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D. Cogollo

Publications and source records attributed to D. Cogollo.

30 records · Page 2Linked to original sources
arXiv2015

Influence of spatially varying pseudo-magnetic field on a 2D electron gas in graphene

The effect of a varying pseudo-magnetic field, which falls as $1/x^2$, on a two dimensional electron gas in graphene is investigated. By considering the second order Dirac equation, we show that its correct general solution is that which might present singular wavefunctions since such field induced by elastic deformations diverges as $x\rightarrow0$. We show that only this consideration yields the known relativistic Landau levels when we remove such elastic field. We have observed that the zero Landau level fails to develop for certain values of it. We then speculate about the consequences of these facts to the quantum Hall effect on graphene. We also analyze the changes in the relativistic cyclotron frequency. We hope our work being probed in these contexts, since graphene has great potential for electronic applications.

cond-mat.mes-hall↗
arXiv2014

Muon anomalous magnetic moment in a $SU(4) \otimes U(1)_N$ model without exotic electric charges

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.

hep-ph↗
arXiv2014

Flavor Changing Neutral Current Processes in a Reduced Minimal Scalar Sector

In this work we overhaul previous studies of Flavor Changing Neutral Current processes in the context of the Reduced Minimal 3-3-1 model(RM331). We sift the individual contributions from the CP even scalars and the $Z^{\prime}$ gauge boson using two different parametrizations schemes and compare our results with current measurements. In particular, studying the $B^{0}-\bar{B^{0}}$ meson system we find the most stringent bounds in the literature on this model, namely $M_{Z^{\prime}} \gtrsim 3326$~GeV, $M_{V^{\pm}} \gtrsim 910$~GeV, $M_{U^{++}} \gtrsim 914$~GeV and $m_{h_2^0} \gtrsim 889$~GeV.

hep-ph↗
arXiv2014

Excluding the Light Dark Matter Window of a 331 Model Using LHC and Direct Dark Matter Detection Data

We sift the impact of the recent Higgs precise measurements, and recent dark matter direct detection results, on the dark sector of an electroweak extension of the Standard Model that has a complex scalar as dark matter. We find that in this model the Higgs decays with a large branching ratio into dark matter particles, and charged scalars when these are kinematically available, for any coupling strength differently from the so called Higgs portal. Moreover, we compute the abundance and spin-independent WIMP-nucleon scattering cross section, which are driven by the Higgs and $Z^{\prime}$ boson processes. We decisively exclude the $1-500$~GeV dark matter window and find the most stringent lower bound in the literature on the scale of symmetry breaking of the model namely $10$~TeV, after applying the LUX-2013 limit. Interestingly, the projected XENON1T constraint will be able to rule out the entire $1$~GeV-$1000$~GeV dark matter mass range. Lastly, for completeness, we compute the charged scalar production cross section at the LHC and comment on the possibility of detection at current and future LHC runnings.

hep-ph↗
arXiv2013

Explaining ATLAS and CMS Results Within the Reduced Minimal 3-3-1 model

Recently the ATLAS and CMS collaborations announced the discovery of a higgs particle with a mass of $\sim 125$ GeV. The results are mildly consistent with the Standard Model Higgs boson. However, the combined data from these collaborations seem to point to an excess in the $h \rightarrow γγ$ channel. In this work we analyze under which conditions this excess may be plausibly explained within the reduced minimal 3-3-1 model, while being consistent with bb, WW, ZZ and $τ^+τ^-$ channels. Moreover, we derive the properties of the heavy neutral and the doubly charged scalars predicted by the model. We then conclude that at a scale of a few TeV, this model provides a good fit to the ATLAS and CMS signal strength measurements, and therefore stands as an appealing alternative to the standard model.

