1. E. MignecoErice ISCRA, July 2-13 2004 Introduction to High energy neutrino astronomy Erice ISCRA School 2004 Emilio Migneco

2. E. MignecoErice ISCRA, July 2-13 2004 Topics 1) Introduction to high energy neutrino astronomy Motivations for HE neutrino astronomy HE neutrino sources Neutrino telescopes operation principles Backgrounds 2) Future cubic kilometer arrays Review of existing detectors and projects Future detectors: impact of site parameters architecture experimental challenges simulations and expected performances 1) Introduction to high energy neutrino astronomy Motivations for HE neutrino astronomy HE neutrino sources Neutrino telescopes operation principles Backgrounds 2) Future cubic kilometer arrays Review of existing detectors and projects Future detectors: impact of site parameters architecture experimental challenges simulations and expected performances

3. E. MignecoErice ISCRA, July 2-13 2004 Neutrino astronomy Neutrinos are elementary particles with “special” properties: light neutral interact by weak force Good astrophysical probes: not deflected  point back to the source not absorbed  travel Gpc distances (overcome GZK effect) But they are difficult to detect I have done a terrible thing I invented a particle that cannot be detected W.Pauli

4. E. MignecoErice ISCRA, July 2-13 2004 The known cosmic neutrino spectrum ? SuperKamiokande neutrino image of the Sun HST image of SN 1987A The measurements of (low energy) solar, SN and atmospheric neutrino fluxes is permitting to solve open questions in astrophysics, nuclear and particle physics... Davis and Koshiba Nobel laureates 2002

5. E. MignecoErice ISCRA, July 2-13 2004 High energy astrophysics The detection of high energy gammas and CR are milestones in modern astrophysics but there are still open questions Particle acceleration mechanism in astrophysical sources Identification of high energy CR sources Solution of UHECR puzzle Heavy dark matter content in the Universe The detection of high energy gammas and CR are milestones in modern astrophysics but there are still open questions Particle acceleration mechanism in astrophysical sources Identification of high energy CR sources Solution of UHECR puzzle Heavy dark matter content in the Universe

6. E. MignecoErice ISCRA, July 2-13 2004 The high energy cosmic ray standard paradigm Ankle Galactic nuclei E -3 Sources of high energy protons exists and dominate the CR spectrum at E> 10 18.5 eV Knee Gaisser protons E -2.7 Galactic protons E -2.7

7. E. MignecoErice ISCRA, July 2-13 2004 Top Down “Top – Down” and “Bottom – Up” processes M X ~10 21  24 eV CR  10 21 eV decay or annihilation acceleration p,e at rest gammas and neutrinos Bottom Up CR  10 21 eV E -2 spectrum flat spectrum

8. E. MignecoErice ISCRA, July 2-13 2004 Astrophysical sources of UHE particles Large cosmic objects Intense magnetic field High shockwave velocity Hillas Fermi acceleration to high energies requires GRB L   10 52 erg/sec Bright AGN L   10 47 erg/sec These values are typical for very bright sources E max =10 20 eV

9. E. MignecoErice ISCRA, July 2-13 2004 Possible extra Galactic sources of CR: AGN QSO GB1508+5714 Chandra The term AGNs (Active Galactic Nuclei) gathers a number of astrophysical objects Massive Black Hole Accretion disk (UV + lines) Collimated jets QSO 3C273 QSO 3C279 EGRET The brightest observed steady sources: L  =10 42  10 47 erg/s When the jet is directed towards the Earth  luminosity increases  ”Blazars”

10. E. MignecoErice ISCRA, July 2-13 2004 Possible extra Galactic sources of CR: GRB GRB (Gamma Ray Bursts) are the most powerful emissions of gamma rays ever observed. Happens at cosmological distances The observation rate is few/day GRB have recentely been shown to be associated with SN, as indicated by the GRB030329 – SN 2003dh correlation GRB 030329 ESO L  = 10 51  10 53 erg/s  t  1  100 s (1/3 <2 sec) (GRB 030329 z=0.17)

11. E. MignecoErice ISCRA, July 2-13 2004 Limits of HE gamma and proton astronomy The UHE CR and gamma horizon is limited by interactions with low energy background radiation

