[Jlab-seminars] Hall C Seminar

[Luci Collins]

Hall C Physics Seminar
Wednesday, April 3, 2013
F113 @ Noon-1 pm
Pi-Jung Chang
Title: "Double Chooz Neutron Detection Systematic Errors and Detector 
Seasonal Stability"

Abstract:  Since March 2012, the Double Chooz reactor neutrino 
experiment has published the newest result, sin22?13 = 0.109 ± 
0.030(stat.) ± 0.025(syst.), and its confidence level is at 99.8% away 
from the no-oscillation hypothesis. The systematic errors from the 
background and the detection efficiency have been corrected a lot. The 
neutron detection efficiency, one of the biggest contributions in the 
detection efficiency, is discussed particularly in this research. The 
neutron detection efficiency, which is studied by 252Cf, are divided 
into three factors: the Gd-captured fraction, the time difference 
(between prompt and delayed signals), and the energy containment. 
Additionally, the neutron detection efficiency from the 252Cf result has 
been confirmed by the electron antineutrino data and Monte Carlo 
simulations. The systematic uncertainty from the neutron detection 
efficiency is 0.91%. The seasonal variation in detector performance and 
the seasonal variations of the muon intensity are described in detail as 
well. The detector is in a stable status based on two results: 1) the 
electron antineutrino rate is not related to the liquid scintillator 
temperature, and 2) the daily muon rate has a high correspondence with 
the integrated atmospheric temperature. Our detector has the ability to 
measure the ratio of kaon to pion in the local atmosphere when the data 
from the detector is combined with a precise simulation of the muon 
threshold energy. The systematic error from the relative instability of 
the neutron detection efficiency is discussed in the final part, and its 
error, 0.13%, is from the Gd-captured fraction and the time difference 
(between prompt and delayed signals). The instability systematic error 
does not affect the final result of sin22?13.
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