Detection of the Diffuse Supernova Neutrino Background in LENA & Study of Scintillator Properties...

Detection of theDetection of theDiffuse Supernova NeutrinoDiffuse Supernova Neutrino

Background in LENA &Background in LENA &Study of Scintillator PropertiesStudy of Scintillator Properties

Michael WurmDPG Spring Meeting, 30.3.06

E15

Neutrinos from SupernovaeNeutrinos from Supernovae

Detection of the DSNB in LENADetection of the DSNB in LENA Michael WurmMichael Wurm 22/11/11

SN explosion:SN explosion:

99% of gravitational binding energy are emitted in the form of v‘s

galactic rate: ~3 in 100 yrs

Diffuse Supernova Neutrinos: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 decay

ve + p n + e+

SK limit: 1.2 cm-2s-1

for Ev > 19.3 MeVS. Ando, K. Sato, astro-ph/0410061

DSNB PredictionsDSNB Predictions


Supernova ModelSupernova Model

SN 1987A: about 20 ve events detected

spectral shape isstrongly model-dependentvisible mainly for Ev > 10 MeV

LL – Lawrence Livermore GroupTBP – Thompson, Burrows, Pinto

KRJ – Keil, Raffelt, Janka

Star Formation RateStar Formation Rate

redshift-dependent

local (z=0): uncertaintycompared to usedmodel 0.7-4.1 due todust extinction

high z: even higheruncertainties

DSN from z > 1are dominant for

Ev < 10 MeV.

Detection of the DSNBwould provide informationboth on SN explosionmechanism and on the Star Formation Rate athigh redshifts.

Ev < 10 MeV : SFR(z)

Ev > 10 MeV : SN models

use …

DSNB Detection in LENADSNB Detection in LENA


detection via inverse beta decayve + p n + e+ (Q = 1.8 MeV)

50x106 l of liquid scintillatorcontaining 2.9x1033 free protons

50-75 events in 10 years50-75 events in 10 years

Observational WindowObservational Window


In a liquid scintillator:In a liquid scintillator:

Inverse beta decay: 1.8 MeV

reactor ve: ~ 10 MeV

atmospheric ve: ~ 30 MeV

Observation: 10 MeV < E < 30 MeVObservation: 10 MeV < E < 30 MeV

Observational WindowObservational Window


In a water In a water ČČerenkov detector:erenkov detector:

Inverse beta decay: 1.8 MeV

reactor ve: ~ 10 MeV

atmospheric ve: ~ 30 MeV

spallation products: < 19 MeV

invisible muons: > 19 MeV

no observational window no observational window background substracted statistically

Reactor BackgroundReactor Background


1. reactor v1. reactor ve e spectrumspectrum

spectral form well knownfor E < 8 MeV

measurements done byTengblad et al. for E < 12 MeV

consideration of high endpointbeta emitters like 94Br

2. NPP power and position2. NPP power and position

200 NPP sites considered

number of ve per GW ofthermal power is ~ 1.3 x 1017

3. include v3. include ve e µ µ oscillationsoscillations

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

Event Rates in LENAEvent Rates in LENA


after 10 years of measurement time in Pyhäsalmi

9.7 MeV < E9.7 MeV < Evv < 30 MeV: < 30 MeV:

LL: 54KRJ: 45TBP: 29

according to MC simulations, a separation between LL & TBP is possible at 90% C.L.after 10 years

DSN spectroscopy DSN spectroscopy in LENA should be in LENA should be possible!possible!

Scintillator PropertiesScintillator Properties

Study of Scintillator PropertiesStudy of Scintillator Properties Michael WurmMichael Wurm 99/11/11

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: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

atte

nuat

ion

setu

p

Photoelectron YieldPhotoelectron Yield

Study of Scintillator PropertiesStudy of Scintillator Properties Michael WurmMichael Wurm 1010/11/11

is the number of photons per MeV registered in the PMs.

Rough estimation for LENA:

ResultsResults for different mixtures of PXE and Dodecane:

corresponds to an energy resolution of ~3% @ 10 MeV!corresponds to an energy resolution of ~3% @ 10 MeV! (lower limit)

ConclusionsConclusions


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 z>1.

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.LENA would allow the detection of DNSB for the first time.New observational data both on SN models and on the Star New observational data both on SN models and on the Star Formation Rate (up to z~2) could be obtained.Formation Rate (up to z~2) could be obtained.

Detection of the Diffuse Supernova Neutrino Background in LENA & Study of Scintillator Properties...

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