12. E. MignecoErice ISCRA, July 2-13 2004 Absorption of high energy photons and protons N  CMBR  N  (GZK) n CMBR ~ 400 cm -3  p  ~ 100  barn E CMBR ~ 6.6·10 -4 eV  E p ~ 10 19.5 eV Guaranteed sources of neutrinos  IR,CMBR  e + e - E CMBR ~ 6.6·10 -4 eV  E  ~ 10 13.5 eV Lower energy photons interact also with IR backgrond See also T. Stanev,2004 for p-IR interactions

13. E. MignecoErice ISCRA, July 2-13 2004 The GZK effect Closest AGNs Galactic radius (15 kpc) 5 Gpc

14. E. MignecoErice ISCRA, July 2-13 2004 High Energy neutrinos production Are the astrophysical sources of High Energy CR also candidate sources of HE neutrinos ? The interaction of protons with ambient gas or photon field may produce neutrino fluxes Are the astrophysical sources of High Energy CR also candidate sources of HE neutrinos ? The interaction of protons with ambient gas or photon field may produce neutrino fluxes

15. E. MignecoErice ISCRA, July 2-13 2004 Neutrino production in cosmic accelerators Halzen Proton acceleration Fermi mechanism proton spectrum dN p /dE ~E -2 Neutrino production Proton interactions p  p (SNR,X-Ray Binaries) p   (AGN, GRB, microQSO) decay of pions and muons Astrophysical jet Particle accelerator electrons are responsible for gamma fluxes (synchrotron, IC)

16. E. MignecoErice ISCRA, July 2-13 2004 HE proton interaction on ambient p or  Beam dump in SNR environment 00 CANGAROO observationsof RXJ1713.7-3946 fit with TeV gamma ray production by  0 decay (?)   +-+- Muons and muon-neutrinos  Beam dump in astrophysical jet environment (GRB,AGN,microQSO) Shock waves Matter shells HE proton Target photons pions muons and neutrinos HE proton SN shells, clouds,.. Shock wave Target protons

17. E. MignecoErice ISCRA, July 2-13 2004 Neutrino fluxes chemical composition If the muon interaction time (IC) is larger than the muon decay time electron neutrinos and antineutrinos are also produced Tau neutrinos are unlikely produced in the sources (M  = 1.7 GeV) They can be detected at the Earth as “oscillated” muon neutrinos:

18. E. MignecoErice ISCRA, July 2-13 2004 Limits of HE gamma and proton astronomy High energy protons 50 Mpc neutrinos Astrophysical source Low energy protons deflected High energy gammas 10 Mpc

19. E. MignecoErice ISCRA, July 2-13 2004 Motivations of high energy neutrino astronomy Extend the high energy CR and  Horizon (<50 Mpc) Identify the sources of UHE particles Explore deep inside the source (where  »1 for CR and  ) Probe hadronic models in astrophysical sources Extend the high energy CR and  Horizon (<50 Mpc) Identify the sources of UHE particles Explore deep inside the source (where  »1 for CR and  ) Probe hadronic models in astrophysical sources

20. E. MignecoErice ISCRA, July 2-13 2004 High energy neutrino fluxes Astrophysical sources are expected to produce a diffuse high energy neutrino flux with spectral index  2 The most powerful and/or the closest sources could give a clear point-like neutrino signal Time correlations between events and photons will be clear signatures for transient source detection Astrophysical sources are expected to produce a diffuse high energy neutrino flux with spectral index  2 The most powerful and/or the closest sources could give a clear point-like neutrino signal Time correlations between events and photons will be clear signatures for transient source detection

21. E. MignecoErice ISCRA, July 2-13 2004 The WB bound The WB bound is valid for: Sources optically thin to UHECR (responsible for the observed spectrum) Sources in which CR acceleration takes place (top-down excluded) “thick sources” “thin sources” atmospheric Waxman Mannheim An upper limit to the diffuse neutrino flux was set by Waxman and Bahcall assuming that the detected UHECR sources are the only neutrino sources MPR bound WB bound GeV

22. E. MignecoErice ISCRA, July 2-13 2004 Possible extragalactic sources and fluxes Learned Mannheim AGN GZK p  AGN cores pp AGN cores p  blazar GRB WB Limit Diffuse neutrino fluxes Bright and nearby GRB could produce intense directional fluxes (e.g. GRB 030329) as well as brightest AGNs (3C273, 3C279) Stecker Nellen Mannheim Bierman Waxman Ruled out by new AMANDA data (preliminary)

