Daya Bay Reactor Neutrino Oscillation Experiment Jen-Chieh Peng University of Illinois at Urbana-Champaign (on behalf of the Daya Bay Collaboration) International Workshop on “Double Beta Decay and Neutrinos” Osaka, Japan, June 11-13, 2007 1
Outline • θ Physics case for a precise measurement 13 • The proposed Daya Bay neutrino oscillation experiment • Schedule and expected sensitivity of the Daya Bay experiment 2
What we have learned from neutrino oscillation experiments 1) Neutrinos are massive − ∆ = − = ± × m m m 2 2 2 5 2 (7.9 0.7) 10 ev (90%c.l.) 21 2 1 ∆ = − = ± × − m m m 2 2 2 3 2 | | | | (2.4 0.6) 10 ev (90% c.l. ) 32 3 2 2) Neutrinos do mix with each ot h r e ν − i δ ν c c s c s e e 12 13 12 13 13 1 = − δ δ ν − i − i ν s c c s s e c c s s s e s c µ 12 23 12 2 3 13 12 23 12 23 13 23 13 2 ν − δ − − δ ν i i s s c c s e c s s c s e c c τ 12 23 12 23 13 12 23 12 23 13 23 13 3 = θ = θ c s ( cos , sin ) ij ij ij ij θ θ θ ≤ � � � � � 34 , 45 , 13 for the l epton MNSP Matrix 12 2 3 1 3 θ θ θ � � � � � � 13 , 2. 2 , 0 .22 for the quark C KM Matrix 12 23 1 3 3) Neutrino masses and mixings have provided clear evidence for physic s beyond the Stand ard Model 3
What we do not know about the neutrinos • Dirac or Majorana neutrinos? • Mass hierachy and values of the masses? • Existence of sterile neutrinos? • Value of the θ 13 mixing angle? • Values of CP-violation phases? • Origins of the neutrino masses? • Other unknown unknowns ….. 4
What we know and do not know about the neutrinos • What is the ν e fraction of ν 3 ? (proportional to sin 2 θ 13 ) − δ ν c c s c s e i ν e 12 13 12 13 13 1 • Contributions from the CP-phase ν = − − i δ − i δ ν s c c s s e c c s s s e s c µ 12 23 12 23 13 12 23 12 23 1 3 23 13 2 δ to the flavor compositions of ν − i δ − − i δ ν s s c c s e c s s c s e c c τ 12 23 12 23 13 12 23 12 23 13 23 1 3 3 neutrino mass eigenstates depend on sin 2 θ 13 ) 5
Why measuring θ 13 ? A recent tabulation of predictions of 63 neutrino mass models on sin 2 θ 13 (hep-ph/0608137) • Models based on the Grand Unified Theories in general give relatively large θ 13 • Models based on leptonic symmetries predict small θ 13 A measurement of sin 2 2 θ 13 at the sensitivity level of 0.01 can rule out at least half of the models! 6
Why measuring θ 13 ? A recent tabulation of predictions of 63 neutrino mass models on sin 2 θ 13 (hep-ph/0608137) A measurement of sin 2 2 θ 13 AND the mass hierarchy can rule out even more models! 7
Why measuring θ 13 ? Leptonic CP violation ν → ν − ν → ν = − P P s c s c s c 2 ( ) ( ) 16 µ µ e e 12 12 13 13 23 23 ∆ ∆ ∆ m m m 2 2 2 δ L L L 12 13 23 sin sin sin sin E E E 4 4 4 If sin 2 2 θ 13 > 0.02-0.03, then NOvA+T2K will have good coverage on CP δ . Size of sin 2 2 θ 13 sets the scale for future leptonic CP violation studies 8
Current Knowledge of θ 13 ���������� ������������� ��� ������ × �� − � �� � � ��� ∆ � � ��� � � θ 13 ������ ��� � � θ θ �� ���������������� θ θ �������������� ��� � � θ θ �� ������ θ θ ��� ����&� × �� − � �� � "����#���$��%���#� ∆ � � ����� ����������������� �!� 9
Some Methods For Determining θ 13 '�������(��))���������*+��������� absorber p decay pipe detector target horn � - µ � ≈ ��� � � θ �� ��� � � θ �� ��� � ∆ � �� . π + + ��� &* ν π + µ + �� / ν µ → ν � ��������)���+�������� / �������������+�������������������+���)�� θ �� / 1�������� 23���������4�5�� ��������##�)���������� / �+�����$� '�������(�,��)����*+��������� � � - �� ≈ � − ��� � � θ �� ��� � ∆ � �� . + )�� & θ �� ��� � � θ �� ��� � ∆ � �� . &* ν &* ν �� / ν � → 0 �����������)���+�������� / 1�������� 23��4�5�� �����������##�)��������1��%��6� / ������$��6�)���� 10
Detecting ν : Inverse β Decay / <������)��������������$����� β β β ���)�6 ������=�9����������>%��� β ν � + �� → � 7 7�� 3������5 �)����������( → 7��� → 8 7� γ 3����'��5����3����6��5 ���1 → 7�9� → 9�: ������1 → 9� 7� γ ;� 3!�'��5��3����6��5 / <���� ���������6������������������������ From Bemporad, Gratta and Vogel Arbitrary ���������%�������1�)4���%����$����� Observable ν Spectrum / *����6��#� ν � �����$���16( Cross Section * ν ≈ < �7 7�< � 7�3� � � � � 5�7��� �7� ≈ < �7 7���!�'�� ���&��4�� F l u x 11 2 3 4 5 6 7 8 9 10 E ν (MeV)
Measuring θ 13 with Reactor Neutrinos Search for θ 13 in new oscillation experiment ∆ ∆ m L m L 2 2 ≈ − θ − θ θ P 2 2 4 2 2 31 21 1 sin 2 si n cos sin 2 sin ee 13 E 13 12 E 4 4 ν ν Small-amplitude oscillation Large-amplitude due to θ 13 integrated over E oscillation due to θ 12 1.1 1 θ θ 13 θ θ 0.9 N osc /N no_osc 0.8 ∆ ∆ m 2 ∆ ∆ ≈ ∆ ∆ ∆ ∆ m 2 13 ≈ ≈ ≈ 23 0.7 0.6 0.5 ~1-1.8 km detector 2 detector 1 0.4 > 0.1 km 0.3 0.1 1 10 100 Baseline (km) 12
Results from Chooz -���!�&�9? �� .��������4� @����� ν � )��������� 8���������� 3��)�%������=�14�5��� ������6� A6�������)�%�)���������� ���������=�9�����������>%����)���������� �������)�� ν �� 7��� → � 7 7�� ,���( @���$�����6�����3#%��������5 ��)�%���� ������&�14����6���� 13
How to Reach a Precision of 0.01 in sin 2 2 θ 13 ? • Increase statistics: – Use more powerful nuclear reactors – Utilize larger target mass, hence larger detectors • Suppress background: – Go deeper underground to gain overburden for reducing cosmogenic background • Reduce systematic uncertainties: – Reactor-related: • Optimize baseline for best sensitivity and smaller reactor-related errors • Near and far detectors to minimize reactor-related errors – Detector-related: • Use “Identical” pairs of detectors to do relative measurement • Comprehensive program in calibration/monitoring of detectors • Interchange near and far detectors (optional) 14
World of Proposed Reactor Neutrino Experiments Krasnoyasrk, Russia Chooz, France Braidwood, USA Kashiwazaki, Japan RENO, Korea Diablo Canyon, USA Daya Bay, China Angra, Brazil 15
Location of Daya Bay / &��4��#��� A���B��� / ���4��#��� C����D��� 16
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