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The Diffuse Flux of Supernova Neutrinos

F n. The Diffuse Flux of Supernova Neutrinos. Cecilia Lunardini Institute for Nuclear Theory University of Washington - Seattle. Colliders to Cosmic Rays 2007 , Lake Tahoe, CA. Abstract. Diffuse neutrinos from supernovae O(1) question: Seen? Not yet BUT: will be seen

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The Diffuse Flux of Supernova Neutrinos

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  1. Fn The Diffuse Flux of Supernova Neutrinos Cecilia Lunardini Institute for Nuclear Theory University of Washington - Seattle Colliders to Cosmic Rays 2007 , Lake Tahoe, CA

  2. Abstract • Diffuse neutrinos from supernovae • O(1) question: Seen? • Not yet • BUT: will be seen • O(e) question: What can we learn? • original n spectrum (at emission)

  3. How do stars die? Supernovae • Massive stars (M>8Msun) gravitational instability • Collapse to nuclear density core • Shock and explosion http://chandra.harvard.edu/resources/animations/

  4. A neutrino phenomenon • 99% of the gravitational energy in neutrinos • GN M2f/rf - GN M2i/rI ~ 1053 ergs • Diffusion from thermal surface • e, , , anti-e, anti-, anti- • Time : (size2)/(mean free path) ~ 10 s • h E i : ~9 – 22 MeV, h Eei < h Eanti-ei < h Exi x=,

  5. The diffuse flux • Cosmological SN rate: RSN(0) ~ 10-4 Mpc-3yr-1

  6. Fit to core collapse SN data only, C.L., astro-ph/0509233 Star Formation fit, Beacom & Hopkins, astro-ph/0601463 Data: Cappellaro et al., A&A 430, 2005; Dahlen et al., APJ 613 2004 (3 extinction-corrected, 1 not corrected) Confidence levels: 68.3,90,95.4%

  7. “Effective” neutrino spectrum after oscillations: • a (“pinching”)~ 2-4 , E0~ 12 - 20 MeV SN1987A-motivated, Mirizzi & Raffelt, PRD72, 2005

  8. Predictions SK limit Ando & Sato F(E>19.3 MeV)/(cm-2 s-1) Kaplinghat et al. Hartmann & Woosley Strigarietal. Lunardini

  9. Seen? Not yet! Limits: anti-ne, ne KamLAND SNO SK+oscillations, Lunardini, PRD73, 2006 F(E)/(MeV-1cm-2 s-1) SuperKamiokande Atmospheric n, invisible m Zhang et al. (Kamiokande) PRL61, 1988; Eguchi et al. (KamLAND),PRL92, 2004; Malek et al. (SK), PRL90, 2003; Aharmim et al., (SNO), PRD70, 2004; Aglietta et al. (LSD), Astrop. Phys. 1, 1992, Aharmim et al., (SNO), hep-ex/0607010, 2006

  10. BUT: will be seen at Mton detectors Anti-e + p  n + e+ Beacom & Vagins, PRL93, 2004 Fogli et al., hep-ph/0412046

  11. Most conservative, C.L., astro-ph/0509233 See also Ando & Sato, New J. Phys., 2004; Fogli et al., JCAP, 2005; Marrodan Undagoitia et al., Prog. Part. Nucl. Phys. 57, 2006 ; Cocco et al. JCAP 0412:002,2004

  12. What can we learn? • Spectrum of e+: • E0 , a (“pinching”), b (SNR power) • Number of e+ events: • Le , RSN(0), E0, a , b

  13. Spectral sensitivity Water only • Original  spectrum? • Yes! • Useful observable: (bin 1)/(rest) • Supernova Rate? • No/difficult Normalized to 60 events C.L., astro-ph/0612701

  14. Water+Gd Normalized to 150 events C.L., astro-ph/0612701

  15. To understand: analytics • Approximations: dominated by z<1 at high energy (redshift): • RSN=0 z>1 • z<<1 & Wm + WL = 1:

  16. Result: h = a + b - (3/2)Wm , zmax=1 • Cruder : neglect upper integration limit • e = E0/(1+a), b only in the polynomial part! • Crudest: “fitted” exponential: F = F0 e-E/<E>

  17. R(0)=10-4 Mpc-1yr-1 , Le=5 1052 ergs, b = 3.28 , a=2.6 E0 =15 MeV • Exact • Result • Cruder (20% accuracy above 20 MeV) • neglect upper integration limit • Crudest • “fitted” exponential

  18. Numbers of events add information • events/4 year • (bin 1)/(rest) R(0)=10-4 Mpc-1yr-1 , Le=5 1052 ergs, 0.4 Mt, 4 yr

  19. Conclusions: likely scenario • Gadzooks and/or LENA and/or HyperK/UNO/MEMPHYS will see the DF • b known from SN surveys (SNAP, JWST) • DF spectrum -> E0 , a • Test of SN numerical models • DF number of events -> break degeneracy between E0, a, Ln, RSN(0) http://snap.lbl.gov/ http://www.jwst.nasa.gov/,

  20. Backup slides

  21. Original n spectrum? YES! C.L., astro-ph/0612701 Normalized to 60 events, b=3.28 Total error, no Gd Total error, with Gd

  22. e/MeV=2 (E0/MeV=12, a=5) e/MeV=4.2 (E0/MeV=15, a=2.6) e/MeV=6.7 (E0/MeV=20, a=2) Original n spectrum? YES! Normalized to 60 events, b=3.28 • Depends on e = E0/(1+a)

  23. Original n spectrum? YES! Normalized to 60 events, b=3.28 • Useful observable: first bin/rest of data

  24. SN population? ..no.. Normalized to 60 events, E0/MeV=15, a=2.6 b=5 b=3.28 b=2

  25. e~ 7 Number of events add information R(0)=10-4 Mpc-1yr-1 , Le=5 1052 ergs, 0.4 Mt, 4 yr, Eth=18 MeV

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