arXiv subjects

A. Rosado

Publications and source records attributed to A. Rosado.

At least 19 recordsLinked to original sources

arXiv2026

Probing Flavor-Violating Higgs Decays in the Type-III Two-Higgs-Doublet Model at the LHC and HL-LHC

We present a comparative collider study of three flavor-violating Higgs signatures in the Type-III Two-Higgs-Doublet Model (\ddHmIII) at $\sqrt{s}=14$~TeV: $pp \to H \to t\bar{c} \ (\bar{t}c)$, $pp \to H^\pm \to c\bar{b} \ (\bar{c}b)$, and $pp \to H^\pm \to t\bar{b} \ (\bar{t}b)$. Using a common cut-based analysis and realistic detector simulation, we identify a clear phenomenological hierarchy. The neutral mode and the heavy charged mode emerge as the most robust signatures, containing parameter regions that already exceed the $5\sigma$ benchmark at an integrated luminosity of $300~\text{fb}^{-1}$. In contrast, the light charged channel $H^{\pm}\to c\bar{b}$ is considerably more sensitive to the event-selection strategy because of large QCD backgrounds, although one competitive benchmark survives. Our results single out the neutral and heavy charged flavor-violating channels as the most promising targets for discovery-oriented searches and for constraining the \ddHmIII\ parameter space at the LHC and HL-LHC. All quoted significances are purely statistical and do not include systematic uncertainties.

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arXiv2019

A classical lower bound on the size of a massive neutrino

In this paper, we calculate the size of a massive neutrino in the following approach. We perform our calculation using its mass, spin, and magnetic moment through the neutrino-electron interaction, $via$ the classical magnetic dipole-dipole interaction. Thus, our estimate is obtained by mimicking the low-energy electroweak scattering process $ν_l$-$l^{\prime}$. This leads to surprisingly accurate result which differs in less than one order of magnitude of more detailed calculations with one-loop corrections based on the neutrino charge radius and the $ν_l$-$l^{\prime}$ scattering process. The resulting estimates are flavour-blind and gauge independent by construction. We also find that our lower bound is below the reported experimental upper bound on the electron neutrino charged radius. So we obtained a constraining range for the neutrino size.

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arXiv2019

Phenomenology of the Partially Aligned 2HDM with leptonic decay of mesons

In this paper we present a phenomenological analysis of the Partially Aligned Two Higgs Doublet Model (PA-2HDM) by using leptonic decays of mesons and $B^0_{d,s}$-$\bar B^0_{d,s}$ mixing. We focus our attention in a scenario where the leading contribution to FCNC is given by the tree level interaction with the light pseudoscalar $A^0$ ($M_{A^0}\sim 250$ GeV). We show how an underlying flavor symmetry controls FCNC in the quark and lepton couplings with the pseudoscalar, without alignment between Yukawa matrices. Upper bounds on the free parameters are calculated in the context of the leptonic decays $B^0_{s,d}\toμ^+μ^-$ and $K^0_L\to μ^+μ^-$ and $B^0_{s,d}$ mixing. Also, our assumptions implies that bounds on New Physics contribution in the quark sector coming from $B^0_{s,d}$ mixing impose an upper bound on the parameters for the leptonic sector. Finally we give predictions of branching ratios for leptonic decay of mesons with FCNC and LFV.

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arXiv2018

Diffraction of particles in free fall

The problem of a beam of quantum particles falling through a diffractive screen is studied. The solutions for single and double slits are obtained explicitly when the potential is approximated by a linear function. It is found that the resulting patterns depend on a quasi-time $τ$ given by a function of the coordinate along the propagation axis in a classical combination $z_0-t^2 F/m$, while the diffraction effects along transverse axes are due solely to $m/\hbar$. The consequences on the precision at which the equivalence principle can be tested are discussed. Realizations with ultra cold neutrons, Bose-Einstein condensates and molecular beams are proposed.

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arXiv2018

Wigner function in the polariton phase space

The Wigner function of a dynamical infinite dimensional lattice is studied. A closed differential equation without diffusion terms for this function is obtained and solved. We map atom-photon interaction systems, such as the Jaynes-Cummings model, into this lattice model, where each dressed or polariton state corresponds to a point in the lattice and the conjugate momenta are described by the eigenvalues of the phase operator. The corresponding Wigner function is defined by these two conjugate variables in what we name the polariton phase space. We derive a general propagator of the Wigner function, which is also valid for other hybrid models.

