Neutrino Burst from Supernovae and Neutrino Oscillation

1
Neutrino Burst from Supernovae and Neutrino
Oscillation
-What is the effect of neutrino OSC on explosion
and the detection? -Can we extract OSC
parameters from the neutrino observations ?

• Katsuhiko Sato (Univ.Tokyo)
• Collaborators
• K. Takahashi, S.Ando, T. Totani, K. Kotake, S.
  Yamada,
• T. Shimizu, S. Ebisuzaki
• J. Wilson, S. Dalhed, A. Burrows and T. Thompson

2
Plan of this talk

• Introduction
• A brief review of gravitational collapse-driven
  supernova
• Neutrino OSC in supernova and the detection
• -Constraint on OSC parameters from the
  detection of supernova neutrino burst
• Effects of rotation on explosion and neutrino
  burst
• (Gravitational wave from supernovae)

3
Supernova1987A in LMC 23Feb.735AM(UT),1987

• 10 trillion neutrinos passed through your body.
• Huge water Cerenkov counters could detect this
  neutrino burst,
• 11 events by Kamiokande
• 8 events by IMB .

Direct evidence that SN is triggered by
gravitational collapse of stellar cores.
Remarkable achievement which remains in history.
4
Nobel Prize was awarded to Dr. M. Koshiba, the
head of Kamiokande, Professor emeritus of the
Univ. of Tokyo.

• From http//www.nobel.se/

We have been waiting the prize more than 15 years
!
5
Now huge neutrino detectors are running!

• If a supernova appears at the Galactic center,
  then almost
• 10,000 events at SK and 350 events at
  SNO are expected.

Total mass10,000t, Fiducial mass3,200t 30xKamII
1,000tD2O, 1.400t H2O
800 events At LVD.
Now we must consider seriously what
astrophysics/physics are obtained from the
detection of supernova neutrino burst.
6

• Collapse of Stellar Cores and Neutrino Trapping
• (K. Sato75)

?
?

• 56Fee-gt56Mn?e

If M gt 8-10 Msolar, Iron core is formed.

• 10 9.5g/cm 3

Unstable and begins to collapse. Neutrinos can
escape from the core without scattering.

• 10 11g/cm 3 The mean free path becomes shorter
  than
• the core radius, core,
  lmfpltR.

• 10 12g/cm 3

The diffusion time tdif
lmfp
becomes longer than the characteristic collapsing
time scale tff .. tdif gttff ..
Neutrinos are trapped, and are degenerate in SN
cores.
7
Neutrino reactions in supernova cores
n-pair creations, annihilations
emission, absorption, scattering on nucleons
scattering on electrons
emission, absorption, scattering on nuclei
Neutrinos are trapped by the effect of coherent
scattering (Sato,75) since the cross section
proportional to A2 ,and is larger.
8
How nuclei melt into supernova matter / neutron
star matter ?
Coherent scattering depends on the size and
shape of nuclei .
Just after the glitches of pulsars were
discovered.
9
How nuclei melt in the course of collapse?
Important for opacity Nuclear Pasta Structure

• With increasing matter density, the shape changes
  from sphere,cylinder,slab, cylindrical
  bubble,spherical bubble and eventually becomes
  homogeneous.
• (Ravenhall Pethick.,83, Hashimoto et al,84,
  Oyamatsu et al., 84,Maruyama et al., 98,
  Watanabe et al., 00, and 01, Iida et al.,01)

Essentially this change is described by the
surface energy minimum principle.
Oyamatsu,93
QMD method is suitable for investigating the
melting by finite temperature (Maruyama et al.
98). Recently we improved this method and
succeeded to construct pasta structure (Watanabe
et. al .,01,02,03).
From Oyamatsu et al., 84
Perturbation analysis with the analogy of liquid
crystal Pethick, Potekhin,98, Watanabe et al., 00
How the structure changes with increasing
temperature?
10
Results of QMD calculation (Watanabe,Sato,Yasuoka,
Ebisusaki PRC 02)

