1 Gianni Fiorentini Solar Neutrinos The previous millenium: e disappearance An appearance experiment SNO: An appearance experiment Solar neutrinos undergo flavor conversion e -> (  or   Non e 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 e Since 1970 Davis has been looking for solar e by means of the Pontecorvo reaction: e + 37 Cl -> 37 Ar + e e + 37 Cl -> 37 Ar + e 37 Ar + e -> e + 37 Cl Collect for one month Ar atoms, extract them and look for their decay: 37 Ar + e -> e + 37 Cl Expt. sensitive only to e, mainly from B, and to a smaller extent from Be. The signal of neutrinos was observed, however: Cl(exp)= 1/3 Cl (SSM) - Cl(exp)= 1/3 Cl (SSM) - No directionality - No real time - (Signal possibly correlated with “11 years” solar cycle) Be

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

5 Superkamiokande (20,000m 3 water detector with 10,000 phototubes)

6 The heart of Kam. and SuperKam. It is in the  =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 Sun -> do come Neutrinos do come from the Sun Neutrino disappearance is confirmed: SK(exp)= 0.45 SK(SSM) 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 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  e ->   or   ) (Villante Lisi GF 98 ). An experiment is needed which can distinguish (  or   ) from e.

8 The Gallium experiments powered by nuclear reactions 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:  e + 71 Ga-> e + 71 Ge A radiochemical method is used. Again a deficit with respect to SSM: Ga(exp) =( )Ga(SSM) Important deficit since predictions on pp and Be are much more robust. Cannot separate the amount of (pp) and (Be).

9 Disappearance vs. Appearance ?

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

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

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

13 Neutrino oscillations 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:  m 2 = eV 2 tan 2 = 0.4 f B =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. differences scale Warning: oscillations are sensitive to mass differences, not to the absolute mass scale.

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

15 Kamland: a crucial test of the LMA solution 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- + p ->e+ +n n+p->d+  In the absence of oscillation, some 400ev/yr are expected (above geo- )

16 Oscillations or what else? 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) Both these explanations predict a null effect for Kamland SFT FCI

17 Neutrons and neutrinos neutron well log 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.05R o. Their flux depends on nuclear physics inputs (branches of ppI, ppII and ppIII) and on astrophysical inputs (Z/X, opacity, diffusion, luminosity). central temperature These latter control the central temperature T : 20  (B) =  (B) SSM (T/T SSM ) 20 (S/S SSM ) Due to high power dependence,  (B) is a good thermometer for the solar interior, if nuclear physics S 17 (S=S 33 s S 17 S e7 -1 ) is well determined. From present data: T=15.7(1+-1%)10 6 K Comparable errors arise from  (B) and S 17 (after LUNA measurements at LNGS) Observational accuracy comparable to that of SSM. Information complementary to helioseismology, which determines u =T/ .

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

20 The success of SSM and helioseismology 33 11 BP2000  U/U (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 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 3 He+ 3 He-> 4 He +2p at the solar Gamow peak, by using a 50 KV underground accelerator at LNGD LUNA-II is measuring the p+ 14 N-> 15 O +  reaction, with a new200 KV accelerator A new measurement of p- 7 Be 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? neutrinos produced in the Earth interior 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 Signal energy [MeV] (anti)- +p-> n+e + e + releases energy and annihilates: S.E.=E(e+) + 2m e Delayed coincidence with 2MeV  from p+n->d+ . Separation from reactor events.  -osc. give  1/2 reduction

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

25 A few references…*) Recent Data: SNO: Ahmad et al nucl- ex/ SK: Fukuda et al hep-ex/ Recent analysis : Fogli et al, hep-ph/ Barger et al hep-ph/ Bahcall et al hep=ph/ Berezinsky and Lisi De Holanda and Smirnov hep-ph/ See also transparencies of Neutrino 2002, Munich at *)and a lot of apologies for missing references

26 Appendix

27 pp-chain

28 Appendix Neutrino Energy (MeV) Neutrino flux

29 Uncertainties on B and Be production Source 8 B 7 Be ___________________________ p-p He+ 3 He He+ 4 He p+ 7 Be Comp Opacity Diffusion Luminosity

30 Energy dependence of different oscillations

31 Summary of ocillation solutions Solution  m 2 (eV) 2 tan2 Solution  m 2 (eV) 2 tan2 2 /d.o.f. LMA5.5E /79 LOW7.3E /79 QVO6.5E /79 SMA5.2E-61.1E-383.1/79 Fogli et al hep-ph LMA gives a good fit, LOW and VO survive at 3 , SMA is excluded at 5 

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

33 Spin flavor precession* Transitions e -> anti- m could be driven by solar magnetic field if neutrino has a transition magnetic moment . Transitions e -> anti- m could be driven by solar magnetic field if neutrino has a transition magnetic moment . Can reconcile strong suppression at intermediate energy (Be) with no distortion at high energy ( B) Can reconcile strong suppression at intermediate energy (Be) with no distortion at high energy ( B) Consistent with data provided: Consistent with data provided: -  = (0.3-1)  B -B max = 10 5 G -Suitable B(r) profile *) Lim, Marciano, Akhmedov, Valle, Miranda.. RSF