The charged Kaon meson ($K^+$) features several hadronic decay modes, but the most relevant contribution to its decay width stems from the leptonic decay $K^+ \rightarrow \mu^+ \nu_\mu $. Given the precision acquired on the rare decay mode $K^+ \rightarrow \mu^+ \nu_\mu + X$, one can use the data to set constraints on sub-GeV hidden sectors featuring light species that could contribute to it. Light gauge bosons that couple to muons could give rise to sizeable contributions. In this work, we will use data from the $K^+ \rightarrow \mu^+\nu_{\mu} l^+l^-$, and $K^+ \rightarrow \mu^+ \nu_{\mu} \nu \bar{\nu}$ decays to place limits on light vector bosons present in Two Higgs Doublet Models (2HDM) augmented by an Abelian gauge symmetry, 2HDM-$U(1)_X$. We put our findings into perpective with collider bounds, atomic parity violation, neutrino-electron scattering, and polarized electron scattering probes to show that rare Kaon decays provide competitive bounds in the sub-GeV mass range for different values of $\tan\beta$.

Light scalars that couple to leptons are common figures in beyond the Standard Model endeavors. Considering a scalar that has universal and couplings to leptons only, we compute this leptophilic scalar contribution to the e^-e^+→τ ^+τ ^- S production cross section with S → e^+e^-(μ ^+μ ^-) . We later compare the expected signal with recent data from the BELLE collaboration collected near the resonance Υ (4S) with ℒ=626 fb^-1 of integrated luminosity to place limits on the couplings-mass plane for the 4 MeV-6.5 GeV mass range. We then extended this analysis to a more general one e^-e^+→ℓ^+ℓ^- S production cross section where ℓ =e,μ ,τ with S → e^+e^-(μ ^+μ ^-) , showing that BELLE constitutes an excellent laboratory for light scalars, where can be derived constraints stronger than those derived stemming from the g-2 of the electron or muon.

Seesaw mechanisms are the simplest and the most elegant way of generating small masses for the active neutrinos (mν). In these mechanisms mν is inversely proportional to the lepton number breaking scale (M) that, in the particular case of the type I seesaw mechanism, is the Majorana mass of the right-handed neutrinos. In the canonical case right-handed neutrinos are supposed to be heavy belonging to the GUT scale. With the advent of the LHC people began to suppose these neutrinos having mass at TeV scale. In this case very tiny Yukawa couplings are required. As far as we know there are no constraints on the energy scales associated to the seesaw mechanisms. In what concern 3-3-1 models, when we trigger the type I seesaw mechanism the lepton number breaking scale that suppresses active neutrino masses contributes to the masses of the standard gauge bosons. Current data on mW demands the mechanism to be performed at GeV scale. As main implication we may have right handed neutrinos with mass varying from few keVs up to hundreds of GeVs. We also investigate the viability of the mechanism and found as interesting result that in the case in which the right-handed neutrino masses belong to the range keV-MeV scale, viability of the mechanism demands that the lightest of the right-handed neutrinos be stable, which makes of it a natural dark matter candidate, and that the lightest of the active neutrinos be ultralight.

In light of the upcoming measurement of the muon anomalous magnetic moment (g-2), we revisit the corrections to g-2 in the context of the $SU(4)_L \times U(1)_X$ gauge symmetry. We investigate three models based on this gauge symmetry and express our results in terms of the energy scale at which the $SU(4)_L \times U(1)_X$ symmetry is broken. To draw solid conclusions we put our findings into perspective with existing collider bounds. Lastly, we highlight the difference between our results and those rising from $SU(3)_L \times U(1)_X$ constructions.

Inverse seesaw is a genuine TeV scale seesaw mechanism. In it active neutrinos with masses at eV scale requires lepton number be explicitly violated at keV scale and the existence of new physics, in the form of heavy neutrinos, at TeV scale. Therefore it is a phenomenologically viable seesaw mechanism since its signature may be probed at the LHC. Moreover it is successfully embedded into gauge extensions of the standard model as the 3-3-1 model with the right-handed neutrinos. In this work we revisit the implementation of this mechanism into the 3-3-1 model and employ deep learning analysis to probe such setting at the LHC and, as main result, we have that if its signature is not detected in the next LHC running with energy of 14 TeVs, then, the vector boson Z′ of the 3-3-1 model must be heavier than 4 TeVs.