• Model
• N 2048
• T0.1MeV
• Xp/(pn)0.3

Sphere(0.1?0)
cylinder (0.18?0)
slab (0.35?0)
Cylinder hole (0.5?0)
Spherical hole (0.55?0)
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Preliminary result on the melting with increasing
temperature
ModelN 2048,?0.35?0 , Xp/(pn)0.5
T1MeV
T0.1MeV (cylinderslab)
T2MeV (slab)
T3MeV
T5MeV
T4MeV (almost homogeneous)
12
Two-point correlation function ? of the nucleon
density fluctuations d
disappearance of long-range correlation at T5MeV
?(r)0 at larger r
uniform phase at Tgt4-5MeV
13
Nucleon Distributions for Xp/(pn)0.3 and
?0.175?0
Cylinder phase at T0 ?0.175?0 N2048, Np614,
Nn1434 box size41.394fm
T3, 4MeV Nuclear surface cannot be identified
by an isodensity surface.
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Nucleon Distributions for x0.3 and ?0.35?0
Slab phase at T0 ?0.35?0 N2048, Np614,
Nn1434 box size32.85fm
T3MeV Nuclear surface cannot be identified by
an isodensity surface.
15
Phase Diagrams for x0.3
? 0 H gt 0
? lt 0 H gt 0
? 0 H 0
? lt 0 H lt 0
? gt 0 H lt 0
? gt 0 H gt 0
? 0 H lt 0
Structure with ?lt0 (intermediate phase)
Sponge-like
Euler characteristic
? (number of isolated regions) (number of
tunnels) (number of cavities)
x0.3
phase-separating region
limit for identification of nuclear surface
Still preliminary, but systematic investigation
is in progress.
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-10 15g/cm 3
shock
The core bounces and the unshocked inner core is
formed.The shock is generated at the
surface. Unshocked core playas a role of spring
for explosion.
Inner core
If the shock is sufficiently strong, the star
explodes Prompt explosion However, most
simulations show it is insufficient for
explosion, and stalled . No prompt explosion
occurs in realistic sim.

• ?

?
?
?
Inner core
?
?
Eventually the shock revived by ? deposition,
and outer shells are expelled. Delayed
Explosion(Wilson)
?
?
?
17
An example of delayed explosion late time
explosion by ?-heating
The stalled shock is revived by the neutrino
deposition from the proto-neutron star. Wilson
82
18
The latest example of LLL group the general
relativistic core-collapse simulation with full
?transport calculation (Totani, Sato, Dalhed,
Wilson,98)Pre-supernova ModelWeaver
Woosley 20 Solar Mass.
Neutrino Burst from SN
108
109
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1.The latest neutrino burst models of the LLL
group (pre-SN modelWeaver, Woosely 20 Msolar )
(Totani,Sato,Dalhed, Wilson,98). Time
evolution of ? luminosity the average energies
(?µ??t and their antiparticles)
ltEgt23MeV
ltEgt15MeV
ltEgt10MeV
20
Latest simulations with updated neutrino
processes and sophisticated neutrino transfer
show no explosion.
Liebendoerfer et al. 01
Rampp et al. 00,03
Thomson et al. 02
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Why no explosion?
1. Microphysics (neutrino processes, EOS etc.)
are still insufficient ?
Something important processes are missed? 2.
Computational methods ( neutrino transfer ,
convection, etc) are still unreliable? 3.
Spherical symmetric simulation is inadequate.
Stellar rotation and/or magnetic field play
essential role for explosion ?

