Supernova neutrinos for neutrino mixing and SN astrophysics

Transcription

1 Supernova neutrinos for neutrino mixing and SN astrophysics Amol Dighe Tata Institute of Fundamental Research TPSC Seminar, IMSc, Chennai, 23 February 2005 Supernova neutrinos forneutrino mixing and SN astrophysics p.1/52

2 Why study a rare event ( Galactic SN: once in a few decades??) Obtaining the news of a SN explosion in advance Tracking the shock wave propagation Deciphering neutrino masses and mixings (normal / inverted hierarchy and θ 13 ) Deciding design parameters of future long baseline experiments (neutrino factories) Tuning existing or proposed long-term detectors to observe relevant signals Supernova neutrinos forneutrino mixing and SN astrophysics p.2/52

3 Production and propagation SN neutrinos... Primary fluxes and model dependence Flavour conversions inside the SN Oscillations inside the Earth... for identifying neutrino mixing scenario comparing signals at multiple detectors through earth effect oscillations... for SN astrophysics: Pointing to the SN in advance tracking the shock wave in neutrinos Supernova neutrinos forneutrino mixing and SN astrophysics p.3/52

4 What we know about neutrinos (ν e, ν µ, ν τ ) (ν 1, ν 2, ν 3 ) Solar, Atmospheric and Reactor neutrino experiments Mass squared differences: m 2 21 m 2 31 m 2 32 m 2 ( ) 10 5 ev 2, m 2 atm ( ) 10 3 ev 2 Mixing matrix: U = U e1 U e2 U e3 U µ1 U µ2 U µ3 U τ1 U τ2 U τ3 U e , U e , U µ , U e3 2 < 0.05 (Two large angles and one small, possibly vanishing and hence interesting angle) SN neutrinos sensitive to the first row of the mixing matrix Supernova neutrinos forneutrino mixing and SN astrophysics p.4/52

5 What we do not know Mass hierarchy: Normal or Inverted? (ν e, ν µ, ν τ ) m 2 m 2 solar m 2 atm m 2 atm m 2 solar CP violation Absolute neutrino masses SNe ν spectra mass hierarchy and U e3 : the small angle Supernova neutrinos forneutrino mixing and SN astrophysics p.5/52

6 A Type II supernova Supernova neutrinos forneutrino mixing and SN astrophysics p.6/52

7 Before the collapse Neutrinos trapped inside neutrinospheres around ρ g/cc. Escaping neutrinos: E νe < E νe < E νx Supernova neutrinos forneutrino mixing and SN astrophysics p.7/52

8 Gravitational core collapse The SN timeline Supernova neutrinos forneutrino mixing and SN astrophysics p.8/52

9 Gravitational core collapse The SN timeline Generation of a shock wave Supernova neutrinos forneutrino mixing and SN astrophysics p.8/52

10 SN timeline continued... Neutronization burst: Shock wave breaks up the nuclei e capture enhanced ν e emitted at the ν e neutrinosphere. Duration: The first 10 ms Supernova neutrinos forneutrino mixing and SN astrophysics p.9/52

11 SN timeline continued... Neutronization burst: Shock wave breaks up the nuclei e capture enhanced ν e emitted at the ν e neutrinosphere. Duration: The first 10 ms Cooling through neutrino emission: ν e, ν e, ν µ, ν µ, ν τ, ν τ Duration: About 10 sec Emission of 99% of the SN energy in neutrinos Can be used for pointing to the SN in advance. ( Early warning ) Supernova neutrinos forneutrino mixing and SN astrophysics p.9/52

12 SN timeline continued... Neutronization burst: Shock wave breaks up the nuclei e capture enhanced ν e emitted at the ν e neutrinosphere. Duration: The first 10 ms Cooling through neutrino emission: ν e, ν e, ν µ, ν µ, ν τ, ν τ Duration: About 10 sec Emission of 99% of the SN energy in neutrinos Can be used for pointing to the SN in advance. ( Early warning ) Explosion??? Supernova neutrinos forneutrino mixing and SN astrophysics p.9/52

