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Neutrinos and the stars

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1 Neutrinos and the stars
Supernova Neutrinos Georg Raffelt, MPI for Physics Lectures at the Topical Seminar Neutrino Physics & Astrophysics 17-21 Sept 2008, Beijing, China

2 Sanduleak -69 202 Supernova 1987A 23 February 1987 Tarantula Nebula
Large Magellanic Cloud Distance 50 kpc ( light years)

3 Supernova Neutrinos 20 Jahre nach SN 1987A

4 Crab Nebula

5 Stellar Collapse and Supernova Explosion
Onion structure Main-sequence star Hydrogen Burning Collapse (implosion) Helium-burning star Helium Burning Hydrogen Degenerate iron core: r  109 g cm-3 T  K MFe  1.5 Msun RFe  8000 km

6 Stellar Collapse and Supernova Explosion
Newborn Neutron Star ~ 50 km Proto-Neutron Star r  rnuc = 3  g cm-3 T  30 MeV Collapse (implosion) Neutrino Cooling

7 Stellar Collapse and Supernova Explosion
Newborn Neutron Star ~ 50 km Proto-Neutron Star r  rnuc = 3  g cm-3 T  30 MeV Neutrino Cooling Gravitational binding energy Eb  3  1053 erg  17% MSUN c2 This shows up as 99% Neutrinos 1% Kinetic energy of explosion (1% of this into cosmic rays) 0.01% Photons, outshine host galaxy Neutrino luminosity Ln  3  1053 erg / 3 sec  3  1019 LSUN While it lasts, outshines the entire visible universe

8 Neutrino Signal of Supernova 1987A
Kamiokande-II (Japan) Water Cherenkov detector 2140 tons Clock uncertainty 1 min Irvine-Michigan-Brookhaven (US) Water Cherenkov detector 6800 tons Clock uncertainty 50 ms Baksan Scintillator Telescope (Soviet Union), 200 tons Random event cluster ~ 0.7/day Clock uncertainty +2/-54 s Within clock uncertainties, signals are contemporaneous

9 SN 1987A Event No.9 in Kamiokande
Kamiokande Detector Hirata et al., PRD 38 (1988) 448

10 Thermonuclear vs. Core-Collapse Supernovae
Thermonuclear (Type Ia) Core collapse (Type II, Ib/c) Carbon-oxygen white dwarf (remnant of low-mass star) Accretes matter from companion Degenerate iron core of evolved massive star by nuclear burning at its surface Chandrasekhar limit is reached MCh  1.5 Msun (2Ye)2 C O L L A P S E S E T S I N Nuclear burning of C and O ignites  Nuclear deflagration (“Fusion bomb” triggered by collapse) Collapse to nuclear density Bounce & shock Implosion  Explosion Powered by gravity Powered by nuclear binding energy Gain of nuclear binding energy ~ 1 MeV per nucleon Gain of gravitational binding energy ~ 100 MeV per nucleon 99% into neutrinos Comparable “visible” energy release of ~ 3  1051erg

11 Supernova Neutrinos 20 Jahre nach SN 1987A
Explosion Mechanism for Core-Collapse SNe

12 Collapse and Prompt Explosion
Velocity Density Movies by J.A.Font, Numerical Hydrodynamics in General Relativity Supernova explosion primarily a hydrodynamical phenomenon

13 Why No Prompt Explosion?
Dissociated Material (n, p, e, n) Collapsed Core Undissociated Iron Shock Wave 0.1 Msun of iron has a nuclear binding energy  1.7  1051 erg Comparable to explosion energy Shock wave forms within the iron core Dissipates its energy by dissociating the remaining layer of iron

14 Neutrinos to the Rescue
Neutrino heating increases pressure behind shock front Picture adapted from Janka, astro-ph/

15 Supernova Delayed Explosion Scenario

16 Standing Accretion Shock Instability (SASI)
Mezzacappa et al.,

17 Gravitational Waves from Core-Collapse Supernovae
Müller, Rampp, Buras, Janka, & Shoemaker, “Towards gravitational wave signals from realistic core collapse supernova models,” astro-ph/ Asymmetric neutrino emission Bounce Convection The gravitational-wave signal from convection is a generic and dominating feature

