Detection of the Diffuse Supernova Neutrino Background in LENA

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Detection of theDiffuse Supernova
NeutrinoBackground in LENA Study of
Scintillator Properties

• Michael WurmDPG Spring Meeting, 30.3.06

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Neutrinos from Supernovae
SN explosion 99 of gravitational binding energy
are emitted in the form of vs galactic rate 3
in 100 yrs
Diffuse Supernova Neutrinos all SN throughout
the Universe contribute to an isotropic
background of vs, the DSNB. all flavours are
equally created fluxes are low, ve are the most
likely to be detected by inverse b decay ve p
? n eSK limit 1.2 cm-2s-1 for Ev gt 19.3 MeV
S. Ando, K. Sato, astro-ph/0410061
Detection of the DSNB in LENA Michael Wurm
2/11
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DSNB Predictions
use
Supernova Model SN 1987A about 20 ve events
detected ? spectral shape isstrongly
model-dependentvisible mainly for Ev gt 10 MeV LL
Lawrence Livermore GroupTBP Thompson,
Burrows, PintoKRJ Keil, Raffelt, Janka
Detection of the DSNBwould provide
informationboth on SN explosionmechanism and on
the Star Formation Rate athigh redshifts. Ev
lt 10 MeV SFR(z)Ev gt 10 MeV SN models
DSN from z gt 1are dominant forEv lt 10 MeV.
Star Formation Rate redshift-dependent local
(z0) uncertaintycompared to usedmodel 0.7-4.1
due todust extinction high z even
higheruncertainties
Detection of the DSNB in LENA Michael
Wurm 3/11
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DSNB Detection in LENA
detection via inverse beta decay ve p ? n e
(Q 1.8 MeV)
50x106 l of liquid scintillatorcontaining
2.9x1033 free protons ? 50-75 events in 10 years
Detection of the DSNB in LENA Michael Wurm
4/11
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Observational Window
In a liquid scintillator Inverse beta decay
1.8 MeV reactor ve 10 MeV atmospheric ve
30 MeV ? Observation 10 MeV lt E lt 30 MeV
Detection of the DSNB in LENA Michael Wurm
5/11
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Observational Window
In a water Cerenkov detector Inverse beta
decay 1.8 MeV reactor ve 10
MeV atmospheric ve 30 MeV spallation
products lt 19 MeV invisible muons gt 19 MeV ?
no observational window ? background
substracted statistically
Detection of the DSNB in LENA Michael Wurm
6/11
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Reactor Background
1. reactor ve spectrum spectral form well
knownfor E lt 8 MeV measurements done byTengblad
et al. for E lt 12 MeV consideration of high
endpointbeta emitters like 94Br 2. NPP power
and position 200 NPP sites considered number of
ve per GW ofthermal power is 1.3 x 1017 3.
include ve ? µ oscillations
detector site reactor ve flux1/cm2s ThresholdMeV DSNB eventsin 10 yrs
Kamioka 2.14 x 106 11.1 23-48
Frejus 1.63 x 106 10.8 24-49
Pyhäsalmi 1.86 x 105 9.7 28-54
Pylos 1.08 x 105 9.3 30-56
Homestake 7.51 x 104 9.0 31-57
Hawaii 1.09 x 104 8.4 34-60
New Zealand 5.38 x 103 8.2 35-61
Detection of the DSNB in LENA Michael Wurm
7/11
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Event Rates in LENA
after 10 years of measurement time in Pyhäsalmi
9.7 MeV lt Ev lt 30 MeV LL 54KRJ 45TBP 29acc
ording to MC simulations, a separation between LL
TBP is possible at 90 C.L.after 10 years
DSN spectroscopy in LENA should be possible!
Detection of the DSNB in LENA Michael Wurm
8/11
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Scintillator Properties
light yield and transparency ofthe scintillator
are vital for energy resolution
spectroscopy!? laboratory measurements of light
yield attenuation length done in Garching
Heidelberg Scintillator Candidates PXE
(C16H18)high light yield, high attenuation
length if purified in Al2O3 column,non-hazardous
Dodecane (C12H26)lowers light yield, very
transparent, increases number of free protons up
to 25
light yield setup
attenuation setup
Study of Scintillator Properties Michael
Wurm 9/11
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Photoelectron Yield
is the number of photons per MeV registered in
the PMs. Rough estimation for LENA
Results for different mixtures of PXE and
Dodecane
? corresponds to an energy resolution of 3 _at_ 10
MeV! (lower limit)
Study of Scintillator Properties Michael
Wurm 10/11
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Conclusions
In a 50 kt liquid scintillator detector like LENA
an energy window for DSNB detection from 10 MeV
to 30 MeV can be found. For LENA in Pyhäsalmi,
the lower threshold will be about 9.7
MeV,allowing the detection of SN neutrinos
emitted at a redshift zgt1. 29 to 54 events in 10
years are awaited for LENA within DSNB model
predictions. After 10 years, the number of
events provided will most likely be sufficient
for a spectroscopic discrimination of some of the
predicted DSNB models. Technical feasability
studies concerning the light yield and
attenuation length of the scintillator look very
promising. LENA would allow the detection of
DNSB for the first time.New observational data
both on SN models and on the Star Formation Rate
(up to z2) could be obtained.
Detection of the DSNB in LENA Michael Wurm
11/11