Energy-Independent New Physics in the Flavour Ratios of High-Energy Astrophysical Neutrinos
We have studied the consequences of breaking the CPT symmetry in the neutrino sector, using the expected high-energy neutrino flux from distant cosmological sources such as active galaxies. For this purpose we have assumed three different hypotheses for the neutrino production model, characterised by the flavour fluxes at production ϕ0 e : ϕ0 μ: ϕ0 τ = 1 : 2 : 0, 0 : 1 : 0, and 1 : 0 : 0, and studied the theoretical and experimental expectations for the muon-neutrino flux at Earth, ϕμ, and for the flavour ratios at Earth, R = ϕμ/ϕ e and S = ϕτ /ϕμ. CPT violation (CPTV) has been implemented by adding an energy-independent term to the standard neutrino oscillation Hamiltonian. This introduces three new mixing angles, two new eigenvalues and three new phases, all of which have currently unknown values. We have varied the new mixing angles and eigenvalues within certain bounds, together with the parameters associated to pure standard oscillations. Our results indicate that, for the models 1 : 2 : 0 and 0 : 1 : 0, it might be possible to find large deviations of ϕμ, R, and S between the cases without and with CPTV, provided the CPTV eigenvalues lie within 10−29 − 10−27 GeV, or above. Moreover, if CPTV exists, there are certain values of R and S that can be accounted for by up to three production models. If no CPTV were observed, we could set limits on the CPTV eigenvalues of the same order. Detection prospects calculated using IceCube suggest that for the models 1 : 2 : 0 and 0 : 1 : 0, the modifications due to CPTV are larger and more clearly separable from the standard-oscillations predictions. We conclude that IceCube is potentially able to detect CPTV but that, depending on the values of the CPTV parameters, there could be a mis-determination of the neutrino production model.
Año de publicación: 2010
We have studied the consequences of breaking the CPT symmetry in the neutrino sector, using the expected high-energy neutrino flux from distant cosmological sources such as active galaxies. For this purpose we have assumed three different hypotheses for the neutrino production model, characterised by the flavour fluxes at production ϕ0 e : ϕ0 μ: ϕ0 τ = 1 : 2 : 0, 0 : 1 : 0, and 1 : 0 : 0, and studied the theoretical and experimental expectations for the muon-neutrino flux at Earth, ϕμ, and for the flavour ratios at Earth, R = ϕμ/ϕ e and S = ϕτ /ϕμ. CPT violation (CPTV) has been implemented by adding an energy-independent term to the standard neutrino oscillation Hamiltonian. This introduces three new mixing angles, two new eigenvalues and three new phases, all of which have currently unknown values. We have varied the new mixing angles and eigenvalues within certain bounds, together with the parameters associated to pure standard oscillations. Our results indicate that, for the models 1 : 2 : 0 and 0 : 1 : 0, it might be possible to find large deviations of ϕμ, R, and S between the cases without and with CPTV, provided the CPTV eigenvalues lie within 10−29 − 10−27 GeV, or above. Moreover, if CPTV exists, there are certain values of R and S that can be accounted for by up to three production models. If no CPTV were observed, we could set limits on the CPTV eigenvalues of the same order. Detection prospects calculated using IceCube suggest that for the models 1 : 2 : 0 and 0 : 1 : 0, the modifications due to CPTV are larger and more clearly separable from the standard-oscillations predictions. We conclude that IceCube is potentially able to detect CPTV but that, depending on the values of the CPTV parameters, there could be a mis-determination of the neutrino production model.
