The Diffuse Supernova
Neutrino Background
Louie Strigari
The Ohio State University
Collaborators: John Beacom, Manoj Kaplinghat,
Gary Steigman, Terry Walker, Pengjie Zhang
The Plan

Diffuse Supernova Neutrino Background
Theoretical Prediction
 Experimental Limits and Detection Prospects
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Sampling Flavors of the DSNB
MeV Neutrino and Gamma-Ray Astronomy
Return to the Crime Scene: SN 1987A
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
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
Evolution of Intermediate Mass Stars
(3-8 Solar Mass)
Main Sequence, Binary
t ~ Gyr
Accreting White Dwarf
t ~ Gyr
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SNIa (+Fe)
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]
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
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
Backgrounds to Detection
Atmosphere
Below ~ 50 MeV, Muon is Invisible
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
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)
Gadolinium Enhanced Super-K
(GADZOOKS!)
The Idea:
The Benefits:
• Neutron Tagging
Flux
Addition of Gadolinium Trichloride to Water
Cerenkov Detectors
• Reduction of Invisible Muon
Background
• Lower Energy Threshold for DSNB
Detection
Threshold Energy
Strigari, Kaplinghat, Steigman, Walker 2004
DSNB Scorecard
Detector
Channel Energy Window†
Super-K
Flux Limit‡
19 - 83
1.2
KamLAND
8 - 14
~102
Mont Blanc
25 - 50
~104
SNO#
21 - 31
~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)
DSNB Detection Channels
Super-K (H20)
SNO (D2O)
DSNB Constrains from SNO
• Solar background < 20 MeV
• Invisible Muon Background
• DSNB Electron Neutrino Flux
Limit at SNO
Beacom & Strigari (in prep)
MeV Neutrino and
Gamma-Ray Astronomy
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
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
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
Additional Physics with the DSNB
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Constraints on Neutrino Properties
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Neutrino Decay
Ando 2003
Fogli, Lisi, Mirizzi, Montanino 2004
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Mini Z Burst
Goldberg, Perez, Sarcevic 2005
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
Return to the Crime Scene:
Supernova 1987A
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)
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?
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)
Conclusions
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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