Search for Long-Lived Heavy Neutrinos at the LHC with a VBF Trigger
The charged current production of long-lived heavy neutrinos at the LHC can use a prompt charged lepton for triggering the measurement of the process. However, in order to fully characterize the heavy neutrino interactions, it is necessary to also probe Higgs or Z mediated neutral current production. In this case the charged lepton is not available, so other means of triggering are required. In this work, we explore the possibility of using a vector boson fusion trigger in the context of a GeV-scale Type I Seesaw model. We consider a minimal model, where both Higgs and Z-mediated contributions produce one heavy neutrino, as well as an extended model where the Higgs can decay into two heavy ones. Both scenarios are tested through displaced dilepton and displaced multitrack jet searches.
Año de publicación: 2020
The charged current production of long-lived heavy neutrinos at the LHC can use a prompt charged lepton for triggering the measurement of the process. However, in order to fully characterize the heavy neutrino interactions, it is necessary to also probe Higgs or Z mediated neutral current production. In this case the charged lepton is not available, so other means of triggering are required. In this work, we explore the possibility of using a vector boson fusion trigger in the context of a GeV-scale Type I Seesaw model. We consider a minimal model, where both Higgs and Z-mediated contributions produce one heavy neutrino, as well as an extended model where the Higgs can decay into two heavy ones. Both scenarios are tested through displaced dilepton and displaced multitrack jet searches.
Año de publicación: 2020
Revisiting neutrino and sneutrino dark matter in natural SUSY scenarios
We study natural supersymmetric scenarios with light right-handed neutrino superfields, and consider the possibility of having either a neutrino or a sneutrino as a dark matter candidate. For the former, we evaluate the possibility of having SUSY corrections on the ν4→νℓγ decay rate, such that the NuStar bounds are relaxed. We find that corrections are too small. For sneutrino dark matter, we consider thermal and nonthermal production, taking into account freeze-out, freeze-in, and super-weakly interacting massive particles mechanisms. For the nonthermal case, we find that the ν˜R can reproduce the observed relic density by adjusting the R-sneutrino mass and Yukawa couplings. For the thermal case, we find the need to extend the model in order to enhance sneutrino annihilations, which we exemplify in a model with an extended gauge symmetry.
Año de publicación: 2020
We study natural supersymmetric scenarios with light right-handed neutrino superfields, and consider the possibility of having either a neutrino or a sneutrino as a dark matter candidate. For the former, we evaluate the possibility of having SUSY corrections on the ν4→νℓγ decay rate, such that the NuStar bounds are relaxed. We find that corrections are too small. For sneutrino dark matter, we consider thermal and nonthermal production, taking into account freeze-out, freeze-in, and super-weakly interacting massive particles mechanisms. For the nonthermal case, we find that the ν˜R can reproduce the observed relic density by adjusting the R-sneutrino mass and Yukawa couplings. For the thermal case, we find the need to extend the model in order to enhance sneutrino annihilations, which we exemplify in a model with an extended gauge symmetry.
Año de publicación: 2020
Effects of the Violation of the Equivalence Principle at DUNE
A number of different effects of the violation of the equivalence principle (VEP), taken as subleading mechanism of neutrino flavor oscillation, are examined within the framework of the DUNE experiment. We study the possibility of obtaining a misleading neutrino oscillation parameter region caused by our unawareness of VEP. Additionally, we evaluate the impact on the measurement of CP violation and the distinction of neutrino mass hierarchy at DUNE. Besides, limits on VEP for a wide variety of textures of the matrix that connects neutrino gravity eigenstates to flavor eigenstates are imposed. An extra task of our study is to set limits on Hamiltonian added terms considering different energy dependencies (Ed-3, with d=3, 4, 5, 6) that can be associated to the usual Lorentz violating terms defined in the Standard Model extension Hamiltonian. In order to understand our results, approximated analytical three neutrino oscillation probability formulae are derived.
