1. Low Energy Neutrino Astrophysics
LENA
LENA Delta
Low Energy Neutrino Astrophysics
L. Oberauer, F. von Feilitzsch, C. Grieb, K. Hochmuth, C. Lendvai, T. Marrodan, L. Niedermeier, W. Potzel, M. Wurm
Technische Universität München

2. Groups interested in LENA
TU Munich, Germany
Univ. Hamburg, Germany (C. Hagner)
CUPP, Finland (J. Peltoniemi)
Univ. Jyväskylä, Finland (J. Aysto)
INR, Russia (L. Bezrukov)
Similar initiative:
HSD („Hyper-Scintillation-Detector“) Kimballton mine, Virginia, USA

3. LENA
Proposal: A large (~50 kt) liquid scintillator underground detector for
Baryon number violation Proton decay
Gravitational collapse SN n detection
Star formation in the early universe Relic SN n
Solar thermonuclear fusion processes CNO, pep, 7Be
Geophysical models U, Th - n
Neutrino properties Long baseline - n

4. LENA Detector and scintillating liquid Muon veto ~12000 Pms (50cm)
Scintillator solvent: PXE, or PXE/mineral oil mixture
non hazardous, flashpoint 145° C easy handling
density high self shielding
high light yield low energy events
low background level U, Th solar n, geo n, srn n

5. PXE as scintillating solvent
PXE Counting Test Facility from BOREXINO at Gran Sasso (physics/ )
372 pe / MeV @ 20% coverage
lattenuation ~ 4 m @ 430 nm
lattenuation ~ 12 m after purification
(alumina-column, S. Schönert MPIK Hd for LENS)
=> ~ 120 pe / MeV in LENA (central events)
=> low energy threshold (sub-MeV)
=> good resolution in energy and position reconstruction
CTF

6. Program for investigations of PXE / dodecane mixtures
C, Buck et al., MPIK Heidelberg
(Double-Chooz)
M. Wurm, K. Hochmuth, TUM
improve compability with detector materials
improve further transparency?
increase free H number (by ~30%)
~90% light yield with 40% PXE and 60% dodecane
M. Wurm

7. Possible locations for LENA
Underground mine
~ 1450 m depth, low radioactivity, low reactor n-background !
Access via trucks

8. LENA at CUPP LENA is feasible in Pyhäsalmi !
transport of PXE via railway
loading of detector via direct pipeline
no fundamental security problem with PXE !
no fundamental problem for excavation
standard technology (PM-encapsulation, electronics etc.)
LENA is feasible in Pyhäsalmi !

9. Pylos (Nestor Institute) in Greece

10. Proton Decay and LENA p K n
This decay mode is favoured in SUSY theories
The primary decay particle K is invisible in Water Cherenkov detectors
The Kaon and the K-decay particles are visible in LENA
Better energy solution further reduces background

11. K->m n
63.4 %
K->p+p0
21.1 %
Teresa Marrodan

12. bg-events
P-decay
bg-events
Event structure p -> K n plus K – decay (T1/2 = 12.8 ns)
3-fold delayed coincidence from m - decay

13. Potential of LENA for p -> Kn
SuperK current limit t = 1.6 x 1033 y:
27 events in 10 years in LENA
(0.7 bg events)
No signal:
t > 3 x 1034 y

14. Galactic Supernova neutrino detection with Lena
Electron Antineutrino spectroscopy
~7800
Electron n spectroscopy ~ 65
~ 480
Neutral current interactions; info on all flavours ~ and ~ 2200
Event rates for a SN type IIa in the galactic center (10 kpc)

15. Visible proton recoil spectrum in a liquid scintillator
all flavors
nm, nt and anti-particles
dominate
J. Beacom, astro-ph/

16. Supernova neutrino luminosity (rough sketch)
Relative size of the different luminosities is not well known: it depends on uncertainties of the explosion mechanism and the equation of state of hot neutron star matter
Supernova neutrino luminosity (rough sketch)
T. Janka, MPA

17. SNN-detection and neutrino oscillations with LENA
Modulations in the energy spectrum due to matter effects in the Earth
Dighe, Keil, Raffelt (2003)

18. SNN-detection and neutrino oscillations
Scintillator
good resolution
Water Cherenkov
Modulations in the energy spectrum due to matter effects in the Earth
Dighe, Smirnov, Keil, Raffelt