13 Initial neutrino spectra Neutrino fluxes: Fν 0 i = Φ 0 (1 + α) 1+α ( ) α ] E exp [ (α + 1) EE0 E 0 Γ(1 + α) E 0 Known properties of the spectra: Energy hierarchy: E 0 (ν e ) < E 0 ( ν e ) < E 0 (ν x ) Spectral pinching: α νi > 2 E 0, α: in general time dependent E 0 (ν e ) MeV E 0 ( ν e ) MeV E 0 (ν x ) MeV α νi 2 4 G. G. Raffelt, M. T. Keil, R. Buras, H. T. Janka and M. Rampp, astro-ph/ E(MeV) Supernova neutrinos forneutrino mixing and SN astrophysics p.10/52

14 Flavor-dependent neutrino fluxes E L [10 52 erg s -1 ] ν e νx Time [s] Time [ms] Model E 0 (ν e ) E 0 ( ν e ) E 0 (ν x ) Φ 0 (ν e ) Φ 0 (ν x ) solid line: ν e dotted line: ν x Φ 0 ( ν e ) Φ 0 (ν x ) Garching (G) Livermore (L) G. G. Raffelt, M. T. Keil, R. Buras, H. T. Janka and M. Rampp, astro-ph/ T. Totani, K. Sato, H. E. Dalhed and J. R. Wilson, Astrophys. J. 496, 216 (1998) Supernova neutrinos forneutrino mixing and SN astrophysics p.11/52

15 he complete range of densities traversed SUPERNOVA envelope VACUUM EARTH core ν ρ=10 10 km 14 g/cc Rsun kpc km SN core (ρ g/cc) SN mantle and envelope (ρ g/cc) Interstellar medium (ρ 0 g/cc) Earth matter (ρ 5 10 g/cc) Matter effects crucial!!! Supernova neutrinos forneutrino mixing and SN astrophysics p.12/52

16 Hamiltonian for a single neutrino Neutrinos with same p H m2 2E H = p 2 + m 2 p + m2 2p p + m2 2E Inside matter, forward scattering gives rise to an effective potential. Neutral current: the same forward scattering amplitude for all neutrino species Charged current: ν e and ν e get additional potential V CC = ± 2G F n e ±ρ Effective m 2 for ν e and ν e linear in matter density Supernova neutrinos forneutrino mixing and SN astrophysics p.13/52

17 2-ν level crossing Effective Hamiltonian: H = 1 4E Eigenvalues: [ m 2 i 2E = 1 2E ( m 2 cos 2θ + 2A m 2 sin 2θ A 2 ( m 2 cos 2θ A) 2 + ( m 2 sin 2θ) 2 ] ) m 2 sin 2θ m 2 cos 2θ (A = 2E V cc ) ν 2 m m 2 ν 2 m ν 1 m ν 1 m ρ, antineutrinos ρ,neutrinos A Supernova neutrinos forneutrino mixing and SN astrophysics p.14/52

18 Adiabaticity at resonance P f exp ( π ) 2 γ 1 P f Landau 1932, Zener P f P f P f γ m2 2E sin 2 2θ cos 2θ ( ) 1 1 dn e n e dr Vacuum Envelope Core γ 1 P f 1 Adiabatic resonance Dependence on: m 2, mixing angle, density profile The exact result: P f [ ( exp π 2 γf ) exp ( π 2 γ F 1 exp ( π 2 γ ) F sin 2 θ sin 2 θ )] Kuo, Pantaleone, PRD 39, 1930 (1989) Supernova neutrinos forneutrino mixing and SN astrophysics p.15/52

19 3-ν mixing (ν e, ν µ, ν τ ) basis: H = 1 2E m 2 ee + A m 2 eµ m 2 eτ m 2 µe m 2 µµ m 2 µτ m 2 τe m 2 τµ m 2 ττ Rotate to (ν e, ν µ, ν τ ) basis for simplification: H = 1 2E m 2 ee + A m 2 eµ m 2 eτ m 2 µ e m 2 µ µ 0 m 2 τ e 0 m 2 τ τ Supernova neutrinos forneutrino mixing and SN astrophysics p.16/52

20 3-ν level crossing schemes Normal mass hierarchy Inverted mass hierarchy H resonance: ( m 2 atm, θ 13 ), ρ 10 3 g/cc L resonance: ( m 2, θ ), ρ 1 g/cc m 2 hierarchy Independent dynamics at resonances Supernova neutrinos forneutrino mixing and SN astrophysics p.17/52

