arXiv subjects

J. C. Montero

Publications and source records attributed to J. C. Montero.

At least 19 recordsLinked to original sources

arXiv2018

Axion dark matter in a $3-3-1$ model

Slightly extending a right-handed neutrino version of the $3-3-1$ model, we show that it is not only possible to solve the strong CP problem but also to give the total dark matter abundance reported by the Planck collaboration. Specifically, we consider the possibility of introducing a $3-3-1$ scalar singlet to implement a gravity stable Peccei-Quinn mechanism in this model. Remarkably, for allowed regions of the parameter space, the arising axions with masses $m_a\approx$ meV can both make up the total dark matter relic density through non-thermal production mechanisms and be very close to the region to be explored by the IAXO helioscope.

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arXiv2016

New constraints on the 3-3-1 model with right-handed neutrinos

In the framework of a 3-3-1 model with right-handed neutrinos and three scalar triplets we consider different spontaneous symmetry breaking patterns seeking for a non-linear realization of accidental symmetries of the model, which will produce physical Nambu-Goldstone (NG) bosons in the neutral scalar spectrum. We make a detailed study of the safety of the model concerning the NG boson emission in energy loss processes which could affect the standard evolution of astrophysical objects. We consider the model with a $\mathbb{Z}_2$ symmetry, conventionally used in the literature, finding that in all of the symmetry breaking patterns the model is excluded. Additionally, looking for solutions for that problem, we introduce soft $\mathbb{Z}_2$-breaking terms in the scalar potential in order to remove the extra accidental symmetries and at the same time maintain the model as simple as possible. We find that there is only one soft $\mathbb{Z}_2$-violating term that can get rid of the problematic NG bosons.

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arXiv2016

Supersymmetric $U(1)_{Y^{\prime}}\otimes U(1)_{B-L}$ extension of the standard model

We build a supersymmetric version with $SU(3)_C\otimes SU(2)_L\otimes U(1)_{Y^\prime}\otimes U(1)_{B-L}$ gauge symmetry, where $Y^\prime$ is a new charge and $B$ and $L$ are the usual baryonic and leptonic numbers. The model has three right-handed neutrinos with identical $B-L$ charges, and can accommodate all fermion masses at the tree level. In particular, the type-I seesaw mechanism is implemented for the generation of the active neutrino masses. We obtain the mass spectra of all sectors and for the scalar one we also give the flat directions allowed by the model.

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arXiv2014

Accidental symmetries and massless quarks in the economical 3-3-1 model

In the framework of a 3-3-1 model with a minimal scalar sector, known as the economical 3-3-1 model, we study its capabilities of generating realistic quark masses. After a detailed study of the symmetries of the model, before and after the spontaneous symmetry breaking, we find a remaining axial symmetry that prevents some quarks to gain mass at all orders in perturbation theory. Since this accidental symmetry is anomalous, we also consider briefly the possibility to generate their masses for non-perturbative effects. However, we find that non-perturbative effects are not enough to generate the measured masses for that three massless quarks. Hence, these results imply that the economical 3-3-1 model is not a realistic description of the electroweak interaction and it has to be modified.

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arXiv2014

Complex Scalar DM in a B-L Model

In this work, we implement a complex scalar Dark Matter (DM) candidate in a $U(1)_{B-L}$ gauge extension of the Standard Model. The model contains three right handed neutrinos with different quantum numbers and a rich scalar sector, with extra doublets and singlets. In principle, these extra scalars can have VEVs ($V_Φ$ and $V_ϕ$ for the extra doublets and singlets, respectively) belonging to different energy scales. In the context of $ζ\equiv\frac{V_Φ}{V_ϕ}\ll1$, which allows to obtain naturally light active neutrino masses and mixing compatible with neutrino experiments, the DM candidate arises by imposing a $Z_{2}$ symmetry on a given complex singlet, $ϕ_{2}$, in order to make it stable. After doing a study of the scalar potential and the gauge sector, we obtain all the DM dominant processes concerning the relic abundance and direct detection. Then, for a representative set of parameters, we found that a complex DM with mass around $200$ GeV, for example, is compatible with the current experimental constraints without resorting to resonances. However, additional compatible solutions with heavier masses can be found in vicinities of resonances. Finally, we address the issue of having a light CP-odd scalar in the model showing that it is safe concerning the Higgs and the $Z_μ$ boson invisible decay widths, and also the energy loss in stars astrophysical constraints.

