LSc development for Solar und Supernova Neutrino detection

17th Lomonosov conference , Moscow, August 2015L. Oberauer, TUM

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

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

Solar MSW effect

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Where is the up-turn in 8B ?

L. Oberauer, TUM

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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

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

Motivation: supernova neutrinos

from K. Scholberg, Taup 2011

Energy distribution (“high” E) Energy distribution (“low” E)

all flavors

from J. BeacomL. Oberauer, TUM 7

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

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L. Oberauer, TUM 8

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

Challenges and approachesLENA (Low Energy Neutrino Astronomy)

LENA design study (LAGUNA consortium) for Pyhäsalmi (Finland) arxive:1104.5620

L. Oberauer, TUM 10

Challenges and approaches

JUNO (Jiagmen Underground Neutrino Observatory)

L. Oberauer, TUM 11

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

LENA Monte-Carlo 8B-neutrinos

MSW

L. Oberauer, TUM 13

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

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

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

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

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%)

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

PSD applied for LENA

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DSNB in LENA

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Signal / background ratio possible after PSD cut

DSNB feasibility?Depends on background uncertainty.5% uncertainty = 0.1% PSD uncertainty

DSNB in LENA

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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>

No DSNB in LENA

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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

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