint
In this work we present an update to a previous calculation of the Next-to-Leading Order (NLO) corrections to the Vector Dark Matter (VDM) direct detection cross section. The model under investigation is a minimal extension of the Standard Model (SM) with one extra vector boson and one extra complex scalar field, where the vector is the DM candidat...
Preprint
We discuss the dark phases of the Next-to-2-Higgs Doublet model. The model is an extension of the Standard Model with an extra doublet and an extra singlet that has four distinct CP-conserving phases, three of which provide dark matter candidates. We discuss in detail the vacuum structure of the different phases and the issue of stability at tree-l...
Preprint
In this paper we explore CP discrimination in the associated production of top-quark pairs ($t\bar{t}$) with a generic scalar boson ($\phi$) at the LHC. We probe the CP-sensitivity of several observables for a varying scalar boson mass and CP-number, either CP-even ($\phi=H$) or CP-odd ($\phi=A$), using dileptonic final states of the $t\bar{t}\phi$...
Preprint
In this talk an investigation into the interference effects between the process $pp\to \bar{t}bH^+$ followed by the decay $H^+ \to t\bar{b}$ and the background process $pp \to t\bar{t}b\bar{b}$ is presented. The level of interference in parts of the parameter space is shown to be high and as such it may spoil the results of typical analyses which t...
Article
Full-text available
In this talk an investigation into the interference effects between the process pp → t ̄ bH ⁺ followed by the decay H ⁺ → tb ̄ and the background process pp → tt ̄ bb ̄ is presented. The level of interference in parts of the parameter space is shown to be high and as such it may spoil the results of typical analyses which treat signal and backgroun...
Article
Full-text available
A bstract The Higgs sector of the Next-to-Minimal Two-Higgs-Doublet Model (N2HDM) is obtained from the Two-Higgs-Doublet Model (2HDM) containing two complex Higgs doublets, by adding a real singlet field. In this paper, we analyse the vacuum structure of the N2HDM with respect to the possibility of vacuum instabilities. We show that while one type...
Preprint
The Higgs sector of the Next-to-Minimal Two-Higgs-Doublet Model (N2HDM) is obtained from the Two-Higgs-Doublet Model (2HDM) containing two complex Higgs doublets, by adding a real singlet field. In this paper, we analyse the vacuum structure of the N2HDM with respect to the possibility of vacuum instabilities. We show that while one type of charge-...
Preprint
Full-text available
In this paper, we investigate sizeable interference effects between a heavy charged Higgs boson signal produced via $gg\to t\bar b H^-$ (+ c.c.) followed by the decay $H^-\to b\bar t$ (+ c.c.) and the irreducible background given by $gg\to t\bar t b \bar b$ topologies at the Large Hadron Collider (LHC). We show how such effects could spoil current...
Article
Full-text available
We discuss the phenomenology of several beyond the Standard Model (SM) extensions that include extended Higgs sectors. The models discussed are the SM extended by a complex singlet field, the 2-Higgs-doublet model with a CP-conserving and a CP-violating scalar sector, the singlet extension of the 2-Higgs-doublet model, and the next-to-minimal super...
Article
Full-text available
We discuss the search for a CP-odd scalar decaying into gauge bosons in the frameworks of a CP-conserving two-Higgs doublet model (2HDM) and of a 2HDM extended with a vectorlike quark (VLQ) at the Large Hadron Collider and at a future 100 TeV collider. The rate of decay of a pseudoscalar to Z bosons could be important to ascertain the CP nature of...
Article
Full-text available
We investigate and compare two simple models of dark matter (DM): a vector and a scalar DM model. Both models require the presence of two physical Higgs bosons h1 and h2 which come from mixed components of the standard Higgs doublet H and a complex singlet S. In the vector model, the extra U(1) symmetry is spontaneously broken by the vacuum of the...
Article
Full-text available
A bstract Recent dark matter (DM) direct searches place very stringent constraints on the possible DM candidates proposed in extensions of the Standard Model. There are however models where these constraints are avoided. One of the simplest and most striking examples comes from a straightforward Higgs-portal pseudo-scalar DM model featured with a s...
