Precision Neutrino Oscillation Measurements using Simultaneous High-Power, Low-Energy Project-X Beams

The first phase of the long-baseline neutrino experiment, LBNE10, will use a broadband, high-energy neutrino beam with a 10-kt liquid argon TPC at 1300 km to study neutrino oscillation. In this paper, we describe potential upgrades to LBNE10 that use Project X to produce high-intensity, low-energy neutrino beams. Simultaneous, high-power operation of 8and 60-GeV beams with a 200-kt water Cerenkov detector would provide sensitivity to νμ → νe oscillations at the second oscillation maximum. We find that with ten years of data, it would be possible to measure sin(2θ13) with precision comparable to that expected from reactor antineutrino disappearance and to measure the value of the CP phase, δCP , with an uncertainty of ±(5− 10)◦. This document is submitted for inclusion in Snowmass 2013. Recent measurements of non-zero sin(2θ13)[1, 2, 3, 4] enable the search for CP violation in the neutrino sector and, ultimately, precision measurement of the CP phase, δCP , using νμ → νe oscillations. The first phase of the longbaseline neutrino experiment, LBNE10, will use 708 kW of 120-GeV protons from Fermilab’s Main Injector (MI) to produce a muon-neutrino or antineutrino beam aimed at a 10-kt liquid argon time projection chamber (LAr TPC) at a distance of 1300 km. The spectrum of neutrino energies detected at the far site in LBNE10 is aligned with the first oscillation maximum, peaking in the range 1 ar X iv :1 30 7. 08 07 v1 [ he pex ] 2 J ul 2 01 3 Eν = (2-4) GeV. As described in its conceptual design report[5], LBNE10, in combination with other neutrino data, is expected to determine the neutrino mass hierarchy and provide an initial measurement of the CP phase in the three-generation framework. Figure 1 shows the total neutrino-antineutrino asymmetry in the probability of νμ → νe appearance as a function of δCP , at the first and second oscillation peaks, for normal and inverted hierarchy, at a distance of 1300 km. This asymmetry includes contributions from both CP and matter effects. It is clear from Fig. 1 that the matter effect is large in the first oscillation maximum, but in the second oscillation maximum, where Eν = (0.2-1.5) GeV, the CP asymmetry is large with very little matter asymmetry. For this reason, measurement of νμ → νe appearance at the second oscillation maximum provides excellent sensitivity to CP violation, independent of the mass hierarchy. Project X[6] will make it possible to produce high-intensity, low-energy neutrino beams. In this paper, we summarize and update [7], which argues that simultaneous, high-power operation of 8and 60-GeV beams with a 200-kt water Cerenkov detector at a long baseline provides sensitivity to νμ → νe oscillations at the second oscillation maximum, allowing precise measurements of neutrino oscillation parameters independent of the mass hierarchy. (Degrees) cp δ -150 -100 -50 0 50 100 150 ) e ν → μ ν