Año de publicación: 2020
A number of different effects of the violation of the equivalence principle (VEP), taken as subleading mechanism of neutrino flavor oscillation, are examined within the framework of the DUNE experiment. We study the possibility of obtaining a misleading neutrino oscillation parameter region caused by our unawareness of VEP. Additionally, we evaluate the impact on the measurement of CP violation and the distinction of neutrino mass hierarchy at DUNE. Besides, limits on VEP for a wide variety of textures of the matrix that connects neutrino gravity eigenstates to flavor eigenstates are imposed. An extra task of our study is to set limits on Hamiltonian added terms considering different energy dependencies (Ed-3, with d=3, 4, 5, 6) that can be associated to the usual Lorentz violating terms defined in the Standard Model extension Hamiltonian. In order to understand our results, approximated analytical three neutrino oscillation probability formulae are derived.
Año de publicación: 2020
A misleading CP violation measurement at DUNE induced by a Majorana phase
We show that the effects of a non-null Majorana phase, due to the existence of a decoherence environment, can cause a sizable distortion of the \textit{CP} violation phase δCP\delta_{\mathrm{CP}}δCP to be measured at DUNE. These distortions are quantified comparing the latter with an eventual T2HK measurement, which would represent an upgrade in precision of the current best fit value obtained at T2K. For a decoherence magnitude of Γ=1.5(2.5)×10−24GeV\Gamma=1.5(2.5)\times 10^{-24} \mathrm{GeV}Γ=1.5(2.5)×10−24GeV, the discrepancies for δCP\delta_{\mathrm{CP}}δCP are below the 2σ2\sigma2σ for null and positive values of the Majorana phase while for negative values, such as −0.5π-0.5\pi−0.5π, it can reach up to 3.8σ(5.8σ)3.8\sigma(5.8\sigma)3.8σ(5.8σ). Therefore, a novel finding of this letter is the possibility to reveal a non-null and negative value for the Majorana phase through oscillation physics.
Año de publicación: 2020
We show that the effects of a non-null Majorana phase, due to the existence of a decoherence environment, can cause a sizable distortion of the \textit{CP} violation phase δCP\delta_{\mathrm{CP}}δCP to be measured at DUNE. These distortions are quantified comparing the latter with an eventual T2HK measurement, which would represent an upgrade in precision of the current best fit value obtained at T2K. For a decoherence magnitude of Γ=1.5(2.5)×10−24GeV\Gamma=1.5(2.5)\times 10^{-24} \mathrm{GeV}Γ=1.5(2.5)×10−24GeV, the discrepancies for δCP\delta_{\mathrm{CP}}δCP are below the 2σ2\sigma2σ for null and positive values of the Majorana phase while for negative values, such as −0.5π-0.5\pi−0.5π, it can reach up to 3.8σ(5.8σ)3.8\sigma(5.8\sigma)3.8σ(5.8σ). Therefore, a novel finding of this letter is the possibility to reveal a non-null and negative value for the Majorana phase through oscillation physics.
Año de publicación: 2020
Neutrino oscillation and CPT violation due to quantum decoherence at DUNE
In this work we study the intrinsic CPT violation in the neutrino oscillations phenomena produced by quantum decoherence as sub-leading effect. In the usual density matrix representation, we find that only fifteen elements of the decoherence matrix violate the CPT symmetry intrinsically. We find exact solutions for the CPT asymmetry function in vacuum . We define an observable to make predictions of this model for the future Long-Baseline experiment, DUNE. We found values of the decoherence parameters with 5σ5σ of discrepancy to standard physics which are allowed by the current experimental limits, suggesting hints for new physics by this model in the context of future experiments.
Año de publicación: 2020
In this work we study the intrinsic CPT violation in the neutrino oscillations phenomena produced by quantum decoherence as sub-leading effect. In the usual density matrix representation, we find that only fifteen elements of the decoherence matrix violate the CPT symmetry intrinsically. We find exact solutions for the CPT asymmetry function in vacuum . We define an observable to make predictions of this model for the future Long-Baseline experiment, DUNE. We found values of the decoherence parameters with 5σ5σ of discrepancy to standard physics which are allowed by the current experimental limits, suggesting hints for new physics by this model in the context of future experiments.
