The Daya Bay Reactor Neutrino Experiment has measured the last unknown neutrino mixing 15 angle, θ 13 , to be non-zero at the 7.7σ level. This is the most precise measurement to θ 13 to date. [1,2] . To 16 further enhance the understanding of the response of the antineutrino detectors (ADs), a detailed calibration 17 of an AD with the Manual Calibration System (MCS) was undertaken during the summer 2012 shutdown. 18The MCS is capable of placing a radioactive source with a positional accuracy of 25 mm in R direction, 12 19 mm in Z axis and 0.5° in Φ direction. A detailed description of the MCS is presented followed by a 20 summary of its performance in the AD calibration run. 21 22

No abstract

We study the radiative decays hc → γη ( ) in the framework of perturbative QCD and evaluate analytically the one-loop integrals with the light quark masses kept. Interestingly, the branching ratios B(hc → γη ( ) ) are insensitive to both the light quark masses and the shapes of η ( ) distribution amplitudes. And it is noticed that the contribution of the gluonic content of η ( ) is almost equal to that of the quark-antiquark content of η ( ) in the radiative decays hc → γη ( ) . By employing the ratio R hc = B(hc → γη)/B(hc → γη ), we extract the mixing angle φ = 33.8 • ± 2.5 • , which is in clear disagreement with the Feldmann-Kroll-Stech result φ = 39.0 • ± 1.6 • extracted from the ratio R J/ψ with nonperturbative matrix elements 0 | G a µνG a,µν | η ( ) , but in consistent with φ = 33.5 • ± 0.9 • extracted from the asymptotic limit of the γ * γ − η transition form factor and φ = 33.9 • ± 0.6 • extracted from R J/ψ in perturbative QCD. We also briefly discuss possible reasons for the difference in the determinations of the mixing angle.

No abstract