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SUPERNOVA NEUTRINO PHYSICS WITH NEXT-GENERATION DETECTORS

Incontri di Fisica delle Alte Energie IFAE 2006 Pavia, 19-21 April 2006. SUPERNOVA NEUTRINO PHYSICS WITH NEXT-GENERATION DETECTORS. Alessandro MIRIZZI Dip.to di Fisica & Sez. INFN, Bari, Italy. OUTLINE. Introduction to Supernova (SN) neutrino physics

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SUPERNOVA NEUTRINO PHYSICS WITH NEXT-GENERATION DETECTORS

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  1. Incontri di Fisica delle Alte Energie IFAE 2006 Pavia, 19-21 April 2006 SUPERNOVA NEUTRINO PHYSICS WITH NEXT-GENERATION DETECTORS Alessandro MIRIZZI Dip.to di Fisica & Sez. INFN, Bari, Italy

  2. OUTLINE • Introduction to Supernova (SN) neutrino physics • Expected n signal from a SN explosion • SN n oscillations effects on the signal • GalacticSN neutrinos detection: status and perspectives • Potentiality of next-generation n detectors • What can we learn (astrophysical and n physics information) • Summary and Conclusions Alessandro MirizziIFAE 2006 Pavia, 19/04/2006

  3. INTRODUCTION TO SUPERNOVA NEUTRINO PHYSICS

  4. n • ENERGY SCALES:99% of the released energy (~ 1053 erg) is emitted by n and n of all flavors n n • TIME SCALES:Neutrino emission lasts ~10 s • EXPECTED:1-3 SN/century in our galaxy (d O(10) kpc). n n n n n CORE-COLLAPSE SUPERNOVAE Core collapse SN corresponds to the terminal phase of a massive star [M ≳8 M] which becomes instable at the end of its life. It collapses and ejects its outer mantle in a shock wave drivenexplosion. Alessandro MirizziIFAE 2006 Pavia, 19/04/2006

  5. EARTH Flavor conversion n emission Shock wave OBSERVING SN NEUTRINOS Core Collapse Event rate spectra • f: from simulations of SN explosions • P : from n oscillations + simulations (density profile) • s : (well) known • e : under control Alessandro MirizziIFAE 2006 Pavia, 19/04/2006

  6. NEUTRONIZATION ACCRETION • NEUTRONIZATION BURST:ne COOLING • Duration: ~ 25 ms after the explosion • Emitted energy : E~ 1051 erg • (1/100 of total energy) • THERMAL BURST (ACCRETION + COOLING): ne , ne , nx , nx • Accretion: ~0.5 s • Cooling: ~10 s • Emitted energy: E~ 1053 erg INPUT NEUTRINO FLUXES (IN TIME) Results of neutrino emission based on the numerical simulations of SN explosion performed by the Livermore group [see, e.g., T. Totani, K.Sato, H.E. Dalhed, and J.R. Wilson, Astrophys. J. 496, 216 (1998)].

  7. INPUT NEUTRINO SPECTRA (IN ENERGY) “quasi-thermal” spectra Hierarchy of the spectra Antineutrino fluxes ~ equal for all flavors at a certain “crossing” energy (Ec~20 MeV in this simulation) ; electron neutrino flavor suppressed at higher energies These original spectra may be strongly modified by the peculiar matter effects associated to n oscillations in the stellar matter.

  8. STATIC NEUTRINO POTENTIAL [T.Shiegeyama and K. Nomoto, Astrophys. J. 360, 242 (1990)] Matter effects on n oscillations crucially depend on neutrino potential in SN: power–law parametrization As we will see in the following, this static potential may be profoundly modified by shock-wave propagation effects.

  9. SN NEUTRINO FLAVOR TRANSITIONS

  10. M2 = - , + , ± Dm2 “solar” “atmospheric” n3 • Dm2 inverted hierarchy n1 • dm2/2 n1 • dm2/2 n2 n2 -dm2/2 -dm2/2 dm2 dm2 2 2 n3 -Dm2 normal hierarchy 3 n framework Mixing parameters:U = U (q12, q13, q23) as for CKM matrix Mass-gap parameters: dm2≈ 7.92  10-5 eV2 sin2q12 ≈ 0.314 Dm2 ≈ 2.4  10-3 eV2 sin2q23 ≈ 0.44 sin2q13 ≲ 0.05 • OPEN QUESTIONS • Mass ordering? normal vs inverted • How large is q13? • Absolute masses? Hierarchical vs degenerate

