Neutrino Workshop@ICRR
June 29th 2005

Neutrino Probes ofExtragalactic Supernovae
Shin’ichiro Ando
University of Tokyo1. Introduction
Core-Collapse Supernova and Neutrino Burst

Gravitational binding energy
E b ≈ 3 × 1053 erg ~ 20% MSun c 2from Beacom

99% Neutrinos
1%Kinetic energy of explosion
0.01% Photons

Supernova Neutrinos
Neutronization burst

Matteraccretion

Proto-neutron star cooling

Totani, Sato, Dalhed & Wilson, ApJ 496, 216 (1998)

Birth of Neutrino Astronomy• Neutrino burst from SN 1987A in LMC (50 kpc)

From Raffelt

Future Supernova Neutrino Burst• Expected event number from a future galactic
supernova neutrino burst:
Detector

Type

Mass (kton)

Super-KWater

32

Expected events(10 kpc)~ 7,000

SNO

Heavy water

1.4 (D2O)~ 500

KamLAND,LVD

Scintillator

1

~ 300

ICARUS

LiquidArgon

3 (planned)~ 300

Statistically sufficient number!

Signal at Super-K

Totani, Sato, Dalhed & Wilson, ApJ 496, 216 (1998)

What Can We Learn?
Supernova Physics

Neutrino Physics

Temperature and binding energy of
proto-neutron stars

Oscillation parameters, mass hierarchy

Jegerlehner et al. 1996; Kachelriess et al. 2001

Explosion mechanism, shock wave
propagation, black hole formation
Totani et al. 1998; Beacom et al. 2001; Takahashi et al. 2003a;Tomas et al. 2004; Fogli et al. 2003, 2005

Dighe & Smirnov 2000; Takahashi et al. 2001, 2003b,c; Fogli et al.
2002; Dighe et al. 2004

Majorana magnetic moment
Athar et al. 1995; Totani & Sato 1996; Nunokawa et al. 1997,1999; Ando & Sato 2003a,b,c; Akhmedov & Fukuyama 2003

Direction

Nonradiative decay model

Beacom & Vogel 1999; Ando & Sato 2002; Tomas et al. 2003

Frieman et al. 1988; Raghavan et al. 1988; Ando 2004

How Lucky Are We?
• Type II supernova rate in the galaxy is estimated to be~1 per century!

• It strongly depends on our luck.
• We cannot observe supernova neutrino burst inother galaxies, yet (expected event would be ~1 at
SK from M31).

• However, we would be able to see these extragalactic
neutrinos in the near future.

• We have good opportunity for detecting them.

Supernova Relic Neutrinos
Supernova Explosion
99% of its gravitational binding
energy is released as neutrinos(supernova neutrino burst)

It is considered to trace
the cosmic star formation
rate (SFR).

There should be a diffuse background of neutrinos
which were emitted from past supernova explosions.

“Supernova Relic Neutrinos (SRN)”

Motivations — Involved Physics• Detection of first extragalactic neutrinos

rate and background estimates are essential• Precise•

Kaplinghat, Steigman & Walker 2000; Ando, Sato & Totani 2003; Beacom & Vagins 2004; Strigari, Kaplinghat, Steigman &Walker 2004; Cocco et al. 2004

• Galaxy evolution and cosmic star formation rateto observations using light• Complementary•
Fukugita & Kawasaki 2003; Ando 2004; Strigari et al. 2005

• Physics of supernova neutrinos• If we do not have any galactic supernovae...

• Neutrino properties as an elementary particle• Neutrino oscillation•
decay (coupling with e.g. Majoron)• Neutrino•
Ando & Sato 2003

Ando 2003; Fogli, Lisi, Mirizzi & Montanino 2004

2. Formulation and Models

How to Calculate the SRN Flux
WE ARE
HERE.

TIME AXIS

z=0

ν
z=1

ν
z=5

We need information
concerning...
1. Neutrino spectrum
emitted from eachsupernova explosion
2. Neutrino oscillation
within supernovae andthe Earth
3. Supernova rateOriginal neutrino spectrum(with η = 0)

• Traditionally, Fermi-Dirac fit is used
to represent neutrino spectrum.

_νe• Simulation by the Lawrence
Totani, Sato, Dalhed & Wilson (1998)

Livermore group (Totani et al. 1998)
basically confirms this.

