Experimental Constraints onShane Squires131310 00 c23s230 s23c23          c130 s13ei 01 0s13ei 0 c13          c23s230s23c230001          ei1000 ei20001          13What is ? Neutrino mixing matrix: and the CP phase(s) are the onlyunmeasured neutrino mixing parameters.Four Types of Experiments Where can you get lots of neutrinos? The Sun: Homestake, SAGE, GALLEX,SuperKamiokande, SNO, etc. Cosmic rays (“atmospheric neutrinos”):Soudan, IMB, SuperKamiokande, etc. Accelerators: K2K, T2K, NOvA, MINOS,OPERA, etc. Nuclear reactors: KamLAND, Palo Verde,(Double) CHOOZ, Daya Bay, etc.Physics of the Four Types Neutrino energy and mass splitting determineoscillation length: The parameter L/E (L=distance to detector)determines range of detectable mass splittings. Advantages of reactor and accelerator expt.s: Spectrum of neutrino energies is well-understood. Length to detector can be chosen. Neutrino flux is high and can be controlled.L0Em2Physics of the Four Types 11-3 mixing 1Reactordepends 10001-3 or 2-3 1000Accel. 10002-3 mixing 1000Cosmic 10s1-2 mixing 1Solar (km)Measures (MeV)TypeL01m2s()E10141031014Results for Other Parameters Solar neutrino experiments: Atmospheric neutrino experiments: Both have contributed to bounds on , but bestresults come from reactor experiments. 12 34o 23 45om122 8 10 5eV2m232 2 10 3eV213CHOOZ and Palo Verde CHOOZ: European team, experiment in France. Palo Verde: American experiment in Arizona. Otherwise, the two are very similar. Both were built to rule out the possibility that theatmospheric deficit comes from .In the process, they created bounds on .μe13CHOOZ and Palo Verde Reactor generates a large flux of . The fluxand energy distribution of the antineutrinos canbe inferred from reactor operation records. The experiment is designed to observe the reaction If the reaction count is lower than expected, themissing must have changed flavor. e e+ p  e++ n eCHOOZ and Palo VerdeCHOOZ Palo VerdeCHOOZ and Palo Verde Detector: approximately 1 km from source.CHOOZ and Palo Verde Detector is filled with liquid scintillator with manyfree protons. Scintillator fluid is .1% Gadolinium. Positron annihilation is detected promptly. Gd-n cross section is extremely large, and neutronabsorption gives a characteristic 8 MeV photoncascade. The neutron is detected within 100 s. Can also see 2.2 MeV cascade from p-n binding. Although positron emission is isotropic, theneutron signal can be used to identify thedirection of the incoming antineutrino.Sample CHOOZ Data Random error: cosmic ray muons, internal/external radioactivity. Apply cut based on energy, time difference, and location of origin.Systematic Error in CHOOZResults from CHOOZLimits on  from Chooz (lines, 90%, 95%, 99%, and 3), and from Chooz+solar+KamLAND(colored regions).Current Status It is now generally accepted that CHOOZdata (together with atmospheric neutrinodata to determine ) demonstrates that orat a 90% confidence level. The results so far are consistent with ,with a best fit around .m232sin2213()< .17 13< 12o 13= 0o 13= 4.4oFuture Experimental Directions New reactor experimentsmeasure to high accuracy. If is not too small,accelerator experimentsmeasure CP-violatingparameters, etc. Precision neutrinomeasurements remainimportant for 20-30 years.1313Daya Bay and Double CHOOZ Daya Bay: US-Chinese collaboration.Experiment will be located east of HongKong near Daya Bay and Ling Ao reactors.Broke ground in October. Double CHOOZ: European collaboration.Experiment at old CHOOZ site. Will begintaking data in 2008.Features of New Experiments Two detectors (near and far) to reduceuncertainty in antineutrino flux. Larger detectors. “Multiple modules” within each detector. Improved shielding from external radiation. Improved muon detection.Prospects for New Experiments After three years of operation, DoubleCHOOZ will be able to detect Daya Bay will ultimately be able to detectsin2213()> .02sin2213()> .01Importance of Measuring is necessary to measure the CP-violating terms in the neutrino matrix: All measurements of other neutrino parametersremain uncertain until is determined. Whether or not turns out to be nonzero, itsvalue has ramifications for solar physics,supernovae, grand unified theories, etc.131310 00 c23s230 s23c23          c130 s13ei 01 0s13ei 0 c13          c23s230s23c230001          ei1000 ei20001          1313Some Good References 554 Class Notes, Chapter 4. hep-ex/0402041: White Paper Report on Using Nuclear Reactors to Search fora Value of . C. Bemporad (Chooz Collaboration), Results from CHOOZ, Nucl. Phys. B(Proc. Suppl.) 77 (1999) 159–165. hep-ex/0003022: Results from the Palo Verde neutrino oscillation experiment. hep-ph/0202058: Neutrino Masses and Mixing: Evidence and Implications. hep-ex/0410081: Proposal for U.S. participation in Double-CHOOZ. hep-ex/0701029: A Precision Measurement of the Neutrino Mixing AngleUsing Reactor Antineutrinos at Daya