Año de publicación: 2010
IceCube expectations for two high-energy neutrino production models at active galactic nuclei
We have determined the currently allowed regions of the parameter spaces of two representative models of diffuse neutrino flux from active galactic nuclei (AGN): one by Koers & Tinyakov (KT) and another by Becker & Biermann (BB). Our observable has been the number of upgoing muon-neutrinos expected in the 86-string IceCube detector, after 5 years of exposure, in the range 105 ≤ Eν/GeV ≤ 108. We have used the latest estimated discovery potential of the IceCube-86 array at the 5σ level to determine the lower boundary of the regions, while for the upper boundary we have used either the AMANDA upper bound on the neutrino flux or the more recent preliminary upper bound given by the half-completed IceCube-40 array (IC40). We have varied the spectral index of the proposed power-law fluxes, α, and two parameters of the BB model: the ratio between the boost factors of neutrinos and cosmic rays, Γν/ΓCR, and the maximum redshift of the sources that contribute to the cosmic-ray flux, zCRmax. For the KT model, we have considered two scenarios: one in which the number density of AGN does not evolve with redshift and another in which it evolves strongly, following the star formation rate. Using the IC40 upper bound, we have found that the models are visible in IceCube-86 only inside very thin strips of parameter space and that both of them are discarded at the preferred value of α = 2.7 obtained from fits to cosmic-ray data. Lower values of α, notably the values 2.0 and 2.3 proposed in the literature, fare better. In addition, we have analysed the capacity of IceCube-86 to discriminate between the models within the small regions of parameter space where both of them give testable predictions. Within these regions, discrimination at the 5σ level or more is guaranteed.
Año de publicación: 2010
We have determined the currently allowed regions of the parameter spaces of two representative models of diffuse neutrino flux from active galactic nuclei (AGN): one by Koers & Tinyakov (KT) and another by Becker & Biermann (BB). Our observable has been the number of upgoing muon-neutrinos expected in the 86-string IceCube detector, after 5 years of exposure, in the range 105 ≤ Eν/GeV ≤ 108. We have used the latest estimated discovery potential of the IceCube-86 array at the 5σ level to determine the lower boundary of the regions, while for the upper boundary we have used either the AMANDA upper bound on the neutrino flux or the more recent preliminary upper bound given by the half-completed IceCube-40 array (IC40). We have varied the spectral index of the proposed power-law fluxes, α, and two parameters of the BB model: the ratio between the boost factors of neutrinos and cosmic rays, Γν/ΓCR, and the maximum redshift of the sources that contribute to the cosmic-ray flux, zCRmax. For the KT model, we have considered two scenarios: one in which the number density of AGN does not evolve with redshift and another in which it evolves strongly, following the star formation rate. Using the IC40 upper bound, we have found that the models are visible in IceCube-86 only inside very thin strips of parameter space and that both of them are discarded at the preferred value of α = 2.7 obtained from fits to cosmic-ray data. Lower values of α, notably the values 2.0 and 2.3 proposed in the literature, fare better. In addition, we have analysed the capacity of IceCube-86 to discriminate between the models within the small regions of parameter space where both of them give testable predictions. Within these regions, discrimination at the 5σ level or more is guaranteed.
Año de publicación: 2010
Resolving CP Violation by Standard and Nonstandard Interactions and Parameter Degeneracy in Neutrino Oscillations
In neutrino oscillation with non-standard interactions (NSI) the system is enriched with CP violation caused by phases due to NSI in addition to the standard lepton Kobayashi-Maskawa phase δ. In this paper we show that it is possible to disentangle the two CP violating effects by measurement of muon neutrino appearance by a near-far two detector setting in neutrino factory experiments. Prior to the quantitative analysis we investigate in detail the various features of the neutrino oscillations with NSI, but under the assumption that only one of the NSI elements, εeμ or εeτ, is present. They include synergy between the near and the far detectors, the characteristic differences between the εeμ and εeτ systems, and in particular, the parameter degeneracy. Finally, we use a concrete setting with the muon energy of 50GeV and magnetized iron detectors at two baselines, one at L = 3000 km and the other at L = 7000 km, each having a fiducial mass of 50 kton to study the discovery potential of NSI and its CP violation effects. We demonstrate, by assuming 4 × 1021 useful muon decays for both polarities, that one can identify nonstandard CP violation down to |εeμ| ≃ a few × 10−3, and |εeτ| ≃ 10−2 at 3σ CL for θ13 down to sin2 2θ13 = 10−4 in most of the region of δ. The impact of the existence of NSI on the measurement of δ and the mass hierarchy is also worked out.