• In the present neutrino OSC analysis of
  supernova neutrino burst,
• We employ two models
• LLL models (Totani et al, 98) as the full
  neutrino burst model ( 15 sec). (only one full
  time neutrino burst model available today)
• 2. Burrowss group model (Thomson et al, 02)
  as an early phase burst model ( 0.2 sec.). (as
  a representative of latest simulations)

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2.TBP (Thompson,Burrows,Pint) Model (early 0.2
sec burst)
(Takahashi, Sato, Burrows, Thompson, PRD03)
Evolution of luminosity
Evolution of average energies
ltEgt15MeV
ltEgt12MeV
ltEgt20MeV
The early phase analysis has advantage in that it
is not affected whether the remnant is a neutron
star or a black hole.
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Neutrino OSC and Neutrino Burst from Supernovae
SK and SNO showed clearly neutrinos have masses,
and oscillate.

• What is the effect on Explosion ?

If we take values of oscillation parameters
suggested by solar ? and atmospheric ? obs., no
resonances occur in the core, but they occur in
the mantle of SN (CO shell, He shell) .No
effect on explosion.
Note If ?m 101-2ev, resonance happens in the
hot bubble region, energy deposition is greatly
enhanced because of the large cross section of
high energy electron type neutrinos. Explosion
is greatly strengthened (Shramm et al , ..)
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2.What are the effects on the detection?
In order to get original information of cores and
to extract the explosion mechanism, it is
essentially important to know how the spectra of
the neutrino burst are modified by neutrino OSC.
3. Can we extract osc parameters from the
neutrino observation if a Galactic supernova
appears ?
Supernova is the strongest source of three type
of neutrinos in the universe. (Sun e- type only,
atmospheric neutrinos e- and µ- type) i) Can we
obtain the implication on the parameter
,which has not yet determined? ii) Can we solve
the mass hierarchy problem ? Inverted mass
hierarchy model (m?µgtm?egtgtm?t) has not yet ruled
out by experiments.
25
Resonance in Supernova Mantle normal hierarchy
model-

• Resonance Condition

Dighe,Smirnov, 00 Lunardini,A.Y.Smirnov,01 Minak
ata, Nunokawa.01 Takahashi,Sato, 01 Takahashi
et al,01 .
He
H
C,O
Ne,Mg
Fe
Si
26
Neutrino OSC Models
Inverted mass hierarchy models are denoted
as Inv-LMA-L, Inv-LMA-S, Inv-SMA-L, Inv-SMA-S.

• from solar neutrinos, upper
  limit from nuclear
• atmospheric neutrinos
  reactor

27
Time evolution of conversion probability for
LMA-L and
LMA-S
?e
?e
?e
?t
?t
?t
28
Event rate at SK for LLL neutrino burst Model

• We calculate the event rate and
• the energy spectra at SK, assuming
• SN appeared at GC(10kpc).

Most of events come from
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Time evolution of event rate expected at SK
30
Time-integrated Energy spectra and Event numbers
Most of events come from .
? effect of vacuum OSC. ?e ?µ?t ?Models with
larger mixing angle deviate from no
osc model.

• Can be distinguished from the ratio of event rate
  at the peak region to the tail region.

31
Event rate at SNO for LLL neutrino burst Model

• 1,000t D2O, (1.400t H2O)

Important reactions
Electron type neutrinos can be detected
efficiently by


We discuss only CC, not NC.
32
Time evolution of event rate expected SNO
33
Energy spectra and Event numbers

• Events come from the both .
• ? both effects, vacuum OSC and MSW.
• with increasing mixing angle, event number
  increases.

Can be distinguished from the ratio of event rate
at 15Mev region to the Egt30Mev region.
34
Crossing diagram for antineutrinos
Case for inverted mass hierarchy

• Case of Normal mass hierarchy

• Case of inverted mass hierarchy

No Level crossing
m3
H-resonance happens for anti neutrinos
m2
m1
If the resonance is adiabatic (large ),
conversion occurs effectively.
ne
H-resonance
Event rate is greatly increased !
35
The time-integrated energy spectra
237
185
111

• ?e events are increased by H-resonance ?t ??e.

68
13,084 events
190
10,245events
82
118
36
In order to extract information of mixing angle,
we define the ratios, R(SK) and R(SNO),

• R(SK) and R(SNO) are good indicators for neutrino
  OSC.

