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LENALENA
Low Energy Neutrino Astrophysics
F. Von Feilitzsch, L. Oberauer, W. Potzel
Technische Universität München
LENALENA
((Low Energy Low Energy Neutrino Neutrino AstrophysicsAstrophysics))
IdeaIdea: A : A large large (~30 (~30 ktkt) liquid ) liquid scintillatorscintillatorunderground detectorunderground detector for for
Galactic supernovaGalactic supernovaneutrino detectionneutrino detection
Relic supernovaeRelic supernovaeneutrino detectionneutrino detection
Terrestrialneutrino detection
Search forProton Decay
Solar NeutrinoSpectroscopy
Neutrinoproperties
Possible locations for Possible locations for LENA ?LENA ?
Underground mine
~ 1450 m depth, lowradioactivity, lowreactor n-background !
Access via trucks
Galactic Supernova neutrinodetection with Lena
protons). off scattering (elastic (6)
electrons) off scattering (elastic (5)
MeV) 15.1 E(Q CC with (4)
MeV) 17.3 (Q (3)
MeV) 13.4(Q (2)
MeV) 1.8 (Q (1)
x
xx
12*12*1212x
1212e
1212
pp
ee
CC
NeC
BeC
nep
x
x
e
e
+Æ+
+Æ+
==+Æ+Æ+
=+Æ+
=+Æ+
=+Æ+
--
-
+
+
nn
nn
gnn
n
n
n
g
Electron Antineutrinospectroscopy
Electron n spectroscopy~ 65~ 65
Neutral current interactions; info on all flavours~ 4000 and ~ 2200~ 4000 and ~ 2200
~7800~7800
~ 480~ 480
Event rates for Event rates for a SN a SN type IIa type IIa in in the galactic center the galactic center (10 (10 kpckpc))
Supernova Supernova neutrino luminosity neutrino luminosity ((rough sketchrough sketch))
Relative size of the different luminositiesis not well known: it depends onuncertainties of the explosionmechanism and the equation of state ofhot neutron star matter
T. Janka, MPA
T. Janka, MPA
Luminosities from core collapses of 11 to 25 solar masses
SupernovaSupernovadiagnosticsdiagnostics by nmeasurements:
• a direct view intothe SN-core
• high high statisticsstatistics onnnee and and nnxx , timeand energyresolution
• perhaps a way tounravel the secretsof the explosionmechanism
Supernova Supernova explosion explosion and and neutrino interactionsneutrino interactions
Gas infall from thecollapsing star dampsshock expansion
Gas between NeutronStar and the shock iscooled and heated byneutrinos
Only when theneutrino heating isstrong enough anexplosion can betriggered
from T. Janka, MPA Garching
Inverse beta decay on p can be tagged by delayedcoincidence in a liquid scintillator
prompt event: Ev – 0.77 MeVn spectroscopy
Delayed event:MeV)2.2(g+Æ+ dpn
180_sec180_sec
Ev > 1.8 MeV
Position reconstruction of both events indicates direction toSupernova! ...good statistics necessary (experiencies @ reactorexperiments)
nepe +Æ+ +n
ne interaction;delayeddelayedcoincidencecoincidence with11.0 msec
All n flavours; mono-energetic 15.1 MeVgamma line
Neutrino proton elastic scattering
• recoil p kinetic energies ~ few MeV
• quenching reduces this to ~ 1 MeV (and below)
• low threshold required (~ 0.2 MeV or so)
(aim of Borexino, KamLAND for solar n)
• proton recoil spectrum reflects the SupernovaSupernovaneutrino spectrumneutrino spectrum
• easy to separate from high energy signals
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
Modulations in the energyspectrum due to mattereffects in the Earth Dighe, Keil, Raffelt (2003)
Preconditions for observation of thosemodulations
• SN neutrino spectra ne and nm,t are different
• distance L in Earth large enough
• very good statistics
• very good energy resolution
Anti-electron-neutrino spectra for 2000 events in each detector
Only ~1000 ~1000 eventsevents required for SC
Scintillator
good resolution
WaterCherenkov
Dighe, Keil, Raffelt (2003)
…frequency k of the modulations independentfrom the shape of the spectrum and indepent intime, but...