21 Adiabaticity at H and L resonances L always adiabatic H adiabatic for U e3 2 > 10 3, non-adiabatic for U e3 2 < 10 3 H in ν e for normal hierarchy H in ν e for inverted hierarchy SN neutrino spectra sensitive to U e3 2 > 10 3 or U e3 2 < 10 3 Normal mass hierarchy or inverted mass hierarchy AD, A. Smirnov, PRD 62, (2000) Supernova neutrinos forneutrino mixing and SN astrophysics p.18/52

22 Fluxes arriving at the Earth Mixture of initial fluxes: F νe = pfν 0 e + (1 p)fν 0 x, F νe = pf 0 ν e + (1 p)fν 0 x, 4F νx = (1 p)fν 0 e + (1 p)f 0 ν e + (2 + p + p)fν 0 x. Survival probabilities in different scenarios: Case Hierarchy sin 2 Θ 13 p p A Normal > cos 2 Θ B Inverted > 10 3 sin 2 Θ 0 C Any < 10 3 sin 2 Θ cos 2 Θ Sensitivity to sin 2 Θ 13 an order of magnitude better than current reactor experiments! Supernova neutrinos forneutrino mixing and SN astrophysics p.19/52

23 SN87A Confirmed the SN cooling mechanism through neutrinos Number of events too small to say anything concrete about neutrino mixing Some constraints on SN parameters obtained (Hubble image) J. Arafune, J. Bahcall, V. Barger, M. Fukugita, B. Jegerlehner, M Kachelrieß, C. Lunardini, D. Marfatia, H. Minakata, F. Neubig, D. Nötzold, H. Nunokawa, G. G. Raffelt, K. Shiraishi, A. Smirnov, D. Spergel, A. Strumia, H. Suzuki, R. Tomàs, J. V. F. Valle, B. Wood, T. Yanagida, M. Yoshimura, et al Supernova neutrinos forneutrino mixing and SN astrophysics p.20/52

24 Detecting a galactic SN Events expected at Super-Kamiokande with a SN at 10 kpc: ν e p ne + : νe νe : ν e + 16 O X + e : Some useful reactions at other detectors: Carbon-based scintillator: ν + 12 C ν + X + γ (15.11 MeV) Liquid Ar: ν e + 40 Ar 40 K + e Supernova neutrinos forneutrino mixing and SN astrophysics p.21/52

25 Distinguishing neutrino mixing scenarios Supernova neutrinos forneutrino mixing and SN astrophysics p.22/52

26 The task at hand Measure the spectra, determine the mixing scenario. A. Bandyopadhyay, S. Choubey, G. Dutta, I. Gil-Botella, S. Goswami, D. Indumathi, M. Kachelrieß, K. Kar, C. Lunardini, H. Minakata, M. V. N. Murthy, H. Nunokawa, G. Raffelt, G. Rajasekaran, A. Rubbia, K. Sato, A. Smirnov, K. Takahashi, R. Tomàs, J. Valle, et al Supernova neutrinos forneutrino mixing and SN astrophysics p.23/52

27 The task at hand Measure the spectra, determine the mixing scenario. A. Bandyopadhyay, S. Choubey, G. Dutta, I. Gil-Botella, S. Goswami, D. Indumathi, M. Kachelrieß, K. Kar, C. Lunardini, H. Minakata, M. V. N. Murthy, H. Nunokawa, G. Raffelt, G. Rajasekaran, A. Rubbia, K. Sato, A. Smirnov, K. Takahashi, R. Tomàs, J. Valle, et al Poorly known initial spectra Only final ν e spectrum cleanly available. Difficult to find a clean observable, i.e. one independent of some assumptions about the initial spectra C. Lunardini, A. Smirnov, JCAP 0306:009 (2003) Supernova neutrinos forneutrino mixing and SN astrophysics p.23/52

