The Diffuse Supernova Neutrino Background

1. The Diffuse Supernova Neutrino Background Louie Strigari The Ohio State University Collaborators: John Beacom, Manoj Kaplinghat, Gary Steigman, Terry Walker, Pengjie Zhang

2. The Plan • Diffuse Supernova Neutrino Background • Theoretical Prediction • Experimental Limits and Detection Prospects • Sampling Flavors of the DSNB • MeV Neutrino and Gamma-Ray Astronomy • Return to the Crime Scene: SN 1987A

3. DSNB: The Big Picture Core Collapse of Massive Star Gives Burst of ~ 1058 Neutrinos + Massive Star Formation Since z ≤ 6 = The Diffuse Supernova Neutrino Background (DSNB) – Cosmological background of neutrinos from all supernovae that have occurred

4. Evolution of Massive Stars (> 8 Solar Mass) Optical SNII or Black Hole Main Sequence Burning: 10-100 Myr Core Collapse: 3 x 1053 ergs released in ~10 seconds

5. Evolution of Intermediate Mass Stars (3-8 Solar Mass) SNIa (+Fe) Main Sequence, Binary Accreting White Dwarf t ~ Gyr t ~ Gyr

6. Cosmic Star Formation Rate • UV luminosity density β ~ 2.5 • Galaxy Surveys β ~ 2-4 SDSS, 2df zp ~ 1 α ~ 0-2 D. Schiminovich et al. (2005) supernova rate = [stellar mass function] x [star formation rate]

7. DSNB Flux Theoretical Predictions Increase in High Redshift Star Formation Best Estimate Model Lower bound from Astronomy Data Supernova Neutrino Spectrum Impact of Oscillations: Dighe & Smirnov 2003, Minakata et al. 2002

8. DSNB Detection Event Rate = [ # of targets ] x [ cross section ] x [ flux ] Largest Yield from Inverse Beta Super-Kamiokande (22.5 kton) 1.5 x 1033 Invisible Visible

9. Backgrounds to Detection Atmosphere Below ~ 50 MeV, Muon is Invisible

10. DSNB Event Rate Predictions • Modern predictions for Super-K: ~ 3 events/yr above 18 MeV ~ 6 events/yr above 10 MeV • Ando, Sato & Totani 2003 • Fukugita & Kawasaki 2003 • Strigari, Kaplinghat, Steigman & Walker 2004 • Atmospheric Background Reduction • Beacom & Vagins 2004

11. Super-K Upper Limit • 4+ years of data gives flux limit: 1.2 cm-2 s-1 • Detection signature is an excess of events • Detection timescale with fiducial model is ≈ 9 years • Strigari, Kaplinghat, Steigman, Walker 2004 Super-Kamiokande Collaboration, PRL 90, 061101 (2003)

12. Gadolinium Enhanced Super-K (GADZOOKS!) The Idea: Addition of Gadolinium Trichloride to Water Cerenkov Detectors The Benefits: Flux • Neutron Tagging • Reduction of Invisible Muon Background • Lower Energy Threshold for DSNB Detection Threshold Energy Strigari, Kaplinghat, Steigman, Walker 2004

13. DSNB Scorecard † Neutrino Energies in MeV ‡ Fluxes in cm-2 s-1 # Beacom & Strigari (in prep.) # Predicted Liquid Argon flux limit: 1.6 cm-2 s-1 (Cocco, Ereditato, Fiorillo, Mangano, Pettorino 2004)

14. DSNB Detection Channels Super-K (H20) SNO (D2O)

15. DSNB Constrains from SNO • Solar background < 20 MeV • Invisible Muon Background • DSNB Electron Neutrino Flux Limit at SNO Beacom & Strigari (in prep)

16. MeV Neutrino and Gamma-Ray Astronomy

17. Constraining the Cosmic Star Formation Rate • Shaded Region- SDSS, 2dF • Curves- models based on UV, IR luminsity • DSNB is the strongest constraint on the massive Star Formation Rate • Fukugita & Kawasaki 2003 • Ando 2004 Concordance Region Strigari, Beacom, Walker, Zhang, JCAP04(2005)017

18. Cosmic Supernova Rates • Test supernova progenitor models • What fraction of core-collapse SNII fail? • What is the average delay time between the formation of a binary star system and a SNIa event? Strigari, Beacom, Walker, Zhang, JCAP04(2005)017

19. Cosmic Gamma-Ray Background(CGB) • CGB Sources • < 1 MeV: Seyferts • > 10 MeV: Blazars • 1-3 MeV: SNIa • Concordance model constrains SNIa contribution to the CGB • What are the sources of the 1-3 MeV CGB? Strigari, Beacom, Walker, Zhang, JCAP04(2005)017

20. Additional Physics with the DSNB • Constraints on Neutrino Properties • Neutrino Decay Ando 2003 Fogli, Lisi, Mirizzi, Montanino 2004 • Mini Z Burst Goldberg, Perez, Sarcevic 2005

21. Supernova Neutrinos from Nearby Galaxies? • Detection potential with megaton detectors • Correlate with optical SNII for the detection of 1 event • 2 event detection essentially background free Ando, Beacom, and Yuksel 2005

22. Return to the Crime Scene: Supernova 1987A

23. Historical Supernovae “You can observe a lot just by watching’ –Yogi Berra Supernova Rate in the Milky Way ≈ 1 per century One identified nearby supernova in telescopic era: SN 1987A Stephenson and Green (2002)

24. A Blast from the Past:Supernova 1987A • 19 neutrinos detected by IMB and Kamiokande • Consistent with core collapse energy budget • What was the flavor content of the flux? • Why were a majority of the events forward?

25. Constraining Flavor Emission • DSNB flux limit at SNO can constrain electron neutrino flux from SN 1987A • Was the electron neutrino flux larger than expected? e.g. Costantini, Ianni, Vissani 2004 • SNO limit more sensitive to higher electron neutrino temperatures Beacom & Strigari (in prep)

26. Conclusions • DSNB: First Detection of Neutrinos Beyond SN1987A? • Current DSNB Limits Constrain the Cosmic Star Formation Rate (CSFR) • Measurements of the CSFR in Agreement with Supernova Rates • DSNB + SN1987A can constrain supernova neutrino emission