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arXiv2018

Prospects for discovering a light charged Higgs boson within the NMSSM at the FCC-eh collider

We analyze the prospects of observing relatively light charged Higgs bosons ($h^{\pm}$) in their decays via $h^{-} \to s \bar c + s \bar u$ at the upcoming Future Circular Collider in hadron-electron mode (FCC-eh) with $\sqrt s \approx 3.5$ TeV. Assuming that the intermediate Higgs boson ($h_2$) is Standard Model (SM)-like, we study the production of $e^- b \to ν_e h^{-} b$ (also $b$ could be $\bar b$ in both initial and final states) in the framework of the Next-to-Minimal Supersymmetric Standard Model (NMSSM). We consider constraints from Dark Matter (DM), super-particle and the Higgs boson data. The charged Higgs boson decays into light flavors leads to a three-jets with missing transverse energy signal with one $b$-tagged jet. Our results show that light charged Higgs bosons with mass close to, e.g., 114(121) GeV have the maximal significance of 3.2(1.8)$σ$, upon using normal cut based selections and after 1 ab$^{-1}$ of luminosity. However, we further adopt an optimization technique to enhance the latter to 4.4 (2.2)$σ$, respectively.

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arXiv2017

A proposal to avoid the ambiguity in the identification of the scale energy parameter $\tilde{Q}^{2}$ of the PDFs in the $Z$-production in $eP$-dis

We discuss $Z$ -production in the deep inelastic process $e + P \to e + Z + X$ in the context of the Standard Model using the Parton Model. In contrast to the deep inelastic $eP$-scattering ($e + P \to e + X$), where the choice of $\tilde{Q}^{2} $ is unambiguous, in this case is not clear since the momentum transfer square, at the quark level, depends on the reaction mechanism. Our aim in this work is to show that the total cross section depends strongly on the prescription used for the scale parameter $\tilde{Q}^{2}$ and on a different option that we have taken for making the convolution of the parton distribution functions and the amplitude of the quark processes. We present results for the total cross section as a function of the total energy $\sqrt{s}$ of the system $eP$, in the range $300 \leq \sqrt{s} \leq 1300$ GeV. We find differences of up to 25\% in the rates of the total cross section for the different prescriptions that we have taken, for $\sqrt{s} \approx 1300$ GeV, which is the expected maximal total energy of the system $eP$ to be reached at the LHeC. Taking an integrated luminosity of $ab^{-1}$, such a difference (25\%) corresponds to $\approx 10^4$ produced $Z$ bosons. Finally, we propose to modify slightly the Parton Model in order to do a simple and practical prescription for the calculation without ambiguities of the $Z$-production in the deep inelastic $eP$ scattering.

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arXiv2016

Fundamental constraints on two-time physics

We show that generalizations of classical and quantum dynamics with two times lead to fundamentally constrained evolution. At the level of classical physics, Newton's second law is extended and exactly integrated in $1+2$ dimensional space, leading to effective single-time evolution for any initial condition. In the domain of quantum mechanics, we follow strictly the hypothesis of probability conservation by extending the Heisenberg picture to unitary evolution with two times. As a result, the observability of two temporal axes is constrained by a generalized uncertainty relation involving level spacings, total duration of the effect and Planck's constant.

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arXiv2016

Flavor violating signatures of lighter and heavier Higgs bosons within the Two Higgs Doublet Model Type-III at the LHeC

We analyze the prospects for observing the CP-even neutral Higgs bosons (h and H) in their decays into flavor violating $b \bar s+ c.c.$ channels at the proposed LHeC, with $\sqrt s \approx 1.3$ TeV, in the 2HDM Type-III, assuming a four-zero texture in the Yukawa matrices and a general Higgs potential. We consider theoretically consistent scenarios in agreement with current experimental data from flavor and Higgs physics. We investigate the charged current production process $ν_e ϕq$ in presence of flavor violating decays of the Higgs bosons, that lead to a 3-jets + $E\!\!\!\!/_T$ signature. We demand exactly two jets, one tagged $b$-jet and one light-flavor jet, all in the central rapidity region. The remaining jet (originated by the remanent quark $q$) is tagged in the forward or backward regions and this together with a central jet veto (not more than one light-flavor jet) are essential criterions to enhance the signal--to--background rates. We consider the most relevant Standard Model (SM) backgrounds, treating $c$-jets separately from light-flavor and gluon ones, while allowing for mis-tagging. We find that the SM-like Higgs boson, $h$, would be accessible within several parameter configurations of our model at approximately the 1-2$σ$ level with 100 fb$^{-1}$ of data. We also find that the heaviest neutral Higgs boson, $H$, with mass up to 150 GeV, would have a 1$σ$ significance for the same data sample. At the end of the LHeC running, one would have ten times data accumulation and for all the Higgs masses the significances are enhanced so as to allow for detection of both the $h$ and $H$ state. Hence, one of the most viable extensions of 2HDMs with FCNC's generated at tree level but controlled by a four-zero texture approach in the Yukawa matrices, as opposed to the adoption of ad hoc discrete symmetries, could be put under scrutiny at a future LHeC.