23. E. MignecoErice ISCRA, July 2-13 2004 Galactic Sources of HE neutrinos Galactic sources do not contribute to UHECR fluxes, therefore are not limited by WB bound. Even if much less intense, their proximity to the Earth may yield detectable neutrino fluxes Another important source of TeV neutrinos could be the Galactic centre (SGR-A*) which is a very active gamma source SNR, extensively discussed: (see T. Stanev) CRAB, Protheroe microquasar Most powerful GX339-4 SS433 Distefano

24. E. MignecoErice ISCRA, July 2-13 2004 High energy neutrino detection Detection of HE astrophysical neutrinos is achieved through CC neutrino interaction with matter with charged lepton production Neutrino astronomy requires reconstruction of direction and energy of the reaction products (charged leptons) Detection of HE astrophysical neutrinos is achieved through CC neutrino interaction with matter with charged lepton production Neutrino astronomy requires reconstruction of direction and energy of the reaction products (charged leptons)

25. E. MignecoErice ISCRA, July 2-13 2004 Neutrino cross section Neutrinos are detected indirectly, following a DIS on a target nucleus N: 1 TeV 1 PeV   X  N At >TeV energies the muon and the neutrino are co-linear Reconstruction of the  trajectory allows the identification of the direction Gandhi 10 -33 cm 2 10 -35 cm 2

26. E. MignecoErice ISCRA, July 2-13 2004 Muon Range E  (GeV) Range (m) Muons have long tracks in water Due to its larger mass (m  / m e ~200) radiative losses of muons are strongly suppressed with respect to electrons Gaisser 1 TeV 1 PeV 2·10 3 2·10 4 In water

27. E. MignecoErice ISCRA, July 2-13 2004 Muon vs electron range Spiering Wiebush Electron Muon 100 TeV 1 TeV 100 GeV 10 GeV Geant 3.21

28. E. MignecoErice ISCRA, July 2-13 2004 Neutrino detection probabilty   Instrumented detector D<R  Due to the long muon range the target volume is much bigger than the detector instrumented volume Probabilty to produce a detectable (E  >E min ) muon 

29. E. MignecoErice ISCRA, July 2-13 2004 P  ·10 -3 LogE  (GeV) E ,min =1GeV Probabilty to produce a detectable (E  >E min ) muon Neutrino-induced muon fluxes deg P Earth 100 TeV 10 TeV 1 TeV Earth transparency to HE neutrinos  >PeV neutrinos search for “horizontal” tracks The number of muon events in units of detection area A and observation time T is: Neutrino flux spectrum

30. E. MignecoErice ISCRA, July 2-13 2004 Detection area for astrophysical UHE neutrino fluxes The observation of TeV neutrino fluxes requires km 2 scale detectors The expected number of events for WB sources is roughly:

31. E. MignecoErice ISCRA, July 2-13 2004 Expected astrophysical neutrino induced muons in 1 km 2 Diffuse Guaranteed (GZK):few / year ? Diffuse GRB:20 / year Diffuse AGN (thin):few / year (thick):>100 / year Point-like GRB (030329):1  10 / burst AGN (3C279):few / year Galactic SNR (Crab):few / year ? Galactic microquasars:1  100 / year Waxman Dermer Distefano Mannheim Protheroe

32. E. MignecoErice ISCRA, July 2-13 2004 km 3 scale neutrino detectors The requirement of large neutrino interaction target induced Markov and Zheleznykh to propose the use of natural targets. Deep seawater and polar ice offers: huge (and inexpensive) target for neutrino interaction; good optical characteristics as Cherenkov radiators; shielding from cosmic background. The requirement of large neutrino interaction target induced Markov and Zheleznykh to propose the use of natural targets. Deep seawater and polar ice offers: huge (and inexpensive) target for neutrino interaction; good optical characteristics as Cherenkov radiators; shielding from cosmic background.

