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
Search for Gamma-ray Counterparts of Newly Discovered Radio Astrophysical Sources
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 radio galaxies known as...
Año de publicación: 2019
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 radio galaxies known as...
Año de publicación: 2019
Revisiting quantum decoherence for neutrino oscillations in matter with constant density
We reexamine the matter neutrino oscillation probabilities considering the decoherence phenomenon as a subleading effect. In this paper we point out the relevance of having the correct interpretation of the decoherence matrix in the different quantum bases, within the framework of neutrino oscillation probabilities in matter. Based on this treatment we develop an analytical formula for matter neutrino oscillation probabilities for three generations, with a range of application up to the decoherence parameter Γ∼10-23 GeV. We observe that, due to decoherence, the amplitudes of the neutrino/antineutrino oscillation probabilities increase in an energy independent way. We also find that decoherence can reduce the absolute value of the CP asymmetry, relative to its value at the pure oscillation case. As a side effect we have found a degeneracy between the decoherence parameter Γ and the CP violation phase δ.
Año de publicación: 2018
We reexamine the matter neutrino oscillation probabilities considering the decoherence phenomenon as a subleading effect. In this paper we point out the relevance of having the correct interpretation of the decoherence matrix in the different quantum bases, within the framework of neutrino oscillation probabilities in matter. Based on this treatment we develop an analytical formula for matter neutrino oscillation probabilities for three generations, with a range of application up to the decoherence parameter Γ∼10-23 GeV. We observe that, due to decoherence, the amplitudes of the neutrino/antineutrino oscillation probabilities increase in an energy independent way. We also find that decoherence can reduce the absolute value of the CP asymmetry, relative to its value at the pure oscillation case. As a side effect we have found a degeneracy between the decoherence parameter Γ and the CP violation phase δ.
Año de publicación: 2018
Matter effects in neutrino visible decay at future long-baseline experiments
Neutrino visible decay in the presence of matter is re-evaluated. We study these effects in two future long-baseline experiments where matter effects are relevant: DUNE (1300 km) and a hypothetical beam aimed towards ANDES (7650 km). We find that matter effects are negligible for the visible component of neutrino decay at DUNE, being much more relevant at ANDES. We perform a detailed simulation of DUNE, considering νμ disappearance and νe appearance channels, for both FHC and RHC modes. The sensitivity to the decay constant α3 can be as low as 2×10−6 eV2 at 90% C.L., depending on the neutrino masses and type of coupling. We also show the impact of neutrino decay in the determination of θ23 and δCP, and find that the best-fit value of θ23 can move from a true value at the lower octant towards the higher octant.
Año de publicación: 2018
Neutrino visible decay in the presence of matter is re-evaluated. We study these effects in two future long-baseline experiments where matter effects are relevant: DUNE (1300 km) and a hypothetical beam aimed towards ANDES (7650 km). We find that matter effects are negligible for the visible component of neutrino decay at DUNE, being much more relevant at ANDES. We perform a detailed simulation of DUNE, considering νμ disappearance and νe appearance channels, for both FHC and RHC modes. The sensitivity to the decay constant α3 can be as low as 2×10−6 eV2 at 90% C.L., depending on the neutrino masses and type of coupling. We also show the impact of neutrino decay in the determination of θ23 and δCP, and find that the best-fit value of θ23 can move from a true value at the lower octant towards the higher octant.
Año de publicación: 2018
Constraining sleptons at the LHC in a supersymmetric low-scale seesaw scenario
We consider a scenario inspired by natural supersymmetry, where neutrino data is explained within a low-scale seesaw scenario. We extend the Minimal Supersymmetric Standard Model by adding light right-handed neutrinos and their superpartners, the R-sneutrinos, and consider the lightest neutralinos to be higgsino-like. We consider the possibilities of having either an R-sneutrino or a higgsino as lightest supersymmetric particle. Assuming that squarks and gauginos are heavy, we systematically evaluate the bounds on slepton masses due to existing LHC data.