  11. Neutrino flavor evolution equations must be solved to obtain the relevant Pee = P( ne ne ) < 1 sin2q12PH (n, normal) cos2q12 (n, normal) sin2q12 (n, inverted) cos2q12PH (n, inverted) ( ) ( ) • Earth matter crossing induces additional n flavor transitions. Under hierarchical hypothesis the crossing probability in the Earth is PE = PE(dm2,q12) • sin2q12PE • cos2q121-PE Substitutions in Pee SUPERNOVA NEUTRINO OSCILLATIONS Matter effects encoded in neutrino level-crossing probability PH=PH(Dm2,q13), strongly dependent on: energy, density profile, and unknown mixing angle q13 The analytical form of Pee is exceedingly simple PH modulates Pee Pee≈ Alessandro MirizziIFAE 2006 Pavia, 19/04/2006

  12. Extremely non adiabatic (PH1) Adiabatic (PH0) ANALYTICAL RECIPE The smallness of q13 suggests Landau-Zener (LZ) form: where is a scale factor sensitive to the matter density profile. It will allow to extract important information on shock wave effects on matter density. • In the next we will focus on the two extreme cases • PH0 (i.e. sin2q13 10-3) • PH1 (i.e. sin2q13 ≲10-5)

  13. In general, ne are sensitive to PH in N.H., while ne in I.H. SN NEUTRINO FLUXES AT EARTH • Normal mass hierarchy (N.H.) • Inverted mass hierarchy (I.H.) Alessandro MirizziIFAE 2006 Pavia, 19/04/2006

  14. DETECTION OF SN NEUTRINOS …. with emphasis on next-generation detectors

  15. Small statistics of events Lot of uncertainties SN 1987A SN 1987A seen by naked-eye (23 February 1987, Large Magellanic Cloud, d 50 kpc) • The best studied SN of all times: • Study of SN dynamics • Study of n physics The birth of SN neutrino astronomy • See, e.g. : • B. Jegerlehner, F. Neubig, and G. Raffelt, astro-ph/9601111; • M. Costantini, A. Ianni, and F.Vissani, astro-ph/0403436; • A.M. and G. Raffelt, astro-ph/0508612 • …. Basic features understood … … but still many questions

  16. LENA GLACIER LAr TPC Scintillator UNO, MEMPHYS, HYPER-K WHAT COULD WE SEE “TOMORROW”? SN 20xxA Next-generation large volume detectors might open a new era in SN neutrino detection: • 0.4 Mton WATER Cherenkov detectors • 100 kton Liquid Ar TPC • 50 kton scintillator Mton Cherenkov Alessandro MirizziIFAE 2006 Pavia, 19/04/2006

  17. Golden channel: Inverse beta decay (IBD) of ne 0.4 Mton WATER CHERENKOV DETECTOR ~2.5×105 events @ 10 kpc Alessandro MirizziIFAE 2006 Pavia, 19/04/2006

  18. Mton Cherenkov detectors detectors would assure a high-statistics measurement of galactic SN neutrinos. • This would allow spectral studies • in time • in energy • in different interaction channels We will mainly focus on the possibility to detect the following signatures in the n signal for a typical galactic SN explosion (d=10 kpc unless otherwise noticed): • Shock wave • Earth matter crossing Alessandro MirizziIFAE 2006 Pavia, 19/04/2006

  19. A few second after the core bounce, shock wave(s) can induce time-dependent matter effects in neutrino oscillations fwdshock fwdshock [R.Schirato, and G. Fuller, astro-ph/0205390] The crossing probability PH is expected to play a significant role when rev shock For t ~ 2-10 s : multiple crossings V(x) ~kH=Dm2/2E Peculiar modifications of PH, w.r.t. to the case of a static matter density profile (see [G.L. Fogli, E.Lisi, A.M., and D. Montanino, hep-ph/0304056] ) SHOCK-WAVE PROPAGATION

  20. Shock-wave effects on PH strongly dependent on q13. • Present on ne (ne) only in NH (IH) due to PH. Neutrino oscillations as a “camera” for shock-wave propagation

  21. How to extract a model-independent signature of shock-wave propagation? [G.L. Fogli, E. Lisi, A.M., and D. Montanino, hep-ph/0412046] It makes sense to compare bins with low and high energy shock effects shock effects In IH and for q13 not too small, SN shock wave(s) induce non-monotonic time spectra at “sufficiently high” energy.

  22. STOCHASTIC SN MATTER DENSITY FLUCTUATIONS [G.L. Fogli, E. Lisi, A.M., and D. Montanino, hep-ph/0603033] Inthe matter blown-off by the shock-wave passage, there could be stochastic matter density fluctuations Small-scale fluctuations with an amplitude x~ few % of the local density might potentially suppress shock-wave effects on n time spectra for large values of q13 Alessandro MirizziIFAE 2006 Pavia, 19/04/2006

  23. ne + p → n + e+ For ne: EARTH MATTER EFFECTS Earth matter crossing induces additional n flavor transitions. The main signature of Earth matter effects – oscillatory modulations of the observed energy spectra – is unambiguous since it can not be mimicked by known astrophysical phenomena • Earth effect is not seen The hierarchy is inverted and sin2q13 10-3 Degeneracy: either normal hierarchy, or inverted hierarchy with sin2q13 ≲10-3. • Earth effect is seen

  24. CHERENKOV SCINTILLATOR A Mton-class Cherenkov with ~105 events is needed LENA (~50 kton) with ~ 9000 events is enough ROBUST STRATEGIES FOR OBSERVING EARTH EFFECTS One detector observes SN shadowed by the Earth • Case I: Identify wiggles in signal of a single detector Problem: Smearing by limited energy resolution [A.Dighe, M.Keil, and G. Raffelt, hep-ph/0304150] • Case II: Another detector observes the SN directly. Identify Earth effects by comparing signals Alessandro MirizziIFAE 2006 Pavia, 19/04/2006

  25. Shadowing probability Earth Core OPTIMAL DETECTOR LOCATIONS [A.M., G. Raffelt, P. Serpico, astro-ph/0604300 ] Theshadowing probabilityis rather insensitive to the details of SN distribution. Nothern locations preferred: Phyäsalmi (Finland) proposed for LENA is the best location On-line tool to evaluate shadowing probability: http://www.mppmu.mpg.de/supernova/shadowing

  26. SHOCK+EARTH SIGNATURES Exploiting these complementary signatures one could extract useful information on the neutrino mass hierarchy and on q13 Alessandro MirizziIFAE 2006 Pavia, 19/04/2006

  27. In particular: • The missing pieces of neutrino mass spectrum and mixing matrix can be probed. • Models of core-collapse, shock-wave propagation, and SN n production can be “calibrated”. • Non-standard n properties can also be tested. SUMMARY AND CONCLUSIONS Observing SN neutrinos is the holy grail of low-energy neutrino astronomy The physics potential of next-generation detectors in this context is enormous, both for particle physics and astrophysics. SN n physics program with next-generation detectors is a no-loose project, and probably a high-winner one. Alessandro MirizziIFAE 2006 Pavia, 19/04/2006

  28. MISCELLANEA n n n n n n n n n n n n

  29. n-proton elastic scattering • How to measure non-electron neutrinos: nm , nt, nm, nt ? Proton spectrum in KamLAND all flavors nm, nt, nm, nt 1 kton ne ne Scintillator [J.Beacom, W. Farr, and P. Vogel, hep-ph/0205220] Exploiting neutrino-proton elastic scattering n + p → n + p in a low-threshold scintillator ~ 7300 ev. in LENA @ 10 kpc The measured proton spectrum is related to the incident non-electron neutrino spectra. It allows to separately measure their average energy andtheir fraction of binding energy Not possible with other neutral current interactions Alessandro MirizziIFAE 2006 Pavia, 19/04/2006

  30. Supernova pointing with neutrinos Angular distribution of events n e →n e ne p → n e+ [A. Bueno, I.Gil-Botella, and A.Rubbia, hep-ph/0307222] • LAr TPC [M.Apollonio, et al., hep-ex/9906011] • Scintillator The neutron associated to ne p → n e+ retains a memory of the neutrino direction A galactic SN can be located several hours before the optical explosion through the neutrino burst [R.Tomas, D.Semikoz, G. Raffelt, and A.Dighe, hep-ph/0307050] • Mton Cherenkov Exploit the directionality of n-e scatterings (fwd peaked). Reduction of bkg by the addition of gadolinium to tag the neutron associated to IBD. The accuracy would be as good as ~0.6° (2° without Gd) Reconstruct the incoming neutrino direction by n-e elastic scattering Accuracy ~28.8°/√N for Ee> 5 MeV For 100 kton: ~ 1° The uncertainty in the location of a SN is ~9° for a 50 kton detector Alessandro MirizziIFAE 2006 Pavia, 19/04/2006

  31. SUPERNOVA EARLY WARNING SYSTEM (SNEWS) Early lightcurve of SN1987A Neutrinos several hours before light Super-K Kamland SNO MiniBooNE LVD ALERT Borexino [P.Antonioli et al., astro-ph/0406214 ] Neutrino observations can alert astronomers several hours in advance to a SN. To avoid false alarms, require alarm from at least two experiments Server @ Brookhaven Alessandro MirizziIFAE 2006 Pavia, 19/04/2006

  32. Silicon burning: SN self-alert During the last stage of a pre-supernova star, while the Silicon core ignites, n’s are produced copiously by e+ e-n n. Betelgeuse Detection reaction:nep n e+ d= 0.2kpc …. Adding gadolinium [J.F.Beacom, and M.R.Vagins, “GADZOOKS! Antineutrino Spectroscopy with Large Water Cerenkov Detectors”, hep-ph/0309300], it would be possible to detect the associated neutron, but only for very close stars (d ≲2 kpc) because of the high neutron background (~2500 ev/day). Possibility to “foresee” the SN collapse (for close by Supernovae) 0.4 Mton Cherenkov [A. Odrzywolek, M. Misiaszek, and M. Kutschera, astro-ph/0311012] For Betelgeuse (d=0.2kpc) will be ~104 e+ in NH (~2.5  103 in IH, PH=0) The detection of e+ is very difficult (because of the threshold ETH = 7 MeV), however ….

  33. Detection of Neutrinos from Supernovae in Nearby Galaxies Cumulative SN rate [S. Ando, J. Beacom, and Y. Yuksel, astro-ph/0503321] Mton Cherenkov Reconstruction of SN neutrino spectrum by the patient accumulation of ~1 neutrino per supernova from galaxies within 10 Mpc, in which there were at least 9 core-collapse SN since 2002. Alessandro MirizziIFAE 2006 Pavia, 19/04/2006

  34. SUPERNOVA RELIC NEUTRINO DETECTION

  35. A galactic SN explosion is a spectacular event which will produce an enormous number of detectable n, but it is a rare event (~ 3/century) … Alessandro MirizziIFAE 2006 Pavia, 19/04/2006

  36. n n n n n n n WHAT CAN WE LEARN FROM SRN? • In principle, we can extract information on: • Star formation rate • Neutrino masses and mixing parameters • SN neutrino energies … not all at the same time, however! (degeneracy of effects) .... Conversly, there is a guaranteed n background produced by all the past Supernovae in the Universe, but leading to much less detectable events. Next-generation detectors will be able to measure this background of neutrinos: Supernova Relic Neutrinos (SRN)

  37. SIMULATION No distortion flux limit Super- Kamiokande collaboration has recently investigated the SRN flux using 1496 days of data [M.Malek et al., Phys.Rev.Lett. 90, 061101 (2003)]. It fixed an upper bound on SRN signal: ~ close to the most recent theoretical predictions SRN signal should manifest as distortion of the bkg spectra. [L. Strigari, J. Beacom, T. Walker, P. Zhang, astro-ph/0502150] Alessandro MirizziIFAE 2006 Pavia, 19/04/2006

  38. Below ~15–20 MeV, bkgd dominated by spallation products (made by atmospheric m) and by reactor ne. For En  [20-30] MeV, the bkg of low-energy atmospheric neis relatively small. But, in this window, there is a large background due to “invisible” m (i.e. below Cherenkov emission threshold) decay products, induced by low energy atmospheric nm and nm. Adding Gd [J.F.Beacom, and M.R.Vagins, hep-ph/0309300], spallation ~eliminated, invisible m reduced by ~5. The analysis threshold lowered. In the window Epos[10,20] MeV, after 1 year, the SRN signal detectable at 6s level A 2-3s signal could emerge after an exposure of 4 years in a 0.4 Mton detector [G.L.Fogli, E.Lisi, A.M., and D.Montanino, hep-ph/0412046] Mton Cherenkov Alessandro MirizziIFAE 2006 Pavia, 19/04/2006

  39. Relevant improvement of the sensitivity to SRN ne by the delayed coincidence between the prompt e+ and the captured n in ne + p → n + e+  • Invisible m • Spallation Threshold analysis may be lowered at E ≈ 9 MeV (reactor ne bkg) SRN ne might be detected at ~ 2s after 4 years of data taking Scintillator [L. Oberauer, talk at NOVE ‘06] No longer a problem In the window between 9.5 < E < 30 MeV: LENA would observe ~ 44-77 SRN/10 years Alessandro MirizziIFAE 2006 Pavia, 19/04/2006

  40. 3 kton LAr [A. Cocco, A. Ereditato, G. Fiorillo, G. Mangano, V. Pettorino, hep-ph/040803] Sensitivity to SRN ne via Ar CC interactions • Invisible m are not a problem: Easily disentangled from SRN by the track topology • Spallationevents do not represent a bkg: different signature w.r.t. SRN In the window 16 MeV ≤ E ≤ 40 MeV, for a 100 kton detector, after 5 years of data-taking, one obtains NSRN≈ 57 for ne in N.H. and large q13 With a 100 kton liquid Ar TPC detector, SRN ne signal may be observed at 4s after 5 years of data-taking (at 1s for 3 kton). Alessandro MirizziIFAE 2006 Pavia, 19/04/2006

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