Año de publicación: 2020
Probing CPT breaking induced by quantum decoherence at DUNE
We show that the decoherence phenomena applied to the neutrino system could lead to an observable breaking of the fundamental CPT symmetry. We require specific textures of nondiagonal decoherence matrices, with nonzero δCP, for making such observations. Using the information from the CPT conjugate channels νμ→νμ and ¯νμ→¯νμ and their corresponding backgrounds, we have estimated the sensitivity of the DUNE experiment for testing CPT under the previous conditions. Four scenarios for energy-dependent decoherence parameters, ΓEν=Γ×(Eν/GeV)n, n=−1, 0, 1, and 2, are taken into account, and for most of them, DUNE is able to achieve a 5σ discovery potential, having Γ in O(10−23 GeV) for δCP=3π/2. Meanwhile, for δCP=π/2, we reach 3σ for Γ in O(10−24 GeV).
Año de publicación: 2019
We show that the decoherence phenomena applied to the neutrino system could lead to an observable breaking of the fundamental CPT symmetry. We require specific textures of nondiagonal decoherence matrices, with nonzero δCP, for making such observations. Using the information from the CPT conjugate channels νμ→νμ and ¯νμ→¯νμ and their corresponding backgrounds, we have estimated the sensitivity of the DUNE experiment for testing CPT under the previous conditions. Four scenarios for energy-dependent decoherence parameters, ΓEν=Γ×(Eν/GeV)n, n=−1, 0, 1, and 2, are taken into account, and for most of them, DUNE is able to achieve a 5σ discovery potential, having Γ in O(10−23 GeV) for δCP=3π/2. Meanwhile, for δCP=π/2, we reach 3σ for Γ in O(10−24 GeV).
Año de publicación: 2019
Gamma-ray counterparts of radio astrophysical sources
In this paper we study two newly discovered classes of radio sources: the highly energetic, short-lived events, known as Fast Radio Bursts (FRBs), and a new category of compact sources known as Fanaroff-Riley type 0 radio galaxies (FR0s). Due to a possible catastrophic event origin for the FRBs and a previous correlation found with an FR0 in the γ-ray spectrum, it is possible that these radio sources could also emit high energy photons in the Fermi-LAT satellite energy range (20 MeV–300 GeV). Here we present an exhaustive time-dependent and spatial search of all up-to-date observed FRBs and FR0s, respectively. We perform a likelihood analysis of the radio sources by modeling the excess flux of gamma rays with a varying index power law function using data from Fermi-LAT and the 4FGL catalog. Sources with test statistic greater than 16 (corresponding to about 4σ) were further analyzed including 2 FRBs and 7 FR0s. No correlations with more than 5σ were found after taking into account nearby sources. Therefore, upper limits for all sources were calculated.
Año de publicación: 2019
In this paper we study two newly discovered classes of radio sources: the highly energetic, short-lived events, known as Fast Radio Bursts (FRBs), and a new category of compact sources known as Fanaroff-Riley type 0 radio galaxies (FR0s). Due to a possible catastrophic event origin for the FRBs and a previous correlation found with an FR0 in the γ-ray spectrum, it is possible that these radio sources could also emit high energy photons in the Fermi-LAT satellite energy range (20 MeV–300 GeV). Here we present an exhaustive time-dependent and spatial search of all up-to-date observed FRBs and FR0s, respectively. We perform a likelihood analysis of the radio sources by modeling the excess flux of gamma rays with a varying index power law function using data from Fermi-LAT and the 4FGL catalog. Sources with test statistic greater than 16 (corresponding to about 4σ) were further analyzed including 2 FRBs and 7 FR0s. No correlations with more than 5σ were found after taking into account nearby sources. Therefore, upper limits for all sources were calculated.
