LSc development for Solar und Supernova Neutrino detection 17 th Lomonosov conference, Moscow, August 2015 L. 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, TUM2

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 8 B – spectrum ? („missing upturn“) => 8 B – spectrum at low E-threshold and with high statistics L. Oberauer, TUM3

Solar MSW effect 4 Where is the up-turn in 8 B ? L. Oberauer, TUM

5 A. Friedland et al., Phys.Lett.B594:347,2004 Non-standard P ee transitions 1,2,4: Flavor changing neutral current models 3: Standard MSW curve Impact on P ee in szenarios with sterile neutrino admixtures P. De Holanda, A.Y. Smirnov, Phys.Rev.D83:113011,2011 arxive: L. Oberauer, TUM

Motivation: supernova neutrinos Flavor and energy determination 2 CC – reactions (on H and 12 C) 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 electronsall active neutrinos L. Oberauer, TUM6

Motivation: supernova neutrinos from K. Scholberg, Taup 2011 Energy distribution (“high” E)Energy distribution (“low” E) all flavors from J. Beacom L. Oberauer, TUM7

Expected rate: 2-20 e /(50 kt y) (in energy window from 10-25MeV) Detection of DSNB flux Isotropic flux of all SN ‘s emitted in the history of the Universe. Faint signal:  ≈ 10 2 /cm 2 s 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, TUM8

Challenges and approaches Large LSc (> 10 kton), safety requirements, price Lab (solvent) Resolution in energy and space Optical quality: high light-yield, long absorption- and scattering-lengths Radiopurity Solar neutrinos ( 208 Tl) Purification methods ? Functional response Quenching behavior Pulse-shape discrimination L. Oberauer, TUM9

Challenges and approaches LENA (Low Energy Neutrino Astronomy) LENA design study (LAGUNA consortium) for Pyhäsalmi (Finland) arxive: L. Oberauer, TUM10

Challenges and approaches JUNO (Jiagmen Underground Neutrino Observatory) L. Oberauer, TUM11

Laboratory achievements LENA Monte-Carlo simulation on solar 8 B-neutrino detection (electron scattering) after stat. Subtraction (1y, 3 sigma limit) Background considerations: 208 Tl Borexino 2007 value -> tagged via (  )-coincidence 10C cosmogenic bg -> muon veto (T 1/2 = 19.3 s) Conclusion: E-threshold of  2 MeV achievable L. Oberauer, TUM12

LENA Monte-Carlo 8 B-neutrinos MSW L. Oberauer, TUM13

LENA Monte-Carlo 8 B-neutrinos Conclusion: MSW-test (“search for the up-turn”) and search for new physics is feasible in LENA …even, if intrinsic background is factor  10 2 larger as in Borexino… For details: R. Möllenberg et al., Phys. Lett. B737, 251 (2014), arxiv: L. Oberauer, TUM14

JUNO Monte-Carlo 8 B-neutrinos Cosmogenic background is severe 3-fold coincidence technique (Borexino) for 10 C feasible ? 11 Be shape measurement and statistical subtraction possible ? JUNO “yellow book”, arxiv: L. Oberauer, TUM15

DSNB L. Oberauer, TUM16 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, – arxiv:

DSNB - Background L. Oberauer, TUM17 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, TUM18 NC – reactions of atmospheric neutrinos on 12 C Monte-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 MeV LAB + 3g/l PPO + 20mg/l bisMSB neutron events gamma events t t = 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 L. Oberauer, TUM20

DSNB in LENA L. Oberauer, TUM21 Signal / background ratio  possible after PSD cut DSNB feasibility? Depends on background uncertainty. 5% uncertainty = 0.1% PSD uncertainty

DSNB in LENA L. Oberauer, TUM22 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

No DSNB in LENA L. Oberauer, TUM23 No DSNB signal in LENA (only background) would significantly (factor  10) improve existing SuperKamiokande limit on DSNB Flux limit (after 10y) would be  0.4 / cm 2 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, TUM24 Improved solar 8 B-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