28 Some possible observables During neutronization burst: R B N CC /N NC Case A R B /R B 0 U e Broadening of spectra: pinched antipinched, i.e. α > 2 α < 2 Pinching parameter 3 E 2 /4 E 2 : Information about the spectrum around the peak Tail fraction: f tail = N(E > E tail) N(E > E th ) Information about the high-energy part of the spectrum Difficult to find a clean observable, i.e. one independent of some assumptions about the initial spectra. M. Kachelrieß, C. Lunardini, H. Minakata, H. Nunokawa, G. Raffelt, K. Sato, A. Smirnov, K. Takahashi, R. Tomàs, J. Valle, et al Supernova neutrinos forneutrino mixing and SN astrophysics p.24/52

29 Earth matter effects The flavour composition of the final fluxes changes: Fν D e F νe = p(fν 0 e Fν 0 x ) F D ν e F νe = p(f 0 ν e Fν 0 x ) Change in survival probabilities in different scenarios: Case Hierarchy sin 2 Θ 13 p p A Normal > P 1e cos 2 Θ B Inverted > 10 3 P 2e sin 2 Θ 0 C Any < 10 3 P 2e sin 2 Θ P1e cos 2 Θ Note: Zeroes at the same place as the p, p table Supernova neutrinos forneutrino mixing and SN astrophysics p.25/52

30 Exploiting Earth matter effects 15 Neutrinos 15 Antineutrinos E E (ν e, ν x, mixed ν) ( ν e, ν x, mixed ν) Supernova neutrinos forneutrino mixing and SN astrophysics p.26/52

31 Exploiting Earth matter effects 15 Neutrinos 15 Antineutrinos E E (ν e, ν x, mixed ν) ( ν e, ν x, mixed ν) Total number of events (in general) decreases Compare signals at two detectors Earth effect oscillations are introduced Scenarios B, C for ν e, scenarios A, C for ν e Compare signals at two detectors, or identify oscillations at a single detector Supernova neutrinos forneutrino mixing and SN astrophysics p.26/52

32 Comparing spectra at multiple detectors C. Lunardini and A. Smirnov, NPB616:307 (2001) Supernova neutrinos forneutrino mixing and SN astrophysics p.27/52

33 IceCube as a co-detector with SK/HK IceCube primarily meant for neutrinos with energy > 150 GeV The number of Cherenkov photons increases beyond statistical background fluctuations during a SN burst This signal can be determined to a statistical accuracy of 0.25% for a SN at 10 kpc. The Earth effects may change the signal by 0 10%. The extent of Earth effects changes by 3 4 % between the accretion phase (first 0.5 sec) and the cooling phase. Absolute calibration not essential. Supernova neutrinos forneutrino mixing and SN astrophysics p.28/52

34 seful SN locations for SK-IC comparison Earth effects detectable in regions (A) and (B) AD, M. Keil, G. Raffelt, JCAP 0306:005 (2003) Supernova neutrinos forneutrino mixing and SN astrophysics p.29/52

35 At a single detector (Identifying Earth oscillation frequency) F νe = sin 2 Θ 12 F 0 ν x + cos 2 Θ 12 F 0 ν e + F 0 Ā sin 2 ( m 2 Ly) (F 0 ν e F 0 ν x ) sin 2 Θ 12 sin(2 Θ 12 2Θ 12) (12.5/E) Oscillation frequency: k 2 m 2 L The highest frequency in the inverse energy dependence of the spectrum Completely independent of the primary neutrino spectra Depends only on solar oscillation parameters, Earth density and the distance travelled through the Earth Can be approximated to within 10% by 2 m 2 L Supernova neutrinos forneutrino mixing and SN astrophysics p.30/52

36 Fourier Transform Power spectrum: G N (k) = 1 N events eiky 2 Energy resolution is a crucial factor Scintillation detector: a few thousand events Water Cherenkov detector: a few ten thousand events AD, M. Keil, G. Raffelt, JCAP 0306:006 (2003) Supernova neutrinos forneutrino mixing and SN astrophysics p.31/52