Año de publicación: 2019
Using a portable muon detector for radioactive source measurements and identification
We have re-purposed portable plastic scintillator muon detectors, designed by the CosmicWatch project, for the measurement of electrons emitted by the decay of radioactive sources. For the latter purpose we have first calibrated the detectors using the local atmospheric muon flux, performing angular distribution and attenuation measurements. In addition, we have simulated the detector using Geant4 in a detailed fashion for a cross-check and better understanding of the device. Then, we have developed a method to evaluate the activity of -sources and to discriminate different -sources by looking into their respective voltage spectrum output.
Año de publicación: 2019
We have re-purposed portable plastic scintillator muon detectors, designed by the CosmicWatch project, for the measurement of electrons emitted by the decay of radioactive sources. For the latter purpose we have first calibrated the detectors using the local atmospheric muon flux, performing angular distribution and attenuation measurements. In addition, we have simulated the detector using Geant4 in a detailed fashion for a cross-check and better understanding of the device. Then, we have developed a method to evaluate the activity of -sources and to discriminate different -sources by looking into their respective voltage spectrum output.
Año de publicación: 2019
Majorana vs pseudo-Dirac neutrinos at the ILC
Neutrino masses could originate in seesaw models testable at colliders, with light mediators and an approximate lepton number symmetry. The minimal model of this type contains two quasi-degenerate Majorana fermions forming a pseudo-Dirac pair. An important question is to what extent future colliders will have sensitivity to the splitting between the Majorana components, since this quantity signals the breaking of lepton number and is connected to the light neutrino masses. We consider the production of these neutral heavy leptons at the ILC, where their displaced decays provide a golden signal: a forward-backward charge asymmetry, which depends crucially on the mass splitting between the two Majorana components. We show that this observable can constrain the mass splitting to values much lower than current bounds from neutrinoless double beta decay and natural loop corrections.
Año de publicación: 2019
Neutrino masses could originate in seesaw models testable at colliders, with light mediators and an approximate lepton number symmetry. The minimal model of this type contains two quasi-degenerate Majorana fermions forming a pseudo-Dirac pair. An important question is to what extent future colliders will have sensitivity to the splitting between the Majorana components, since this quantity signals the breaking of lepton number and is connected to the light neutrino masses. We consider the production of these neutral heavy leptons at the ILC, where their displaced decays provide a golden signal: a forward-backward charge asymmetry, which depends crucially on the mass splitting between the two Majorana components. We show that this observable can constrain the mass splitting to values much lower than current bounds from neutrinoless double beta decay and natural loop corrections.
Año de publicación: 2019
Testing quantum decoherence at DUNE
We address some theoretical issues of the quantum decoherence phenomenon within the neutrino oscillation framework and carry out various tests the under DUNE simulated experimental environment. On the theoretical side, we provide a general expression for an invariant decoherence matrix under a quantum basis rotation. On the simulated experimental side, considering a rotation-invariant and noninvariant decoherence matrix, we study the impact on the fitting of the standard oscillation parameters, the sensitivity in the mass hierarchy, and the CP violation, combining the neutrino and antineutrino mode and all available neutrino oscillation probabilities channels. Furthermore, a sensitivity for the decoherence parameter of the order 10−24 GeV at 3σ is obtained for our best case. We also note that a degeneracy between the decoherence parameter and the CP violation phase remains, even though our analysis includes neutrino/antineutrino mode and all probabilities channels.
Año de publicación: 2019
We address some theoretical issues of the quantum decoherence phenomenon within the neutrino oscillation framework and carry out various tests the under DUNE simulated experimental environment. On the theoretical side, we provide a general expression for an invariant decoherence matrix under a quantum basis rotation. On the simulated experimental side, considering a rotation-invariant and noninvariant decoherence matrix, we study the impact on the fitting of the standard oscillation parameters, the sensitivity in the mass hierarchy, and the CP violation, combining the neutrino and antineutrino mode and all available neutrino oscillation probabilities channels. Furthermore, a sensitivity for the decoherence parameter of the order 10−24 GeV at 3σ is obtained for our best case. We also note that a degeneracy between the decoherence parameter and the CP violation phase remains, even though our analysis includes neutrino/antineutrino mode and all probabilities channels.
Año de publicación: 2019