37
Plots on RSK-RSNO plane (Error bars represent
only statistical errors.)
Anti neutrino events can be subtracted by neutron
detection.

• nor-LMA-s and inv-LMA-s are degenerate, but
  inv-LMA-L is clearly discriminated from
  nor-LMA-L. If the mixing parameter is -L,
  mass hierarchy problem is solved.

38
Analysis by using the TBP burst model

• This simulation was done by using the updated
  neutrino processes and sophisticate neutrino
  transfer program.
• Available data are only the initial 0.2
  second of the neutrino burst, but this early
  phase analysis has advantage that it is not
  affected whether the remnant is a neutron star or
  a black hole.
• We investigated the dependence on the
  pre-supernova mass. We found the results are
  almost independent of the masses.

39
Evolution of the burst and time-integrated energy
spectra
(TBP model)
40
Presupernova-mass dependence on R(SK)-R (SNO)
Plots
Error bars come from only statistical errors,
which are increased because the event numbers
becomes small.
nor-LMA-s and inv-LMA-s are degenerate, but
inv-LMA-L is clearly discriminated from
nor-LMA-L. If the mixing parameter is -L,
mass hierarchy problem is solved.
41
The Earth effects on the supernova neutrinos
Supernova neutrinos oscillate and are reconverted
each other in the earth. The spectra are greatly
modified if they pass through the earth.
(Dighe Smirnov (00,01), Takahashi Sato (00,
01) )
SK 9500 events
LVD 850 events
Earth
SNO 300 events
Pass length when SN occurs at Galactic center.
t0 the time at which the SN is aligned with
the Greenwich meridian.
42
In order to analyze the earth effect and to get
information on OSC parameters, we need to know
supernova direction, which is determined
accurately by electron scattering.

• Electron scattering has sharp forward peak, but
  the fraction of is 3 (282 events/total 8441
  for Galactic Center Supernova at SK)

By using the least-square method, we get the
direction within the accuracy 7degree (1s)? Ando
Sato, 01
Monte Carlo Simulation of recoiled e- (e)
direction for SK Most of the events are by
43
Modification of the spectra
Spectra are greatly modified by MSW effects in
the earth. Case LMA-S, nadir angle 0 (pass
through the center)
44
The spectra depend sensitively on the nadir angle
and
Since the nadir angle can be determined from the
scattering by electrons at SK or SNO,
could be determined more precisely by the earth
effects.
nadir angle dependence
dependence
45
Supernova Relic Neutrinos and its detectability
Ando, Sato, Totani 02, Ando , Sato 03

• There should be a diffuse background of neutrinos
  emitted from past supernovae. (Supernova Relic
  Neutrino Background, or SRN)

Flux depends on the history of supernova rate
and neutrino oscillation parameters.
We investigated the dependence of the flux on the
OSC parameters, and effects on the
detectability. Flux is increased greatly if
LMA, and if inverted mass hierachy.
46
History of Supernova Rate

• The SN rate model is evaluated from corresponding
  SFR model based on optical/UV observation by HST.
• Particularly, behavior at high redshift is not
  known well. (Luminosity function is not
  established and dust extinction is unknown.)
• However, owing to energy redshift, neutrinos
  emitted at high-z contribute only to low energy
  region (, where SK does not have sensitivity).

Madau et al. (1996)
The uncertainty around here is not important so
much.
47
Flux for Various OSC Models

• We obtain the hardest spectrum for the INV-L
  model.
• The spectra for the other LMA models are
  degenerated.
• We also set upper limit for these oscillation
  models, by analyzing the spectrum with the SK
  observational result.

