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Elena Couce (IFIC - U. Valencia)

β-beam background in a Water Cherenkov Detector. Elena Couce (IFIC - U. Valencia) Based on a collaboration with D. Casper, JJ Gomez-Cadenas and P. Hernandez. April 27 2006 ISS meeting at RAL (UK). Experimental Challenge. Next generation neutrino oscillation experiments:

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Elena Couce (IFIC - U. Valencia)

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  1. β-beam background in a Water Cherenkov Detector Elena Couce (IFIC - U. Valencia) Based on a collaboration with D. Casper, JJ Gomez-Cadenas and P. Hernandez April 27 2006 ISS meeting at RAL (UK)

  2. Experimental Challenge • Next generation neutrino oscillation experiments: • Need for precision measurements of very small oscillation probabilities at E/L m2atm: • High Statistics • Low Systematics Very intense and well-known beams Very large detectors with low backgrounds

  3. In this talk we’re presenting the results of a complete and realistic MC simulation of a Water Cherenkov detector exposed to a β-beam So why a Water Cherenkov Detector? At least ~10 times larger than for any other technology! • Because water is cheap… so we can make it large! Let’s say… 20 x ! • It has other uses: atmospherics, proton decay, supernova… • However it cannot detect the charge… • Is signal/background ratio good enough? SK ≈ 1000 kTon √ √ • β-beam • SuperBeam • -Factory

  4. Low  β-Beam High  β-Beam • L = 130 Km • = 100 • 5 + 5 years • 5.8 1018 d.p.y. of 6He • 2.2 1018 d.p.y. of 18Ne • L = 700 Km • = 350 • 5 + 5 years • 5.8 1018 d.p.y. of 6He • 2.2 1018 d.p.y. of 18Ne Procedure • Fluxes: • Nature’s oscillation parameters: • Analysis cuts: G.L. Fogli hep-ph/0506083 • Distance to walls > 2 m • Maximum of 10 hits in outer det. • Fiducial: • PID • Michel e- • Selection:

  5. Fiducial cuts: Signal and Background spectra High--beam Low--beam

  6. + - o + + + - - - o o o Fiducial cuts : Absolute # of events Low--beam after fiducial cuts: 18Ne 6He High--beam after fiducial cuts: 18Ne 6He

  7. PID cut • Electron/muon separation: μ-like event e-like event Selecting 1 ring -like events

  8. PID cut : Signal and Background spectra Low--beam: FIDUCIAL PID cut High--beam: FIDUCIAL PID cut

  9. + + + + - - - - o o o o PID cut: Absolute # of events Low--beam after fiducial + PID cuts: 18Ne 6He High--beam after fiducial + PID cuts: 18Ne 6He

  10. Michel e- cut Signal Michel e- t ~  decay time Selecting events with a second delayed ring after the first

  11. Michel e- cut: Signal and Background spectra Low--beam: PID Delayed ring cut High--beam: PID Delayed ring cut

  12. + + + + - - - - o o o o Michel e- cut: Absolute # of events Low--beam after fiducial + PID + Michel e- cuts: 18Ne 6He High--beam after fiducial + PID + Michel e- cuts: 18Ne 6He

  13. + + + + - - - - o o o o Michel e- cut: Absolute # of events Low--beam after fiducial + PID + Michel e- cuts: 18Ne 6He High--beam after fiducial + PID + Michel e- + Energy > 500 MeV cuts: 18Ne 6He

  14. SIGNAL BKGND Signal/Bkgd final composition Low--beam after fiducial + PID + Michel e- cuts: 18Ne 6He SIGNAL BKGND SIGNAL BKGND High--beam after fiducial + PID + Michel e- cuts: 18Ne 6He SIGNAL BKGND SIGNAL BKGND

  15. SIGNAL BKGND Signal/Bkgd final composition Low--beam after fiducial + PID + Michel e- cuts: 18Ne 6He SIGNAL BKGND SIGNAL BKGND High--beam after fiducial + PID + Michel e- + Energy > 500 MeV cuts: 18Ne 6He SIGNAL BKGND SIGNAL BKGND

  16. Cuts evaluation: Relative effect of each cut  e Low--beam: 18Ne 6He Normalized to fiducial events

  17. Cuts evaluation: Relative effect of each cut  e High--beam: 18Ne 6He Normalized to fiducial events

  18. Cuts evaluation: Signal to noise ratio High--beam Low--beam

  19. Conclusions • Aβ-beam with a Water Cherenkov should have good signal to noise ratio well below θ13 = 3º (s/n = 60) • Water Ckov detectors might not be the best choice in terms of performance for β-beam experiments (particularly at high ). However the increase in statistics compensates, up to  ~ 350 • The s/n is better for high  β-beam, particularly for . In addition it allows energy binning.

  20. Conclusions HELP WANTED! • From this study we know the relevant processes contributing to signal and background. With some knowledge on the corresponding cross section errors it should be possible to obtain, if not a good estimate, at least an educated guess on the systematic errors… possibly good enough?

  21. The End Coming next: Study of T2HK signal and background and Realistic comparison of β-beam and Superbeam performances to be continued…

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