1. Nucleon Decay Search with LENA DOANOW 07 Honolulu, Hawaii M. Wurm Technische Universität München, Germany mwurm@ph.tum.de http://www.e15.physik.tu-muenchen.de/research/lena.html

2. 30m 100m DETECTOR DIMENSIONS inner detector - 50kt of organic liquid scintillator (Ø 26m) - 13,500 photomultipliers outer muon veto - water Čerenkov detector - 2m of active shielding LOCATION - mine or deep see plateau - depth of 4,000 m.w.e. to reduce -&cosmogenic background proton decay solar neutrinos terrestrial neutrinos atmospheric neutrinos artificial neutrino sources supernova neutrinos diffuse SN neutrino background PHYSICS GOALS THE LENA DETECTOR AN OVERVIEW LENA OverviewTU MünchenMichael Wurm

3. attenuation length scattering length light yield LENA OVERVIEW THE SCINTILLATOR SOLVENT feasible candidates - purified PXE - 20/80 mixture of PXE/Dodecane - LAB all provide attenuation length of >10m @430nm but light yield, scattering length and number of free protons are also important parameters WAVELENGTH SHIFTERS - fluorescence times and therefore time resolution currently under investigation - secondary shifter like bisMSB is needed for emission at 430nm - maybe new shifters with large Stokes shift? fluorescence time LENA OverviewTU MünchenMichael Wurm

4. various sources emit e, inverse -decay allows precision measurements LENA OverviewTU MünchenMichael Wurm LENA OVERVIEW ANTINEUTRINO SPECTROSCOPY _ interaction of solar e s spin with magnetic fields can flip them to e 5,000 7 Be e per day _ Supernova @10kpc: ~9,000 e events matter effects in SN envelope and earth diffuse SN neutrinos ~10 e per year, test of SNR & SN models _ _ terrestial e ~1,000 events per year _ reactor e 50-25,000 ev. per year, precision measurement of 12 ~1%, m 12 ~10% _ Petcov,Schwetz hep-ph/0607155 Wurm et al. PRD 75 023007 astro-ph/0701305 Hochmuth et al. Astrop.Phys 27, 21 hep-ph/0509136 _

5. LENA OVERVIEW ALTERNATIVE CONFIGURATIONS LENA OverviewTU MünchenMichael Wurm 3 detectors à 25kt plus storage tank simpler repair & service detector permanently online vertical detector cheaper excavation avoids bouyant forces

6. LAGUNA L arge A pparatus for G rand U nification and N eutrino A strophysics 30m 100m MEMPHYS Water Čerenkov Detector 500 kt target in 3 shafts, 3x 81,000 PMs LENA Liquid-Scintillator Detector 13,500 PMs for 50 kt of target water Čerenkov muon veto GLACIER Liquid-Argon Detector 100 kt target, 20m drift length, LEM-foil readout 28,000 PMs for Čerenkov- and scintillation light coordinated R+D design study in European collaboration, on-going application for EU funding LENA OverviewTU MünchenMichael Wurm

7. LENA OverviewTU MünchenMichael Wurm LAGUNA DETECTOR LOCATIONS COLLABORATING INSTITUTES France APC, Paris, France France CEA, Saclay, France France CPPM, IN2P3-CBRS, Marseille, France Finland CUPP, Pyhäsalmi, Finland Switzerland ETHZ, Zürich, Switzerland Russia Institute for Nuclear Research, Moscow, Russia France IPNO, Orsay, France France LAL, IN2P3-CNRS, Orsay, France France LPNHE, IN2P3-CNRS, Paris, France Germany MPI-K Heidelberg, Germany Germany Max Planck für Physik, München, Germany Germany Technische Universität München, Germany Spain Universidad de Granada, Spain Germany Universität Hamburg, Germany Switzerland University of Bern, Switzerland Finland University of Helsinki, Finland Finland University of Jyväskylä, Finland Finland University of Oulu, Finland Italy University of Padova, Italy Poland University of Silesia, Katowice, Poland UK University of Sheffield, UK