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arXiv2015

Flavor violating signatures of neutral Higgs bosons at the LHeC

We analyze the prospect for observing the lightest and heaviest CP-even neutral Higgs bosons ($ϕ=h,\;H$) in their decays to flavor violating $b\bar{s}$ (with charge conjugate) final states at the future Large Hadron electron Collider (LHeC), in the framework of the Two Higgs Doublet Model type III (2HDM-III) assuming a four-zero texture in the Yukawa matrices and a general Higgs potential. We consider the charge current production processes $e^- p \to ν_e ϕq_f$ ($ϕ= h, \; H$), with the flavor violating decays of the Higgs bosons. We consider scenarios of the model which are consistent with current experimental data from flavor and Higgs physics. We also consider the most relevant Standard Model (SM) backgrounds. We find that the lightest (SM-like) CP-even Higgs boson $h$ and the heaviest one $ H$ (with mass up to 150 GeV) would have 1--2 $Σ$ and 1 $Σ$ significances, respectively, with 100 fb$^{-1}$ of data. At the end of the LHeC running, the significances would be increased by ten times and the detection of both Higgs bosons ($h, H$) would be guaranteed.

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arXiv2015

Analysis of the quark sector in the 2HDM-III with a four-zero Yukawa texture using the most recent data on the CKM matrix

In this letter we analyse, in the context of the general 2-Higgs Doublet Model, the structure of the Yukawa matrices, $\widetilde{ \bf Y}_{ _{1,2} }^{q}$, by assuming a four-zero texture ansatz for their definition. In this framework, we obtain compact expressions for $\widetilde{ \bf Y}_{ _{1,2} }^{q}$, which are reduced to the Cheng and Sher ansatz with the difference that they are obtained naturally as a direct consequence of the invariants of the fermion mass matrices. Furthermore, in order to avoid large flavour violating effects coming from charged Higgs exchange, we consider the main flavour constraints on the off-diagonal terms of Yukawa texture {{$\left( \widetildeχ_{j}^q \right)_{kl}$}} ($k\neq l$). We perform a $χ^2$-fit based on current experimental data on the quark masses and the Cabibbo-Kobayashi-Maskawa mixing matrix ${ \bf V}_{\rm CKM }$. Hence, we obtain the allowed ranges for the parameters $\widetilde{ \bf Y}_{ _{1,2} }^{q}$ at 1$σ$ for several values of $\tan β$. The results are in complete agreement with the bounds obtained taking into account constraints on Flavour Changing Neutral Currents reported in the literature.

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arXiv2014

Impact of a four-zero Yukawa texture on $h\to γγ$ and $γZ$ in the framework of the Two Higgs Doublet Model Type III

We study the substantial enhancement, with respect to the corresponding Standard Model rates, that can be obtained for the branching ratios of the decay channels $h \to γγ$ and $h\to γZ$ within the framework of the Two Higgs Doublet Model Type III, assuming a four-zero Yukawa texture and a general Higgs potential. We show that these processes are very sensitive to the flavor pattern entering the Yukawa texture and to the triple coupling structure of the Higgs potential, both of which impact onto the aforementioned decays. We can accommodate the parameters of the model in such a way to obtain the $h \to γγ$ rates reported by the Large Hadron Collider and at the same time we get a $h\to γZ$ fraction much larger than in the Standard Model, indeed within experimental reach. We present some scenarios where this phenomenology is realized for spectrum configurations that are consistent with current constraints. We also discuss the possibility of obtaining a light charged Higgs boson compatible with all such measurements, thereby serving the purpose of providing a hallmark signal of the scenario considered.

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arXiv2013

Off-diagonal terms in Yukawa textures of the Type-III 2-Higgs doublet model and light charged Higgs boson phenomenology

We discuss flavor-violating constraints and consequently possible charged Higgs boson phenomenology emerging from a four-zero Yukawa texture embedded within the Type-III 2-Higgs Doublet Model (2HDM-III). Firstly, we show in detail how we can obtain several kinds of 2HDMs when some parameters in the Yukawa texture are absent. Secondly, we present a comprehensive study of the main B-physics constraints on such parameters induced by flavor-changing processes, in particular on the off-diagonal terms of such a texture: i.e., from $μ-e$ universality in $τ$ decays, several leptonic B-decays ($B \to τν$, $D \to μν$ and $D_s \to {l} ν$), the semi-leptonic transition $B\to D τν$, plus $B \to X_s γ$, including $B^0-\bar B^0$ mixing, $B_s \to μ^+ μ^-$ and the radiative decay $Z\to b \bar{b}$. Thirdly, having selected the surviving 2HDM-III parameter space, we show that the $H^- c \bar{b}$ coupling can be very large over sizable expanses of it, in fact, a very different situation with respect to 2HDMs with a flavor discrete symmetry (i.e., ${\mathcal{Z}}_2$) and very similar to the case of the Aligned-2HDM (A2HDM) as well as of models with three or more Higgs doublets. Fourthly, we study in detail the ensuing $H^\pm$ phenomenology at the Large Hadron Collider (LHC), chiefly the $c\bar b \to H^+$ production mode and the $H^+\to c\bar b$ decay channel while assuming $τ^+ν_τ$ decays in the former and $t\to bH^+$ production in the latter, showing that significant scope exists in both cases.