hep-ph↗
arXiv2012

Combining type I and type II seesaw mechanisms in the minimal 3-3-1 model

The minimal 3-3-1 model is perturbative until energies around 4-5TeV, posing a challenge to generate neutrino masses at eV scale, mainly if one aims to take advantage of the seesaw mechanism. As a means to circumvent this problem we propose a modification of the model such that it accommodates the type I and type II seesaw mechanisms altogether. We show that the conjunction of both mechanisms yield a neutrino mass expression suppressed by a high power of the cutoff scale, $M^5$, in its denominator. With such a suppression term we naturally obtain neutrino masses at eV scale when $M$ is around few TeV. We also investigate the size of lepton flavor violation through the process $μ\rightarrow eγ$.

hep-ph↗
arXiv2012

Novel sources of Flavor Changed Neutral Currents in the $331_{RHN}$ model

Sources of Flavor Changed Neutral Currents (FCNC) naturally emerge from a well motivated framework called 3-3-1 with right-handed neutrinos model, $331_{RHN}$ for short, mediated by an extra neutral gauge boson $Z^{\prime}$. Following previous works we calculate these sources and in addition we derive new ones coming from CP-even and -odd neutral scalars which appear due to their non-diagonal interactions with the physical standard quarks. Furthermore we show that bounds related to the neutral mesons systems $K_L-K_S$ and $D_1^0 - D_2^0$ may be significantly strengthened in the presence of these new interactions allowing us to infer stronger constraints on the parameter space of the model.

hep-ph↗
arXiv2012

Quantum harmonic oscillator for dipoles

In this work we investigate which radial field configuration yields bound states for neutral particles showing non-zero magnetic and electric dipole moments. The main result is that, in contrast with previous works, the Landau analog levels only exist if these radial magnetic and electric external fields are proportional to the third power of distance, not proportional to the distance. We derive the wave functions and the energy levels in the context of commutative and non-commutative quantum mechanics. We also show that, in the case of non-commutative phase space, these harmonic oscillator like spectrum do exist even if there is no external radial magnetic and electric fields. They are only consequence of the non-commutativity in the momenta.

hep-th↗
arXiv2010

Triple seesaw mechanism

On fitting the type II seesaw mechanism into the type I seesaw mechanism, we obtain a formula to the neutrino masses which get suppressed by high-scale $M^3$ in its denominator. As a result, light neutrinos are naturally obtained with new physics at TeV scale. As interesting consequence, the mechanism may be directly probed at the LHC by directly producing the TeV states intrinsic of the mechanism. We show that the 3-3-1 model with right-handed neutrinos realizes naturally such seesaw mechanism.

hep-ph↗
arXiv2009

KeV right-handed neutrinos from type II seesaw mechanism in a 3-3-1 model

We adapt the type II seesaw mechanism to the framework of the 3-3-1 model with right-handed neutrinos. We emphasize that the mechanism is capable of generating small masses for the left-handed and right-handed neutrinos and the structure of the model allows that both masses arise from the same Yukawa coupling. For typical values of the free parameters of the model we may obtain at least one right-handed neutrino with mass in the KeV range. Right-handed neutrino with mass in this range is a viable candidate for the warm component of the dark matter existent in the universe.

hep-ph↗
arXiv2008

The seesaw mechanism at TeV scale in the 3-3-1 model with right-handed neutrinos

We implement the seesaw mechanism in the 3-3-1 model with right-handed neutrinos. This is accomplished by the introduction of a scalar sextet into the model and the spontaneous violation of the lepton number. We identify the Majoron as a singlet under $SU_L(2)\otimes U_Y(1)$ symmetry, which makes it safe under the current bounds imposed by electroweak data. The main result of this work is that the seesaw mechanism works already at TeV scale with the outcome that the right-handed neutrino masses lie in the electroweak scale, in the range from MeV to tens of GeV. This window provides a great opportunity to test their appearance at current detectors, though when we contrast our results with some previous analysis concerning detection sensitivity at LHC, we conclude that further work is needed in order to validate this search.

hep-ph↗