37 Passage through the Earth core 7 Fē D = sin 2 θ 12 F 0 x + cos 2 θ 12 Fē 0 + F 0 Ā i sin 2 (k i y/2), i=1 i k i y Ā i 1 φ m /2 1 2 sin(2θ 12 4θ m ) sin(4θ c 4θ m ) O(ω) 2 (φ m /2 + φ c ) cos 2 (θ c θ m ) sin(2θ 12 4θ m ) sin(2θ c 2θ m ) O(ω) 3 (φ m + φ c ) sin(2θ 12 2θ m ) cos 4 (θ c θ m ) sin(2θ m ) O(ω) 4 φ c sin 2 (2θ c 2θ m ) [cos(2θ 12 4θ m ) 1 2 sin(2θ 12 2θ m ) sin(2θ m )] O(ω 2 ) 5 φ m 1 2 sin(2θ 12 2θ m ) sin 2 (2θ c 2θ m ) sin(2θ m ) O(ω 3 ) 6 (φ m /2 φ c ) 2 sin(2θ 12 4θ m ) cos(θ c θ m ) sin 3 (θ c θ m ) O(ω 3 ) 7 (φ m φ c ) sin(2θ 12 2θ m ) sin 4 (θ c θ m ) sin(2θ m ) O(ω 5 ) Supernova neutrinos forneutrino mixing and SN astrophysics p.32/52

38 At a scintillation detector Model independence of peak positions: Supernova neutrinos forneutrino mixing and SN astrophysics p.33/52

39 At a water Cherenkov detector High-k suppression: Supernova neutrinos forneutrino mixing and SN astrophysics p.34/52

40 Efficiencies of detectors High-k suppression affects the efficiency of HK for 35 < η < 55. (η: nadir angle) Large number of events compensates for poorer energy resolution AD, M. Kachelrieß, G. Raffelt, R. Tomàs, JCAP 0401:004 (2004) Observation of a Fourier peak in ν e Eliminate scenario B independently of SN models!!! Supernova neutrinos forneutrino mixing and SN astrophysics p.35/52

41 Neutrinos for SN astrophysics Pointing to the SN in advance Learning about the shock wave Supernova neutrinos forneutrino mixing and SN astrophysics p.36/52

42 Pointing to the SN in advance J. Beacom and P. Vogel, PRD60: (1999) Needed if no optical observation ν e p ne + : nearly isotropic background νe νe : forward-peaked signal Background-to-signal ratio: N B /N S Decrease N B /N S : neutron tagging with Gd Pointing accuracy improved 2 3 times using Gd R. Tomàs, D. Semikoz, G. Raffelt, M. Kachelrieß, AD PRD 68, (2003). GADZOOKS (Gadolinium Antineutrino Detector Zealously Outperforming Old Kamiokande, Super!) J. F. Beacom and M. R. Vagins, hep-ph/ Supernova neutrinos forneutrino mixing and SN astrophysics p.37/52

43 Shock wave and level crossings When shock wave passes through a resonance region, adiabatic resonances may become non-adiabatic for some time scenario A scenario C scenario B scenario C May cause sharp changes in the final spectra even if the primary spectra are unchanged / smoothly changing R. C. Schirato, G. M. Fuller, astro-ph/ G. L. Fogli, E. Lisi, D. Montanino and A. Mirizzi, PRD 68, (2003) Supernova neutrinos forneutrino mixing and SN astrophysics p.38/52

44 ν e Survival probability _ p E 40 E 60 E E 1b 2b 2a 1a Shifts right as shock propagates to lower densities Correspondence between densities and energies: ρ i = m N m 2 atm cos 2θ G F Y e E i 600 g/cm 3 cos 2θ MeV E i 1 Y e E For sharp changes in the density profile: p = sin 2 (θ a θ b ) cos 2 θ Supernova neutrinos forneutrino mixing and SN astrophysics p.39/52

45 Time evolution of observables Primary spectra: F 0 i (E) = Φ i E i β β i i Γ(β i ) ( ) βi 1 ( E E i exp β i ) E E i Number of events: N obs = N where g i k E νx [Φ νx 2 Γ(β νx + 2) β 2 ν x Γ(β νx ) = E νx k β k i Γ(β i) [ ( Γ a, E 1 E i β i, ] + cos 2 θ g ν e (Φ νe 2 Φ ν g ν x x 2 ) ) E 2 E i β i + Γ ( a, E 3 E i β i, )] E 4 E i β i (Time dependence through the time evolution of E 1, E 2, E 3, E 4 ) Energy moments: E m obs = N [ E νx 2+m Γ(β νx m) Φ νx β ν 2+m x Γ(β νx ) ] + cos 2 θ g ν e (Φ νe 2+m Φ ν g ν x x 2+m ) Supernova neutrinos forneutrino mixing and SN astrophysics p.40/52

