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Precision Measurement of Neutrino Oscillation Parameters with KamLAND
This dissertation describes a measurement of the neutrino oscillation parameters #1;{Delta}m{sup 2}{sub 21}, &#952;{sub 12} and constraints on &#952;{sub 13} based on a study of reactor antineutrinos at a baseline of &#8764; 180 km with the KamLAND detector. The data presented here was collected between April 2002 and November 2009, and amounts to a total exposure of 2.64 � 0.07 � 10{sup 32} proton-years. For this exposure we expect 2140 � 74(syst) antineutrino candidates from reactors, assuming standard model neutrino behavior, and 350�88(syst) candidates from background. The number observed is 1614. The ratio of background-subtracted candidates observed to expected is (N{sub Obs} &#8722; N{sub Bkg})/N{sub Exp} = 0.59 � 0.02(stat) � 0.045(syst) which confirms reactor neutrino disappearance at greater than 5&#963; significance. Interpreting this deficit as being due to neutrino oscillation, the best-fit oscillation parameters from a three-flavor analysis are #1;{Delta}m{sup 2}{sub 21} = 7.60{sup +0.20}{sub &#8722;0.19}�10{sup &#8722;5}eV{sup 2}, &#952;{sub 12} = 32.5 � 2.9 degrees and sin{sup 2} &#952;{sub 13} = 0.025{sup +0.035}{sub &#8722;0.035}, the 95% confidence-level upper limit on sin{sup 2} &#952;{sub 13} is sin{sup 2} &#952;{sub 13} < 0.083. Assuming CPT invariance, a combined analysis of KamLAND and solar neutrino data yields best-fit values: #1;{Delta}m{sup 2}{sub 21} …
Date:
December 12, 2011
Creator:
KamLAND, & O'Donnell, Thomas
System:
The UNT Digital Library