Spontaneous Symmetry Breaking in Supernova Neutrinos

Transcription

1 NOW 2014, 7 14 September Crab Nebula 2014, Otranto, Lecce, Italy Spontaneous Symmetry Breaking in Supernova Neutrinos Georg Raffelt, Max-Planck-Institut für Physik, München

2 Some Developments since NOW 2010 Probing neutrinos with SNe (flavor oscillations) Collective oscillations (nu-nu refraction): - Far more complicated than expected - Much more complicated hierarchy effects (spontaneous breaking of nu-flux axial symmetry) Experimental measurement of large Θ 13 - Hierarchy determination foreseen in the lab - SN neutrinos less crucial - New large (SN neutrino) detectors foreseen Probing SN physics with neutrinos First full 3-dimensional simulations available Explosion mechanism remains unsettled Fast time-variations can be probed (SASI instability) New symmetry-breaking phenomenon LESA: SN deleptonization mostly into one hemisphere (spontaneous breaking of spherical symmetry, unrelated to SASI, new neutrino/hydro effect)

3 Spontaneous Symmetry Breakings in Supernovae Spontaneous symmetry breaking in collective neutrino oscillations G. Raffelt, S. Sarikas & D. de Sousa Seixas Axial symmetry breaking in self-induced flavor conversion of SN neutrino fluxes PRL 111 (2013) [arxiv: ] G. Raffelt & D. de Sousa Seixas Neutrino flavor pendulum in both mass hierarchies PRD 88 (2013) [arxiv: ] Follow-up papers by Mirizzi et al. and Hansen et al. Spontaneous symmetry breaking in supernova neutrino emission (LESA effect) I. Tamborra, F. Hanke, H.-T. Janka, B. Müller, G. Raffelt & A. Marek Self-sustained asymmetry of lepton-number emission: A new phenomenon during the SN shock-accretion phase in three dimensions ApJ 792 (2014) 96 [arxiv: ] I. Tamborra, G. Raffelt, F. Hanke, H.-T. Janka & B. Müller Neutrino emission characteristics and detection opportunities based on three-dimensional supernova simulations PRD 90 (2014) [arxiv: ]

4 Core-Collapse Supernova Explosion End state of a massive star M 6 8 M Collapse of degenerate core Bounce at ρ nuc Shock wave forms explodes the star Grav. binding E ~ erg emitted as nus of all flavors Neutrino cooling by diffusion Huge rate of low-e neutrinos (tens of MeV) over few seconds in large-volume detectors A few core-collapse SNe in our galaxy per century Once-in-a-lifetime opportunity

5 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, all signals are contemporaneous

6 Operational Detectors for Supernova Neutrinos SNO+ (300) HALO (tens) LVD (400) Borexino (100) Baksan (100) Super-K (10 4 ) KamLAND (400) Daya Bay (100) IceCube (10 6 ) In brackets events for a fiducial SN at distance 10 kpc

7 IceCube Neutrino Telescope at the South Pole Instrumentation of 1 km 3 antarctic ice with ~ 5000 photo multipliers completed December 2010

8 IceCube as a Supernova Neutrino Detector Accretion SN signal at 10 kpc 10.8 M sun simulation of Basel group [arxiv: ] Cooling Each optical module (OM) picks up Cherenkov light from its neighborhood ~ 300 Cherenkov photons per OM from SN at 10 kpc, bkgd rate in one OM < 300 Hz SN appears as correlated noise in ~ 5000 OMs Significant energy information from time-correlated hits Pryor, Roos & Webster, ApJ 329:355, Halzen, Jacobsen & Zas, astro-ph/ Demirörs, Ribordy & Salathe, arxiv:

9 Next Generation Large-Scale Detectors Enlargement of IceCube - Dense infill (PINGU) - Larger volume (statistics for high-e events) Doubling the number of optical modules? Megaton water Cherenkov detector Notably Hyper-Kamiokande SN neutrino statistics comparable to IceCube, but with event-by-event energy information Scintillator detector (tens of kilotons) - Original LENA concept 50 kt - JUNO (20 kt) in China for reactor nus - WATCHMAN (US) large-scale detector? Liquid argon time projection chamber for long-baseline oscillation experiments - Unique SN capabilities (CC ν e signal) - But cross section poorly known

