Towards a sub-percent precision measurement of sin2 θ13 with reactor antineutrinos

Measuring the neutrino mixing parameter \ensuremath{\sin^2\theta_{13}} to sub-percent precision level could be necessary in next ten years for unitary test of PMNS matrix. In this work, we discuss possibility such a measurement with reactor antineutrinos. We find that single liquid scintillator detector on reasonable scale achieve goal. propose install $\sim10$\% energy resolution at about 2.0~km from reactors JUNO-like overburden. The integrated luminosity requirement is 150~${\rm kton}\cdot {\rm GW}\cdot year}$, corresponding 4 years' operation 4~kton near complex 9.2 GW thermal power like Taishan reactor. Unlike previous $\theta_{13}$ experiments identical and far detectors, which can suppress systematics especially rate uncertainty by near-far relative optimal baseline first oscillation maximum 1.8~km, single-detector prefers offset maximum. At low statistics $\lesssim 10$~${\rm dominates systematics, 1.3~km. higher statistics, spectral shape becomes dominant, shifts 2.0~km. keeps being $\sim 2.0$~km an up $10^6$~${\rm year}$. have assumed TAO experiment will improve our understanding uncertainty, gives highest antineutrino spectrum range 3--6~MeV. 2.9$~km flat input provided future summation or conversion methods' prediction.