Two Higgs Doublet Models (2HDM) are popular extensions of the Standard Model for several reasons, but do not explain neutrino masses. In this work, we investigate how one can incorporate neutrino masses within the framework of the 2HDM-U(1), where U(1) is an abelian gauge symmetry used to nicely address the absence of flavor changing neutral currents in 2HDM. In particular, we explore realizations of the type I and type II seesaw since they are mechanisms that we dote on for being able to generate elegantly small active neutrino masses. We show that one can build several models featuring type I, type II and type I+II seesaw mechanism with different phenomenological implications.

The LAGO (Latin American Giant Observatory) observatory is an experiment that spans over Latin America in a wide range of latitudes that gives different rigidity cut offs for the enter of cosmic rays in the atmosphere. The motivation of the Observatory is to study atmospheric radiation and space weather through the measurement of the secondary emission of low energy cosmic rays at ground level using Water Cherenkov Detectors (WCD). This work presents the contributions of the LAGO collaboration to the 2019 36th ICRC.

This white paper summarizes the activities of the Brazilian community concerning dark matter physics and highlights the importance of financial support to Brazilian groups that are deeply involved in experimental endeavours. The flagships of the Brazilian dark matter program are the Cherenkov Telescope Array, DARKSIDE, SBN and LHC experiments, but we emphasize that smaller experiments such as DAMIC and CONNIE constitute important probes to dark sectors as well and should receive special attention. Small experimental projects showing the potential to probe new regions of parameter space of dark matter models are encouraged. On the theoretical and phenomenological side, some groups are devoted to astrophysical aspects such as the dark matter density profile while others explore the signature of dark matter models at colliders, direct and indirect detection experiments. In summary, the Brazilian dark matter community that was born not long ago has grown tremendously in the past years and now plays an important role in the hunt for a dark matter particle.

The effect of a pseudo Aharonov-Bohm (AB) magnetic field generated by a disclination on a two-dimensional electron gas in graphene is addressed in the continuum limit within the geometric approach. The influence of the coupling between the spinor fields and the singular conical curvature is investigated, which shows that singularities have pronounced impact in the Hall conductivity. Moreover, the degeneracy related to the Dirac valleys is broken for negative values of the angular momentum quantum numbers, l, including l equivalent to 0. In this case, a Hall plateau develops at the null filling factor. Obtaining the Hall conductivity by summing over the positive and the negative l's, the null Landau level is recovered and the plateau at the null filling factor disappears. In any case, the standard plateaus, which are seen in a flat graphene are not obtained with these curvature and singular effects.

In this work we compute all relevant contributions stemming from the economical 3-3-1 model to the muon magnetic moment and the lepton flavor violation decay μ→ eγ. Using the current bounds on these phenomena, we derive lower limits on the scale of symmetry breaking of the model. Moreover, taking into account existing limits from meson and collider studies we show that there is still room for a possible signal in μ→ eγ in the near future.

We propose several Two Higgs Doublet Models with the addition of an Abelian gauge group which free the usual framework from flavor changing neutral interactions and explain neutrino masses through the seesaw mechanism. We discuss the kinetic and mass-mixing gripping phenomenology which encompass several constraints coming from atomic parity violation, the muon anomalous magnetic moment, rare meson decays, Higgs physics, LEP precision data, neutrino-electron scattering, low energy accelerators and LHC probes.

We study all implementations of the ${S}_{3}$ symmetry in the two Higgs doublet models with quarks, consistent with nonzero quark masses and a Cabibbo-Kobayashi-Maskawa (CKM) matrix, which is not block diagonal. We study the impact of the various soft-breaking terms and vacuum expectation values and find an interesting relation between the mixing angles $\ensuremath{\alpha}$ and $\ensuremath{\beta}$. We also show that, in this minimal setting, only two types of assignments are possible: Either all field sectors are in singlets or all field sectors have a doublet.