18 Supernova Neutrinos 20 Jahre nach SN 1987A
Some Particle-Physics Lessons from SN 1987A

19 Neutrino Mass Sensitivity by Signal Dispersion
Time-of-flight delay of massive neutrinos SN 1987A (50 kpc) E  20 MeV, Dt  10 s Simple estimate or detailed maximum likelihood analysis give similar results mn ≲ 20 eV Future Galactic SN at 10 kpc (Super-K) Rise-time of signal ~ 10 ms (Totani, PRL 80:2040, 1998) mn ~ 3 eV Full signal (Nardi & Zuluaga, NPB 731:140, 2005) mn ~ 1 eV With late black-hole formation Cutoff “infinitely” fast (Beacom et al., PRD 63:073011, 2001) mn ~ 2 eV Future SN in Andromeda (Megatonne) D  750 kpc, Dt  10 s few tens of events mn ~ 1-2 eV

20 Early Lightcurve of SN 1987A
Expected bolometric brightness evolution Expected visual brightness evolution Neutrinos several hours before light Adapted from Arnett et al., ARAA 27 (1989)

21 Do Neutrinos Gravitate?
Neutrinos arrive a few hours earlier than photons  Early warning (SNEWS) SN 1987A: Transit time for photons and neutrinos equal to within ~ 3h Shapiro time delay for particles moving in a gravitational potential Longo, PRL 60:173,1988 Krauss & Tremaine, PRL 60:176,1988 Equal within ~ 10-3 Proves directly that neutrinos respond to gravity in the usual way because for photons gravitational lensing already proves this point Cosmological limits DNn ≲ 1 much worse test of neutrino gravitation Provides limits on parameters of certain non-GR theories of gravitation Photons likely obscured for next galactic SN, so this result probably unique to SN 1987A

22 The Energy-Loss Argument
Neutrino sphere SN 1987A neutrino signal Neutrino diffusion Late-time signal most sensitive observable Emission of very weakly interacting particles would “steal” energy from the neutrino burst and shorten it. (Early neutrino burst powered by accretion, not sensitive to volume energy loss.) Volume emission of novel particles

23 Too much hot dark matter
Axion Bounds 103 106 109 1012 [GeV] fa eV keV meV ma Experiments Tele scope CAST Direct search ADMX Too much hot dark matter Too much cold dark matter Globular clusters (a-g-coupling) Too many events Too much energy loss SN 1987A (a-N-coupling)

24 Sterile Neutrinos sin2(2Qes) ≲ 3  10-10 Active-sterile mixing
Electron neutrino appears as sterile neutrino in ½ sin2(2Qes) of all cases Average scattering rate in SN core involving ordinary left-handed neutrinos To avoid complete energy loss in ~ 1 s sin2(2Qes) ≲ 3  10-10

25 Sterile Neutrino Limits
See also: Maalampi & Peltoniemi: Effects of the 17-keV neutrino in supernovae PLB 269:357,1991 Hidaka & Fuller: Dark matter sterile neutrinos in stellar collapse: alteration of energy/lepton number transport and a mechanism for supernova explosion enhancement PRD 74:125015,2006

26 Supernova 1987A Limit on Large Extra Dimensions
SN core emits large flux of KK gravity modes by nucleon-nucleon bremsstrahlung Large multiplicity of modes RT ~ 1011 for R ~ 1 mm, T ~ 30 MeV Cullen & Perelstein, hep-ph/ Hanhart et al., nucl-th/ SN 1987A energy-loss argument: R < 1 mm, M > 9 TeV (n = 2) R < 1 nm, M > 0.7 TeV (n = 3) Originally the most restrictive limit on such theories, except for cosmological arguments

27 Supernova Neutrinos 20 Jahre nach SN 1987A
Neutrinos from the Next Galactic Supernova

28 Local Group of Galaxies
Events in a detector with 30 x Super-K fiducial volume, e.g. Hyper-Kamiokande 30 60 250

29 Core-Collapse SN Rate in the Milky Way
SN statistics in external galaxies Core-collapse SNe per century 1 2 3 4 5 6 7 8 9 10 van den Bergh & McClure (1994) Cappellaro & Turatto (2000) Gamma rays from 26Al (Milky Way) Diehl et al. (2006) Historical galactic SNe (all types) Strom (1994) Tammann et al. (1994) No galactic neutrino burst 90 % CL (25 y obserservation) Alekseev et al. (1993) References: van den Bergh & McClure, ApJ 425 (1994) 205. Cappellaro & Turatto, astro-ph/ Diehl et al., Nature 439 (2006) 45. Strom, Astron. Astrophys. 288 (1994) L1. Tammann et al., ApJ 92 (1994) 487. Alekeseev et al., JETP 77 (1993) 339 and my update.

