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

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

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

4. 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

5. 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

6. 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

7. 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

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

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

10. 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

11. 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

12. 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

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

14. 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

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

16. 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

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

18. 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

19. 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

20. 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

21. 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

22. Thank you!

23. Back up

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

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