33. E. MignecoErice ISCRA, July 2-13 2004 Underwater Cherenkov detectors: detection principles neutrino muon Cherenkov light ~5000 PMT Connection to the shore neutrino atmospheric muon depth >3000m

34. E. MignecoErice ISCRA, July 2-13 2004 The km3 telescope: a downward looking detector Neutrino telescopes search for muon tracks induced by neutrino interactions The downgoing atmospheric  flux overcomes by several orders of magnitude the expected  fluxes induced by interactions. On the other hand, muons cannot travel in rock or water more than  50 km at any energy Upgoing and horizontal muon tracks are neutrino signatures

35. E. MignecoErice ISCRA, July 2-13 2004 Cherenkov light emission and propagation The Cherenkov light is efficiently emitted by relativistic particles in water at UV-blue wavelengths under the condition:  n( ) > 1 Superkamiokande muon event  C ~ 42° n ( 300  700nm ) ~ 1.35

36. E. MignecoErice ISCRA, July 2-13 2004 Cherenkov track reconstruction pseudo vertex De Jong Cherenkov photons emitted by the muon track are correlated by the causality relation: The track can be reconstructed during offline analysis of space- time correlated PMT signals (hits).

37. E. MignecoErice ISCRA, July 2-13 2004 Detector granularity Spacing of optical sensors inside the instrumented volume must be of the order of the light absorption lenght in water (  70 m for blue light) About 5000 optical sensors are needed to fill up one km 3 Visible light

38. E. MignecoErice ISCRA, July 2-13 2004 Backgrounds Neutrino detectors must identify few astrophysical events on top of diffuse atmospheric backgrounds

39. E. MignecoErice ISCRA, July 2-13 2004 Backgrounds: atmospheric muons and neutrinos Atmospheric neutrinos: upward tracks are good neutrino candidates; event direction and energy criteria can be used to discriminate background from astrophysical signals. Atmospheric muons: downgoing events background is due to mis- reconstructed (fake) tracks; improve analysis filters for atmospheric muon background rejection. ANTARES

40. E. MignecoErice ISCRA, July 2-13 2004 Atmospheric muon background vs depth Downgoing muon background is strongly reduced as a function of detector installation depth. Depth >3000 m (  1 km rock) is suggested for detector installation NEMO NESTOR ANTARES AMANDA Bugaev BAIKAL

41. E. MignecoErice ISCRA, July 2-13 2004 First detection of HE neutrino events Proof of the underwater (and underice) Cherenkov detection technique has been achieved by AMANDA (South Pole) and BAIKAL-NT (Lake Baikal) detectors

42. E. MignecoErice ISCRA, July 2-13 2004 The AMANDA neutrino sky AMANDA and BAIKAL have demontrated the viability of neutrino detection with underwater and underice Cherenkov detectors at TeV energy scale AMANDA PRELIMINARY (neutrino 2004 conference) The atmospheric neutrino spectrum has been measured by AMANDA and BAIKAL See Silvestri’s talk

43. E. MignecoErice ISCRA, July 2-13 2004 The future neutrino telescopes The quest to reach the km 2 effective area is open ! Southern Hemisphere ICECUBE Northern Hemisphere Mediterranean km 3 1400 m 2400 m IceTop >3000 m

44. E. MignecoErice ISCRA, July 2-13 2004 Summary High energy astrophysical neutrino fluxes are expected on the base of CR and  observations Neutrino detection will provide unique informations on astrophysical sources: overcomes the limitations of  and CR astronomy due to absorption on CMBR at cosmological distances; evidence on the role of hadronic processeses in astrophysics Neutrino events correlated in space and time with point-like (transient) sources will be probably the first evidence of detection of astrophysical neutrinos The expected fluxes from sources implies >1km 2 effective area to detect TeV-PeV neutrinos High energy astrophysical neutrino fluxes are expected on the base of CR and  observations Neutrino detection will provide unique informations on astrophysical sources: overcomes the limitations of  and CR astronomy due to absorption on CMBR at cosmological distances; evidence on the role of hadronic processeses in astrophysics Neutrino events correlated in space and time with point-like (transient) sources will be probably the first evidence of detection of astrophysical neutrinos The expected fluxes from sources implies >1km 2 effective area to detect TeV-PeV neutrinos

45. E. MignecoErice ISCRA, July 2-13 2004 Other scientific goals Galactic SN: search for intense fluxes of electron anti-neutrinos need low optical background  task for AMANDA-ICECUBE Dark Matter: search for neutrinos (  10 GeV) originated by the annihilation of neutralinos in the Sun, Earth, Galactic Centre low energy threshold, good event direction reconstruction Galactic SN: search for intense fluxes of electron anti-neutrinos need low optical background  task for AMANDA-ICECUBE Dark Matter: search for neutrinos (  10 GeV) originated by the annihilation of neutralinos in the Sun, Earth, Galactic Centre low energy threshold, good event direction reconstruction