30 Nearby Galaxies with Many Observed Supernovae
M83 (NGC 5236, Southern Pinwheel) D = 4.5 Mpc NGC 6946 D = (5.5 ± 1) Mpc Observed Supernovae: 1923A, 1945B, 1950B, 1957D, 1968L, 1983N Observed Supernovae: 1917A, 1939C, 1948B, 1968D, 1969P, 1980K, 2002hh, 2004et, 2008S

31 Large Detectors for Supernova Neutrinos
MiniBooNE (200) LVD (400) Borexino (100) Baksan (100) Super-Kamiokande (104) KamLAND (400) In brackets events for a “fiducial SN” at distance 10 kpc IceCube (106)

32 SuperNova Early Warning System (SNEWS)
Neutrino observation can alert astronomers several hours in advance to a supernova. To avoid false alarms, require alarm from at least two experiments. Super-K IceCube Coincidence Server @ BNL Alert LVD Supernova 1987A Early Light Curve Others ? astro-ph/

33 Simulated Supernova Signal at Super-Kamiokande
Accretion Phase Kelvin-Helmholtz Cooling Phase Simulation for Super-Kamiokande SN signal at 10 kpc, based on a numerical Livermore model [Totani, Sato, Dalhed & Wilson, ApJ 496 (1998) 216]

34 Supernova Pointing with Neutrinos
95% CL half-cone opening angle Neutron tagging efficiency None 90 % SK 7.8º 3.2º SK  30 1.4º 0.6º Beacom & Vogel: Can a supernova be located by its neutrinos? [astro-ph/ ] Tomàs, Semikoz, Raffelt, Kachelriess & Dighe: Supernova pointing with low- and high-energy neutrino detectors [hep-ph/ ]

35 IceCube as a Supernova Neutrino Detector
Each optical module (OM) picks up Cherenkov light from its neighborhood. SN appears as “correlated noise”. About 300 Cherenkov photons per OM from a SN at 10 kpc Noise < 500 Hz Total of 4800 OMs in IceCube IceCube SN signal at 10 kpc, based on a numerical Livermore model [Dighe, Keil & Raffelt, hep-ph/ ] Method first discussed by Halzen, Jacobsen & Zas astro-ph/

36 LAGUNA - Approved FP7 Design Study
Large Apparati for Grand Unification and Neutrino Astrophysics (see also arXiv: )

37 Supernova Neutrinos 20 Jahre nach SN 1987A
Neutrinos From All Cosmic Supernovae

38 Diffuse Background Flux of SN Neutrinos
1 SNu = 1 SN / 1010 Lsun,B / 100 years Lsun,B = 0.54 Lsun = 2  1033 erg/s En ~ 3  1053 erg per core-collapse SN 1 SNu ~ 4 Ln / Lg,B Average neutrino luminosity of galaxies ~ photon luminosity Photons come from nuclear energy Neutrinos from gravitational energy For galaxies, average nuclear & gravitational energy release comparable Present-day SN rate of ~ 1 SNu, extrapolated to the entire universe, corresponds to ne flux of ~ 1 cm-2 s-1 Realistic flux is dominated by much larger early star-formation rate  Upper limit ~ 54 cm-2 s-1 [Kaplinghat et al., astro-ph/ ]  “Realistic estimate” ~ 10 cm-2 s-1 [Hartmann & Woosley, Astropart. Phys. 7 (1997) 137] Measurement would tell us about early history of star formation

39 Experimental Limits on Relic Supernova Neutrinos
Super-K upper limit 29 cm-2 s-1 for Kaplinghat et al. spectrum [hep-ex/ ] Upper-limit flux of Kaplinghat et al., astro-ph/ Integrated 54 cm-2 s-1 Cline, astro-ph/

