1. Supernovas Neurino Signals in WATCHMAN Mark Vagins UC Irvine/Kavli IPMU 4 th Full WATCHMAN Collaboration Meeting UC Davis October 29, 2014

3. A core-collapse supernova is a nearly perfect “neutrino bomb”. It releases >98% of its huge energy as neutrinos. In 1987, we saw the evidence firsthand... Neutrinos provide a window into core collapses’ inner dynamics.

4. Kamiokande IMB Baksan

5. Event Displays of Actual Neutrinos from SN1987A IMB (in USA) Kamiokande (in Japan)

6. Full list of reactions expected in WATCHMAN (Neutrino oscillations are taken into account.)

7. e e+e+ 2.2 MeV  -ray p n Possibility 1: 10% or less n+Gd → ~8MeV   T = ~30  sec Possibility 2: 90% or more   n+p →d +  p Gd Inverse Beta Decay (~88% of events) Elastic Scattering (~3%  directional) I’ve talked about these signals before, but what about the remaining 9% of the events?

8. In the case of a galactic supernova, having a Gd 2 (SO 4 ) 3 -loaded WATCHMAN in operation will provide many important benefits:  Allows the exact e flux, energy spectrum, and time profile to be determined via the extraction of a tagged, pure sample of inverse beta events.  Instantly identifies a burst as genuine via “Gd heartbeat”.  Doubles the ES pointing accuracy. Error circle cut by 75%.  Helps to identify other neutrino signals, especially the CC events on oxygen and weak neutronization burst of e.  Provides for very early warning of the most spectacular, nearby explosions so we can be sure not to miss them.

9. Based on the IVB “Gd heartbeat”, we’ll send out an announcement within one second of the SN neutrino burst’s arrival in WATCHMAN!  Could provide a special, millisecond-scale “express lane” trigger for LBNE/F.

10. Full list of reactions expected in WATCHMAN (Neutrino oscillations are taken into account.)

12. Until the discovery of large neutrino oscillations and the advent of Gd-loading! These are precious events, because one thing the world is lacking is a good e detector.

13. Full list of reactions expected in WATCHMAN (Neutrino oscillations are taken into account.)

14. [Phys.Rev.Lett. 76 (1996) 2629-2632]

15. Unfortunately, the need to Compton scatter the photons and make relativistic electrons smears out this narrow structure, and also shifts the visible energies down below 5 MeV.  However, this is a supernova signal mode which would benefit greatly from using water-based liquid scintillator during some later WATCHMAN phase. 

18. The famous SN1987A time plot from Kamiokande-II They almost never show a wider view. That’s because the detector was intentionally turned off for maintenance until just a few minutes before the burst!

19. Odrzywodek et al. have calculated that late-stage Si burning in very large, very close stars could provide a useful early warning of a core collapse supernova as long as neutron detection is possible. e + + e -  e + e (just above inverse beta threshold) [Odrzywodek, Misiaszek, and Kutschera, Astropart.Phys. 21:303-313, 2004] e + p  e + + n (e + non-relativistic)

22. The dying star does have to be big and pretty close for this trick to work. So in addition to learning about nucleosynthesis, think of it an insurance policy: we won’t miss the most important, dramatic naked eye events! Okay, so who’s on the stellar deathwatch in our galactic neighborhood?

24. The Neighborhood (Death)watch Rasalgethi380 +/- 120 ly~8 solar masses (100 – 300 neutron singles per day in WATCHMAN) Betelgeuse 640 +/- 150 ly~12 solar masses (40 – 100 neutron singles per day in WATCHMAN) Antares600 +/- 150 ly~12 solar masses (40 – 100 neutron singles per day in WATCHMAN) Rigel780 +/- 150 ly~18 solar masses (20 – 50 neutron singles per day in WATCHMAN) Deneb2600 +/- 220 ly~19 solar masses (3 – 4 neutron singles per day in WATCHMAN)

25. Naturally we will have to be rather lucky to see a galactic supernova in WATCHMAN. But supernova ’s are inevitable, unlike many things experiments look for, so let’s get our bets on the table!  Odds are the neutrinos are already on their way! 