Measuring the mass hierarchy with muon and hadron events in atmospheric neutrino experiments

Abstract

Neutrino mass hierarchy can be measured in atmospheric neutrino experiments through the observation of earth matter effects. Magnetized iron calorimeters have been shown to be good in this regard due to their charge identification capabilities. The charged current interaction of ν µ in this detector, produces a muon track and a hadron shower. The direction of the muon track can be measured very accurately. We show the improvement expected in the reach of this class of experiments to the neutrino mass hierarchy, as we improve the muon energy resolution and the muon reconstruction efficiency. We next propose to include the hadron events in the analysis, by tagging them with the zenith angle of the corresponding muon and binning the hadron data first in energy and then in zenith angle. To the best of our knowledge this way of performing the analysis of the atmospheric neutrino data has not be considered before. We show that the hadron events increase the mass hierarchy sensitivity of the experiment. Finally, we show the expected mass hierarchy sensitivity in terms of the reconstructed neutrino energy and zenith angle. We show how the detector resolutions spoil the earth matter effects in the neutrino channel and argue why the sensitivity obtained from the neutrino analysis cannot be significantly better than that obtained from the analysis using muon data alone. As a result, the best mass hierarchy sensitivity is obtained when we add the contribution of the muon and the hadron data. For sin 2 2θ 13 = 0.1, sin 2 θ 23 = 0.5, a muon energy resolution of 2%, reconstruction efficiency of 80% and exposure of 50 × 10 kton-year, we could get up to 4.5σ signal for the mass hierarchy from combining the muon and hadron data. The signal will go up when the atmospheric data is combined with data from other existing experiments, particularly NOνA.

Neutrino physics with non-standard interactions at INO

“…Finally, the muon reconstruction efficiency, charge identification efficiency, and muon energy and angular resolutions are folded in as described in refs. [5][6][7][8][9]. The new ingredient in the simulations performed for this work is that while all the earlier papers used muon sample in the energy range (1-11) GeV, we consider in this work a much larger energy range of (1-100) GeV.…”

“…The sensitivity reach of this experiment for measuring standard neutrino oscillation parameters have been studied extensively in refs. [5][6][7][8][9].…”

Enhancing sensitivity to neutrino parameters at INO combining muon and hadron information

“…However in the process of adding E µ and E had in ICAL, the advantage of high precision in the measurement of E µ is partially lost in case of MH discrimination. It has been claimed in [80] that the MH discovery reach can be improved by treating the reconstructed muon momentum and calibrated E had as two separate variables. However, since the fraction of neutrino energy carried by the muon, or equivalently the inelasticity y ≡ E had /E ν , is different for each event, the correlation between these quantities constitutes an important part of the information about the event that should not be missed.…”

Neutrino mass ordering at DUNE: An extra ν bonus

“…These pioneer studies focused mostly on muon calorimeter detectors, such as MONOLITH [23], MINOS [24] or INO 2 in which the muon charge can be determined, see also Refs. [25][26][27][28][29][30][31][32][33][34][35][36][37]. Furthermore, in the absence of a charged current event by event final muon charge discrimination, the addition of the atmospheric neutrino oscillation data to the analysis performed in Ref.…”