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![Page 1: LSc development for Solar und Supernova Neutrino detection 17 th Lomonosov conference, Moscow, August 2015 L. Oberauer, TUM.](https://reader035.fdocuments.us/reader035/viewer/2022062720/56649f165503460f94c2cc6d/html5/thumbnails/1.jpg)
LSc development for Solar und Supernova Neutrino detection
17th Lomonosov conference , Moscow, August 2015L. Oberauer, TUM
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Content
• Motivation
Solar neutrinos: 8B – upturn?Supernova neutrinos: burst and DSNB (diffuse supernova neutrino background)
• Experimental challenges and approaches
LENA and JUNO
• Laboratory achievements
Pulse shape discrimination
L. Oberauer, TUM 2
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Motivation: solar neutrios
Big success in the past: discovery of neutrino oscillations
...but two questions (perhaps more...) are open
Solar metallicity ?
CNO neutrino measurement required (Borexino?, SNO+?)
MSW effect in 8B – spectrum ? („missing upturn“)
=> 8B – spectrum at low E-threshold and with high statistics
L. Oberauer, TUM 3
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Solar MSW effect
4
Where is the up-turn in 8B ?
L. Oberauer, TUM
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5
A. Friedland et al., Phys.Lett.B594:347,2004
Non-standard Pee transitions1,2,4: Flavor changing neutral current models
3: Standard MSW curve
Impact on Pee in szenarios with sterile neutrino admixtures
P. De Holanda, A.Y. Smirnov, Phys.Rev.D83:113011,2011 arxive:1012.5627
1 10
L. Oberauer, TUM
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Motivation: supernova neutrinos
Flavor and energy determination
•2 CC – reactions (on H and 12C) for anti-electronneutrinos
•CC – reaction (on 12C) for electronneutrinos
•NC – reaction (on 12C) for all active neutrinos
•NC – elastic-scattering off H for all active neutrinos
•CC/NC – elastic scattering off electrons all active neutrinos
L. Oberauer, TUM 6
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Motivation: supernova neutrinos
from K. Scholberg, Taup 2011
Energy distribution (“high” E) Energy distribution (“low” E)
all flavors
from J. BeacomL. Oberauer, TUM 7
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Expected rate: 2-20 e /(50 kt y)(in energy window from 10-25MeV)
Detection of DSNB fluxIsotropic flux of all SN‘s emittedin the history of the Universe.
Faint signal: ≈ 102 /cm2s
Detection of e by inverse decay:
e + p e+ + n
Remaining background sources reactor and atmospheric e‘s cosmogenic backgrounds
Scientific gain first detection of DSNB information on average SN spectrum
_
_
L. Oberauer, TUM 8
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Challenges and approaches
• Large LSc (> 10 kton), safety requirements, priceLab (solvent)
• Resolution in energy and space Optical quality: high light-yield, long absorption- and scattering-lengths
• Radiopurity Solar neutrinos (208Tl)Purification methods ?
• Functional responseQuenching behaviorPulse-shape discrimination
L. Oberauer, TUM 9
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Challenges and approachesLENA (Low Energy Neutrino Astronomy)
LENA design study (LAGUNA consortium) for Pyhäsalmi (Finland) arxive:1104.5620
L. Oberauer, TUM 10
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Challenges and approaches
JUNO (Jiagmen Underground Neutrino Observatory)
L. Oberauer, TUM 11
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Laboratory achievements
LENA Monte-Carlo simulation on solar 8B-neutrino detection (electron scattering)
after stat. Subtraction(1y, 3 sigma limit)
Background considerations:
208Tl Borexino 2007 value-> tagged via ()-coincidence
10C cosmogenic bg-> muon veto (T1/2 = 19.3 s)
Conclusion: E-threshold of 2 MeV achievable
L. Oberauer, TUM 12
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LENA Monte-Carlo 8B-neutrinos
MSW
L. Oberauer, TUM 13
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LENA Monte-Carlo 8B-neutrinos
Conclusion: MSW-test (“search for the up-turn”) and search for new physics is feasible in LENA
…even, if intrinsic background is factor 102 larger as in Borexino…
For details: R. Möllenberg et al., Phys. Lett. B737, 251 (2014), arxiv:1408.0623
L. Oberauer, TUM 14
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JUNO Monte-Carlo 8B-neutrinos
Cosmogenic background is severe3-fold coincidence technique (Borexino) for 10C feasible ?11Be shape measurement and statistical subtraction possible ?
JUNO “yellow book”, arxiv:1507.05613
L. Oberauer, TUM 15
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DSNB
L. Oberauer, TUM 16
Monte-Carlo for LENA in Pyhäsalmi
DSNB events in 50 kton in 10 y:(12 < E/MeV < 21)
R. Möllenberg et al., Phys. Rev. D 91 (2015) 3, 032005 – arxiv:1409.2240
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DSNB - Background
L. Oberauer, TUM 17
Fast neutron background in LENA
high-E neutrons, generated outside the detector by muons
Fast neutrons are a forming a considerable background:-Reducing fiducial volume-Pulse shape discrimination
fast neutrons
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DSNB - Background
L. Oberauer, TUM 18
NC – reactions of atmospheric neutrinos on 12CMonte-Carlo simulation for LENA in Pyhäsalmi
About 40% of the events can be tagged via delayed coincidence- Pulse shape discrimination (PSD) is mandatory (efficiency > 90%)
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PSD results from TUM
L. Oberauer, TUM 19
1-1.5 MeV
LAB + 3g/l PPO + 20mg/l bisMSB
neutron events
gamma events
tt = 28.5ns
Pulsed neutron beam at 11 MeV
LAB scintillator exhibits excellent PSD behavior
Similar results from B. von Krosigk et al., Eur.Phys.J. C73 (2013) 4, 2390
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PSD applied for LENA
L. Oberauer, TUM 20
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DSNB in LENA
L. Oberauer, TUM 21
Signal / background ratio possible after PSD cut
DSNB feasibility?Depends on background uncertainty.5% uncertainty = 0.1% PSD uncertainty
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DSNB in LENA
L. Oberauer, TUM 22
Together with an improved astrophysical measurement of the SN-rate (green, dashed band shows the current limits) a future DSNB measurement at LENA allows determination of <E>
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No DSNB in LENA
L. Oberauer, TUM 23
No DSNB signal in LENA (only background) would significantly (factor 10) improve existing SuperKamiokande limit on DSNBFlux limit (after 10y) would be 0.4 / cm2 s
In this scenario all current DSNB models would be ruled out at 90% CL,a large parameter space would be ruled out at 3 sigma
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Conclusions
L. Oberauer, TUM 24
• Improved solar 8B-spectral measurement is feasible with future large LSc detectors
-> Probing the MSW-upturn and searching for new physics-> Precondition: radiopurity, cosmogenic bg rejection
• DSNB measurement feasible with future LSc detectors
-> Probing astrophysical SN-models-> Precondition: pulse shape rejection