The neutrino mass hierarchy and supernova n Cristina VOLPE (AstroParticule et Cosmologie -APC)

Core-collapse supernovae Massive stars (M > 6-8 Msun) emit 1057 neutrinos in 10 seconds, during the gravitational collapse and cooling of the neutron star. Neutrino fluxes encode imprints of the explosion. cooling accretion Time after bounce (s) Hüdepohl et al. PRL 104 (2010) Supernova n fluxes from simulations NS ne nt nm ne nt nm NS

Supernova observations Time and energy signal from a supernova explosion. In our galaxy, 1-3 events/century; one explosion/year at 4 Mpc. The Diffuse Supernova Neutrino Background (DSNB) : The SN fluxes integrated over cosmological redshift. Solar abundance of heavy elements Element nucleosynthesis (r-process, np-process, n-nucleosynthesis). log Y(A) with n-n A Duan, Friedland, McLaughlin, Surman JPG 38 (2010)

SN1987A et SN simulations SN1987A events Star radius (km) Time (ms) A. Suzuki, J. of Physics, Conf. (2008) SN1987A events (LMC, 50 kpc) see e.g. Pagliaroli et al, Astropart. Phys. 31 (2009) SN simulations have reached a high degree of complexity : 2D-3D, convection, realistic neutrino transport, SASI. Marek & Janka, ApJ (2009) Star radius (km) Time (ms)

n flavour conversion in supernovae nm ne neutrinosphere shock waves n-e (MSW) the n interaction with matter – MSW effect – and with n . dynamical aspects - shock waves and turbulence. Numerous aspects require investigation. In fact, flavour conversion effects arise because of Novel conversion phenomena discovered in the last years.

The MSW effect ne Hmatter GF re =ne n2 =nm n1 e Neutrino interaction with matter induces a resonant flavour conversion. Wolfenstein PRD (1978) Mikheev and Smirnov, Sov. J. Nucl. Phys. (1985) n2 n1 MSW resonance location Effective mass matter basis =ne =nm high density flavour basis vacuum detection on earth DENSITY

The MSW effect : established Borexino coll, PRL 108 (2012) n e Survival Probability Neutrino Energy (MeV) pep pp MSW solution 7Be n 8B n the beautiful explanation of the « solar neutrino deficit » problem !

The MSW in supernovae The MSW effect is encountered twice : Dighe, Smirnov, PRD62 (2000) n-fluxes at the neutrinosphere Effective mass detection on earth DENSITY vacuum Low r High r SN core FLAVOUR CONVERSION at the H-RESONANCE DEPENDS ON THE NEUTRINO MASS HIERARCHY - either n or anti-n.

Distance in the star (a.u.) The MSW in supernovae At MSW resonance(s) efficient (adiabatic) conversion depends on : star density profile neutrino energy mixing angles, Dm2 sign Distance in the star (a.u.) n e Survival Probability full conversion (adiabatic) no conversion (non-adiabatic) ne -> nm ne -> ne Well understood.

depending on the hierarchy. The shock wave effects Dasgupta and Dighe, PRD 75 (2007). Kneller, McLaughlin, Brockman, PRD 77 (2008). Profile with shock waves Neutrino conversion in MSW region non-adiabatic t=1s t=1.5s density (g/cm3) anti-n e Survival Prob. inverted hierarchy E=20 MeV adiabatic distance in SN (cm) Time (s) before the shock - adiabatic conversion It occurs either in ne or in anti-ne channel depending on the hierarchy. the shock arrives - non-adiabatic multiple MSW (phase effects) the shock has gone

Turbulence effects Potential (a.u.) distance in SN (cm) Kneller and Volpe, PRD 82 (2010) Profile with turbulence Matter density fluctuations induce multiple MSW resonances and phase effects. Potential (a.u.) distance in SN (cm) Same imprint as shock waves