40 DSNB Measurement with Neutron Tagging
Future large-scale scintillator detectors (e.g. LENA with 50 kt) Inverse beta decay reaction tagged Location with smaller reactor flux (e.g. Pyhäsalmi in Finland) could allow for lower threshold Pushing the boundaries of neutrino astronomy to cosmological distances Beacom & Vagins, hep-ph/ [Phys. Rev. Lett., 93:171101, 2004]

41 Supernova Neutrinos 20 Jahre nach SN 1987A
Oscillations of Supernova Neutrinos

42 Structure of Supernova Neutrino Signal
1. Collapse (infall phase) 2. Shock break out 3. Matter accretion 4. Kelvin-Helmholtz cooling Traps neutrinos and lepton number of outer core layers

43 Neutronization Burst as a Standard Candle
Different Mass Neutrino Transport Nuclear EoS If mixing scenario is known, perhaps best method to determine SN distance, especially if obscured (better than 5-10%) Kachelriess, Tomàs, Buras, Janka, Marek & Rampp, astro-ph /

44 Flavor-Dependent Fluxes and Spectra
Prompt ne deleptonization burst Broad characteristics Duration a few seconds En ~ MeV En increases with time Hierarchy of energies Approximate equipartition of energy between flavors nx _ However, in traditional simulations transport of nm and nt schematic Incomplete microphysics Crude numerics to couple neutrino transport with hydro code ne ne Livermore numerical model ApJ 496 (1998) 216

45 Flavor-Dependent Neutrino Fluxes vs. Equation of State
Wolff & Hillebrandt nuclear EoS (stiff) Lattimer & Swesty nuclear EoS (soft) Kitaura, Janka & Hillebrandt, “Explosions of O-Ne-Mg cores, the Crab supernova, and subluminous Type II-P supernovae”, astro-ph/

46 Level-Crossing Diagram in a SN Envelope
Normal mass hierarchy Inverted mass hierarchy Dighe & Smirnov, Identifying the neutrino mass spectrum from a supernova neutrino burst, astro-ph/

47 Spectra Emerging from Supernovae
Primary fluxes for After leaving the supernova envelope, the fluxes are partially swapped Normal Inverted sin2(2Q13) ≲ 10-5 ≳ 10-3 Any Mass ordering sin2(Q12)  0.3 cos2(Q12)  0.7 Case A B C Survival probability

48 Oscillation of Supernova Anti-Neutrinos
Measured spectrum at a detector like Super-Kamiokande Assumed flux parameters Flux ratio No oscillations Earth effects included Oscillations in SN envelope Mixing parameters P(Dighe, Kachelriess, Keil, Raffelt, Semikoz, Tomàs), hep-ph/ , hep-ph/ , hep-ph/ , hep-ph/

49 Model-Independent Strategies for Observing Earth Effects
One detector observes SN shadowed by Earth Case 1: Another detector observes SN directly Identify Earth effects by comparing signals Case2: Identify “wiggles” in signal of single detector Problem: Smearing by limited energy resolution If 13-mixing angle is known to be “large”, e.g. from Double Chooz, observed “wiggles” in energy spectrum signify normal mass hierarchy Scintillator detector ~ 2000 events may be enough Water Cherenkov Need megaton detector with ~ 105 events Dighe, Keil & Raffelt, “Identifying Earth matter effects on supernova neutrinos at a single detector” [hep-ph/ ]

50 Supernova Shock Propagation and Neutrino Oscillations
Schirato & Fuller: Connection between supernova shocks, flavor transformation, and the neutrino signal [astro-ph/ ] Resonance density for R. Tomàs, M. Kachelriess, G. Raffelt, A. Dighe, H.-T. Janka & L. Scheck: Neutrino signatures of supernova forward and reverse shock propagation [astro-ph/ ]

51 Shock-Wave Propagation in IceCube
Inverted Hierarchy No shockwave Inverted Hierarchy Forward & reverse shock Inverted Hierarchy Forward shock Normal Hierarchy Choubey, Harries & Ross, “Probing neutrino oscillations from supernovae shock waves via the IceCube detector”, astro-ph/