10 Local Group of Galaxies With megatonne class (30 x SK) 60 events from Andromeda Current best neutrino detectors sensitive out to few 100 kpc

11 SN Distance Distribution and Peak Count Rate Peak count rate in JUNO (20 kt) depending on SN distance JUNO Yellow Book, in preparation (2014) SN distance probability in Milky Way

12 Shock Revival by Neutrinos Stalled shock wave must receive energy to start re-expansion against ram pressure of infalling stellar core Shock can receive fresh energy from neutrinos! O Si n PNS S n Si n Shock wave NOW 2014, Sept 2014, Otranto, Italy

13 Three Phases of Neutrino Emission Explosion triggered Shock breakout De-leptonization of outer core layers Shock stalls ~ 150 km Neutrinos powered by infalling matter Cooling on neutrino diffusion time scale Spherically symmetric Garching model (25 M ) with Boltzmann neutrino transport

14 Three Phases of Neutrino Emission in JUNO (20 kt) ν e burst Accretion Cooling Inverse beta decay Elastic proton scattering Shock breakout De-leptonization of outer core layers Shock stalls ~ 150 km Neutrinos powered by infalling matter Cooling on neutrino diffusion time scale

15 Early Phase Signal in Anti-Neutrino Sector Garching Models with M = M Average Energy Luminosity IceCube Signature ν x ν x ν e ν x ν e ν e In principle very sensitive to hierarchy, notably IceCube Standard candle to be confirmed beyond Garching models Abbasi et al. (IceCube Collaboration) A&A 535 (2011) A109 Serpico, Chakraborty, Fischer, Hüdepohl, Janka & Mirizzi, arxiv:

16 SN 1987A Explosion Hits Inner Ring

17 Growing Set of 2D Exploding Models Florian Hanke, PhD Project MPA, Garching, 2013 Georg Raffelt, MPI Physics, Slide from Munich Thomas Janka at Fifty-One Ergs, NC State University, Raleigh, North Carolina, NOW , 7 14 May Sept , Otranto, Italy

18 Large-Scale Convection in 3D (11.2 M SUN ) Tamborra et al., arxiv:

19 Convection and SASI (27 M SUN ) Hanke et al., arxiv:

20 Status Explosion Mechanism Standard paradigm for many years: Neutrino-driven explosion (delayed explosion, Wilson mechanism) Numerical explosions ok for small-mass progenitors in 1D (spherical symmetry) Numerical explosions ok for broad mass range in 2D (axial symmetry) 3D studies only beginning no clear picture yet Better spatial resolution needed? Strong progenitor dependence? 3D progenitor models needed?

21 Variability seen in Neutrinos (3D Model) Tamborra, Hanke, Müller, Janka & Raffelt, arxiv: See also Lund, Marek, Lunardini, Janka & Raffelt, arxiv:

22 Examples for Different Progenitor Masses IceCube and Hyper-Kamiokande rates at 10 kpc SASI episodes Convection only 27 M Progenitor Two SASI episodes Otherwise convection 20 M Progenitor One SASI episodes Otherwise convection 11.2 M Progenitor No SASI Large-scale convection

23 Frequency Power Spectrum of Event Rate IceCube Rate for 3D Garching models ( ms) at 10 kpc Tamborra et al., arxiv: Strong peak at the SASI frequency of ~ 80 Hz for the 20 and 27 M SUN progenitors

24 SASI Detection Perspectives (27 M SUN Model) Optimistic Observer Direction (along SASI dipole) Pessimistic Observer Direction With shot noise

25 Directional SASI Detection Perspectives (27 M SUN ) Relative signal variance over the first SASI interval ms High detection opportunity Tamborra et al., arxiv: Typically, the sky fraction with a strong signal is > 50%

26 Sky Map of Lepton-Number Flux (11.2 M SUN Model) Lepton-number flux (ν e ν e ) relative to 4p average Deleptonization flux into one hemisphere, roughly dipole distribution (LESA Lepton Emission Self-Sustained Asymmetry) Positive dipole direction and track on sky Tamborra, Hanke, Janka, Müller, Raffelt & Marek, arxiv:

27 Spectra in the two Hemispheres Neutrino flux spectra (11.2 M SUN model at 210 ms) in opposite LESA directions Direction of maximum lepton-number flux Direction of minimum lepton-number flux ν e ν e ν x ν e ν x ν e During accretion phase, flavor-dependent fluxes vary strongly with observer direction!