The impact of the n-n interaction Neutrino conversion near the neutrinosphere Spectral-split Neutrino Fluxes Neutrino Energy (MeV) n-fluxes after 200 km Distance in SN n e Survival Probability 1- 2- 3- all neutrinos stick together - synchronization instability in flavour - bipolar regime Duan,Fuller,Qian PRD74 (2006) 76 (2007), Hannestad, et al. PRD 74 (2006), Galais, Kneller, Volpe JPG 39 (2012) full or no conversion depending on energy - spectral split Duan, Fuller, Qian, PRD76(2007); Meng and Qian, PRD (2011); Raffelt and Smirnov PRD 76 and PRL (2007); Pehlivan et al, PRD 84 (2011); Galais and Volpe, PRD 84 (2011)

The impact of the n-n interaction Large matter densities appear to suppress n-n effects during the accretion phase. Further work is needed to test some of the approximations, either geometrical or inherent to the equations commonly used, such as the mean-field approximation. see e.g. Chakraborty, et al. PRL 107 (2011) Cherry et al, PRL 108 (2012) Volpe, Vaenaeaenen, Espinoza, 1302.2374 n-anti-n pairing correlations

Current SN observatories Borexino Baksan SK (104) LVD HALO Daya-Bay MiniBOONE KamLAND (400) IceCube (106) Different detection channels available : scattering of anti-ne with p, ne with nuclei, nx with e, p

The Diffuse Supernova n Background Calculation that treats both the n-n and shock wave effects : Malek et al. PRL (2003) NH IH 928 862 MEMPHYS (440 kton) 106 99 GLACIER (100 kton) 105 98 LENA (50 kton) Events/y/22.5 kton/4 MeV Neutrino Energy (MeV) Galais, Kneller, Gava, Volpe, PRD 81 (2010) Upper limits on DSNB fluxes : 1.4-1.9 anti-ne /cm2/s 73-154 ne/cm2/s THE HIERARCHY effect small. Lunardini and Peres, JCAP (2008) Difficult to have unambiguous information seen astrophysical uncertainties (star formation rate).

n mass hierarchy with SN n The mass hierarchy signatures studied so far are roughly of three kinds. They exploit : either earth matter effects with one or two-detectors ; or the early time signal ; or the full time and energy signal of the explosion.

Predictions for the time rise From the early time signal SN n fluxes at accretion phase Predictions for the time rise in Icecube The hierarchy appear to be distinguishable. Serpico, Chakraborty, Fischer, Hudepohl, Janka, Mirizzi, PRD 85 (2012).

From late time and energy signal ne + p n + e+ Time signal (s) Prediction including the n-n interaction and shock wave effects. inverted hierarchy e+ flux (/MeV/s/ton) 29 MeV ON EARTH adiabatic non-adiabatic anti-n e fluxes Energy (MeV) 15 MeV 15 MeV 29 MeV Gava, Kneller, Volpe, McLaughlin, PRL 103 (2009) . Bump (dip) at 3.5 (1) sigma in Super-Kamiokande if a supernova at 10 kpc explodes...

Combining information Vaeaenaenen, Volpe, JCAP 1110 (2011) . (CC+NC) events in HALO-2 (1 kton lead) for a SN at 10 kpc Predictions include nn and n-matter interaction Two-neutron events One-neutron events Detection channels with different energy thresholds allow to identify solutions.

Conclusions Simulations of core-collapse supernovae and of neutrino flavour conversion in supernovae are steadily progressing. Several features established but various aspects needs further studies. For the mass hierarchy : - the effect in the DSNB too small to be disentagled from astrophysical uncertainties; - the measurement of the early time rise and late time and energy signal in water Cherenkov or scintillator detectors are promising.

Danke. Gracias Thank you Grazie Life tree Merci

Core-collapse supernovae Massive stars (M > 8 Msun) emit 1057 neutrinos in 10 seconds, during the gravitational collapse and cooling of the neutron star. Hüdepohl et al.PRL 2010. Neutrino fluxes encode imprints of the explosion. NS ne nt nm ne nt nm NS