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arXiv2013

FCNC in the minimal 3-3-1 model revisited

We show that in the minimal 3-3-1 model the flavor changing neutral currents (FCNCs) do not impose necessarily strong constraints on the mass of the $Z^\prime$ of the model if we also consider the neutral scalar contributions to such processes, like the neutral mesons mass difference and rare semileptonic decays. We first obtain numerical values for all the mixing matrices of the model i.e., the unitary matrices that rotate the left- and right-handed quarks in each charge sector which give the correct mass of all the quarks and the CKM mixing matrix. Then, we find that there is a range of parameters in which the neutral scalar contributions to these processes may interfere with those of the $Z^\prime$, implying this vector boson may be lighter than it has been thought.

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arXiv2012

On fermion masses and mixing in a model with $A_4$ symmetry

In a recently proposed multi-Higgs extension of the standard model in which discrete symmetries, $A_4$ and $Z_3$ are imposed we show that, after accommodating the fermion masses and the mixing matrices in the charged currents, the mixing matrices in the neutral currents induced by neutral scalars are numerically obtained. However, the flavor changing neutral currents are under control mainly by mixing and/or mass suppressions in the neutral scalar sector.

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arXiv2011

Neutrino masses and the scalar sector of a B-L extension of the standard model

We consider an electroweak model based on the gauge symmetry SU(2)_L X U(1)_Y' X U(1)_B-L which has right-handed neutrinos with different exotic B-L quantum numbers. Because of this particular feature we are able to write Yukawa terms, and right-handed neutrino mass terms, with scalar fields that can develop vacuum expectation values belonging to different energy scales. We make a detailed study of the scalar and the Yukawa neutrino sectors to show that this model is compatible with the observed solar and atmospheric neutrino mass scales and the tribimaximal mixing matrix.We also show that there are dark matter candidates if a Z_2 symmetry is included.

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arXiv2011

Natural PQ symmetry in the 3-3-1 model with a minimal scalar sector

In the framework of a 3-3-1 model with a minimal scalar sector we make a detailed study concerning the implementation of the PQ symmetry in order to solve the strong CP problem. For the original version of the model, with only two scalar triplets, we show that the entire Lagrangian is invariant under a PQ-like symmetry but no axion is produced since an U(1) subgroup remains unbroken. Although in this case the strong CP problem can still be solved, the solution is largely disfavored since three quark states are left massless to all orders in perturbation theory. The addition of a third scalar triplet removes the massless quark states but the resulting axion is visible. In order to become realistic the model must be extended to account for massive quarks and invisible axion. We show that the addition of a scalar singlet together with a Z_N discrete gauge symmetry can successfully accomplish these tasks and protect the axion field against quantum gravitational effects. To make sure that the protecting discrete gauge symmetry is anomaly free we use a discrete version of the Green-Schwarz mechanism.

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arXiv2011

$Z^{\prime}_{B-L}$ phenomenology at LHC

We study the $Z^\prime$ phenomenology for two extensions of the Electroweak Standard Model (SM) which have an extra $U(1)_{B-L}$ gauge factor. We show the capabilities of the LHC in distinguishing the signals coming from these two extensions and both of them from the Standard Model background. In order to compare the behavior of these $B-L$ models we consider the reaction $p + p\longrightarrow μ^+ + μ^- + X$ and compute some observables as the total cross sections, number of events, forward-backward asymmetry, final particle distributions like rapidity, transverse momentum, and dimuon invariant mass, for two LHC regimes: $\sqrt{s}\,({\cal L})=7$ TeV ($1\, \textrm{fb}^{-1}$) and $14 $ TeV ($100\, \textrm{fb}^{-1}$) for $M_{Z^{\prime}}$ = 1000 GeV and 1500 GeV. We show that by using appropriate kinematic cuts some of the observables considered here are able to extract different properties of the $Z^\prime$ boson, and hence providing information about to which $B-L$ model it belongs to.

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arXiv2011

Three-Higgs-doublet model with $A_4$ symmetry

We worked out in detail the three-Higgs-doublet extension of the standard model when the $A_4$ symmetry, which is imposed to solve the flavor problem, is extended to the scalar sector. The three doublets may be related to the fermion mass generation and, in particular, they may be the unique responsible for the generation of the neutrino masses. If this is the case, the respective VEVs have to be quite smaller than the electroweak scale if no fine tuning in the Yukawa couplings is assumed. We consider here the mass spectra in the scalar sector in three different situations. In one of them there are no light scalars at all, but in the other ones a light or two massless scalars, at the tree level, may survive. The later fields are safe, from the phenomenological point of view, since it couples mainly with neutrinos and/or becomes enough massive at the tree level if there exist trilinear interactions. Quantum effects may be important too.