28 Growth of Lepton-Number Flux Dipole Tamborra et al., arxiv: Monopole Dipole Overall lepton-number flux (monopole) depends on accretion rate, varies between models Maximum dipole similar for different models Dipole persists (and even grows) during SASI activity SASI and LESA dipoles uncorrelated

29 Schematic Theory of LESA Convective overturn Accretion flow Feedback loop consists of asymmetries in accretion rate lepton-number flux neutrino heating rate dipole deformation of shock front Electron distribution Tamborra et al. arxiv:

30 LESA Dipole and PNS Convection Neutrino sphere Neutrino sphere PNS Convection Color-coded lepton-number flux along radial rays (11.2 M SUN model at 210 ms) Lepton flux dipole builds up mostly below the neutrino sphere in a region of strong convection in the proto-neutron star (PNS)

31 Is the LESA Phenomenon Real? Couch & O Connor (2014) also find LESA in their 3D models Dolence, Burrows & Zhang (arxiv: ), 2D models: No LESA dipole at all Red curve: Lepton-number dipole 5 No evidence for beyond-noise dipole evolution (Fig.11 of arxiv: ) Different method of neutrino radiative transfer, different interaction rates, and many other physics differences needs to be understood

32 Three Phases Three Opportunities Standard Candle (?) SN theory Distance Flavor conversions Multi-messenger time of flight Strong variations (progenitor, 3D effects, black hole formation, ) Testing astrophysics of core collapse Flavor conversion has strong impact on signal EoS & mass dependence Testing nuclear physics Nucleosynthesis in neutrino-driven wind Particle bounds from cooling speed (axions )

33 Symmetry Breaking in Supernovae Supernova explosions are not spherically symmetric 3D simulations are becoming available No clear picture about explosion mechanism yet SASI sloshing in higher-mass models may be generic, can be seen in large-scale detectors Lepton emission develops dipole pattern (LESA), impacts flavor oscillations Neutrino signal (during accretion phase) strongly depends on direction of observation Self-induced flavor conversion breaks axial symmetry Lots of theoretical work to do until next galactic SN!

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35 Backup

36 Sky Distribution of Number Fluxes (11.2 M SUN ) Neutrino number flux distribution for 11.2 M SUN model integrated over ms Heavy-flavor neutrino fluxes (ν x ) nearly isotropic Flux of ν e + ν e nearly isotropic Lepton-number flux (ν e ν e ) has strong dipole distribution

37 Asymmetries of Elements Relevant for LESA Accretion Rate 11.2 M SUN 20 M SUN 27 M SUN Shock Radius Heating Rate

38 LESA vs. SASI Dipole Motions LESA SASI Dipole SASI Dipole LESA orthogonal to SASI Plane LESA orthogonal to SASI Plane LESA No apparent directional correlation between SASI and LESA

39 Symmetry Breaking in Collective Flavor Oscillations Assume globally spherically symmetric neutrino emission from SN core Axial symmetry in chosen direction f Self-induced neutrino flavor conversion in both hierarchies (unless suppressed by multi-angle matter effect) Axially symmetric solution: Conversion for inverted hierarchy (usual result) Spontaneous breaking of axial symmetry: Dipole solution ( cos φ or sin φ) Conversion for normal hierarchy (Was missed by enforcing axial symmetry because of axially symmetric emission) G. Raffelt, S. Sarikas & D. de Sousa Seixas Axial symmetry breaking in self-induced flavor conversion of SN neutrino fluxes PRL 111 (2013) [arxiv: ]