8. PROTON DECAY THEORETICAL PREDICTIONS GUT SU(5) dominant decay mode: p 0 + e + predicted proton lifetime: ~ 10 31 yrs current best limit: 5.4 10 33 yrs K+K+K+K+ P _ 0 e+e+e+e+ P Supersymmetry (SUSY) dominant decay mode: p K + + predicted proton lifetime: 10 35 yrs current best limit: 2.3 10 33 yrs _ Supergravity (SUGRA) dominant decay modes: p + + (65.7%) p K + + (33.5%) _ _ Proton DecayTU MünchenMichael Wurm

9. PROTON DECAY SIMULATION IN GEANT4 10 4 pK + events were simulated in LENA using the GEANT4 toolkit, implementing detector physics … SCINTILLATOR MODEL light yield110pe/MeV excitation decay times3.4ns, 17ns absorption length12m scattering length60m quenching (Birks formula) PHOTOMULTIPLIERS coverage30% quantum efficiency17% time jitter~1ns by Teresa Marrodán Undagoitia, PRD 72 (2005) 075014 Proton DecayTU MünchenMichael Wurm _

10. PROTON DECAY EVENT SIGNATURE K+K+K+K+ P _ leaves the detector unnoticed … _ K+K+K+K+ K+K+K+K+ 63.43% E kin = 105MeV = 12.8ns 21.13% E kin = 152MeV = 2.2µs E kin = 110MeV = 84ns E kin = 128MeV = 26ns e+e+e+e+ _ _ e 1 st signal 2 nd signal Proton DecayTU MünchenMichael Wurm

11. PROTON DECAY EVENT SIGNATURE Challenge: short decay time of the Kaon (12.8ns) Kaon decay after 18ns Kaon decay after 5ns Proton DecayTU MünchenMichael Wurm

12. BACKGROUND SOURCES ATMOSPHERIC NEUTRINOS Kaon decay after 5ns double stucture hard to see atmospheric neutrinos flux: 4.8×10 -2 MeV -1 kt -1 yr -1 CC reaction of on target nuclei: + A Z A (Z+1) + - fast K + events are undistinguishable pulse-shape analysis cut on signal rise-time Proton DecayTU MünchenMichael Wurm

13. signal is on average faster in rise efficiency of the time cut T = 65% background suppression B ~ 5×10 -5 … Kaon rise-time spread more widely ATMOSPHERIC NEUTRINOS RISE-TIME ANALYSIS Proton DecayTU MünchenMichael Wurm

14. Proton DecayTU MünchenMichael Wurm BACKGROUND SOURCES HADRON PRODUCTION PION PRODUCTION KAON PRODUCTION Calculated background rate: 0.064 per year

15. Proton DecayTU MünchenMichael Wurm PROTONS OF 12 C NUCLEAR EFFECTS BINDING ENERGY S-state:~ 37 MeV P-state:~ 16 MeV FERMI MOTION momenta< 250 MeV/c shift and broadening of lines K+ energy window: E ~ 0.995

16. Proton DecayTU MünchenMichael Wurm PROTON DECAY SENSITIVITY IN LENA protons in LENA:~1.4×10 34 detection efficiency:0.65 measuring time:10yrs background rate:0.64 for current limit from SuperK: = 2.3×10 33 yrs 40 events if no event is seen in 10 yrs: > 4×10 34 yrs (90% C.L.)

17. Summary&OutlookTU MünchenMichael Wurm SUMMARY AND OUTLOOK A 50kt detector like LENA will be a multi-purpose detector, contributing to the fields of geo- and astro- physics as well as particle physics. Concerning the search of proton decay, LENA will be able to test the SUSY-predicted decay channel p K + +. Within 10 years of measurement, the current limit could be improved by more than a factor of 10, resulting in a new limit: p > 4×10 34 yrs. _