Conversion Probabilities
Probability ofνe ⇔ νxconversion

Probabilityof__νe ⇔ νxconversion

Large θ13

Small θ13

100%70%70%70%

Large θ13

Small θ13

Normal30%30%

Inverted

100%30%Normal(m1 < m3)
Inverted(m1 > m3)

Spectrum after Oscillation• Here, we only consider

the case of normal masshierarchy.

• Oscillation enhances thehigh-energy tail.

• But not dramatically at

detectable energy range(<30 MeV).

L50

Recent GALEX Result
SCHIMINOVICH ET AL.

••

Schiminovich
et al.from
2005
Fig. 5.—SFR density
vs. z. Filled circles
measurements at 1500 Å
(uncorrected for dust) same as in Fig. 1. Blue comparison points are rest-frame(2002) and Lilly et al. (1996) b
our measured values despite
slope obtained in the two studrespectively). The local LD rep
RecentGALEX
appears
high,
as noted in Wyde
adetermination
likely range of dust-correcteofminmeas
average AFUV, AFUV to the best
starformation
rateconv
theKennicutt(1998) SFR
corrected(SFR) Ha measurements
corrected range. Although we hlution in the dust correction
Supernova
rateweismight
flux-limited
samplesdust-attenuation
correction
inferred fromSFR. vers
this further in future work.
The FUV is tracing a predo
lation (star-forming and starbur
integrated measures much mor
wavelengths (cf. Wolf et al.
significant population of UV(0.6 ! z ! 1.2). We will compar
axies with their high-redshift L2003). In the near future our s3. Flux and Event Rate
• Integrated flux (cmAndo, Astrophys. J. 607, 20 (2004)−2 s −1)Eν > 11.3 MeV

Eν > 19.3 MeV

5.1

1.1

3. Flux and Event Rate
• Integrated flux (cm−2 s −1)

Eν > 11.3 MeV

Eν > 19.3 MeV

5.1

1.1

• Event rate at Super-K (yr )−1Ando, Astrophys. J. 607, 20 (2004)

Ee > 10 MeV

Ee > 18 MeV

5.2

2.5of the event comes from the• Most
relatively nearby universe (z<1).

4. Detectability and Current Status
Background Events
10SRN10.1
1010.10204060

80

10001020304050

Ando, Sato & Totani, Astropart. Phys. 18, 307 (2003)

Atmospheric νµ → invisible µ → decay eEvents / year / 22.5 kton / 4 MeV

Observational Result
by Super-K
3• Analysis using data for141496 days (4.1 yr).

12

• As the result, they could10

not find positive signal.

8• Upper limit on the SRN

6flux (Eν > 19.3 MeV):

41.2 cm −2 s −12020304050607080(90% C.L.)

Energy (MeV)

Malek ofetSRN
al. 2003
FIG. 2: Energy spectrum
candidates. The dotted anddash-dot histograms are the fitted backgrounds from invisible
muons and atmospheric νe . The solid histogram is the sum ofJust above the prediction(1.1 cm-2 s-1)

Implication from the Limite Concordance Cosmic Star Formation Rate

5

• Super-K limit can beused constrain thesupernova rate.

• It excludes someregion, which is allowedby the astronomical
observations.

Strigari, Beacom, Walker & Zhang 2005
Figure 1. Observational results for the Cosmic Star Formation Rate, with theconversion
SNII Fukugita
rate on the rightaxis using Equation(4). Theentire cross-hatchedseetoalso,& Kawasaki
2003; Ando
2004
plus shaded region is consistent with the results of the 2dF and SDSS cosmic opticalspectrum [30, 31]. The upper cross-hatched region is ruled out by the limit on theConstraint on Supernova Parameters
4015.

Super-K with GdCl3

10..

5bdc0..

a30

52aIMBL! [10 erg]

dN/dE 1/[year 4MeV 22.5kton]

Super-K Analysis

Excluded by Super-K
DSNB Flux Limit

Kam-II2010bc102030
Visible Energy [MeV]

001020
Average Energy [MeV]

30In preparation with J. F. Beacom and H.Yuksel

Constraint on Supernova Parameters
4015.

10..

5bdc010..

2030
Visible Energy [MeV]

a3052

a

Super-K with GdCl3

L! [10 erg]

dN/dE 1/[year 4MeV 22.5kton]

Super-K Analysis

Excluded by Super-K
DSNB Flux Limit

2010bd001020
Average Energy [MeV]c30

In preparation with J. F. Beacom and H.Yuksel5. Prospects of Future Detectors
GADZOOKS!

