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

3. DSNB: The Big Picture Core Collapse of Massive Star Gives Burst of ~ 10 58 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) Main Sequence Burning: 10-100 Myr Core Collapse: 3 x 10 53 ergs released in ~10 seconds Optical SNII or Black Hole

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

6. Cosmic Star Formation Rate D. Schiminovich et al. (2005) UV luminosity density β ~ 2.5 Galaxy Surveys β ~ 2-4 SDSS, 2df z p ~ 1 α ~ 0-2 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 DSNB Detection Event Rate = [ # of targets ] x [ cross section ] x [ flux ] Largest Yield from Inverse Beta 1.5 x 10 33 Visible Invisible Super-Kamiokande (22.5 kton)

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

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-Kamiokande Collaboration, PRL 90, 061101 (2003) 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

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

13. DSNB Scorecard DetectorChannel Energy Window † Flux Limit ‡ Super-K 19 - 83 19 - 83 1.2 1.2 KamLAND 8 - 14 8 - 14 ~10 2 ~10 2 Mont Blanc 25 - 50 25 - 50 ~10 4 ~10 4 SNO # 21 - 31 21 - 31 ~10 ~10 † 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 DSNB Detection Channels Super-K (H 2 0) SNO (D 2 O)

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

16. MeV Neutrino and Gamma-Ray Astronomy

17. 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 Constraining the Cosmic Star Formation Rate

18. 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? Cosmic Supernova Rates Strigari, Beacom, Walker, Zhang, JCAP04(2005)017

19. 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? Cosmic Gamma-Ray Background (CGB) Strigari, Beacom, Walker, Zhang, JCAP04(2005)017

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

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

22. Return to the Crime Scene: Supernova 1987A

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

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 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 Was the electron neutrino flux larger than expected? e.g. Costantini, Ianni, Vissani 2004 SNO limit more sensitive to higher electron neutrino temperatures 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