Diffuse Supernova Neutrino Background (DSNB): status and updates

Transcription

1 Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini 1 Department of Physics May 15, Cecilia.Lunardini@asu.edu

2 Table of contents Introduction: the question of detectability modeling the DSNB: updates theory-based : advances in SN theory and oscillation physics data-based : new supernova rate measurements Discussion and summary implications for next generation detectors Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 2 / 30

3 Diffuse SN Neutrino Background (DSNB) cm 2 MeV 1 s reactor solar Atmospheric from cosmological SNe: peak at 5 7 MeV, due to SNe at z > 1 energy window: MeV Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 3 / 30

4 Physics potential continuous flux: from rare event to constant data-taking Test physics of core collapse and of neutrinos similarly to SN1987A (or better) without the wait! Complementary to individual SN: image of entire SN population of the universe diversity of progenitors, rare types (ONeMg, failed SNe, PopIII) independent, complementary probe of star formation history neutrino propagation on cosmological scale Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 4 / 30

5 Theory and experiment status e + candidates>16mev/22.5kton year 9 SK Days 8 Excluded (E>16MeV) 7 e e + (90%C.L.) HMA LMA 3 6 MeV 2 CE FS 4 MeV 1 CGI T in MeV SuperK limit, E ν > 17.3 MeV (90% C.L.) φ νe cm 2 s 1 lower threshold background-limited theory: O(10 1 ) cm 2 s 1 factor of several uncertainty Bays et al. [SuperKamiokande coll.] PRD 85, (2012) Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 5 / 30

6 Future prospects: a conservative revision detectable at a future realistic detector? 1 Mt-scale may be unrealistic 2 depth may be unrealistic 3... may be unrealistic can any physics be extracted, from multitude of effects at play? 1 SN rates 2 progenitor dependence 3 neutrino spectra 4 oscillations 5 SN demographics Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 6 / 30

7 Recession-style approach: improve the theory Theory-based reduce theoretical uncertainties evaluate theoretical errors evaluate the size of all participating effects and estimate detectability C. L. and I. Tamborra, JCAP 1207, 012 (2012) Phenomenological (data-based) establish a model-independent, conservative range of flux using current observations C. L. and L. Yang, in preparation Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 7 / 30

8 Calculating the DSNB Φ νβ (E) = c Mmax dm H 0 M 0 zmax 0 dz ρ SN(z, M)F νβ (E, M) ΩM (1 + z) 3 + Ω Λ, F νβ (E, M) oscillated ν β flux, M progenitor mass, M 0 = 8 M, M max 125 M ρ SN cosmological SN rate (SNR) Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 8 / 30

9 Supernova rate and star formation rate η(m) ρ SN (z, M) = Mmax 0.5M dm Mη(M) ρ (z). ρ Star Formation Rate (SFR) η(m) M 2.35, mass distribution of stars at birth { (1 + z) δ z < 1 ρ (1 + z) α 1 < z < 4.5. (1 + z) γ 4.5 < z from SFR data: δ = 3.28, α = 0.26, γ = 7.8 Mmax M 0 dm ρ SN (0, M) = Mpc 3 yr 1. Hopkins and Beacom, ApJ. 651 (2006) Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 9 / 30

10 Neutrino emission quasi-thermal, α-spectrum: ( ) E αβ ϕ νβ (E) L νβ e (α β+1)e/ E νβ. E νβ α β (t) shape parameter, L νβ (t) luminosity E νµ,τ (t) > E νe(t) > E νe (t) in cooling phase. ν x =ν µ, ν τ Keil, Raffelt and Janka, ApJ. 590 (2003) Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 10 / 30

11 Contributors Krauss, Glashow, Schramm, Beacom, Kistler, Vagins, Horiuchi, Yuksel, Lunardini, Lien, Fields, Strigari, Kaplinghat, Hartmann, Woosley, Malaney, Steigman, Walker Ando, Sato, Fukigita, Kawasaki, Totani Dasgupta, Goswami, Dighe, Chakraborty, Choubey, Kar Bisnovatyi-Kogan, Seidov, Tamborra, Cocco, Mangano, Ereditato, Fiorillo, Pettorino, Volpe, Galais, Gava, Kneller, Welzel, Daigne, Iocco, Raffelt, Miele, Serpico, Wurm Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 11 / 30

