Prospects of supernova neutrino observation by large detectors
Download
Report
Transcript Prospects of supernova neutrino observation by large detectors
Prospects of supernova
neutrino observation by
large detectors
Hisakazu Minakata
Tokyo Metropolitan University
Two attitudes
• Use SN data to learn about particle
physics properties of neutrinos
• Use known particle physics properties
of neutrinos to learn about physics
inside SN core
My personal view; 2nd viewpoint is
becoming more and more important!
October 2-5, 2007
NNN07@Hamamatsu
oscillation has been seen!
SK
October 2-5, 2007
KamLAND 07
K2K
NNN07@Hamamatsu
MINOS 07
1st
message;
mass &
mixing must
be taken
into account
October 2-5, 2007
NNN07@Hamamatsu
Matter profile of a progenitor star
Nomoto et al. model of SN1987a
October 2-5, 2007
NNN07@Hamamatsu
level crossing diagram in SN
Classification of SN spectrum pattern possible =>
October 2-5, 2007 next page; SN
NNN07@Hamamatsu
may distinguish mass hierarchy
October 2-5, 2007
NNN07@Hamamatsu
Classical picture
October 2-5, 2007
NNN07@Hamamatsu
Neutrino flux inside core
• 1st approximation =
LTE
• Departure from LTE
because strength of
interactions different
for e, e-bar, x (= e,
e-bar, , -bar)
spectrum depends
on flavor
• pinching of
spectrum
October 2-5, 2007
NNN07@Hamamatsu
Neutrino energy spectra in SN core
Livermore flux
Garching flux
Generally, <Ee> < <Ee-bar> < <Ex, >
but to what extent?
Unlike the case of solar , we still
do NOT have Standard SN model !
October 2-5, 2007
NNN07@Hamamatsu
Early era
of
optimism
October 2-5, 2007
NNN07@Hamamatsu
mass hierarchy from SN data?
Inverted mass hierarchy +
measurable 13 =>
e-bar-x-bar swap
obs. consequences if
sizable spectrum
difference between e-bar
and x
HM-H.Nunokawa 01,
Lunardini-Smirnov 0204, Kachelriess et al. 0
２ Beacom et al. 06 +
many others
October 2-5, 2007
NNN07@Hamamatsu
Invitation
to SN
model
independent
methods
October 2-5, 2007
NNN07@Hamamatsu
Determining mass hierarchy by earth
matter effect
SN simulation independent, it works even
for very similar e-bar and x spectra
• Use earth matter effect
• Suppose that 13 is so large that it can be
measured by the next generation experiments
=> PH=0 (adiabatic H resonance)
• earth matter effect YES＝＞normal hierarchy
• earth matter effect NO＝＞inverted hierarchy
October 2-5, 2007
NNN07@Hamamatsu
It is a very good idea, but rather demanding …
Effect of a few % S/N=106/107
October 2-5, 2007
NNN07@Hamamatsu
Dighe et al. 03
2nd method for detecting earth
matter effect; Detecting wiggles
Dighe et al. 03
October 2-5, 2007
NNN07@Hamamatsu
In reality, however, ..
October 2-5, 2007
NNN07@Hamamatsu
Does shock wave help ?
How reliable is the estimation
October
2-5, 2007
of shock
wave strength?NNN07@Hamamatsu
R. Tomas et al. 04
Neutronization burst
• Neutronization burst
=> robust signature of
many SN simulations
• Normal mass
hierarchy +
measurable 13 =>
disappearance of
neutronization peak
• Requires megaton
detector + Gd
October 2-5, 2007
100% neutron tag assumed,
Kachelriess et al 04
NNN07@Hamamatsu
Observatio
nal
diagnostics
of SN core
October 2-5, 2007
NNN07@Hamamatsu
There have been some interests in flavor dependent
reconstruction of SN fluxes since sometime ago
EuroConference on Neutrinos in
Seminar@INT,Seattle 00 (JB)
2-5, 2007
NNN07@Hamamatsu
theOctober
Universe,
Lenggries 01 (HM)
Flavor dependent reconstruction of
fluxes; water Cherenkov only
• SN@10 kpc, 3 effective
fluxes e, e-bar, x
• Parametrize the fluxes with
(1) total energy (2)
average energy (3)
pinching parameter
• 3 parameters / flavor => 9
parameter fit
e-bar absorption reaction
in water Cherenkov (HK
with fiducial mass 720 kton
assumed)
• What’s else in 2050?
October 2-5, 2007
NNN07@Hamamatsu
Reduced analysis; only e-bar data +
pinching parameter fixed
= Ee-bar/Ex
HM, Nunokawa,
Tomas, Valle 02
October 2-5, 2007
= Lx/Le-bar
NNN07@Hamamatsu
A full
analysis
leads to an
unexpected
degeneracy
!
October 2-5, 2007
NNN07@Hamamatsu
Continuous degeneracy in SN flux
parameters
pinching
parameter fixed
or varied
6 parameter fit, assume Case A or C; HMNunokawa-Tomas-Valle,
toNNN07@Hamamatsu
appear soon
October
2-5, 2007
SN parameter degeneracy continued 1
October 2-5, 2007
NNN07@Hamamatsu
SN parameter degeneracy continued 2
October 2-5, 2007
NNN07@Hamamatsu
Simple reason for the degeneracy
October 2-5, 2007
NNN07@Hamamatsu
How to
resolve
degeneracy
?
October 2-5, 2007
NNN07@Hamamatsu
Possible ways out
• More reactions in water Cherenkov
detector;
e+16O -> 16F+e-, x+16O -> x+16O*,
e+e -> e+e etc.
• Combine other detectors;
• Liquid scintillator etc.
• Resolution of degeneracy looks
nontrivial because e-bar absorption
reaction is statistically overwhelming
Of course neutron tag (Gd) helps
October 2-5, 2007
NNN07@Hamamatsu
Supplement
ary
detector;
an example
October 2-5, 2007
NNN07@Hamamatsu
Running !
October 2-5, 2007
NNN07@Hamamatsu
K.Scholberg@Nu2006
HALO - a Helium and Lead Observatory
Philosophy - to produce a
– Very low cost
– Low maintenance
– Low impact in terms of lab
resources (space)
– Long-term, high livetime
dedicated supernova detector
Slides taken/modified from:
October 2-5, 2007
NNN07@Hamamatsu
HALO – Phase 1 and 2
Phase 1: 80 tonnes of Pb
from decommissioned
Deep River Cosmic-ray
station
~285 m 3He proportional
counter neutron
detectors (NCDs) plus
DAQ from SNO
Phase2: Full ~700m of
3He counters and
possibly 130 m of 10BF3
counters
Increased volume of lead
October 2-5, 2007
NNN07@Hamamatsu
HALO - Monte Carlo Studies
Tonnes of Pb
Neutron
Capture
Efficiency
(fid. volume)
Length of
NCDs used (m)
Detected
Neutrons
(SN @ 10kpc)
14 kg/cm
--1000
--55%
--700
--372
8 kg/cm
80
560
31%
60%
95
700
22
246
4 kg/cm
80
280
48%
79%
190
700
31
167
2.7 kg/cm
80
189
57%
83%
285
700
36
127
Pb / 3He ratio
F. Fleurot
October 2-5, 2007
NNN07@Hamamatsu
New developments;
October 2-5, 2007
NNN07@Hamamatsu
Collective transformation at high
densities; long history
•
•
•
•
•
•
•
•
Pantaleone 92
Samuel et al. 93-96
Fuller-Qian 95-96
Pastor-Raffelt-Semikoz 02
Duan-Fuller-Qian 05-07
Raffelt et al. 06-07
Fogli et al. 07
Raffelt-Smirnov 07, and more ? …
October 2-5, 2007
NNN07@Hamamatsu
Spin precession analogy
flavor oscillation/conversion can be cast into an
analogous form with spin precession in magnetic field
B=(sin2, 0, -cos2)
Mikheyev-Smirnov 86, Smirnov in ``New Era in Neutrino
Physics’’@TMU,
Tokyo
98
October 2-5,
2007
NNN07@Hamamatsu
9
Neutrino mass hierarchy (and 13) set initial conditions and fate.
Normal hierarchy:
Pendulum starts in ~downward
(stable) position and stays nearby.
No significant flavor change.
Inverted hierarchy:
((
))
((
Pendulum starts in ~upward (unstable)
position and eventually falls down.
Significant flavor changes.
13 sets initial misalignment with vertical. Specific value
not much relevant (provided that 13 >0).
Only for 13 =0 exactly, initial conditions are “frozen”.
This slide taken from: Eligio Lisi@TAUP07
Normal
Pee
1-Pee
Inverted
October 2-5, 2007
NNN07@Hamamatsu
11
Our results for the spectral split/swap
(inv. hier.)
Initial fluxes at the
neutrinosphere (r~10 km)
Final fluxes at the end of
collective effects (r~200 km)
[Single-angle approximation]
This slide taken from: Eligio Lisi@TAUP07
Conclusion
• If 13 extremely small, SN may contribute to
determination of mass hierarchy and (if s132 < 10-5
or s132 > 10-3 )
• But, SN flux model independent method required
• Collective transformation in high density region
=> good hope to distinguish hierarchy
• Flavor-dependent reconstruction of SN fluxes
important but highly nontrivial
what is
the required minimal set of detectors that can run
for a long time?
• Other methods for SN core diagnostics? Gwave?
October 2-5, 2007
NNN07@Hamamatsu
Supplement
ary slides
October 2-5, 2007
NNN07@Hamamatsu
Garching vs pinched Fermi-Dirac
Garching parametrization
Keil et al.
Pinched Fermi-Dirac
parametrization
October 2-5, 2007
NNN07@Hamamatsu