Solar parameters in long-baseline accelerator neutrino oscillations

Abstract

Long-baseline (LBL) accelerator neutrino oscillation experiments, such as NOvA and T2K in the current generation, and DUNE-LBL and HK-LBL in the coming years, will measure the remaining unknown oscillation parameters with excellent precision. These analyses assume external input on the so-called “solar parameters,” θ12 and $$ \Delta {m}_{21}^2 $$ ∆ m 21 2 , from solar experiments such as SNO, SK, and Borexino, as well as reactor experiments like KamLAND. Here we investigate their role in long-baseline experiments. We show that, without external input on $$ \Delta {m}_{21}^2 $$ ∆ m 21 2 and θ12, the sensitivity to detecting and quantifying CP violation is significantly, but not entirely, reduced. Thus long-baseline accelerator experiments can actually determine $$ \Delta {m}_{21}^2 $$ ∆ m 21 2 and θ12, and thus all six oscillation parameters, without input from any other oscillation experiment. In particular, $$ \Delta {m}_{21}^2 $$ ∆ m 21 2 can be determined; thus DUNE-LBL and HK-LBL can measure both the solar and atmospheric mass splittings in their long-baseline analyses alone. While their sensitivities are not competitive with existing constraints, they are very orthogonal probes of solar parameters and provide a key consistency check of a less probed sector of the three-flavor oscillation picture. Furthermore, we also show that the true values of $$ \Delta {m}_{21}^2 $$ ∆ m 21 2 and θ12 play an important role in the sensitivity of other oscillation parameters such as the CP violating phase δ.

The impact of different parameterizations on the interpretation of CP violation in neutrino oscillations

“…In the upcoming generation of experiments, JUNO will measure the νe disappearance probability with unprecedented precision by directly observing all three oscillation frequencies. Long-baseline experiments like DUNE and HK will measure ν µ disappearance primarily focused on the weighted average of the ∆m 2 31 and ∆m 2 32 frequencies, but will also detect at a subleading level the ∆m 2 21 frequency [74]. This is enough to provide some information about δ.…”