Precision Measurement of Neutrino Oscillation Parameters with KamLAND

Thesis/Dissertation · Thu Dec 01 00:00:00 EST 2011

DOI:https://doi.org/10.2172/1082203· OSTI ID:1082203

O'Donnell, Thomas ^[1]

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1. Univ. of California, Berkeley, CA (United States)

This dissertation describes a measurement of the neutrino oscillation parameters m² ₂₁, θ₁₂ and constraints on θ₁₃ based on a study of reactor antineutrinos at a baseline of ~ 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 × 10³² 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_Obs - N_Bkg)/ (N_Exp) = 0.59 ± 0.02(stat) ± 0.045(syst) which confirms reactor neutrino disappearance at greater than 5σ significance. Interpreting this deficit as being due to neutrino oscillation, the best-fit oscillation parameters from a three-flavor analysis are m² ₂₁= 7.60^+0.20 _-0.19×10^-5eV², θ₁₂ = 32.5 ± 2.9 degrees and sin² θ₁₃ = 0.025^+0.035 _-0.035, the 95% confidence-level upper limit on sin² θ₁₃ is sin² θ₁₃ < 0.083. Assuming CPT invariance, a combined analysis of KamLAND and solar neutrino data yields best-fit values: m² ₂₁ = 7.60^+0.20 _-0.20 × 10^-5eV², θ₁₂ = 33.5^+1.0 _-1.1 degrees, and sin² θ₁₃ = 0.013 ± 0.028 or sin² θ₁₃ < 0.06 at the 95% confidence level.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• DOE Contract Number: AC02-05CH11231; FG03-00ER41138; FG02-01ER41166
• OSTI ID: 1082203
• Report Number(s): LBNL-5404E
• Resource Relation: Related Information: Designation of Academic Dissertation: Doctoral; Academic Degree: PhD; Name of Academic Institution: University of California, Berkeley
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS