Prospects of supernova neutrino observation by large detectors

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Prospects of supernova neutrino observation by
large detectors

• Hisakazu Minakata
• Tokyo Metropolitan University

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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!
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n oscillation has been seen!
SK
K2K
MINOS 07
KamLAND 07
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1st message ? mass mixing must be taken into
account
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Matter profile of a progenitor star
Nomoto et al. model of SN1987a
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? level crossing diagram in SN
Classification of SN ? spectrum pattern possible
gt next page SN ? may distinguish mass hierarchy
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Classical picture
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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

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Neutrino energy spectra in SN core
Garching flux
Livermore flux
Generally, ltE?egt lt ltE?e-bargt lt ltE?x, gt but to
what extent?
Unlike the case of solar ?, we still do NOT have
Standard SN model !
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Early era of optimism
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? mass hierarchy from SN ? data?
Inverted mass hierarchy measurable ?13 gt
?e-bar-?x-bar swap obs. consequences
if sizable spectrum difference between ?e-bar and
?x
HM-H.Nunokawa 01, Lunardini-Smirnov 02-04,
Kachelriess et al. 02 Beacom et al. 06 many
others
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Invitation to SN model independent methods
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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 gt
  PH0 (adiabatic H resonance)
• earth matter effect YESgtnormal hierarchy
• earth matter effect NOgtinverted hierarchy

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It is a very good idea, but rather demanding
Effect of a few S/N106/107
Dighe et al. 03
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2nd method for detecting earth matter effect
Detecting wiggles
Dighe et al. 03
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In reality, however, ..
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Does shock wave help ?
R. Tomas et al. 04
How reliable is the estimation of shock wave
strength?
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Neutronization burst

• Neutronization burst gt robust signature of many
  SN simulations
• Normal mass hierarchy measurable ?13 gt
  disappearance of neutronization peak
• Requires megaton detector Gd

100 neutron tag assumed, Kachelriess et al 04
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Observational diagnostics of SN core
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There have been some interests in flavor
dependent reconstruction of SN ? fluxes since
sometime ago
EuroConference on Neutrinos in the Universe,
Lenggries 01 (HM)
Seminar_at_INT,Seattle 00 (JB)
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Flavor dependent reconstruction of ? fluxes
water Cherenkov only

• SN_at_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 gt 9 parameter fit
• ?e-bar absorption reaction in water Cherenkov (HK
  with fiducial mass 720 kton assumed)
• Whats else in 2050?

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Reduced analysis only ?e-bar data pinching
parameter fixed
? E?e-bar/E?x
HM, Nunokawa, Tomas, Valle 02
? L?x/L?e-bar
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• A full analysis leads to an unexpected degeneracy
  !

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Continuous degeneracy in SN flux parameters
pinching parameter fixed or varied
6 parameter fit, assume Case A or C
HM-Nunokawa-Tomas-Valle, to appear soon
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SN parameter degeneracy continued 1
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SN parameter degeneracy continued 2
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Simple reason for the degeneracy
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How to resolve degeneracy?
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Possible ways out

• More reactions in water Cherenkov detector
• ?e16O -gt 16Fe-, ?x16O -gt ?x16O, ?ee -gt
  ?ee 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
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Supplementary detector an example
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Running !
K.Scholberg_at_Nu2006
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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
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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
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HALO - Monte Carlo Studies
Pb / 3He ratio Tonnes of Pb Neutron Capture Efficiency (fid. volume) Length of NCDs used (m) Detected Neutrons (SN _at_ 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
F. Fleurot
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New developments
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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 ?

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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_at_TMU, Tokyo 98
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Neutrino mass hierarchy (and ?13) set initial
conditions and fate.
This slide taken from Eligio Lisi_at_TAUP07
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Normal
Pee
1-Pee
Inverted
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Our results for the spectral split/swap (inv.
hier.)
Initial fluxes at the neutrinosphere (r10 km)
Final fluxes at the end of collective effects
(r200 km) Single-angle approximation
This slide taken from Eligio Lisi_at_TAUP07
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Conclusion

• If ?13 extremely small, SN may contribute to
  determination of mass hierarchy and (if s132 lt
  10-5 or s132 gt 10-3 )
• But, SN flux model independent method required
• Collective ? transformation in high density
  region gt 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? G-wave?

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Supplementary slides
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Garching vs pinched Fermi-Dirac
Garching parametrization Keil et al.
Pinched Fermi-Dirac parametrization