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arXiv2010

Asymmetries in $e^+e^-\to f\bar{f}$ processes at ILC for models with an extra neutral vector boson $Z^\prime$

Many extensions of the standard model predict the existence of extra neutral vector bosons, generically referred as $Z^\prime$. This boson may be discovered at the LHC but in this case it will be necessary to study the respective parameters in order to discriminate to which model it belongs to. This is a task for a much clean lepton linear collider as the future ILC. In this paper we develop an exemplary study of the capability of several asymmetries on and off $Z^\prime$ peak in discriminating among those extensions with (almost) no ambiguities.

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arXiv2009

Gauging U(1) symmetries and the number of right-handed neutrinos

In this letter we consider that assuming: a) that the only left-handed neutral fermions are the active neutrinos, b) that $B-L$ is a gauge symmetry, and c) that the $L$ assignment is restricted to the integer numbers, the anomaly cancellation imply that at least three right-handed neutrinos must be added to the minimal representation content of the electroweak standard model. However, two types of models arise: i) the usual one where each of the three identical right-handed neutrinos has total lepton number L=1; ii) and the other one in which two of them carry L=4 while the third one carries $L=-5$.

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arXiv2006

Custodial Symmetry and Extensions of the Standard Model

We show that the extension of the approximate custodial $SU(2)_{L+R}$ global symmetry to all the Yukawa interactions of the standard model Lagrangian implies the introduction of sterile right-handed neutrinos and the seesaw mechanism in this sector. In this framework, the observed quark and lepton masses may be interpreted as an effect of physics beyond the standard model. The mechanism used for breaking this symmetry in the Yukawa sector could be different from the one at work in the vector boson sector. We give three model independent examples of these mechanisms.

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arXiv2006

Closing the $SU(3)_L\otimes U(1)_X$ Symmetry at Electroweak Scale

We show that some models with $SU(3)_C\otimes SU(3)_L\otimes U(1)_X$ gauge symmetry can be realized at the electroweak scale and that this is a consequence of an approximate global $SU(2)_{L+R}$ symmetry. This symmetry implies a condition among the vacuum expectation value of one of the neutral Higgs scalars, the $U(1)_X$'s coupling constant, $g_X$, the sine of the weak mixing angle $\sinθ_W$, and the mass of the $W$ boson, $M_W$. In the limit in which this symmetry is valid it avoids the tree level mixing of the $Z$ boson of the Standard Model with the extra $Z^\prime$ boson. We have verified that the oblique $T$ parameter is within the allowed range indicating that the radiative corrections that induce such a mixing at the 1-loop level are small. We also show that a $SU(3)_{L+R}$ custodial symmetry implies that in some of the models we have to include sterile (singlets of the 3-3-1 symmetry) right-handed neutrinos with Majorana masses, being the see-saw mechanism mandatory to obtain light active neutrinos. Moreover, the approximate $SU(2)_{L+R}\subset SU(3)_{L+R}$ symmetry implies that the extra non-standard particles of these 3-3-1 models can be considerably lighter than it had been thought before so that new physics can be really just around the corner.

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arXiv2006

3-3-1 Models at Electroweak Scale

We show that in 3-3-1 models there exist a natural relation among the $SU(3)_L$ coupling constant $g$, the electroweak mixing angle $θ_W$, the mass of the $W$, and one of the vacuum expectation values, which implies that those models can be realized at low energy scales and, in particular, even at the electroweak scale. So that, being that symmetries realized in Nature, new physics may be really just around the corner.

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arXiv2006

Soft CP violation in K-meson systems

We consider a model with soft CP violation which accommodate the CP violation in the neutral kaons even if we assume that the Cabibbo-Kobayashi-Maskawa mixing matrix is real and the sources of CP violation are three complex vacuum expectation values and a trilinear coupling in the scalar potential. We show that for some reasonable values of the masses and other parameters the model allows to explain all the observed CP violation processes in the $K^0$-$\bar{K}^0$ system.

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arXiv2004

Supersymmetric 3-3-1 model with right-handed neutrinos

We consider the supersymmetric extension of the 3-3-1 model with right-handed neutrinos. We study the mass spectra in the scalar and pseudoscalar sectors, and for a given set of the input parameters, we find that the lightest scalar in the model has a mass of 130 GeV and the lightest pseudoscalar has mass of 5 GeV. However, this pseudoscalar decouples from the $Z^0$ at high energy scales since it is almost a singlet under $SU(2)_L\otimes U(1)_Y$.

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