Año de publicación: 2017
We consider a scenario inspired by natural supersymmetry, where neutrino data is explained within a low-scale seesaw scenario. We extend the Minimal Supersymmetric Standard Model by adding light right-handed neutrinos and their superpartners, the R-sneutrinos, and consider the lightest neutralinos to be higgsino-like. We consider the possibilities of having either an R-sneutrino or a higgsino as lightest supersymmetric particle. Assuming that squarks and gauginos are heavy, we systematically evaluate the bounds on slepton masses due to existing LHC data.
Año de publicación: 2017
Visible neutrino decay in the light of appearance and disappearance long-baseline experiments
We investigate the present constraints from MINOS and T2K experiments for the neutrino decay scenario induced by non-diagonal couplings of Majorons to neutrinos. As novelty, on top of the typical invisible decay prescription, we add the contribution of visible decay, where final products can be observed. This new effect depends on the nature of the neutrino-Majoron coupling, which can be of scalar or pseudoscalar type. Using the combination of disappearance data from MINOS and disappearance and appearance data from T2K, for normal ordering, we constrain the decay parameter α ≡ E Γ for the heaviest neutrino, where E and Γ are the neutrino energy and width, respectively. We find that when considering visible decay within appearance data, one can improve current neutrino long-baseline constraints up to 𝛼<(10−5) eV2, at 90% C.L., for both kinds of couplings, which is better by one order of magnitude compared to previous bounds.
Año de publicación: 2017
We investigate the present constraints from MINOS and T2K experiments for the neutrino decay scenario induced by non-diagonal couplings of Majorons to neutrinos. As novelty, on top of the typical invisible decay prescription, we add the contribution of visible decay, where final products can be observed. This new effect depends on the nature of the neutrino-Majoron coupling, which can be of scalar or pseudoscalar type. Using the combination of disappearance data from MINOS and disappearance and appearance data from T2K, for normal ordering, we constrain the decay parameter α ≡ E Γ for the heaviest neutrino, where E and Γ are the neutrino energy and width, respectively. We find that when considering visible decay within appearance data, one can improve current neutrino long-baseline constraints up to 𝛼<(10−5) eV2, at 90% C.L., for both kinds of couplings, which is better by one order of magnitude compared to previous bounds.
Año de publicación: 2017
Testing FLUKA on neutron activation of Si and Ge at nuclear research reactor using gamma spectroscopy
Samples of two characteristic semiconductor sensor materials, silicon and germanium, have been irradiated with neutrons produced at the RP-10 Nuclear Research Reactor at 4.5 MW. Their radionuclides photon spectra have been measured with high resolution gamma spectroscopy, quantifying four radioisotopes (28Al, 29Al for Si and 75Ge and 77Ge for Ge). We have compared the radionuclides production and their emission spectrum data with Monte Carlo simulation results from FLUKA. Thus we have tested FLUKA’s low energy neutron library (ENDF/B-VIIR) and decay photon scoring with respect to the activation of these semiconductors. We conclude that FLUKA is capable of predicting relative photon peak amplitudes, with gamma intensities greater than 1%, of produced radionuclides with an average uncertainty of 13%. This work allows us to estimate the corresponding systematic error on neutron activation simulation studies of these sensor materials.
Año de publicación: 2017
Samples of two characteristic semiconductor sensor materials, silicon and germanium, have been irradiated with neutrons produced at the RP-10 Nuclear Research Reactor at 4.5 MW. Their radionuclides photon spectra have been measured with high resolution gamma spectroscopy, quantifying four radioisotopes (28Al, 29Al for Si and 75Ge and 77Ge for Ge). We have compared the radionuclides production and their emission spectrum data with Monte Carlo simulation results from FLUKA. Thus we have tested FLUKA’s low energy neutron library (ENDF/B-VIIR) and decay photon scoring with respect to the activation of these semiconductors. We conclude that FLUKA is capable of predicting relative photon peak amplitudes, with gamma intensities greater than 1%, of produced radionuclides with an average uncertainty of 13%. This work allows us to estimate the corresponding systematic error on neutron activation simulation studies of these sensor materials.
Año de publicación: 2017