Año de publicación: 2010
In neutrino oscillation with non-standard interactions (NSI) the system is enriched with CP violation caused by phases due to NSI in addition to the standard lepton Kobayashi-Maskawa phase δ. In this paper we show that it is possible to disentangle the two CP violating effects by measurement of muon neutrino appearance by a near-far two detector setting in neutrino factory experiments. Prior to the quantitative analysis we investigate in detail the various features of the neutrino oscillations with NSI, but under the assumption that only one of the NSI elements, εeμ or εeτ, is present. They include synergy between the near and the far detectors, the characteristic differences between the εeμ and εeτ systems, and in particular, the parameter degeneracy. Finally, we use a concrete setting with the muon energy of 50GeV and magnetized iron detectors at two baselines, one at L = 3000 km and the other at L = 7000 km, each having a fiducial mass of 50 kton to study the discovery potential of NSI and its CP violation effects. We demonstrate, by assuming 4 × 1021 useful muon decays for both polarities, that one can identify nonstandard CP violation down to |εeμ| ≃ a few × 10−3, and |εeτ| ≃ 10−2 at 3σ CL for θ13 down to sin2 2θ13 = 10−4 in most of the region of δ. The impact of the existence of NSI on the measurement of δ and the mass hierarchy is also worked out.
Año de publicación: 2010
Resolving Standard and Nonstandard CP Violation Phases in Neutrino Oscillations
Neutrino oscillations can exhibit extra CP violation effects, beyond those expected from the standard Kobayashi‐Maskawa phase δ, if non‐standard neutrino interactions are at play. We show that it is possible...
Año de publicación: 2010
Neutrino oscillations can exhibit extra CP violation effects, beyond those expected from the standard Kobayashi‐Maskawa phase δ, if non‐standard neutrino interactions are at play. We show that it is possible...
Año de publicación: 2010
High energy astrophysical neutrino flux and modified dispersion relations
Motivated by the interest in searches for violation of CPT invariance, we study its possible effects in the flavor ratios of high-energy neutrinos coming from cosmic accelerators. In particular, we focus on the effect of an energy-independent new physics contribution to the neutrino flavor oscillation phase and explore whether it is observable in future detectors. Such a contribution could be related not only to CPT violation but also to a nonuniversal coupling of neutrinos to a torsion field. We conclude that this extra phase contribution only becomes observable, in the best case, at energies greater than 1016.5 GeV, which is about five orders of magnitude higher than the most energetic cosmological neutrinos to be detected in the near future. Therefore, if these effects are present only in the oscillation phase, they are going to be unobservable, unless a new mechanism or source capable to produce neutrinos of such energy were detected.
Año de publicación: 2009
Motivated by the interest in searches for violation of CPT invariance, we study its possible effects in the flavor ratios of high-energy neutrinos coming from cosmic accelerators. In particular, we focus on the effect of an energy-independent new physics contribution to the neutrino flavor oscillation phase and explore whether it is observable in future detectors. Such a contribution could be related not only to CPT violation but also to a nonuniversal coupling of neutrinos to a torsion field. We conclude that this extra phase contribution only becomes observable, in the best case, at energies greater than 1016.5 GeV, which is about five orders of magnitude higher than the most energetic cosmological neutrinos to be detected in the near future. Therefore, if these effects are present only in the oscillation phase, they are going to be unobservable, unless a new mechanism or source capable to produce neutrinos of such energy were detected.
Año de publicación: 2009
Extreme scenarios of new physics in the UHE astrophysical neutrino flavour ratios
We add an energy-independent Hamiltonian to the standard flavour oscillation one. This kind of physics might appear in theories where neutrinos couple differently to a plausible non-zero torsion of the...
Año de publicación: 2009
We add an energy-independent Hamiltonian to the standard flavour oscillation one. This kind of physics might appear in theories where neutrinos couple differently to a plausible non-zero torsion of the...