52 Supernova Neutrinos 20 Jahre nach SN 1987A
Collective Supernova Neutrino Oscillations

53 Neutrino Density Streaming off a Supernova Core
Typical luminosity in one neutrino species Corresponds to a neutrino number density of Current-current structure of weak interaction causes suppression of effective potential for collinear-moving particles Nu-nu refractive effect decreases as Appears to be negligible Equivalent Neutrino density ∝ R-2 Nu-nu refraction ∝ R-4

54 Collective Effects in Neutrino Flavor Oscillations
Collapsed supernova core or accretion torus of merging neutron stars: Neutrino flux very dense: Up to 1035 cm-3 Neutrino-neutrino interaction energy much larger than vacuum oscillation frequency Large “matter effect” of neutrinos on each other Non-linear oscillation effects Assume 80% anti-neutrinos Vacuum oscillation frequency w = 0.3 km-1 Neutrino-neutrino interaction energy at nu sphere (r = 10 km) m = 0.3105 km-1 Falls off approximately as r-4 (geometric flux dilution and nus become more co-linear)

55 Self-Induced Flavor Oscillations of SN Neutrinos
Survival probability ne Normal Hierarchy atm Dm2 Q13 close to Chooz limit Inverted No nu-nu effect Realistic nu-nu effect MSW effect Realistic nu-nu effect Bipolar collective oscillations (single-angle approximation) MSW

56 Mass Hierarchy at Extremely Small Theta-13
Using Earth matter effects to diagnose transformations Ratio of spectra in two water Cherenkov detectors (0.4 Mton), one shadowed by the Earth, the other not Dasgupta, Dighe & Mirizzi, arXiv:

57 Collective SN neutrino oscillations 2006-2008 (I)
“Bipolar” collective transformations important, even for dense matter Duan, Fuller & Qian astro-ph/ Numerical simulations Including multi-angle effects Discovery of “spectral splits” Duan, Fuller, Carlson & Qian astro-ph/ , Pendulum in flavor space Collective pair annihilation Pure precession mode Hannestad, Raffelt, Sigl & Wong astro-ph/ Duan, Fuller, Carlson & Qian astro-ph/ Self-maintained coherence vs. self-induced decoherence caused by multi-angle effects Sawyer, hep-ph/ , Raffelt & Sigl, hep-ph/ Esteban-Pretel, Pastor, Tomàs, Raffelt & Sigl, arXiv: Theory of “spectral splits” in terms of adiabatic evolution in rotating frame Raffelt & Smirnov, arXiv: , Duan, Fuller, Carlson & Qian arXiv: , Independent numerical simulations Fogli, Lisi, Marrone & Mirizzi arXiv:

58 Collective SN neutrino oscillations 2006-2008 (II)
Three-flavor effects in O-Ne-Mg SNe on neutronization burst (MSW-prepared spectral double split) Duan, Fuller, Carlson & Qian, arXiv: Dasgupta, Dighe, Mirrizzi & Raffelt, arXiv: Theory of three-flavor collective oscillations Dasgupta & Dighe, arXiv: Identifying the neutrino mass hierarchy at extremely small Theta-13 Dasgupta, Dighe & Mirizzi, arXiv: Second-order mu-tau refractive effect important in three-flavor context Esteban-Pretel, Pastor, Tomàs, Raffelt & Sigl, arXiv: But for high density, conversions suppressed by geometric effect Esteban-Pretel, Mirizzi, Pastor, Tomàs, Raffelt, Serpico & Sigl, arXiv: Collective oscillations along flux lines for non-spherical geometry Dasgupta, Dighe, Mirizzi & Raffelt, arXiv:

59 Neutrino Oscillations in a Neutrino Background
Neutrinos in a medium suffer flavor-dependent refraction (Wolfenstein, PRD 17:2369, 1978) f W, Z f Z n n n n If neutrinos form the background, the refractive index has “offdiagonal elements” (Pantaleone, PLB 287:128, 1992) n Z n n One can not operationally distinguish between “beam” and “background” Problem is fundamentally nonlinear

60 Matrices of Density in Flavor Space
Neutrino quantum field Spinors in flavor space Destruction operators for (anti)neutrinos Variables for discussing neutrino flavor oscillations Quantum states (amplitudes) “Matrices of densities” (analogous to occupation numbers) Neutrinos Anti- neutrinos Sufficient for “beam experiments” “Quadratic” quantities, required for dealing with decoherence, collisions, Pauli-blocking, nu-nu-refraction, etc.

