Neutrino sources. Atmospheric neutrinos Solar neutrinos Supernova neutrinos High energy neutrino sources Cosmic neutrino background

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1 Neutrino sources Natural sources: Atmospheric neutrinos Solar neutrinos Supernova neutrinos High energy neutrino sources Cosmic neutrino background Artificial sources Accelerator neutrinos Reactor neutrinos Plans for future 1

2 Natural sources of neutrinos 2

3 Atmospheric neutrinos Primary cosmic rays coming from Universe, broad mass spectrum, dominated by protons energy spectrum: mostly in GeVs Interactions in upper layers of atmosphere (average height km) Secondary cosmic rays products of interactions: many mesons( pions, kaons) mesons interact or decay meson interactions develop cascades 3

4 gora1 4

5 Atmospheric Neutrinos Weak decays are sources of neutrinos: π, K mesons decay on the way to Earth some muons also decay but many reach the surface (m μ =106 MeV; cτ=659 m) 5

6 Atmosph 6

7 Atmosph 7

8 How the Sun burns The Sun emits light because nuclear fusion produces a lot of energy where L sun is the Sun luminosity 1AU is the distance from Sun to Earth 8

9 Thermonuclear fusion reactions p+p > ν e +e + +d 0.42MeV max p+ e - + p > ν e +d 1.44 MeV d+p > γ+ 3 He 3 He+ 3 He > 4 He+p+p ppi (85%) 3 He+ 4 He > 7 Be+ γ 7 Be+ e - > ν e + 7 Li.86 MeV 7 Li+p > 4 He+ 4 He 7 Be+p > 8 B+γ 8 B > e - +ν e + 8 Be 15 MeV max 8 Be > 4 He+ 4 He rare but easier to measure ppii (15%) ppiii (0.01%) 9

10 Solar Neutrino Spectrum 10

11 Stellar evolution Interplaneta ry nebula Gravitation energy is transformed into heat; A large, dense, cool nebula (up to 10 6 M o, temp.~10 K) Protostar A gravitating matter condensation grows to ~ M o Star Fusion reactions start changing H into He M ~ Red Giant Super nova Neutron Star Black Hole Black Dwarf S N M >> White Dwarf Energy supply is depleted, radiation pressure decreases. Core contracts, its temperature grows, igniting hydrogen in the envelope. This leads to expansion of external layers. M ~ Red Super- Giant M ~ 8M Increase of surface leads to decreased envelope temperature. Stellar core contracts, temperature rises, making possible nuclear fusion of heavier elements. 11

12 Origins of Supernovae Major thermonuclear reactions: Reaction Ignition temperature (in millions of deg K) 4 1 H --> 4 He He --> 8 Be + 4 He --> 12 C C + 4 He --> 16 O 2 12 C --> 4 He + 20 Ne Ne + 4 He --> n + 23 Mg 2 16 O --> 4 He + 28 Si O --> 2 4 He + 24 Mg Si --> 56 Fe 6000 Onion structure with some fuel still burning at boundaries 12

13 Neutrinos from Supernovae 56 Fe has maximum binding energy no more fusion and no more heat production When a core of iron reaches a mass of 1.4 solar masses the gravitation wins and the core collapses Electrons of iron atoms are absorbed by protons: Heat gives rise to gammas which produce e + e - pairs: prompt neutrinos neutron star thermal neutrinos 13

14 SN 1987A More pictures in a special lecture on SN1987A 14

15 Cosmic sources of very high energy Not yet observed neutrinos - many experiments current and future to search for them. Many cosmic, rotating sources have strong mgt fields, giving rise to electric fields They can act as accelerators of high energy particles Many are binary systems i.e. have a partner which supplies target matter for meson, muon and neutrino production 15

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17 High-Energy Neutrino Astrophysics Proton accelerators generate roughly equal numbers of gamma rays and neutrinos! Neutrinos are not absorbed in the sources because they interact only weakly during propagation Many gammas are absorbed or their energy decreased during propagation Background: atmospheric neutrinos Expected signals from cosmic accelerators AGN active galactic nucleus 17

18 Active Galactic Nuclei Powered by accretion onto massive black holes (masses M Solar ) Accretion transpot matter inwards and angular momentum outwards Corona c- inverse Compton scatter of photons up to x-ray energies Relativistic jets The environment around AGN, collimated relativistic plasma Jets escaping along the pole of the Supermasive black hole 18