Preprint
Full-text available
The Compact Linear Collider (CLIC) is a mature option for the future of high energy physics. It combines the benefits of the clean environment of $e^+e^-$ colliders with operation at high centre-of-mass energies, allowing to probe scales beyond the reach of the Large Hadron Collider (LHC) for many scenarios of new physics. This places the CLIC proj...
Preprint
Recent dark matter (DM) direct searches place very stringent constraints on the possible DM candidates proposed in extensions of the Standard Model. There are however models where these constraints are avoided. One of the simplest and most striking examples comes from a straightforward Higgs portal pseudoscalar DM model featured with a softly broke...
Preprint
Full-text available
We discuss the search for a CP-odd scalar decaying into gauge bosons in the framework of a CP-conserving two-Higgs doublet model (2HDM) and of a 2HDM extended with a vector-like quark (VLQ) at the Large Hadron Collider and at a future 100 TeV collider. The rate of decay of a pseudoscalar to $Z$-bosons could be important to ascertain the CP-nature o...
Preprint
We investigate and compare two simple models of dark matter (DM): a vector and a scalar DM model. Both models require the presence of two physical Higgs bosons $h_1$ and $h_2$ which come from mixed components of the standard Higgs doublet $H$ and a complex singlet $S$. In the Vector model, the extra $U(1)$ symmetry is spontaneously broken by the va...
Preprint
We discuss the phenomenology of several Beyond the Standard Model (SM) extensions that include extended Higgs sectors. The models discussed are: the SM extended by a complex singlet field (CxSM), the 2-Higgs-Doublet Model with a CP-conserving (2HDM) and a CP-violating (C2HDM) scalar sector, the singlet extension of the 2-Higgs-Doublet Model (N2HDM)...
Preprint
We build a model containing two scalar doublets and a scalar singlet with a specific discrete symmetry. After spontaneous symmetry breaking, the model has Standard Model-like phenomenology, as well as a hidden scalar sector which provides a viable dark matter candidate. We show that CP violation in the scalar sector occurs exclusively in the hidden...
Article
p>We investigate in the Large Hadron Collider (LHC) environment the possibility that sizeable interference effects between a heavy charged Higgs boson signal produced via bg→tH- (+c.c.) scattering and decaying via H-→W-A→W-bb (+c.c.) and the irreducible background given by bg→tW-bb topologies could spoil current search approaches where the former a...
Article
Full-text available
We investigate in the Large Hadron Collider (LHC) environment the possibility that sizeable interference effects between a {\sl heavy} charged Higgs boson signal produced via $bg\to tH^-$ (+ c.c.) scattering and decaying via $H^-\to W^- A\to W^- b\bar b$ (+ c.c.) and the irreducible background given by $bg\to t W^- b\bar b$ topologies could spoil c...
Article
The complex two-Higgs doublet model is one of the simplest ways to extend the scalar sector of the Standard Model to include a new source of CP-violation. The model has been used as a benchmark model to search for CP-violation at the LHC and as a possible explanation for the matter-antimatter asymmetry of the Universe. In this work, we re-analyse i...
Article
Full-text available
The two-Higgs doublet model (2HDM) provides an excellent benchmark to study physics beyond the Standard Model (SM). In this work we discuss how the behaviour of the model at high energy scales causes it to have a scalar with properties very similar to those of the SM -- which means the 2HDM can be seen to naturally favor a decoupling or alignment l...
Article
Full-text available
The Next-to-Minimal 2-Higgs-Doublet Model (N2HDM) is an interesting benchmark model for a Higgs sector consisting of two complex doublet and one real singlet fields. Like the Next-to-Minimal Supersymmetric extension (NMSSM) it features light Higgs bosons that could have escaped discovery due to their singlet admixture. Thereby, the model allows for...
Article
Full-text available
If no new physics signals are found, in the coming years, at the Large Hadron Collider Run-2, an increase in precision of the Higgs couplings measurements will shift the dicussion to the effects of higher order corrections. In Beyond the Standard Model (BSM) theories this may become the only tool to probe new physics. Extensions of the Standard Mod...