19. Dependence on hierarchy and Q13:
Preconditions for observation of those modulations:
SN neutrino spectra ne and nm,t are different
distance L in Earth large enough
Dependence on hierarchy and Q13:

20. Survival probability :
Mixing angle between ne and n2 in Earth matter
Mass difference squared in Earth matter:

21. LENA and relic Supernovae Neutrinos !
SuperK limit very close to theoretical expectations
Threshold reduction from ~19 MeV (SuperK) to ~ 9 MeV with LENA
Method: delayed coincidence of ne p -> e n
Low reactor neutrino background !
Information about star formation in the early universe

22. Reactor SK No background for LENA ! SRN: ~ 6 counts/y
Reactor bg LENA !
SRN:
~ 6 counts/y
Atmospheric neutrinos

23. Low energy atmospheric neutrinos and LENA
LENA can measure the low energy part of atmospheric neutrinos, esp. ne
30 MeV MeV ne :
Losc ~ 103 km to 7 x 103 km
(Dm2 solar neutrinos!)
ne <-> nm atmospheric oscillations, but based on Dm2solar
observable ?
...difficult (low statistics); needs further investigations

24. Thermal nuclear fusion and LENA
high statistic 7Be-solar n detection (~104 d-1)
test of even small flux variations
look for coincidences with helioseismological data !
CNO – and pep-n (~300 d-1)
solar neutrino luminosity
precise determination of solar nuclear fusion processes

25. Long baseline n - oscillations and LENA ?
To be investigated in detail:
n spectrum (off-axis)
e, m - separation potential
potential in Q13 !

26. Solar Neutrinos and LENA:
Probes for Density Profile Fluctuations !
Balantekin, Yuksel
TAUP 2003
hep-ph/
7-Be
~200 / h LENA

27. Geo - neutrinos and LENA
what is the source of the terrestrial heat flow ?
what is the contribution of natural radioactivity ?
how much of U, Th is in the mantle ?
is there a natural reactor at the Earth‘s center?

28. Angular distribution information
reconstruct vertices of prompt and delayed events
resolution ~ 30o (MonteCarlo)
maximum model
Core enhanced
minimal model
K. Hochmuth
Q (rad)
Events per year
0° <  < 60°
60° < 
total
ref
618 ± 25
822 ± 29
1440 ± 38
min
453 ± 21
653 ± 27
1106 ± 33
max
1255 ± 35
1365 ± 37
2620 ± 51
core
950 ± 31
858 ± 29
1807 ± 43

29. P -> K+ n event structure:
T (K+) = MeV
t (K+) = nsec
K+ -> m+ n (63.5 %) K+ -> p+ p0 (21.2 %)
T (m+) = MeV T (p+) = MeV electromagnetic shower
E = MeV
m+ -> e+ n n (t = 2.2 ms) p+ -> m+ n (T = 4 MeV)
m+ -> e+ n n (t = 2.2 ms)

30. the first 2 events are monoenergetic !
3 - fold coincidence !
the first 2 events are monoenergetic !
use time- and position correlation !
How good can one separate the
first two events ?
....results of a first Monte-Carlo calculation

31. Signal in LENA m m K K
time (nsec)
P decay into K and n

32. Background Rejection: monoenergetic K- and m-signal!
position correlation
pulse-shape analysis
(after correction on
reconstructed position)

33. Sensitivity of LENA ?
SuperKamiokande has 170 background events in days (efficiency 33% )
In LENA, this would scale down to a background of ~ 5 / y and after PSD-analysis this could be suppressed in LENA to
~ 0.25 / y ! (efficiency ~ 70% )
A 30 kt detector (~ protons as target) would have a sensitivity of t < a few years for the K-decay after ~10 years measuring time
The minimal SUSY SU(5) model predicts the K-decay mode to be dominant with a partial lifetime varying from 1029y to 1035 y !
actual best limit from SK: t > 6.7 x 1032 y (90% cl)

34. Conclusions complemntary to high energy neutrino astrophysics
LENA a new observatory
complemntary to high energy neutrino astrophysics
fundamental impact on e.g. proton decay, astrophysics, neutrino physics, geophysics
feasibility studies very promising (CUPP, Pyhäsalmi)
costs ca M€