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Gianni Fiorentini Solar Neutrinos

Gianni Fiorentini Solar Neutrinos. The previous millenium: n e disappearance SNO: An appearance experiment Solar neutrinos undergo flavor conversion n e -> ( n m or n t ) Non n e are the main component of the flux at E >5 MeV Main issue: mechanism of conversion?

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Gianni Fiorentini Solar Neutrinos

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  1. Gianni FiorentiniSolar Neutrinos • The previous millenium: ne disappearance • SNO: An appearance experiment • Solar neutrinos undergo flavor conversion ne -> (nm or nt) • Non ne are the main component of the flux at E >5 MeV • Main issue: mechanism of conversion? • What have we learnt on the Sun ? • What can we learn from neutrinos ?

  2. The 2002 Nobel prize:new ways of looking at the sky Riccardo Giacconi “for pioneering contributions to astrophysics, which have led to the discovery of cosmic X-ray sources" Ray Davis and Masatoshi Koshiba “for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos”

  3. Davis: a formidable radiochemical experiment • Since 1970 Davis has been looking for solar ne by means of the Pontecorvo reaction: • ne+ 37Cl -> 37Ar + e • Collect for one month Ar atoms, extract them and look for their decay: 37Ar + e ->ne+ 37Cl • Expt. sensitive only to ne, mainly from B, • and to a smaller extent from Be. • The signal of neutrinos was observed, however: • - Cl(exp)= 1/3 Cl (SSM) • - No directionality • - No real time • - (Signal possibly correlated with • “11 years” solar cycle) < B > Be < pp >

  4. Neutrino telescopes:Kamiokande and Superkamiokande • Koshiba and his school have developed directional and real timen-detectors: • Study of elastic collisions of n with electrons in a huge water tank • n+ e(at rest) -> n + e( moving) • Electron direction is strongly correlated • with that of neutrinos (n-telescope). • Electrons are detected by means of the emitted Cerenkov light in water. • The energy spectrum of electrons can be measured. • Sensitive to ne with E>6MeV (B only) • nm/t also detected (sm= st= 1/6 se) but cannot be distinguished from ne

  5. Superkamiokande (20,000m3 water detector with 10,000 phototubes)

  6. The heart of Kam. and SuperKam. • It is in the F=50 cm phototubes especially developed by Hamamatsu. • MITI financed a joint R&D project between • Hamamatsu and the Metropolitan Tokyo University. • As a return, Japan has a got a Nobel prize and the world leader for phototube production. 50 cm

  7. The results of Kamiokande and SuperKamiokande • Neutrinos do come from the Sun • Neutrino disappearance is confirmed: • SK(exp)= 0.45 SK(SSM) • The B-neutrino spectrum looks undistorted • Seasonal variations consistent with geometry • No day-night variation observed, at the % level • No apparent correlation with the solar cycle Sun -> • Why is the SK signal higher than Davis? • The two expts become consistent with each other and with SSM if some 2/3 of Boron ne->(nm or nt) (Villante Lisi GF 98). • An experiment is needed which can distinguish (nm or nt ) from ne.

  8. The Gallium experiments • Gallex (now GNO) at LNGS and SAGE in Russia have shown that the Sun is powered by nuclear reactions, measuring (mainly) the pp and Be neutrinos by means of: • ne+ 71Ga-> e + 71Ge • A radiochemical method is used. • Again a deficit with respect to SSM: • Ga(exp) =(0.59 +-0.06)Ga(SSM) • Important deficit since predictions on pp and Be are much more robust. • Cannot separate the amount of n(pp) and n(Be).

  9. Disappearance vs. Appearance ?

  10. SNO: the appearance experiment • A 1000 tons heavy water detector sensitive to B-neutrinos by means of: • CC: ne+d -> p + p + e • sensitive to ne only, provides a • good measurement of ne spectrum, • weak directionality • NC: nx+d -> p + n + nx • Equal cross section for alln flavours. • Measures total 8B flux from Sun. • ES: nx+e -> e + nx • Mainly sensitive to ne, strong directionality The important point is that SNO can determine both: F(ne) andF(ne + nm + nt )

  11. Total measured B-flux is in excellent agreement with SSM • 2/3 of produced B-neutrinos transform into nm or nt . SNO results

  12. Implications for neutrinos • From exp.tal rates one can deduce the energy dependence of the survival probability Pee: • SNO&SK give Boron: Pee(E>5MeV) »1/ 3 • Cl- SNO&SK -> Be+CNO: • Pee(0.8<E<5MeV) »0.2-0.5 • Ga-Cl- SNO&SK -> pp: • Pee(0.2<E<0.4MeV) »3/4 • Energy dependence is found. • Be is worst determined (wait for Borexino) < Pee> Neutrino Energy (MeV) • Complete analysis include all other observables (spectra, day/night, seasonal variations…), • see e.g Fogli@Lisi, Smirnov, Bahcall...

  13. Neutrino oscillations • The total 81 data are well fitted within the simplest scheme of oscillations between two active neutrinos • The best fit is provided by the LMA solution, with: • Dm2= 6.2 10-5 eV2 • tan2J = 0.4 • fB=1.06 • The energy dependence (and large suppression) is related to matter effect in the Sun. • Other oscillation solutions (SMA, Just-So,LOW, sterile…) are presently disfavoured by data. Warning: oscillations are sensitive to mass differences, not to the absolute mass scale.

  14. Crucial predictions of the LMA solution NC/CC Day/night asymmetry % SNO will get significant improvement on NC in near future, by adding salts with large n-absorption x-section. Earth matter effect. So far 1s effect in SK and 2s in SNO. It needs time…..