Article
Full-text available
We discuss the prospects for charged Higgs boson searches at the LHC, within the two-Higgs-doublet models (2HDM). The 2HDM is generally less constrained than the corresponding sector of the MSSM, but there are still severe theoretical and experimental constraints that already exclude significant regions of the naive parameter space. Explicit search...
Article
The N2HDM is based on the CP-conserving 2HDM extended by a real scalar singlet field. Its enlarged parameter space and its fewer symmetry conditions as compared to supersymmetric models allow for an interesting phenomenology compatible with current experimental constraints, while adding to the 2HDM sector the possibility of Higgs-to-Higgs decays wi...
Conference Paper
We discuss the prospects for charged Higgs boson searches at the LHC, within the two-Higgs-doublet models (2HDM). The 2HDM is generally less constrained than the corresponding sector of the MSSM, but there are still severe theoretical and experimental constraints that already exclude significant regions of the naive parameter space. Explicit search...
Article
Full-text available
We review the prospects of the Large Hadron Collider in accessing heavy charged Higgs boson signals in $b\bar b W^\pm$ final states, wherein the contributing channels can be $H^+\to t\bar b$, $hW^\pm$, $HW^\pm$ and $AW^\pm$. In particular, we devise a selection strategy which optimizes their global yield. We consider a 2-Higgs Doublet Model Type-II...
Article
Full-text available
The detailed investigation of the Higgs sector at present and future colliders necessitates from the theory side as precise predictions as possible, including higher order corrections. An important ingredient for the computation of higher order corrections is the renormalization of the model parameters and fields. In this paper we complete the reno...
Article
Full-text available
The goal of this report is to summarize the current situation and discuss possible search strategies for charged scalars, in non-supersymmetric extensions of the Standard Model at the LHC. Such scalars appear in Multi-Higgs-Doublet models (MHDM), in particular in the popular Two-Higgs-Doublet model (2HDM), allowing for charged and more neutral Higg...
Article
Full-text available
The 2-Higgs-Doublet Model (2HDM) belongs to the simplest extensions of the Standard Model (SM) Higgs sector that are in accordance with theoretical and experimental constraints. In order to be able to properly investigate the experimental Higgs data and, in the long term to distinguish between possible models beyond the SM, precise predictions for...
Article
Full-text available
In the light of the most recent data from Higgs boson searches and analyses, we re-assess the scope of the Large Hadron Collider in accessing heavy charged Higgs boson signals in $b\bar b W^\pm$ final states, wherein the contributing channels can be $H^+\to t\bar b$, $hW^\pm, HW^\pm$ and $AW^\pm$. We consider a 2-Higgs Doublet Model Type-II and we...
Article
Full-text available
The Complex singlet extension of the Standard Model (CxSM) is the simplest extension which provides scenarios for Higgs pair production with different masses. The model has two interesting phases: the dark matter phase, with a Standard Model-like Higgs boson, a new scalar and a dark matter candidate; and the broken phase, with all three neutral sca...
Article
Full-text available
A UFO model describing general top quark Flavour Changing Neutral Currents is presented. We use it to study t$\gamma$, tH and tZ production via FCNCs anomalous couplings at the Large Hadron Collider, in particular how the distributions of physical observables depend on the anomalous couplings. A sensitivity study of the Large Hadron Collider experi...
Article
Full-text available
With the discovery of the Higgs boson at the Large Hadron Collider the high energy physics community's attention has now turned to understanding the properties of the Higgs boson, together with the hope of finding more scalars during run 2. In this work we discuss scenarios where using a combination of three decays, involving the 125 GeV Higgs boso...
Article
Full-text available
We discuss the CP nature of the Yukawa couplings of the Higgs boson in the framework of a complex two Higgs doublet model (C2HDM). After analysing all data gathered during the Large Hadron Collider run 1, the measurement of the Higgs couplings to the remaining SM particles already restricts the parameter space of many extensions of the SM. However,...
Article
Full-text available
We present a study of the high energy stability of a minimal complex singlet extension of the Standard Model with or without dark matter (CxSM). We start by obtaining the beta functions of the couplings of the theory from the effective potential and then perform the RGE evolution for the allowed parameter space of the model at the electroweak scale...