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
artificial neutrino
sources
Search for
Proton Decay
Terrestrial
neutrino detection
Npe ~ 100 / MeV beta
P - decay event
Scintillator: PXE , non hazard, flashpoint 145° C, density 0.99,
Light absorption L= 12m, ultrapure (as proven in Borexino design
studies)
Possible locations for LENA ?
Underground mine
~ 1450 m depth, low
radioactivity, low
reactor nbackground !
Access via trucks
• loading of detector via pipeline
• transport of 30 kt PXE via railway
• no security problem with PXE !
• no problem for excavation
• standard technology (PM-encapsulation,
electronics etc.)
• LENA is feasible in Pyhäsalmi !
Pylos (Nestor Institute) in Greece,
on the Cern Neutrino beam (off axis) 1500 km
Construction at a convinient site
transportation to phylos in the sea
sinking to apropriate depth
density of whole construction = 1
Galactic Supernova neutrino
detection with Lena (ca 14000
events for 30 kt)
(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)
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
Visible proton recoil spectrum in a liquid scintillator
all flavors
nm, nt and anti-particles
dominate
J. Beacom, astro-ph/0209136
SNN-detection and neutrino oscillations
SNN
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
• very good energy resolution
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 early star formation period
Jap. Reactors
in SK
Reactor bg
LENA !
Europ.
Reactors
@800 km
No background for
LENA !
LENA SNR rate:
SNR
~ 6 counts/y
Atmospheric neutrinos
Solar Neutrinos and LENA:
Probes for Density Profile Fluctuations (p-modes)!
Balantekin,
Yuksel
TAUP 2003
hepph/0303169
7-Be
~200 / h
LENA
Where is the U, Th
terrestrial neutrinos in
LENA
.what is the source of the terretrial
heat flow?
•What is the contribution from
radioactivity?
•How much U, Th is in the mantel?
• is there a TW reactor in the center
of the earth?
Heat flow from
the earth
•Measured:
F  80 mW / m2
•Integral:
HE  4x1013 W = 40 TW
(uncertainty ~20%):
•This corresponds to 104
nuclear power plants!
Where is U, Th?
crust
Upper mantle
• The crust and mantel may be
analyzed directly.
• Theory: U, K und Th may
be“lithophil”, may accumulate
in the continental crust.
• U In the (kont.) crust
• ~30 km crust may content as
Mc(U)  (0.2-0.4)1017 kg.
much as 300 km of mantel.
• Still higher uncertaities for
• U, Th in lower part of mantel
mantel:
presently estimated by
17Kg ?
M
(U)

(0.2-0.8)10
m
extrapolation from upper
mantel .
KAMLAND: a first insight to terrestrial neutrinos
6 months of data
•N(Th+U) = 9  6*
_
•@E νe <2,6 MeV
•Uncertainty dominated
•by 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
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)
•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
P decay into K and n
m
m
K
K
Signal in LENA
time (nsec)
Background
Rejection :
• mono energetic K- and
m-signal!
• position correlation
• pulse-shape analysis
(after correction on
reconstructed position)
• 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)
LENA a new observatory
• complementarely to high energy neutrino
astrophysics
• fundamental impact on e.g. geophysics,
astrophysics, neutrino physics, proton decay
• feasibility studies very promising (Pyhäsalmi)
• costs ca. 100 - 200 M€ (30KT)
•make it bigger = longer, several
modules
Electron antineutrtino detection
from artificial ß-decay sources
Delayed coincidence => background rejection
_
νe + p => n +e
+
200μs
n + p => D +2,2 MeV
Remaining dominant background from fast n
 pulse shape discrimination, Veto by H2O cerencov shield
Self shielding of scitillator
Δ ~ 35% @5 MeV
Burn up of U in PWR (Gösgen)
_
Example: νe Spectrum as a function of burn up
(Gösgen Reaktor)
Expected rates in LENA 50 KT
1 c/d @100Km/ 1GW reactor (with oscillations)
Is this enough for identification of Pu production?
Shape of 235U/239Pu 20% diff.
_
@ E(νe) =5 MeV after full burn up
100 events after 3 months
LENA up to 100 KT may be movable
Go to the source
(Total density of LENA may be = 1)
Similar to size of oil tanker or submarine
For test of burn up in reactor
Low energy threshold very helpful
For background rejection (cosmic rays)
at shalow depths puls shape discrimination useful
(Fast neutron background in BOREXINO<< 1 event/a 100T)