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<span style="font-size:12.0pt;line-height:115%;font-family:
"Times New Roman","serif""><font
color="#ff0000">Hall C Physics Seminar </font><br>
Wednesday, April 3, 2013 <br>
F113 @ Noon-1 pm <br>
Pi-Jung Chang <br>
Title: “Double Chooz Neutron Detection Systematic Errors and
Detector Seasonal Stability” <br>
<br>
Abstract: Since March 2012, the Double Chooz reactor neutrino
experiment has published the newest result, sin22θ13 = 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 sin22θ13.</span>
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