  15. Kamland: a crucial test of the LMA solution • If LMA is the solution, the oscillation length of MeV (anti) neutrinos is L»100 Km. • Kamland, an 800 ton scintillator detector, is measuring events from a dozen reactors, through: • anti-n + p ->e+ +n • n+p->d+g • In the absence of oscillation, some 400ev/yr are expected (above geo-n)

  16. Oscillations or what else? • Kamland is a crucial test for the LMA solution, which predicts a large reduction of reactor events. • Remind that other solutions are possible for the solar neutrinos, e.g: • Spin-flavour transitions, induced by the solar magnetic field (Okun, Akhmedov. ..) • Hypothetical flavour changing interactions, inside the sun (Wolfenstein) FCI SFT • Both these explanations predict a null effect for Kamland

  17. Neutrons and neutrinos • In 1940 Pontecorvo applied the recent slow neutron studies of the Rome group to invent the neutron well log, an instrument still used for oil (and water) prospection. • Now that we have learnt enough on neutrinos, we have to learn from neutrinos The Oil And Gas Journal, 1940, p.32

  18. Implications for the Sun • Boron neutrinos are a probe of the deep solar core, their production being peaked at .05Ro. • Their flux depends on nuclear physics inputs (branches of ppI, ppII and ppIII) and on astrophysical inputs (Z/X, opacity, diffusion, luminosity). • These latter control the central temperature T : • F(B) = F(B)SSM (T/TSSM)20 (S/SSSM) • Due to high power dependence, F(B) is a good thermometer for the solar interior, if nuclear physics • (S=S33s34-0.5S17Se7-1) is well determined. • From present data: • T=15.7(1+-1%)106K • Comparable errors arise from F(B) and S17(after LUNA measurements at LNGS) • Observational accuracy comparable to that of SSM. • Information complementary to helioseismology, which determines u =T/m.

  19. Bruno Pontecorvo Three great ideas: i)The Sun as a neutrino source ii) The Cl-Ar method iii)Neutrino oscillations

  20. 3s BP2000 1s DU/U The success of SSM and helioseismology (Model-Sun)/Model Model=BP2000 Sun=from inversion of helioseismic data Error estimate: from Dziembowki et al. Astrop. Phys. 7 (1997) 77 Agreement to the level of few in 10-3. Systematic errors from the inversion procedure dominate accuracy (starting solar models, interpolation…)

  21. LUNA at LNGS Laboratory for Underground Nuclear Astrophysics at Gran Sasso. LUNA-I has measured the 3He+3He->4He +2p at the solar Gamow peak, by using a 50 KV underground accelerator at LNGD LUNA-II is measuring the p+14N->15O + g reaction, with a new200 KV accelerator A new measurement of p-7Be is planned.

  22. (Anti)- neutrinos from Earth • What is the content of radioactive material (U, Th and K) inside Earth? • What is the radiogenic contribution to heat flow? • Detection of (anti) neutrinos produced in the Earth interior is the way for measuring Earth radioactivity, once we know the fate of neutrinos. • This is becoming possible now...

  23. Expectations for Kamland and Borexino • (anti)-n+p-> n+e+ • e+ releases energy and annihilates: • S.E.=E(e+) + 2me • Delayed coincidence with 2MeV g from • p+n->d+g. • Separation from reactor events. • n-osc. give » 1/2 reduction Signal energy [MeV]

  24. From Sun to Earth:Kamland (Jap) and Borexino (LNGS) Detectors built for studying neutrinos from reactors and Sun, will also have the first signal of anti neutrinos from Earth..

  25. A few references…*) • Recent Data: • SNO: Ahmad et al nucl- ex/204009 • SK: Fukuda et al hep-ex/0205075 • Recent analysis : • Fogli et al, hep-ph/0106247 + 0203138+ 0206162 • Barger et al hep-ph/0204253 • Bahcall et al hep=ph/024314 • Berezinsky and Lisi • De Holanda and Smirnov hep-ph/0205241 • See also transparencies of Neutrino 2002, Munich at • http://neutrino2002.ph.tum.de *)and a lot of apologies for missing references

  26. Appendix

  27. pp-chain

  28. Neutrino flux Neutrino Energy (MeV) Appendix

  29. Uncertainties on B and Be production Source 8B 7Be ___________________________ p-p 0.04 0.02 3He+3He 0.02 0.02 3He+4He 0.08 0.08 p+7Be +0.14-0.07 0 Comp. 0.08 0.03 Opacity 0.05 0.03 Diffusion 0.04 0.02 Luminosity 0.03 0.01

  30. Energy dependence of different oscillations

  31. Summary of ocillation solutions Solution dm2(eV)2 tan2J c2/d.o.f. LMA 5.5E-5 0.42 71.3/79 LOW 7.3E-8 0.67 79.7/79 QVO 6.5E-10 1.33 74.9/79 SMA 5.2E-6 1.1E-3 83.1/79 Fogli et al hep-ph0206162 LMA gives a good fit, LOW and VO survive at 3s, SMA is excluded at 5s

  32. Pull off diagrams P de Hollanda and Smirnov LMA gives a good fit, LOW and VO survive at 3s, SMA is excluded at 5s

  33. Spin flavor precession* • Transitions ne-> anti- nm could be driven by solar magnetic field if neutrino has a transition magnetic moment m. • Can reconcile strong suppression at intermediate energy (Be) with no distortion at high energy ( B) • Consistent with data provided: • -m = (0.3-1)10-11mB • -Bmax= 105 G • -Suitable B(r) profile • *)Lim, Marciano, Akhmedov, Valle, Miranda.. RSF

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