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تسجيل مستخدم جديدAtmospheric neutrino and Long Baseline neutrino experiments
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The results obtained by several experiments on atmospheric neutrino oscillations are summarized and discussed. Then the results obtained by different long baseline neutrino experiments are considered. Finally conclusions and perspectives are made.
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One of the unknown parameters in neutrino oscillations is the octant of the mixing angle theta_{23}. In this paper, we discuss the possibility of determining the octant of theta_{23} in the long baseline experiments T2K and NOvA in conjunction with f
uture atmospheric neutrino detectors, in light of non-zero value of theta_{13} measured by reactor experiments. We consider two detector technologies for atmospheric neutrinos - magnetized iron calorimeter and non-magnetized Liquid Argon Time Projection Chamber. We present the octant sensitivity for T2K/NOvA and atmospheric neutrino experiments separately as well as combined. For the long baseline experiments, a precise measurement of theta_{13}, which can exclude degenerate solutions in the wrong octant, increases the sensitivity drastically. For theta_{23} = 39^o and sin^2 2 theta_{13} = 0.1, at least ~2 sigma sensitivity can be achieved by T2K+NOvA for all values of delta_{CP} for both normal and inverted hierarchy. For atmospheric neutrinos, the moderately large value of theta_{13} measured in the reactor experiments is conducive to octant sensitivity because of enhanced matter effects. A magnetized iron detector can give a 2 sigma octant sensitivity for 500 kT yr exposure for theta_{23} = 39^o, delta_{CP} = 0 and normal hierarchy. This increases to 3 sigma for both hierarchies by combining with T2K+NOvA. This is due to a preference of different theta_{23} values at the minimum chi^2 by T2K/NOvA and atmospheric neutrino experiments. A Liquid Argon detector for atmospheric neutrinos with the same exposure can give higher octant sensitivity, due to the interplay of muon and electron contributions and superior resolutions. We obtain a ~3 sigma sensitivity for theta_{23} = 39^o for normal hierarchy. This increases to > ~4 sigma for all values of delta_{CP} if combined with T2K+NOvA. For inverted hierarchy the combined sensitivity is ~3 sigma.
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Non-unitary neutrino mixing in the light neutrino sector is a direct consequence of type-I seesaw neutrino mass models. In these models, light neutrino mixing is described by a sub-matrix of the full lepton mixing matrix and, then, it is not unitary
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