Solar & Supernova Neutrinos Detection Methods and Prospects Shirley Li SLAC Theory Group NNN17, University of Warwick

Why MeV astrophysics? Shirley Li (SLAC) 2/24

Solar neutrino Where we are Shirley Li (SLAC) 3/24

Solar neutrino physics What we know Solar neutrino spectra Survival probability Borexino 2014 Confirmed Standard Solar Model and neutrino oscillation Shirley Li (SLAC) 4/24

Open questions Challenging measurements remaining Data from SK 2016 Branches not measured Solar & reactor tension Borexino 2014 Why are these challenging? Shirley Li (SLAC) 5/24

How to better reject backgrounds? Obstacles for CNO 𝜈 Borexino CNO 𝜈+𝑒→𝜈+𝑒 210Bi 𝛽 decay Borexino 2014 How to better reject backgrounds? Shirley Li (SLAC) 6/24

What are the backgrounds? Obstacles for 8B 𝜈 Super-Kamiokande 8B 𝜈 𝜈+𝑒→𝜈+𝑒 Backgrounds Super-K 2016 What are the backgrounds? Shirley Li (SLAC) 7/24

Spallation backgrounds Muon rate 2 Hz, isotope lifetime ~ s How to better reject backgrounds? Shirley Li (SLAC) 8/24

Solar neutrino Going forward Shirley Li (SLAC) 9/24

Borexino: CNO 𝜈 Reject 210Bi Thermal insulation Calaprice talk at 10th anniversary of Borexino Reject 210Bi Thermal insulation 210Pb → 210Bi → 210Po→ 206Pb (22 yr) (5 d) (138 d) 210Pb long lived 210Po can be measured 210Bi can be extracted Equilibrium in decay chain is required Summer 2017: stable T achieved! Shirley Li (SLAC) 10/24

Super-K: 8B 𝜈 Comprehensive studies of spallation backgrounds Li and Beacom, 2015 Spallations are produced in muon-induced showers Using neutrons and light to tag showers! Shirley Li (SLAC) 11/24

Super-K analysis in progress 𝑛+H→2.2 MeV 𝛾 Neutron capture time Spallation-neutron correlation Super-K can see neutrons! Stay tuned Shirley Li (SLAC) 12/24

Supernova neutrino Where we are Shirley Li (SLAC) 16/24

Supernova neutrino physics See O’connor’s talk What we predict Diffuse supernova neutrino background Milky Way supernova Scholberg 2012 Horiuchi et al., 2009 Non-negligible theoretical uncertainties Shirley Li (SLAC) 17/24

Supernova neutrino Going forward Shirley Li (SLAC) 18/24

How long does the 𝜈 burst last? Supernova late-time neutrinos Li, Roberts, Beacom, in prep 𝜈 𝑒 +𝑝→ 𝑒 + +𝑛 in SK 10 kpc, 22.5 kton Detect the birth of neutron star or black hole in neutrinos NS! Plenty of events after 10 s, last one ~ 1 min Shirley Li (SLAC) 19/24

Alternative outcome -- BH Different mechanisms for BH formation Li, Roberts, Beacom, in prep BH may form at late times Shirley Li (SLAC) 20/24

Detecting BH formation Detection significance of BH formation Li, Roberts, Beacom, in prep We can detect BH formation at late times Shirley Li (SLAC) 21/24

SN neutrinos in DUNE 𝜈 𝑒 +40Ar→ 𝑒 − +40 K ∗ Nikrant, Laha, Horiuchi, in prep Ongoing effort to improve DUNE MeV capability New opportunities in understanding SN 𝜈 Shirley Li (SLAC) 22/24

Enhance sensitivity for DSNB, solar physics, etc SK-Gd See Nakajima’s talk 𝜈 𝑒 +𝑝→ 𝑒 + +𝑛 Beacom & Vagins, 2004 𝑛+Gd→~ 8 MeV 𝛾’s Next JUNE! Horiuchi et al., 2009 Enhance sensitivity for DSNB, solar physics, etc Shirley Li (SLAC) 23/24

Conclusions Ongoing effort to measure CNO 𝜈 Backgrounds for 8B in Super-K being reduced Solar neutrino in DUNE: incredible potential SK-Gd scheduled, possible detection of DSNB… Stay tuned! Shirley Li (SLAC) 24/24

Thank you!

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Solar metallicity problem Vinyoles et. al., 2017 Shirley Li (SLAC)

Solar metallicity problem Vinyoles et. al., 2017 Shirley Li (SLAC)