Measuring theta12 Despite an Uncertain Reactor Neutrino Spectrum

Abstract

The recently discovered 5 MeV bump highlights that the uncertainty in the reactor neutrino spectrum is far greater than some theoretical estimates. Medium baseline reactor neutrino experiments will deliver by far the most precise ever measurements of theta12. However, as a result of the bump, such a determination of theta12 using the theoretical spectrum would yield a value of sin^2(2theta12) which is more than 1% higher than the true value. We show that by using recent measurements of the reactor neutrino spectrum the precision of a measurement of theta12 at a medium baseline reactor neutrino experiment can be improved appreciably. We estimate this precision as a function of the 9Li spallation background veto efficiency and dead time.