shirley li ph.d. advisor: john beacom the ohio state ... · simulation & measurement in oil...

Shirley LiPh.D. Advisor: John Beacom

The Ohio State University

�� Calculation of isotope yields with FLUKA

1402.4687� Isotopes are made in muon-induced showers

1503.04823� Reconstruction showers in water-Cherenkov detector

1508.05389� More to come!

Our Papers on Super-K

�� 50 kton water Cherenkov detector� Depth 2700 m.w.e., with muon rate 2 Hz� Solar neutrino 5.5 – 20 MeV; DSNB 16 – 30 MeV� Radioactivity below 6 MeV; spallation dominates 6 –

18 MeV� In the final solar data sample:

solar neutrino event rate ≈ spallation background rate

Basics about Super-K

�� Lots of previous works on neutron production� Available packages: FLUKA, GEANT4 � Simulation & measurement in oil

0907.0066 by KamLAND1304.7381 by Borexino

� Accuracy: hard to quantify, about a factor of 2

Isotope Yield Calculation

�� Only 4% isotopes are made by muons

Isotopes are made by secondary particles

Secondary particle spectra Parent particle spectra

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Secondary particles are made in showers

A 10 GeV showerin water

Heitler’smodel

AveragedShower profile

�Isotopes are made in showers

Hadronic and electromagneticShowers:Make plenty electrons, which emitCherenkov light.

Low energy neutron showers:No charged particles, no light

�A new way to tag backgrounds!

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How to identify showers in water-Cherenkov detector?

�Simulation vs. Measurement

�The Key: electron deflection

Muon &forward electron

Deflected electron

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Solution: choose the most deflected electrons

Focus on the comparison between SK method and Improvement 1+2+3

�� FLUKA gives reasonable isotope yield for O.� Almost every isotope with A <= 16 is produced� Isotopes are made in muon-induced showers, and

this should be the case for other materials� Electron deflection leads to smeared shower profiles

in water Cherenkov detectors, and scintillator detectors

Conclusion