Transcript LENA - Rencontres de Moriond

LENA
LENA Delta
Low Energy Neutrino Astrophysics
F
.
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
H2O Cerenkov veto
Npe ~ 100 / MeV beta
P - decay event
30 KT scintillator
Scintillator: PXE , non hazard, 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
•loading of detector via pipeline
• transport of 30 kt PXE via railway
•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,
on the Cern Neutrino beam (off axis) D~1700 km
Neutrino interactions in the scintillator
υ elastic scattering
υ(x) + e  υ(x) + e
υ (x) + p  υ(x) + p
ν- inverse ß-decay
_
ν(e) + p  n + e(+)
υ nuclear excitation
15.1MeV
υ(x) interaction
1+ 11ms
1+
1+ 20ms
12N
12B
υ(e) interaction
17.3 MeV
13.4MeV
ec delayed
coincidence
12C
Galactic Supernova neutrino
detection with Lena
(1) n e  p  e   n
(Q  1.8 MeV)
(2) n e  12 C  e   12 B
(Q  13.4 MeV)
Electron Antineutrino
spectroscopy ~7800
(4) n x  12 C  n x  12 C *
Electron n spectroscopy
(Q  17.3MeV)
~ 65
12 *
12
wit h C  C   (Q  E   15.1 MeV)
(5) n x  e -  n x  e -
(elast icscat t eringoff elect rons)~ 480
(6) n x  p  n x  p
(elast icscat t eringoff prot ons).
(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
with LENA
Modulations in the energy
spectrum due to matter
effects in the Earth
Dighe, Keil, Raffelt (2003)
SNN-detection and neutrino oscillations
Scintillator
good resolution
Water
Cherenkov
SNN-detection and neutrino oscillations
Modulations in the energy
spectrum due to matter
effects in the Earth
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
Reactor SK
Reactor bg
LENA !
No background for
LENA !
LENA SNR rate:
SRN
~ 6 counts/y
Atmospheric neutrinos
Solar Neutrinos and LENA:
Probes for Density Profile Fluctuations !
Balantekin,
Yuksel
TAUP 2003
hepph/0303169
7-Be
~200 / h
LENA
Terrestrische Neutrinos
und LENA
• was ist die Quelle des
terrestrischen
Wärmeflusses?
• welchen Beitrag liefert die
Radioaktivität?
• wieviel U, Th ist im
Mantel?
• ist ein gigantischer natürlicher
Kernreaktor im Zentrum die Energiequelle
des Erdmagnetfelds?
Wärmefluss aus
der Erde
•Es wird ein kleiner
Wärmefluss aus der Erde
gemessen.
F  80 mW / m2
•Integral:
HE  4 1013 W = 40 TW
(Unsicherheit ~20%):
•Das entspricht der Leistung
von etwa 104
Kernkraftwerken!
Wo befindet sich U,
Th?
crust
Upper mantle
• Die Kruste und der oberste Teil des
Mantels sind einer direkten
geochemischen Analyse
zugänglich.
• Die Theorie: U, K und Th sind
“lithophil”, sie akkumulieren in der • U In der (kont.) Kruste
(kontinentalen) Kruste.
17 kg.
M
(U)

(0.2-0.4)10
c
• Danach könnte die ~30 km Kruste
• Noch größere Unsicherheiten
soviel U, Th wie der ~3000 km
dicke Mantel enthalten.
für den Mantel:
• U, Th im unteren Teil des Mantels
Mm(U)  (0.2-0.8)1017Kg ?
wird extrapoliert von Daten aus
dem oberen Mantel.
KAMLAND: ein erster Blick…
•6 Monate Daten ergibt einen Fit
für N(Th+U) für E< 2.6 MeV
•N(Th+U) = 9  6*
•Die Unsicherheit* ist dominiert
durch Fluktuation der
Reaktorsignale
•Das Ergebnis ist mit jedem
geophysikalischen Modell
konsistent: Hrad=(0-100 TW).
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:
• monoenergetic K- and msignal!
• 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)
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€