Determination of mass hierarchy with medium baseline reactor neutrino experiments

Abstract

We study the sensitivity of future medium baseline reactor antineutrino experiments on the neutrino mass hierarchy. By using the standard χ 2 analysis, we find that the sensitivity depends strongly on the baseline length L and the energy resolution (δE/E) 2 = a/ E/MeV 2 + b 2 , where a and b parameterize the statistical and systematic uncertainties, respectively. The optimal length is found to be L ∼ 40 − 55 km, where a slightly shorter L in the range is preferred for poorer energy resolution. The running time needed to determine the mass hierarchy also depends strongly on the energy resolution; for a 5 kton detector (with 12% weight fraction of free proton) placed at L ∼ 50 km away from a 20 GW th reactor, 3σ determination needs 14 years of running with a = 3% and b = 0.5%, which can be reduced to 5 years if a = 2% and b = 0.5%. On the other hand, the experiment can measure the mixing parameters accurately, achieving δ sin 2 2θ 12 ∼ 4 × 10 −3 , δ(m 2 2 − m 2 1 ) ∼ 0.03 × 10 −5 eV 2 , and δ|m 2 3 − m 2 1 | ∼ 0.007 × 10 −3 eV 2 , in 5 years, almost independently of the energy resolution for a < 3% and b < 1%. In order to compare our simple (∆χ 2 ) min results with those obtained by simulating many experiments, we develop an efficient method to estimate the uncertainty of (∆χ 2 ) min , and the probability for determining the right mass hierarchy by an experiment is presented as a function of the mean (∆χ 2 )

A to Z of Flavour with Pati-Salam

“…The predictions of a normal neutrino mass hierarchy and maximal atmospheric angle will both be either confirmed or excluded over the next few years by current or near future neutrino experiments such as SuperKamiokande, T2K, NOνA and PINGU [64][65][66][67][68]. The Daya Bay II reactor upgrade, including the short baseline experiment JUNO [69][70][71], will also test the normal neutrino mass hierarchy and measure the reactor and solar angles to higher accuracy, enabling precision tests of the predictions θ l 13 = 9 • ± 0. figure 11.…”

A model of quark and lepton mixing

“…The "binary" predictions of a normal neutrino mass hierarchy and an atmospheric angle in the first octant will both be tested over the next few years by current and planned neutrino experiments such as SuperKamiokande, T2K, NOνA and PINGU [49][50][51][52]. The Daya Bay II reactor experiment, including the short baseline detectors [59,60], will also test the neutrino mass hierarchy and in addition measure the reactor and solar angle to high accuracy, enabling precision tests of the predictions θ l 13 = 9.0 • ±0.5 • and θ l 12 = 34 • ± 1 • . In the longer term, superbeam and neutrino factory proposals such as WBB and LENF [61] would measure the atmospheric mixing angle to high accuracy, confronting the prediction θ l 23 = 40 • ±1 • , and ultimately testing the prediction of the Dirac CP violating oscillation phase δ l = 260 • ± 5 • .…”

A novel approach to study atmospheric neutrino oscillation

“…Note that the result of this method, χ 2 min corresponds to the so-called "average experiment" [116] or "Asimov data set" [117]. The uncertainty from statistical fluctuation can be easily estimated to be ∆(χ 2 min ) ≈ 2 ∆(χ 2 min ) [118][119][120]. It not only applies to the case of discrete variables such as the neutrino mass hierarchy and the octant, but actually applies generally as long as the binned event number is large enough such that statistical fluctuation can be approximated by Gaussian distribution.…”

“…The first could be achieved with a medium baseline reactor experiment [8][9][10][11][12][13][14][15][16][17][18][19][20][21] and long baseline accelerator experiments [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]44] could measure all three of them. Atmospheric neutrino experiments could offer alternative ways to accomplish the same.…”