Optimization of neutrino oscillation facilities for large θ 13

Pilar Coloma,Enrique Fernandez-Martinez

doi:10.1007/jhep04(2012)089

Pilar Coloma, Enrique Fernandez-Martinez

Open Access

https://doi.org/10.1007/jhep04(2012)089

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Abstract

Abstract Up to now, future neutrino beam experiments have been designed and optimized in order to look for CP violation, θ 13 and the mass hierarchy under the conservative assumption that θ 13 is very small. However, the recent results from T2K and MINOS favor a θ 13 which could be as large as 8°. In this work, we propose a re-optimization for neutrino beam experiments in case this hint is confirmed. By switching from the first to the second oscillation peak, we find that the CP discovery potential of future oscillation experiments would not only be enhanced, but it would also be less affected by systematic uncertainties. In order to illustrate the effect, we present our results for a Super-Beam experiment, comparing the results obtained at the first and the second oscillation peaks for several values of the systematic errors. We also study its combination with a β-beam facility and show that the synergy between both experiments would also be enhanced due to the larger L/E. Moreover, the increased matter effects at the longer baseline also significantly improve the sensitivity to the mass hierarchy.

Highlights

By switching from the first to the second oscillation peak, we find that the CP discovery potential of future oscillation experiments would be enhanced, but it would be less affected by systematic uncertainties
We will show how the performance of the SPL Super-Beam at probing the mass hierarchy and leptonic CP-violation can improve for large θ13 when moving from the first to the second oscillation peak, given the stronger matter effects at longer baselines
The recent hint for large θ13 opens the window to the search for leptonic CP violation and the neutrino mass hierarchy at the generation of neutrino oscillation facilities, bringing within reach the last unknowns in the picture of neutrino mixing

Summary

Introduction

In order to maximize the interference between the two terms, they should both be of the same order, i.e. for large θ13 a longer L/E would be preferable so that “solar” oscillations develop to a similar size: sin 2θ13 ∼ ∆m221L/(4E), while the first oscillation peak corresponds to ∆m213L/(4E) ∼ π/2. These two criteria only coincide when sin 2θ13 ∼ π/2∆m221/∆m231 ∼ 0.05. Given that systematics errors dominate the sensitivity of Super-Beams at large θ13 [11] this will be desirable unless they can be controlled to a very low level

Objectives

Results

Conclusion