LENA
LENA Delta
Low Energy Neutrino Astrophysics
F. von Feilitzsch, L. Oberauer, W. Potzel
Technische Universität München
LENA
(Low Energy Neutrino Astrophysics)
Idea: A large (~30 kt) liquid scintillator
underground detector for
Galactic supernova
neutrino detection
Solar Neutrino
Spectroscopy
Relic supernovae
neutrino detection
Neutrino
properties
Search for
Proton Decay
Terrestrial
neutrino detection
Npe ~ 100 / MeV beta
~ 12000 PMs (20 inch)
P - decay event
Scintillator: PXE , non hazardous, flashpoint 145° C, density
0.99, ultrapure (as proven in Borexino design studies)
Possible locations for LENA ?
Underground mine
~ 1450 m depth, low
radioactivity, low
reactor nbackground !
Access via trucks
LENA at CUPP
• transport of 30 kt PXE via railway
• loading of detector via pipeline
• no fundamental security problem with PXE !
• no fundamental problem for excavation
• standard technology (PM-encapsulation,
electronics etc.)
• LENA is feasible in Pyhäsalmi !
Pylos (Nestor Institute) in Greece
Galactic Supernova neutrino
detection with Lena
(1) n e  p  e   n
(Q  1.8 MeV)
(2) n e  12C  e   12B
(Q  13.4 MeV)
Electron Antineutrino
spectroscopy ~7800
(4) n x  12C  n x  12C *
Electron n spectroscopy
(Q  17.3 MeV)
~ 65
12 *
12
with C  C   (Q  E   15.1 MeV)
(5) n x  e -  n x  e -
(elastic scattering off electrons) ~ 480
(6) n x  p  n x  p
(elastic scattering off protons).
(3) n e  C  e  N
12
-
12
Neutral current interactions; info on all flavours
~ 4000 and ~ 2200
Event rates for a SN type IIa in the galactic center (10 kpc)
Visible proton recoil spectrum in a liquid scintillator
all flavors
nm, nt and anti-particles
dominate
J. Beacom, astro-ph/0209136
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
SNN-detection and neutrino oscillations
ne
Scintillator
good resolution
Modulations in the energy
spectrum due to matter
effects in the Earth
Water
Cherenkov
Dighe, Keil, Raffelt (2003)
Preconditions for observation of those
modulations
• SN neutrino spectra ne and nm,t are different
• distance L in Earth large enough
• very good statistics (~ 5 kt minimum)
• very good energy resolution (scintillator !)
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
Reactor SK
Reactor bg
LENA !
No background for
LENA !
LENA SNR rate:
SRN
~ 6 counts/y
Atmospheric neutrinos
Low energy atmospheric
neutrinos and LENA
• LENA can measure the low energy part of
atmospheric neutrinos, esp. ne
30 MeV - 200 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
Long baseline n - oscillations
and LENA ?
To be investigated:
• n spectrum
• e, m - separation
potential
• potential in Q13
!
Solar Neutrinos and LENA:
Probes for Density Profile Fluctuations !
Balantekin,
Yuksel
TAUP 2003
hepph/0303169
7-Be
~200 / h
LENA
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 ?
(very low bg due to reactors!)
Proton Decay and LENA
p
Kn
• This decay mode is favoured in SUSY theories
• The primary decay particle K is invisible in Water
Cherenkov detectors
• It and the K-decay particles are visible in
scintillation detectors
• Better energy solution further reduces
background
See also R. Swoboda (Taup 03)
P ->
+
K
n
event structure:
T (K+) = 105 MeV
t (K)  12.8 nsec
K+ -> m n
(63.5 %)
T (m+) = 152 MeV
K+ -> p p0 (21.2 %)
T (p+) = 108 MeV
electromagnetic shower
E = 135 MeV
m -> e+ n n (t  2.2 ms)
p -> m n
(T  4 MeV)
m -> e+ n n (t  2.2 ms)
Signal in LENA
m
m
K
K
P decay into K and n
time (nsec)
Background
Rejection:
• monoenergetic K- and msignal!
• position correlation
• pulse-shape analysis
(after correction on
reconstructed position)
Sensitivity of LENA ?
• SuperKamiokande has 170 background events in 1489
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 (~ 1034 protons as target) would have a
sensitivity of t < a few 1034 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)
Conclusions
• LENA
a new observatory
• complemntary to high energy neutrino
astrophysics
• fundamental impact on e.g. geophysics,
astrophysics, neutrino physics, proton
decay
• feasibiluty studies very promising
(Pyhäsalmi)
• costs ca. 100 - 200 M€