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arXiv2013

Update of the 2HDM-III with a four-zero texture in the Yukawa matrices and phenomenology of the charged Higgs Boson

We update the flavor-violating constraints on the charged Higgs sector of the 2-Higgs Doublet Model Type-III (2HDM-III), using a four-zero texture in the Yukawa matrices. We give a generic Lagrangian of the 2HDM-III. In order to show the relevance of the off-diagonal terms of such a texture, we utilize the main constraints from $B$-physics, $μ-e$ universality in $τ$ decays and the radiative decay $Z\to b \bar{b}$ presented recently in arXiv:1212.6818 [hep-ph]. In particular, we show that the $H^- c \bar{b}$ coupling can be very large and very different with respect to 2HDMs with a flavor discrete symmetry (i.e., ${\mathcal{Z}}_2$). We also discuss the possible enhancements of the vertices $H^\pm W^\mp V$ ($V=Z, γ$) that arise at one-loop level.

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arXiv2012

Couplings of quarks in the Partially Aligned 2HDM with a four-zero texture Yukawa matrix

The Two Higgs Doublets Model (2HDM) has provided a very useful way to describe a minimal extension of the scalar sector of the Standard Model. In this work, it is shown a scheme that we call Partial Aligned Two Higgs Doublet Model (PA-2HDM) which allows a description of the distinct versions of the 2HDM in a simple way, including those with flavor symmetries. In addition, it is shown a method to diagonalize Yukawa matrices of four-zero texture coming from the 2HDM-III. We provide some phenomenological applications in order to show the model's predictive power.

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arXiv2011

Lepton electric and magnetic dipole moments via lepton flavor violating spin-1 unparticle interactions

The magnetic dipole moment (MDM) and the electric dipole moment (EDM) of leptons are calculated under the assumption of lepton flavor violation (LFV) induced by spin-1 unparticles with both vector and axial-vector couplings to leptons,including a CP-violating phase. The experimental limits on the muon MDM and LFV process such as the decay l_i->i_jl_kl_k are then used to constrain the LFV couplings for particular values of the unparticle operator dimension d_U and the unparticle scale Λ_U, assuming that LFV transitions between the tau and muon leptons are dominant. It is found that the current experimental constraints favor a scenario with dominance of the vector couplings over the axial-vector couplings. We also obtain estimates for the EDMs of the electron and the muon, which are well below the current experimental limits.

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arXiv2010

Electroweak right-handed neutrinos and new signals at the LHC

We explore in detail the Higgs phenomenology that results in a model where right-handed neutrinos have a mass scale of the order of the electroweak scale. In this model all scales arise from spontaneous symmetry breaking, and this is achieved with a Higgs sector that includes an extra Higgs singlet in addition to the standard model Higgs doublet. The scalar spectrum includes two neutral CP-even states ($h$ and $H$ with $m_{h} < m_{H}$)and a neutral CP-odd state ($σ$) that can be identified as a pseudo-Majoron. The parameter of the Higgs potential are constrained using a perturbativity criteria. Higgs BR and cross-sections are discussed, with special emphasis on the detection at the LHC.

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arXiv2010

A Numerical Analysis of the Supersymmetric Flavor Problem and Radiative Fermion Masses

We study the SUSY flavor problem in the MSSM, we are namely interested in estimating the size of the SUSY flavor problem and its dependence on the MSSM parameters. For that, we made a numerical analysis randomly generating the entries of the sfermion mass matrices and then determinated which percentage of the points are consistent with current bounds on the flavor violating transitions on lepton flavor violating (LFV) decays $l_i \to l_j γ$. We applied two methods, mass-insertion approximation method (MIAM) and full diagonalization method (FDM). Furthermore, we determined which fermion masses could be radiatively generated (through gaugino-sfermion loops) in a natural way, using those random sfermion matrices. In general, the electron mass generation can be done with 30% of points for large $\tanβ$, in both schemes the muon mass can be generated by 40% of points only when the most precise sfermion splitting (from the FDM) is taken into account.

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