61 General Equations of Motion
Vacuum oscillations M is neutrino mass matrix Note opposite sign between neutrinos and antineutrinos Usual matter effect with Nonlinear nu-nu effects are important when nu-nu interaction energy exceeds typical vacuum oscillation frequency (Do not compare with matter effect!)

62 Oscillations of Neutrinos plus Antineutrinos in a Box
Equal and densities, single energy E, with Equal self terms Opposite vacuum oscillations “Pendulum in flavor space” Inverted mass hierarchy  Inverted pendulum  Unstable even for small mixing angle Normal mass hierarchy  Small-amplitude oscillations

63 Flavor Conversion Without Flavor Mixing?
Equal ne and ne densities in a box (inverted hierarchy) _ Inverted pendulum: Time to fall depends logarithmically on small initial angle Q Stays up forever only for Q = 0 Unstable by quantum uncertainty relation (“How long can a pencil stand on its tip?”) This is no real “flavor conversion”, rather a “coherent pair conversion” Occurs anyway at second order GF Coherent “speed-up effect” (Sawyer) Not clear (to me) if coherent transformations can be triggered by quantum fluctuations alone (mixing angle Q = 0)

64 Supernova Neutrino Conversion
Neutrinos in a box Permanent pendular oscillations Neutrinos streaming off a supernova core Complete conversion Nu-nu interaction energy decreases Pendulum’s moment of inertia m-1 increases Conservation of angular momentum  kinetic energy decreases  amplitude decreases ∝ m1/2 Envelope declines as ∝ m1/2 ∝ r -2

65 Flavor Conversion in Toy Supernova
Assume 80% anti-neutrinos Vacuum oscillation frequency w = 0.3 km-1 Neutrino-neutrino interaction energy at nu sphere (r = 10 km) m = 0.3105 km-1 Falls off approximately as r-4 (geometric flux dilution and nus become more co-linear) Pendular Oscillations Decline of oscillation amplitude explained in pendulum analogy by inreasing moment of inertia (Hannestad, Raffelt, Sigl & Wong astro-ph/ )

66 Synchronized vs. Pendular Oscillations
Ensemble of unequal densities (antineutrino fraction a < 1) Equal energies (equal oscillation frequency w = Dm2/2E) Interaction energy Synchronized oscillations Pendular oscillations Free oscillations

67 Synchronized vs. Pendular Oscillations
Supernova Core R = km R  200 km Synchronized oscillations Pendular oscillations Free oscillations

68 Pendulum in Flavor Space
Polarization vector for neutrinos plus antineutrinos Precession (synchronized oscillation) Nutation (pendular oscillation) Very asymmetric system - Large spin - Almost pure precession - Fully synchronized oscillations Perfectly symmetric system - No spin - Simple spherical pendulum - Fully pendular oscillation [Hannestad, Raffelt, Sigl, Wong: astro-ph/ ] Spin (Lepton Asymmetry) Mass direction in flavor space

69 Multi-Energy and Multi-Angle Effects
Different modes oscillate with different frequencies  kinematical decoherence Self-maintained coherence by nu-nu interactions Can lead to “spectral split” Multi-angle effects for non-isotropic nu distribution (streaming from SN): Different modes should oscillate differently  kinematical decoherence However, nu-nu interaction can lead to “Angular synchronization” (quasi-single angle behavior) Self-accelerated multi-angle decoherence Isotropic matter background affects all modes the same

70 Spectral Split (Stepwise Spectral Swapping)
Initial fluxes at nu sphere After collective trans- formation For explanation see Raffelt & Smirnov arXiv: Duan, Fuller, Carlson & Qian arXiv: Fogli, Lisi, Marrone & Mirizzi, arXiv:

71 Spectral split in terms of the w variable
Collective conversion of thermal spectra of ne and ne as in a supernova _ Energy spectrum Spectrum in terms of w = Dm2/2E Flavor lepton number conservation: Equal integrals Raffelt & Smirnov, arXiv:

72 Lots of theoretical work to do!
SN 1006 No problem May take a long time Lots of theoretical work to do! Looking forward to the next galactic supernova

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