12 Theory-based: including recent advancements more realistic SN simulations 1 10 s long cooling phase 2 dependence on progenitor mass 3 constantly improving microphysics more advanced oscillation studies 1 collective oscillations + MSW resonances 2 measured θ 13 goal: evaluate quantitative effect of each C. L. and I. Tamborra, JCAP 1207, 012 (2012) Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 12 / 30

13 Long-term, progenitor dependent simulations (from Fischer et al.) solar masses 18 M solar masses 8.8 solar masses 10.8 M 8.8 M νe Luminosity (erg ergs s Lνβ s 1 1 ) νx νe Luminosity ergs s Luminosity ergs s times times times Eνβ EMeV (MeV) times t(s) t(s) t(s) three mass bins, neglect failed SNe cooling phase: colder spectra, smaller differences between flavors Fischer, et al. Astron. Astrophys. 517 (2010); Müller, Janka, Marek, ApJ. 756 (2012). Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 13 / 30

14 Collective oscillations + MSW resonances vacuum + matter + neutrino-neutrino interaction : H E = H vac E + Hm E + Hνν E ( ω L ) H vac E = U diag 2, +ω L 2, ω H U, H m = 2G F diag(n e, 0, 0) H νν E = de (ρ E ρ E )(1 cos θ EE ) ω L = δm 2 sol /2E, ω H = δm 2 atm/2e, θ EE angle between incident momenta normal hierarchy (NH): δm 2 atm > 0 inverted hierarchy (IH): δm 2 atm < 0) Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 14 / 30

15 collective oscillations (multi-angle): [see Balantekin s talk] step-like ν e, ν e survival probabilities ( splits, swaps ) P c (F c ν e, F c ν e, E), P c (F c ν e, F c ν e, E) suppressed in accretion phase P c (blue, solid) and P c (red, dashed) as functions of energy, for M = 8.8 M and t = 3 s pb. Left: NH. Right: IH Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 15 / 30

16 factorization of collective and MSW resonances (spatial separation) sin 2 θ : adiabatic MSW resonance, P H = 0 ν e ν 3 for normal hierarchy (NH, δm 2 atm > 0) ν e ν 3 for inverted hierarchy (IH, δm 2 atm < 0) ν 3 ν x total flavor permutation Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 16 / 30

17 spectra at exit of the star F NH ν e = sin 2 θ 12 [1 P c (F c ν e, F c ν e, E)](F 0 ν e F 0 ν y ) + F 0 ν y, F NH ν e = cos 2 θ 12 Pc (F c ν e, F c ν e, E)(F 0 ν e F 0 ν y ) + F 0 ν y, F IH ν e = sin 2 θ 12 P c (F c ν e, F c ν e, E)(F 0 ν e F 0 ν y ) + F 0 ν y, F IH ν e = cos 2 θ 12 [1 P c (F c ν e, F c ν e, E)](F 0 ν e F 0 ν y ) + F 0 ν y. collective effects decrease (increase) flavor permutation for resonant (non resonant) channels Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 17 / 30

18 Single star, time-integrated, with cooling NH, νe Normal hierarchy no osc. MSW MSW + ν ν Normal hierarchy NH, νe E 2 Fνe, νe (MeV) E 2 Fνe, νe (MeV) IH, νe Inverted hierarchy E 2 FEMeV Inverted hierarchy IH, νe oscillations suppressed by similarity of cooling spectra splits are smeared by t-integration suppressed by accretion contribution E(MeV) E(MeV) Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 18 / 30

19 DSNB, with cooling and progenitor mass dependence E 2 Φνe (MeVcm 2 s 1 ) NH NH, 10.8 M IH IH, 10.8 M E 2 Φ νe (MeVcm 2 s 1 ) E(MeV) Thick: with progenitor mass dependence Thin : 10.8 M as representative of all E(MeV) Black: ν e, Red: ν e Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 19 / 30

