Prospects of supernova neutrino observation by large detectors Hisakazu Minakata Tokyo Metropolitan University Hisakazu Minakata Tokyo Metropolitan University

October 2-5, 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, oscillation has been seen! K2K SK MINOS 07 KamLAND 07

October 2-5, 1st message; mass & mixing must be taken into account

October 2-5, Matter profile of a progenitor star Nomoto et al. model of SN1987a

October 2-5, level crossing diagram in SN Classification of SN spectrum pattern possible => next page; SN may distinguish mass hierarchy

October 2-5,

October 2-5, Classical picture

October 2-5, 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, Neutrino energy spectra in SN core Garching flux Livermore flux Generally, but to what extent? Unlike the case of solar, we still do NOT have Standard SN model !

October 2-5, Early era of optimism

October 2-5, mass hierarchy from SN data? HM-H.Nunokawa 01, Lunardini-Smirnov , Kachelriess et al. 0 ２ Beacom et al many others Inverted mass hierarchy + measurable  13 => e-bar - x-bar swap obs. consequences if sizable spectrum difference between e-bar and x Inverted mass hierarchy + measurable  13 => e-bar - x-bar swap obs. consequences if sizable spectrum difference between e-bar and x

October 2-5, Invitation to SN model independent methods

October 2-5, Determining mass hierarchy by earth matter effect Use earth matter effect Suppose that  13 is so large that it can be measured by the next generation experiments => P H =0 (adiabatic H resonance) earth matter effect YES ＝＞ normal hierarchy earth matter effect NO ＝＞ inverted hierarchy SN simulation independent, it works even for very similar e -bar and x spectra

October 2-5, Effect of a few % S/N=10 6 /10 7 Dighe et al. 03 It is a very good idea, but rather demanding …

October 2-5, 2nd method for detecting earth matter effect; Detecting wiggles Dighe et al. 03

October 2-5, In reality, however,..

October 2-5, Does shock wave help ? R. Tomas et al. 04 How reliable is the estimation of shock wave strength?

October 2-5, Neutronization burst Neutronization burst => robust signature of many SN simulations Normal mass hierarchy + measurable  13 => disappearance of neutronization peak Requires megaton detector + Gd 100% neutron tag assumed, Kachelriess et al 04

October 2-5, Observatio nal diagnostics of SN core

October 2-5, EuroConference on Neutrinos in the Universe, Lenggries 01 (HM) There have been some interests in flavor dependent reconstruction of SN fluxes since sometime ago 00 (JB)

October 2-5, Flavor dependent reconstruction of fluxes; water Cherenkov only 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, Reduced analysis; only e -bar data + pinching parameter fixed  = E e-bar /E x HM, Nunokawa, Tomas, Valle 02  = L x /L e-bar

October 2-5, A full analysis leads to an unexpected degeneracy !

October 2-5, 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

October 2-5, SN parameter degeneracy continued 1

October 2-5, SN parameter degeneracy continued 2

October 2-5, Simple reason for the degeneracy

October 2-5, How to resolve degeneracy ?

October 2-5, Possible ways out More reactions in water Cherenkov detector;  e + 16 O -> 16 F+e-, x + 16 O -> x + 16 O*, 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, Supplement ary detector; an example

October 2-5, Running !

October 2-5, Philosophy - to produce a –Very low cost –Low maintenance –Low impact in terms of lab resources (space) –Long-term, high livetime dedicated supernova detector HALO - a Helium and Lead Observatory Slides taken/modified from:

October 2-5, HALO – Phase 1 and 2 Phase 1: 80 tonnes of Pb from decommissioned Deep River Cosmic-ray station ~285 m 3 He proportional counter neutron detectors (NCDs) plus DAQ from SNO Phase2: Full ~700m of 3 He counters and possibly 130 m of 10 BF 3 counters Increased volume of lead

October 2-5, Pb / 3 He ratio Tonnes of Pb Neutron Capture Efficiency (fid. volume) Length of NCDs used (m) Detected Neutrons 10kpc) 14 kg/cm % kg/cm % 60% kg/cm % 79% kg/cm % 83% HALO - Monte Carlo Studies F. Fleurot

October 2-5, New developments;

October 2-5, Collective transformation at high densities; long history Pantaleone 92 Samuel et al Fuller-Qian Pastor-Raffelt-Semikoz 02 Duan-Fuller-Qian Raffelt et al Fogli et al. 07 Raffelt-Smirnov 07, and more ? …

October 2-5, 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 Tokyo 98

9 Neutrino mass hierarchy (and  13 ) set initial conditions and fate.  13 sets initial misalignment with vertical. Specific value not much relevant (provided that  13 >0). Only for  13 =0 exactly, initial conditions are “ frozen ”. 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. (( )) (( This slide taken from: Eligio

October 2-5, Pee 1-Pee Inverted Normal

11 Initial fluxes at the neutrinosphere (r~10 km) Final fluxes at the end of collective effects (r~200 km) [Single-angle approximation] Our results for the spectral split/swap (inv. hier.) This slide taken from: Eligio

October 2-5, Conclusion If  13 extremely small, SN may contribute to determination of mass hierarchy and (if s ) 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? G- wave?

October 2-5, Supplement ary slides

October 2-5, Garching vs pinched Fermi-Dirac Garching parametrization Keil et al. Pinched Fermi-Dirac parametrization