19 Jets and observation Elliptical Gallaxy M87 emitting a relativistic jet, as seen by Habble Space Telescope in visible spectrum Artist s conception of a binary star system with one black hole and one main sequence star M87 jet seen by the VLA in radio frequency, Field bigger and rotated compared to the above. 19

20 Models of imply neutrino emission sources, lecture 3pierwsze światło i GRB 20

21 Temperatures of decoupling from primary plasma 2.4 MeV (ν e ) and 3.7 MeV (ν µ, ν τ ) After that: e+e- annihilation CMB photons From that point T ν /T γ is constant Present temperature of cosmic neutrino background is T ν =1,95 K (E mev) Average density about 340 cm -3 (all flavors) Presently not measerable 21

22 (Wo)Man-made sources of neutrinos Accelerator neutrinos Reactor antineutrinos Plans for future: β - beams Neutrino factories 22

23 Neutrinos produced in accelerators In order to have high energy neutrinos one needs to: Accelerate protons Make those protons interact in a target to produce many mesons Allow pions to decay Collimate pions to form a beam Absorb remaining charged particles at the end of the beam line To avoid admixtures try to reduce decays: 23

24 protons/year Neutrino beams: proton fluxes MiniBOONE (2001) JHF (200x) Japan (JPARC) NUMI (2003) Fermilab (USA) Neutrino production starts with acceleration of protons K2K Japan (KEK) CERN CNGS (2005) WANF NuTeV proton beam energy, GeV 24

25 K2K - KEK to Kamioka 250 km 25

26 1.1µs 2.2s Front Detectors Decay pipe Pion monitor Horn Traget beam composition ν µ 98.2% ν e 1.3% 0.5 % <E ν > = 1.3 GeV peak E ν 1.0 GeV p intensity p/pulse p beam 12GeV-PS 26

27 K2K neutrino beam we need only those in the detectors Muons are slowed down; they mostly decay at rest and constitute only 1% background 27

28 Neutrinos at KEK Neutrino spectrum obtained with 2 horns and 250 ka current 28

29 New idea: off axis beams Neutrino energy For angles >0: Quasi monochromatic neutrino beam Tunable peak energy Reduced tail at high ν energies helps to reduce background due to production of pions 29

30 New neutrino beam J-PARC J-PARC Japan Proton Accelerator Research Complex w Tokai, at Pacific coast Proton beam 50GeV 3.3*10 14 protons per pulse Pulses of 5µs length every 3.5 seconds Power of 0.75MW 30

31 Reactors as Neutrino Sources Nuclear reactor is an excellent source of electron antineutrinos from β decay. Large power reactor produces about antineutrinos/sec From bound neutron decays: 31

32 Reactor Power vs. Neutrino Flux Reactor neutrino rate is proportional to its power! Chooz (Belgium) Antineutrino emission is isotropic and therefore its flux decreases with square of distance from reactor! Daily! Candidates all data Reactor Power (GW) 32

33 Expected interactions in the detector: ~ 2 events/day 33

34 Spectrum of reactor antineutrinos E! (MeV) 34

35 Contributions of Different Decay Chains to Reactor Neutrino Flux More than 99.9% of ν e s are products of fissions in 235 U, 238 U, 239 Pu, 241 Pu. Uncertainty of neutrino yield < 1% 35

36 Neutrino future beams Conventional high power beams - a problem of background for e- Neutrino factories - a new type of accelerator Magnetic field is necessary in detectors β beams electron neutrinos or anti-neutrinos 36

37 Neutrino factory muonstoragerings.web.cern.ch/muonstoragerings/ Similar to US scheme. 37

38 Beta-beam Basics Aim: production of (anti-)neutrino beams from the beta decay of radioactive ions circulating in a storage ring Similar concept to the neutrino factory, but parent particle is a beta-active isotope instead of a muon. Beta-decay at rest ν spectrum well known from electron spectrum Reaction energy Q typically of a few MeV Only electron (anti-)neutrinos Accelerated parent ion to relativistic γ max Boosted neutrino energy spectrum Forward focusing of neutrinos Beta-beam 6 He ν boost ν γ=100 sources, lecture 3 38

39 Which Radioactive ion is best? Factors influencing ion choice Need to produce reasonable amounts of ions. Noble gases preferred - simple diffusion out of target, gaseous at room temperature. Not too short half-life to get reasonable intensities. Not too long half-life as otherwise no decay at high energy. Avoid potentially dangerous and long-lived decay products. - Use electron capture to get monoenergetic neutrinos Best compromise Helium-6 to produce antineutrinos: Neon-18 to produce neutrinos: sources, lecture 3 39

40 Injection into Decay ring sources, lecture 3 40