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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 - PowerPoint PPT Presentation
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Colliders to Cosmic Rays 2007 , Lake Tahoe, CA
The Diffuse Flux of Supernova Neutrinos
Cecilia LunardiniInstitute for Nuclear Theory
University of Washington - Seattle
Abstract
• Diffuse neutrinos from supernovae
• O(1) question: Seen? – Not yet – BUT: will be seen
• O() question: What can we learn?– original spectrum (at emission)
How do stars die? Supernovae
• Massive stars (M>8Msun) gravitational instability–Collapse to nuclear density core–Shock and explosion
ht t
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A neutrino phenomenon
• 99% of the gravitational energy in neutrinos– GN M2
f/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-e i < h Exix=,
The diffuse flux
• Cosmological SN rate: RSN(0) 10-4 Mpc-3yr-1
ddE
c
H0
RSN (z)dNw ( E )
d E we,,
0
zmax Pwe (E,z)dz
m (1 z)3
E (1 z)E
H0 70Km /(sMpc), m 0.3, 0.7, zmax 5
RSN (z) RSN (0) (1 z) z 1, 3
RSN (0)2 z 1
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%
• “Effective” neutrino spectrum after oscillations:– (“pinching”) 2-4 , E0 12 - 20 MeV
SN1987A-motivated, Mirizzi & Raffelt, PRD72, 2005
Predictions
Str
iga
ri e
t al.
Ka
plin
gh
at e
t al.
Lun
ard
ini
An
do &
Sa
to
Ha
rtm
an
n &
Woo
sle
y
SK limit
(E
>19
.3 M
eV)/
(cm
-2 s
-1)
Seen? Not yet! Limits: anti-e, e
KamLAND
SuperKamiokande
(E
)/(M
eV-1cm
-2 s
-1)
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
Atmospheric , invisible
SK+oscillations, Lunardini, PRD73, 2006
SNO
BUT: will be seen at Mton detectors
Fogli et al., hep-ph/0412046
Beacom & Vagins, PRL93, 2004
Anti-e + p n + e+
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
UNO/HyperK:Water, 0.4 Mton fiducial, E > 19.3 MeV
GADZOOKSWater+Gd, 20 Kt fiducial, E>11.3 MeV
Anti-e + p Events/4 yr (99% CL, from SN1987A)
7 - 60 1.1 - 6.4
What can we learn?
• Spectrum of e+:– E0 , (“pinching”), (SNR power)
• Number of e+ events: – Le , RSN(0), E0, ,
• Original spectrum?– Yes!– Useful observable:
(bin 1)/(rest)
• Supernova Rate?– No/difficult
Water only
C.L., astro-ph/0612701
Normalized to 60 events
Spectral sensitivity
Water+Gd
Normalized to 150 events
C.L., astro-ph/0612701
To understand: analytics
• Approximations: dominated by z<1 at high energy (redshift):– RSN=0 z>1
– z<<1 & m + = 1:
ddE
c
H0
RSN (z)dNw ( E )
d E we,,
0
zmax Pwe (E,z)dz
m (1 z)3
• Result: = + - (3/2)m , zmax=1
• Cruder : neglect upper integration limit– = E0/(1+), only in the polynomial part!
• Crudest: “fitted” exponential: = 0 e-E/<E>
• Exact• Result• Cruder (20%
accuracy above 20 MeV)– neglect upper
integration limit
• Crudest– “fitted”
exponential
R(0)=10-4 Mpc-1yr-1 , Le=5 1052 ergs, b = 3.28 , a=2.6 E0 =15 MeV
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
Conclusions: likely scenario
• Gadzooks and/or LENA and/or HyperK/UNO/MEMPHYS will see the DF
• known from SN surveys (SNAP, JWST)
• DF spectrum -> E0 , – Test of SN numerical models
• DF number of events -> break degeneracy between E0, , L, RSN(0)
http://snap.lbl.gov/ http://www.jwst.nasa.gov/,
Backup slides
Original spectrum? YES!
Normalized to 60 events, =3.28 Total error, no GdTotal error, with Gd
C.L., astro-ph/0612701
Original spectrum? YES!
• Depends on = E0/(1+)
Normalized to 60 events, =3.28
/MeV=2 (E0/MeV=12, =5)
/MeV=4.2 (E0/MeV=15, =2.6)
/MeV=6.7 (E0/MeV=20, =2)
Original spectrum? YES!
• Useful observable: first bin/rest of data
Normalized to 60 events, =3.28
SN population? ..no..
Normalized to 60 events, E0/MeV=15, =2.6
=2
=3.28
=5
Number of events add information
=3.28 E0/MeV=11 E0/MeV=15 E0/MeV=20
=2 21.6 71.6 163
=4 7.4 37.5 110
R(0)=10-4 Mpc-1yr-1 , Le=5 1052 ergs, 0.4 Mt, 4 yr, Eth=18 MeV
7
=5 E0/MeV=11 E0/MeV=15 E0/MeV=20
=2 34 129 326
=4 10 59 200