arXiv subjects

Andrea Donini

Publications and source records attributed to Andrea Donini.

24 records · Page 2Linked to original sources

arXiv2012

Precision on leptonic mixing parameters at future neutrino oscillation experiments

We perform a comparison of the different future neutrino oscillation experiments based on the achievable precision in the determination of the fundamental parameters theta_{13} and the CP phase, delta, assuming that theta_{13} is in the range indicated by the recent Daya Bay measurement. We study the non-trivial dependence of the error on delta on its true value. When matter effects are small, the largest error is found at the points where CP violation is maximal, and the smallest at the CP conserving points. The situation is different when matter effects are sizable. As a result of this effect, the comparison of the physics reach of different experiments on the basis of the CP discovery potential, as usually done, can be misleading. We have compared various proposed super-beam, beta-beam and neutrino factory setups on the basis of the relative precision of theta_{13} and the error on delta. Neutrino factories, both high-energy or low-energy, outperform alternative beam technologies. An ultimate precision on theta_{13} below 3% and an error on delta of < 7^{\circ} at 1 sigma (1 d.o.f.) can be obtained at a neutrino factory.

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arXiv2009

Optimized Two-Baseline Beta-Beam Experiment

We propose a realistic Beta-Beam experiment with four source ions and two baselines for the best possible sensitivity to theta_{13}, CP violation and mass hierarchy. Neutrinos from 18Ne and 6He with Lorentz boost gamma=350 are detected in a 500 kton water Cerenkov detector at a distance L=650 km (first oscillation peak) from the source. Neutrinos from 8B and 8Li are detected in a 50 kton magnetized iron detector at a distance L=7000 km (magic baseline) from the source. Since the decay ring requires a tilt angle of 34.5 degrees to send the beam to the magic baseline, the far end of the ring has a maximum depth of d=2132 m for magnetic field strength of 8.3 T, if one demands that the fraction of ions that decay along the straight sections of the racetrack geometry decay ring (called livetime) is 0.3. We alleviate this problem by proposing to trade reduction of the livetime of the decay ring with the increase in the boost factor of the ions, such that the number of events at the detector remains almost the same. This allows to substantially reduce the maximum depth of the decay ring at the far end, without significantly compromising the sensitivity of the experiment to the oscillation parameters. We take 8B and 8Li with gamma=390 and 656 respectively, as these are the largest possible boost factors possible with the envisaged upgrades of the SPS at CERN. This allows us to reduce d of the decay ring by a factor of 1.7 for 8.3 T magnetic field. Increase of magnetic field to 15 T would further reduce d to 738 m only. We study the sensitivity reach of this two baseline two storage ring Beta-Beam experiment, and compare it with the corresponding reach of the other proposed facilities.

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arXiv2009

The discovery channel at the Neutrino Factory: $ν_μ\toν_τ$ pointing to sterile neutrinos

We study the potential of a Neutrino Factory in constraining the parameter space of a scheme with one sterile neutrino separated from three active ones by an O(1) eV^2, mass-squared difference. We present approximated analytic expressions for the oscillation probabilities, showing that the greatest sensitivity to sterile neutrinos at a Neutrino Factory can be achieved using the ν_μ->ν_μand the ν_μ->ν_τoscillations. We have studied two setups: a Neutrino Factory with 50 GeV (20 GeV) stored muons, with two detectors of the Hybrid-MIND type (a magnetized ECC next to a magnetized iron calorimeter), located at L=3000, 7500 km (L=4000, 7500 km) from the source. Four channels have been used: ν_e -> ν_μ,ν_τ; ν_μ-> ν_μ,ν_τ. The relevant backgrounds, efficiencies and systematic errors have been taken into account, and we have discussed dependence of the sensitivities on the systematic errors. We have found that the 50 GeV (20 GeV) setup can constrain \sin^2 2 θ^{(4fam)}_{13} <= 7x10^{-5} (2x10^{-4}); θ_{34} <= 12 deg (14 deg); and θ_{24}<= 7.5 deg (8 deg). Our results hold for any value of Δm^2_{Sbl} >~ 0.1 eV^2. Eventually we have shown that, if a positive signal is found, the proposed setup is able to measure simultaneously θ_{34} and δ_3 with a precision of few degrees and few tens of degrees, respectively, solving the so-called "intrinsic" and "sign degeneracies". Combination of ν_μdisappearance and of the ν_μ->ν_τchannel, that will be called "the discovery channel", at the two baselines is able to measure at 99% CL a new CP-violating phase δ_3 for \sin^2 2 θ_{34} >= 0.06.

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arXiv2008

Signatures of sterile neutrino mixing in high-energy cosmic neutrino flux

Even after the negative result by the MiniBooNE experiment, we can still have a (3+1)-scheme with one sterile neutrino whose mixing lies within the allowed region by MiniBooNE. In this note we discuss the possible effects of such a scheme on the flavor ratio of high-energy cosmic neutrinos from cosmologically distant astrophysical sources. It is shown that in principle there is still a chance to observe deviation from the standard three flavor scenario in the flavor ratio of the high-energy cosmic neutrinos. It is proposed to see the energy spectrum to cope with the theoretical uncertainties which were recently pointed out by Lipari, Lusignoli and Meloni. It is emphasized that the $ν_μ-ν_τ$ ratio is relatively insensitive to the theoretical uncertainties and therefore this ratio is the key ingredient to look for the signatures of the sterile neutrino scheme. Although the statistics of data from one source in the next generation of neutrino telescopes are estimated not to be sufficient to distinguish the three and four family schemes, if we can gain statistics by, e.g., summing over data from many sources, then it might be possible to have a signature for the (3+1)-scheme.

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arXiv2008

$θ_{13}$, $δ$ and the neutrino mass hierarchy at a $γ=350$ double baseline Li/B $β$-Beam

We consider a $β$-Beam facility where $^8$Li and $^8$B ions are accelerated at $γ= 350$, accumulated in a 10 Km storage ring and let decay, so as to produce intense $\bar ν_e$ and $ν_e$ beams. These beams illuminate two iron detectors located at $L \simeq 2000$ Km and $L \simeq 7000$ Km, respectively. The physics potential of this setup is analysed in full detail as a function of the flux. We find that, for the highest flux ($10 \times 10^{18}$ ion decays per year per baseline), the sensitivity to $θ_{13}$ reaches $\sin^2 2 θ_{13} \geq 2 \times10^{-4}$; the sign of the atmospheric mass difference can be identified, regardless of the true hierarchy, for $\sin^2 2 θ_{13} \geq 4\times10^{-4}$; and, CP-violation can be discovered in 70% of the $δ$-parameter space for $\sin^2 2 θ_{13} \geq 10^{-3}$, having some sensitivity to CP-violation down to $\sin^2 2 θ_{13} \geq 10^{-4}$ for $|δ| \sim 90^\circ$.

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arXiv2007

Physics and Performance Evaluation Group

We summarize the objectives and results of the ``international scoping study of a future neutrino factory and superbeam facility'' (ISS) physics working group. Furthermore, we discuss how the ISS study should develop into a neutrino factory design study (IDS-NF) from the point of view of physics and performance evaluation.

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