48
Theoretical prediction and Observational Limit
(SK)
Malek et al,03
The upper limit is more severe for the INV-L
model. (In spite of difficult observation, SK
upper limit is approaching the theoretical
prediction. It is expected constraints on OSC
parameters could be obtained near future.)
49
Effects of Rotation on the Supernova Explosion

• Massive stars have large angular momentum
• q J/(GM2/C) 10
• Implications of rotational collapse and Jet-like
  explosion from SN1987A observations.
• 1.Observation of asymmetry of expanding
  envelope by SPECKLE (Papalios, et. al. 89)
• 2.Observation of linear polarization of
  scattered photons (Cropper et al.88)
• 3. Rings suggest pre-supernova was rapidly
  rotating.

50
Many groups have been challenging the simulation
of rotational collapse of stellar cores.
Mesh code 2dim. LeBranc, Wilson Symbalisty Moenchm
eier et al (91) Yamada, Sato Shimizu, Yamada,
Sato(94,01) .. 3-dim. Shimizu, Yamada, Sato (94)
SPH (Smoothed Particle Hydrodynamics) Herant et
al (94) Fryer (99), Fryer et al (01)
Difficulties in simulation multi-dimension
neutrino transport general relativistic
treatment
All simulations are still preliminary ones.
51
Asymmetric n-heating due to rotation
Shimizu, Ebisuzaki, Sato, Yamada ,01

• If oblate proto neutron stars are formed due to
  centrifugal forces,
• more neutrinos are emitted in the direction of
  rotation axis.
• Assuming an oblate proto neutron star is formed,
  we carried out
• hydrodynamic simulation, and found that
  n-heating is enhanced
• near the rotation axis, and global convections
  are induced in heating regions.
• As the result, Jet like explosion is induced.

oblate proto neutron star
52
2D Rotational Collapse Simulations
Kotake, Yamada, Sato , ApJ595, 304 (03)
t 256ms
Shape of neutrino sphere becomes spheroid.
Temperature on the sphere
Density
5
Radius cm
T MeV
entropy
3
90
0
Neutrino luminosity and the average energy depend
on what direction we observe. We are
investigating whether implication on OSC
parameter could be obtained or not.
53
Gravitational Radiation from Axisymmetric
Rotational Core Collapse
Kotake, Yamada, Sato, PRD68, 044023 (03)

• Preceding works and recent works
• Moenchmeyer et al . 91
• Yamada, Sato, 97
• Zwerger Mueller 97
• Dimmelmeier et al. 02
• Shibata 03
• Kotake,Yamada, Sato 03
• Ott et al., 03

We calculated gravitational radiation by using
quadrupole radiation formula. Most preceding
works took simplified EOS, i.e. , pK?? , and
neutrino emission/ absorption/transport are
neglected. We carried out collapse simulation by
using realistic EOS (Relativistic MFA Shen et
al. 98 ) and included neutrino processes.
54
Theoretical prediction of hTT when SN appear at
Galactic center and detection limit
We carried out for various rotation models, and
found most of them are higher than TAMA detection
limit.
55
Example of wave pattern
Case of Moderate rotation
Case of strong differential rotation
Small fluctuations disappear because of
centrifugal force in the central core region.
If the gravitational wave is detected and wave
pattern is observed, information on the rotation
would be obtained.
Wave patterns depend on rotational speed and
distribution of angular momentum.
56
Summary

• ? Now huge neutrino detectors (SK, SNO,LVD,..)
• and supersensitive GW detectors (TAMA,LIGO,..)
  are working.
• 1.If SN appears at Galactic center, 10,000
  events (SK) , and 350 events (SNO) will
  be detected, and fruitful information on the
  explosion mechanism and neutrino OSC parameters
  would be obtained.
• More huge detector Hyper Kamiokande is
  proposed.
• 2.TAMA and LIGO would detect gravitational
  waves from Galactic supernovae if precise time of
  explosion is informed by SK, and implication on
  the rotational speed and the stiffness of EOS
  could be obtained.

Despite almost 40 years of intensive and
extensive studies, we still do not figure out how
the collapse-driven supernova occurs ? More
extensive and systematic studies on gravitational
collapse including realistic EOS and neutrino
transfer are necessary.