The effect of an Aharonov-Bohm (AB) pseudo magnetic field on a two dimensional electron gas in graphene is investigated. We consider it modeled as in the usual AB effect but since such pseudo field is supposed to be induced by elastic deformations, the quantization of the field flux is abandoned. For certain constraints on the orbital angular momentum eigenvalues allowed for the system, we can observe the zero Landau level failing to develop, due to the degeneracy related to the Dirac valleys $K$ and $K^\prime$ which is broken. For integer values of the pseudo AB flux, the actual quantum Hall effect is preserved. Obtaining the Hall conductivity by summing over all orbital angular momentum eigenvalues, the zero Landau levels is recovered. Since our problem is closed related to the case where topological defects on a graphene sheet are present, the questions posed here are helpful if one is interested to probe the effects of a singular curvature in these systems.

We study all implementations of the S-3 symmetry in the two Higgs doublet models with quarks, consistent with nonzero quark masses and a Cabibbo-Kobayashi-Maskawa (CKM) matrix, which is not block diagonal. We study the impact of the various soft-breaking terms and vacuum expectation values and find an interesting relation between the mixing angles a and beta. We also show that, in this minimal setting, only two types of assignments are possible: Either all field sectors are in singlets or all field sectors have a doublet.

The Latin American Giant Observatory (LAGO) is an extended cosmic ray observatory composed by a network of water-Cherenkov detectors spanning over different sites located at significantly different altitudes (from sea level up to more than $5000$\,m a.s.l.) and latitudes across Latin America, covering a huge range of geomagnetic rigidity cut-offs and atmospheric absorption/reaction levels. This detection network is designed to measure the temporal evolution of the radiation flux at ground level with extreme detail. The LAGO project is mainly oriented to perform basic research in three branches: high energy phenomena, space weather and atmospheric radiation at ground level. LAGO is built and operated by the LAGO Collaboration, a non-centralized collaborative union of more than 30 institutions from ten countries. These are the contributions of the LAGO Collaboration to the 34th International Cosmic Ray Conference, 30 July - 6 August 2015, The Hague, The Netherlands

In light of the ongoing effort on reducing the theoretical uncertainties and an upcoming experiment concerning muon magnetic moment, we perform a detailed study of an 3-4-1 electroweak gauge extension of the standard model that contains exotic charged leptons in its spectrum. We discuss flavor changing neutral current, collider and electroweak bounds on the model and derive [Formula: see text] limits using current and projected limits on the muon magnetic moment. In summary, we exclude the masses of new gauge bosons that couple to muons and heavy charged leptons up to 700 GeV. Moreover, we find a projected lower bound on the scale of symmetry breaking to be 2 TeV.

We study an electroweak gauge extension of the standard model, so called 3-4-1 model, which does not contain exotic electric charges and it is anomaly free. We discuss phenomenological constraints of the model and compute all the corrections to the muon magnetic moment. Mainly, we discuss different mass regimes and their impact on this correction, deriving for the first time direct limits on the masses of the neutral fermions and charged vector bosons. Interestingly, the model could address the reported muon anomalous magnetic moment excess, however it would demands a rather low scale of symmetry breaking, far below the current electroweak constraints on the model. Thus, if this excess is confirmed in the foreseeable future by the g-2 experiment at FERMILAB, this 3-4-1 model can be decisively ruled out since the model cannot reproduce a sizeable and positive contribution to the muon anomalous magnetic moment consistent with current electroweak limits.

General two Higgs doublet models suffer excessive flavor changing neutral currents (FCNC) mediated by the neutral Higgs. A way to avoid this problem is to impose a discrete symmetry of type Z(2). However, it is known that spontaneously broken discrete symmetries can lead to the problem of domain walls, as indeed happens in the case of the 2HDM. In this work we review the consequences of the substitution of the Z(2) symmetry by a new U(1)(H) gauge symmetry, associated with the Higgs flavors, in which H-1 and H-2 have different charges of the U(1)(H) group.

We study the muon anomalous magnetic moment in an electroweak model based on the gauge symmetry SU(4)L ⊗ U(1)N, which has right-handed neutrinos in its spectrum, and no flavor changing neutral currents at tree level. We discuss relevant collider and electroweak constraints on the model, and derive the most stringent upper bounds on the scale of symmetry breaking based on the corrections to the muon magnetic moment. We conclude that a scale of symmetry breaking of around 2 TeV might explain the muon magnetic moment anomaly. In case the anomaly is otherwise resolved, using the current and projected sensitive of g-2 experiments, we rule out scales of symmetry breaking smaller than 3.5 TeV (5.5 TeV) at 1σ level.