46 Time dependence of observables Model E 0 (ν e ) E 0 ( ν e ) E 0 (ν x ) Φ 0 (ν e ) Φ 0 (ν x ) Φ 0 ( ν e ) Φ 0 (ν x ) L G G Supernova neutrinos forneutrino mixing and SN astrophysics p.41/52

47 At a water Cherenkov (HK) Double dip feature for E e Double peak feature for E 2 e / E e 2 R. Tomás, M. Kachelrieß, G. Raffelt, AD, H. T. Janka, L. Scheck, JCAP09(2004)015 Supernova neutrinos forneutrino mixing and SN astrophysics p.42/52

48 Single/double dip Single/double dip robust under monotonically decreasing average energy features like contact discontinuity Single/double dip visible for sin 2 2θ 13 > 10 5 In ν e for normal hierarchy In ν e for inverted hieratchy Supernova neutrinos forneutrino mixing and SN astrophysics p.43/52

49 Splitting events into energy bins Dip-times energy-bin dependent!!! Supernova neutrinos forneutrino mixing and SN astrophysics p.44/52

50 Tracking the shock fronts Example: At t 4.5 sec, (reverse) shock at ρ 40 At t 7.5 sec, (forward) shock at ρ 40 Multiple energy bins the times the shock fronts reach different densities of ρ g/cc Supernova neutrinos forneutrino mixing and SN astrophysics p.45/52

51 Summary SN ν spectra can help identifying the neutrino mixing scenario: normal / inverted mass hierarchy small / large θ 13 A positive identification of the Earth effects rules out scenario B (inverted hierarchy sin 2 Θ 13 > 10 3 ) from ν e or scenario A (normal hierarchy sin 2 Θ 13 > 10 3 ) through ν e. comparison between multiple detectors [SK/HK, IceCube] identifying earth matter oscillations [SK/HK, LENA, liquid Ar] Advance SN pointing accuracy with neutrinos: less than 10 can be improved 2 3 times using Gd [SK/HK] to tag neutrons. Tracking the shock fronts in neutrinos recognizes the presence / absence of a reverse shock determines the times the shocks pass through ρ g/cc confirms the scenario A [liquid Ar] or scenario B [SK/HK]. Supernova neutrinos forneutrino mixing and SN astrophysics p.46/52

52 Extra slides Supernova neutrinos forneutrino mixing and SN astrophysics p.47/52

53 Things to do while waiting for a SN Better theoretical understanding of neutrino transport inside the SN and the explosion mechanism More accurate measurements of the neutrino mixing parameters Tuning of long-term detectors to observe SN neutrino signals Supernova neutrinos forneutrino mixing and SN astrophysics p.48/52

54 Things to do while waiting for a SN Better theoretical understanding of neutrino transport inside the SN and the explosion mechanism More accurate measurements of the neutrino mixing parameters Tuning of long-term detectors to observe SN neutrino signals A rare event is a lifetime opportunity Anon Supernova neutrinos forneutrino mixing and SN astrophysics p.48/52

55 hock propagation in astrophysics languag Supernova neutrinos forneutrino mixing and SN astrophysics p.49/52

56 Shock wave at SK Supernova neutrinos forneutrino mixing and SN astrophysics p.50/52

57 Role of neutrinos in explosion cooling Neutrino heating dm/dt Neutrino 70 km 200 km Proto Neutron Star (n,p) 20 km p e n Stalled Shock Neutrinosphere Neutrino heating essential, but not enough No spherically symmetric (1-D) simulations show robust explosions Supernova neutrinos forneutrino mixing and SN astrophysics p.51/52

58 Ingredients required for explosion R. Buras, H.-T. Janka, M. Rampp, K. Kifonidis, astro-ph/ [ms] Neutrino heating: higher neutrino opacity Large scale convenction modes Stiffer equation of state for the core Rotation of the star O. E. Bronson Messer, S. Bruenn, C. Cardall, M. Liebendoerfer, A. Mezzacappa, W. Raphael Hix, F.-K. Thielemann et al Supernova neutrinos forneutrino mixing and SN astrophysics p.52/52