20 DSNB: comparing different effects Φtot(cm 2 s 1 ) ν e a b c neutrinos NH IH ν e antineutrinos DSNB above the SuperKamiokande threshold, E ν > 17.3MeV (a) with t pb = 0.5 s as representative of all post-bounce times and the 10.8 M progenitor as representative of the whole stellar population, no oscillations; (b) with time-dependent fluxes for the 10.8 M model, no flavor oscillations; (c) with time-dependent fluxes for the 10.8 M model, MSW flavor conversions; (d) with time-dependent fluxes for the 10.8 M model, MSW + ν ν interactions; (e) with progenitor mass dependence, time-dependent fluxes, MSW + ν ν interactions; (f) same as (e) for SN rate favored by direct SN observations Error bars: normalization uncertainty of supernova rate d e f a b c d e f Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 20 / 30

21 a b c d e E νe NH (MeV) Eν 2 e NH (MeV 2 ) E νe NH (MeV) E 2 ν e NH (MeV 2 ) E νe IH (MeV) Eν 2 e IH (MeV 2 ) E νe IH (MeV) E 2 ν e IH (MeV 2 ) Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 21 / 30

22 Good news: hierarchy of effects MSW resonance dominates All other effects of O(10%), less than SN rate uncertainty Data well reproduced with effective permutation P P MSW extract original spectra? Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 22 / 30

23 Phenomenological: use direct observations SN1987A : ν e oscillated spectra applicable, if progenitor mass dependence is negligible direct measurement of SN rate from SN observations, up to z 1 idea: (1) find statistically allowed region of parameters: χ 2 = χ χ2 SNR (2) marginalize to find allowed interval of the DSNB pro : robust, (quasi) model-independent con : large (but meanigful) interval of flux allowed Fukugita and Kawasaki, Mon. Not. Roy. Astron. Soc. 340 (2003) L7 C.L., Astropart. Phys. 26 (2006) C. L. and L. Yang, in preparation Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 23 / 30

24 SN1987A: ν e data N 10 8 K E/MeV N 10 8 IMB E/MeV Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 24 / 30

25 Fit: NH (composite spectrum) favored Hierarchy of energy Hierarchy of energy free parameters (time-integrated/averaged): L νe, L νx, E νe, E νx, mass hierarchy collective effects neglected C.L., Astropart. Phys. 26 (2006) Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 25 / 30

26 Fit of direct SNR measurement SNR$h 3 10 )4 yr )1 Mpc )3 $ Li$et$al$2011$ Bo9cella$et$al$2008$ Cappellaro$et$al$1999$ Melinder$et$al$2012$ Graur$et$al$2012$ Bazin$et$al$2009$ Dahlen$et$al$2012$ SFR (1 + z) 3, SNR (1 + z) 4 factor of 2 difference in local rate (z = 0) physics? systematics? Z" Black: SNR inferred from star formation data. Blue: SNR from SN counting. Only statistical errors shown here. Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 26 / 30

27 Fit of direct SNR measurement 3 SNRH0L h yr -1 Mpc b 68.3, 90, 95.4% C.L.. Solid: stat. only. Dashed: stat + sys. : parameters favored by SNR data. Horizontal line: lower limit of Smarrtt et al., including systematic errors lessens tension C. L. and L. Yang, in preparation Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 27 / 30

28 Results: allowed ν e flux and event rate ν e normal mass hierarchy (composite spectrum) E > 19.3 MeV (older SuperK threshold),at 99% C.L. flux, stat. only flux, stat. + sys event rate in 1 Mt water cm 2 s 1 cm 2 s 1 yr factor of several below SuperK limit uncertainty dominated by SN1987A valid only if SN1987A is typical Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 28 / 30

29 For equal flavor spectra: ν e flux and event rate ν e, inverted hierarchy (single α-spectrum) or any flavor for equal spectra E > 19.3 MeV,at 99% C.L. flux, stat. only flux, stat. + sys ν e event rate in 100 kt LAr (equal spectra) cm 2 s 1 cm 2 s 1 yr Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 29 / 30

30 DSNB: take home message unique potential: cosmological neutrinos image the SN population experiments are becoming more (financially) conservative theory is becoming more conservative: φ O(0.1) cm 2 s 1 theory-based predictions: softer spectra, cooling phenomenology-based predictions: lower direct SN rate Can we learn anything? hierarchy of effects: there is hope a deep, 100 kt liquid argon detector is the bare minimum Diffuse Supernova Neutrino Background (DSNB): status and updates Cecilia Lunardini Physics 30 / 30