• Delayed coincidence

signal of neutrons taggedby Gd.

• It_ enables to distinguishνe from other flavors orµ-induced events.

• It opens up energy
Beacom and Vagins 2004

window at 10-30 MeV
for the SRN detection.

Energy Window for the SRN Detection
SRN

Energy Window

1010.1020

Energy Window

1010.14060

80100010203040

50

Atmospheric νµ → invisible µ → decay e• Solar ν or invisible µ events becomeereducible!!

SRN Event at Gd-H2O Detectorsfrom Beacom

Strigari, Kaplinghat, Steigman & Walker 2004

SRN at Liquid Argon Detector
Cline 1990s; Cocco et al. 2004

• Liquid argon detectors aresensitive to νe.

•• Detectors:

νe + 40Ar → 40K* + e• ICARUS (3 kton)• Large mass TPC detector (100kton)• Several advantages comparedwith water Cerenkov.

SRN at Liquid Argon Detector
Cocco et al. 2004

Flux sensitivity: 1.6 cm−2 s−1 (for > 16 MeV; 3 kton 5 yr)
Complementary to Super-K, since it is mainly sensitive to νe.

Large Volume Detectors• Megaton water Cerenkov detectors• 5σ detection would be possible for acouple of years (pure water).

• Detection rate: ~ 100 /yr (Gd-loaded)• 100 kton liquid argon detectors•NSRN = 57 +/- 12 for 16–40 MeV(100 kton 5 yr; Cocco et al. 2004)

Neutrino Detection fromSupernovae in Nearby Galaxies
S. Ando, J. F. Beacom & H.Yüksel, astro-ph/0503321

If I don’t have enough time, click
here to jump to conclusions...

Supernova Rate in Nearby Galaxies
Karachentsev et al. 2004;
Cappellaro et al. 1999

NearbyNearbySupernovae
NearbySupernovae
Supernovae

JohnJohnBeacom,Beacom,TheTheOhi
OhiooState
StateUni
Universi
versityty

Partinar,versi
ty,ty,March2005
Particle
cleTheory
TheorySemi
Semi
nar,YaleYaleUni
Uni
versi
March2005

3 (1) supernovae per year within 10 (4) Mpc!

Detection Probabilities• Real chance to detect more

10.8

Detection Probability

than 1 or 2 events

P(!1) ; 12-38 MeV
P(!1) ; 18-30 MeV
P(!2) ; 15-35 MeV• More than 2-event
detection• Essentially background-

0.6

free0.4

0.2 Super-Kamiokande0021-Mton
detector
46
Distance D [Mpc]8• Accidental coincidence
rate of backgrounds: ~0.3 /yr• 1-event detection
10• Need astronomers’ help
to restrict time-bin.

Event and Background Spectra (in 1 day)• Backgrounds are:• Invisible μ (significantly0.15

dN/dE 1/[MeV Mton]

SN !!(4 Mpc)
DSNB (1 day)Invisible "!(1 day)suppressed with future
Gd-loaded detectors)

H 2O0.1• Diffuse supernova
H2O + GdCl3

0.05

neutrino background(DSNB): irreducible• Spallation products• SN ν from 4 Mpc will0010203040
Visible Energy [MeV]50

dominate the backgroundespecially with Gd-detectors

What’s the detection rate?
• Let us discuss only within 4 Mpc (If we extend up to 10 Mpc,
this could enhance further)• Multiple events (more than 2ν signal from burst):• SN rates are ~1 per year (from direct count)• Probability per SN is ~0.25• Therefore, rate would be >1×0.25×2=0.5 / yr
• Single events (1ν signal correlated with optical)• From similar argument, we get 1×0.4×1=0.4 / yr
• Then, total detection rate would be ~1 per year

6. Conclusions• SRN is a diffuse background of neutrinos

emitted from past (cosmological) supernovae.

• Current Super-K limit just above theoreticalpredictions.

• The detection would be within reach if we use
observational data for 5-10 years.

• Future larger volume detectors have a goodchance to detect them!

6. Conclusions (continued)• Supernova neutrinos from nearby galaxies could
be detectable with megaton detectors.

• Multiples are robust; singles can also be used withthe optical information.

• Physical implications are:• construction of supernova neutrino spectrum;• exact timing of the core collapse, which helps
gravitational wave searches.