• SuperK is not good enough in energy resolution
• KamLAND is not large enough
Required:
• Liquid scintillator experiment ~ 10 kt(or larger!)
• Megaton Cherenkov detector ?
SupernovaeSupernovae RelicRelic Neutrinos (SRN) Neutrinos (SRN)
••Flux dependsFlux depends on on thetheevolutionevolution of of the starthe starformationformation rate rate
••Flux estimates varyFlux estimates varybetweenbetween
10 to 20 cm10 to 20 cm-2-2 sec sec-1-1
••No No signal observed signal observed sosofarfar
••Best Best limit comes fromlimit comes fromSKSK
ne
SRN - SRN - spectrum as observed spectrum as observed inininverse beta decay reactioninverse beta decay reaction
SK-threshold
LENA-LENA-
thresholdthreshold
~ 9 MeV !~ 9 MeV !
LENA: LENA: delayeddelayedcoincidencecoincidenceprompt eprompt e++ and anddelayed delayed n.n.
This reducesThis reducesbackgroundbackgroundand and hence thehence thethresholdthreshold!!
LENA SNRLENA SNRrate:rate:
~ 6 ~ 6 countscounts/y/y
((better as better as SKSKby factor by factor ~6)~6)
Background:
Nuclearreactors!
SRN
No background forLENA !
Reactor SK
Reactor bgLENA !
Atmospheric neutrinos
LENA SNR rate:LENA SNR rate:
~ 6 ~ 6 countscounts/y/y
Sensitivity Sensitivity on on proton decayproton decay
p K p K nn
• This decay mode is favoured in SUSYSUSY theories
• The primary decay particle K is invisible inWater Cherenkov detectors
• It and the K-decay particles are visible inscintillation detectors
• Better energy solution further reducesbackground
P P -> -> KK+ + nn event structureevent structure:: T (K+) = 105 MeV
t (K+) = 12.8 nsec
KK++ -> m-> m++ n n ( (63.5 %) K63.5 %) K++ -> p-> p+ + p p00 (21.2 %) (21.2 %)
T (m+) = 152 MeV T (p+) = 108 MeV electromagnetic shower
E = 135 MeV
mm+ + -> -> ee++ n n (t = 2.2 mn n (t = 2.2 ms) s) pp++ -> m -> m++ n n (T = 4 MeV)
mm+ + -> -> ee++ n n (t = 2.2 mn n (t = 2.2 ms)s)
••3 - 3 - fold coincidence fold coincidence !!
••the first the first 2 2 events are monoenergetic events are monoenergetic !!
••useuse time- and time- and position correlation position correlation !!
HowHow good good can onecan one separate separate thethe
first two eventsfirst two events ? ?
........results results of a of a first first Monte-Carlo Monte-Carlo calculationcalculation
Background
Rejection:
• monoenergetic K- and m-signal: DE/E ~ 1 % !
• position correlation
• pulse-shape analysis
(after correction on
reconstructed position)
• SuperKamiokandeSuperKamiokande has 170 170 background events in 14891489days (efficiency 33% 33% ))
•In LENALENA, this would scale down to a background of ~ 5 / y~ 5 / y andafter PSD-analysis this could be suppressed in LENALENA to
~ ~ 0.25 / y0.25 / y ! (efficiency ~ ~ 70%70% )
•A 30 kt detector (~ 10103434 protons as target) would have a
sensitivity of t t << a a few few 10103434 yearsyears for the K-decayK-decayafter ~10 years measuring time
•The minimal SUSYSUSY SU(5) SU(5) model predicts the K-decayK-decay mode tobe dominantdominant with a partial lifetime varying from 10102929y to 10y to 1035 35 yy !
actual best limit from SKSK: t < 6.7 x 1032 y (90% cl)
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