Speaker
Description
With the 1-3 mixing angle measured at reator neutrino experiments Daya Bay and RENO, there are still three unknown oscillation variables: the neutrino mass hierarchy, the octant of the atmospheric mixing angle, and the leptonic CP phase. Of these three, the CP phase is the most difficult to be measured precisely and important for distinguishing flavor symmetries. I will first review the status of CP measurement and then introduce a new proposal with muon decay at rest (muDAR). Currently, accelerator neutrino
experiments such as T2K, NOvA, and DUNE are the most promising for CP measurement. Nevertheless, they suffer from several problems of degeneracy, efficiency, sensitivity, and theoretical armbiguities such as non-unitarity mixing (NUM) and
non-standard interaction (NSI). The situation can be improved by adding a muon decay at rest (muDAR) source. With T2(H)K running
in neutrino mode and muDAR in anti-neutrino mode, both using the same detector, the CP measurement becomes more precise can break
the degeneracy between \delta and 180^o - \delta. Most importantly, muDAR can guarantee the CP sensitivity against NUM and NSI.
The same configuration can also apply to next-generation medium baseline reactor neutrino experiments like JUNO and RENO-50,
enhancing their physics potential from just mass hierarchy to also CP. With only one source and no extra detectors, this dessign
is much better than DAEdLAS which requires 3 sources, but only 20% duty factor and 4 times higher luminosity for each.
Summary
This new proposal of muDAR experiment can significantly
improve the CP sensitivity at accelerator neutrino experiment,
including T2K, NOvA, and DUNE.
1) Better CP measurement than T2K
1a) Much larger event numbers
1b) Much better CP sensitivity around maximal CP
1c) Solve degeneracy between δ_D & π − δ_D
1d) Guarantee CP sensitivity against NUM
1e) Guarantee CP sensitivity against NSI
2) Better configuration than DAEδLUS
2a) Only one cyclotron is needed
2b) 100% duty factor
2c) Much lower flux intensity
2d) Much easier in cyclotron technology
2e) Much cheaper
2f) Single near detector
Refs:
Jarah Evslin, SFG, Kaoru Hagiwara, JHEP 1602 (2016) 137 [arXiv:1506.05023]
SFG, Pedro Pasquini, Mariam Tortola, Jose W.F. Valle [arXiv:1605.01670]
SFG, Alexei Smirnov, in preparation