Año de publicación: 2009
BeamLine Design for MINERvA TestBeam Detector
The MINERνA TestBeam Detector calibrations will take place in the MTEST facility at Fermilab. It will use a beam of hadrons between 300 and 1500 MeV/c to analyze the response...
Año de publicación: 2008
The MINERνA TestBeam Detector calibrations will take place in the MTEST facility at Fermilab. It will use a beam of hadrons between 300 and 1500 MeV/c to analyze the response...
Año de publicación: 2008
On the Sensitivity of Neutrino Telescopes to a Modified Dispersion Relation
We consider a modified dispersion relation and its effect on the flavour ratios of high‐energy neutrinos originated at distant astrophysical sources such as active galactic nuclei. This dispersion relation arise...
Año de publicación: 2008
We consider a modified dispersion relation and its effect on the flavour ratios of high‐energy neutrinos originated at distant astrophysical sources such as active galactic nuclei. This dispersion relation arise...
Año de publicación: 2008
Revising the solution of the neutrino oscillation parameter degeneracies at neutrino factories
In the context of neutrino factories, we review the solution of the degeneracies in the neutrino oscillation parameters. In particular, we have set limits to sin22θ13 in order to accomplish the unambiguous determination of θ23 and δ. We have performed two different analysis. In the first, at a baseline of 3000 km, we simulate a measurement of the channels νe→νμ, νe→ντ, and ¯νμ→¯νμ, combined with their respective conjugate ones, with a muon energy of 50 GeV and a running time of five years. In the second, we merge the simulated data obtained at L=3000 km with the measurement of νe→νμ channel at 7250 km, the so-called “magic baseline.” In both cases, we have studied the impact of varying the ντ detector efficiency-mass product, (ϵντ×Mτ), at 3000 km, keeping unchanged the νμ detector mass and its efficiency. At L=3000 km, we found the existence of degenerate zones, that correspond to values of θ13, which are equal or almost equal to the true ones. These zones are extremely difficult to discard, even when we increase the number of events. However, in the second scenario, this difficulty is overcome, demonstrating the relevance of the “magic baseline.” From this scenario, the best limits of sin22θ13, reached at 3σ, for sin22θ23=0.95, 0.975, and 0.99 are: 0.008, 0.015, and 0.045, respectively, obtained at δ=0, and considering (ϵντ×Mτ)≈125, which is 5 times the initial efficiency-mass combination.
Año de publicación: 2007
In the context of neutrino factories, we review the solution of the degeneracies in the neutrino oscillation parameters. In particular, we have set limits to sin22θ13 in order to accomplish the unambiguous determination of θ23 and δ. We have performed two different analysis. In the first, at a baseline of 3000 km, we simulate a measurement of the channels νe→νμ, νe→ντ, and ¯νμ→¯νμ, combined with their respective conjugate ones, with a muon energy of 50 GeV and a running time of five years. In the second, we merge the simulated data obtained at L=3000 km with the measurement of νe→νμ channel at 7250 km, the so-called “magic baseline.” In both cases, we have studied the impact of varying the ντ detector efficiency-mass product, (ϵντ×Mτ), at 3000 km, keeping unchanged the νμ detector mass and its efficiency. At L=3000 km, we found the existence of degenerate zones, that correspond to values of θ13, which are equal or almost equal to the true ones. These zones are extremely difficult to discard, even when we increase the number of events. However, in the second scenario, this difficulty is overcome, demonstrating the relevance of the “magic baseline.” From this scenario, the best limits of sin22θ13, reached at 3σ, for sin22θ23=0.95, 0.975, and 0.99 are: 0.008, 0.015, and 0.045, respectively, obtained at δ=0, and considering (ϵντ×Mτ)≈125, which is 5 times the initial efficiency-mass combination.
Año de publicación: 2007
Optical Simulation for V0A
The V0A detector is one of the forward detectors that will be used for trigger in the ALICE experiment at CERN. Simulation results of the optical response of the V0A...
Año de publicación: 2006
The V0A detector is one of the forward detectors that will be used for trigger in the ALICE experiment at CERN. Simulation results of the optical response of the V0A...
Año de publicación: 2006