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Episode II

Episode II. Neutrino: a spy of the innermost solar interior Nuclear reactions in the Sun and solar neutrinos. The spy of nuclear reactions in the Sun. The real proof of the occurrence of nuclear processes is in the detection of reaction products (holds for Sun & Earth)

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Episode II

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  1. Episode II Neutrino: a spy of the innermost solar interior Nuclear reactions in the Sun and solar neutrinos

  2. The spy of nuclear reactions in the Sun • The real proof of the occurrence of nuclear processes is in the detection of reaction products (holds for Sun & Earth) • For the Sun, only neutrinos can escape freely from the production region. • By measuring solar neutrinos one can learn about the deep solar interior (and about neutrinos…)

  3. = if L and Le are conserved ? 2ne The luminosity constraint • The total neutrino flux is immediately derived from the solar constant Ko: • If one assumes that Sun is powered by transforming H into He (Q=26,73MeV): 4p+2e- -> 4He + ? • Then one has 2ne for each Q of radiated energy, and the total neutrino produced flux is:

  4. Towards neutrino energy spectra • To determine Ftot we did not use anything about nuclear reactions and solar models. • In order to determine the components (Fpp, FBe FB…)one has to know the relative efficiencies of nuclear reactions in the Sun (branches ppi/ppII/ppIII…)

  5. 8B 8Be*+ e+ +e 2 The pp-chain 99,77% p + p  d+ e+ + e 0,23% p + e - + p d + e 84,7% d + p 3He + ~210-5 % 13,8% 3He + 4He 7Be +  13,78% 0,02% 7Be + e-7Li + e 7Be + p 8B +  3He+3He+2p 7Li + p ->+ 3He+p+e++e pp I pp II pp III hep

  6. A group picture Neutrino flux [cm-2 s-1 ] Neutrino Energy [Mev]

  7. Another group picture The production region of neutrinos

  8. A 40 year long journey In 1963 J Bahcall and R Davis, based on ideas from Bruno Pontecorvo, started an exploration of the Sun by means of solar neutrinos. Their trip had a long detour, generating the “solar neutrino puzzle” All experiments, performed at Homestake, Kamioka, Gran Sasso and Baksan exploring different portions of the solar spectrum, presented a deficit of ne. Were all experiments wrong? Was the SSM wrong? Was nuclear physics wrong? Or did something happen to neutrinos during their trip from Sun to Earth?

  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 with weak directionality • NC: nx+d -> p + n + nx Equal cross section for alln flavors. It measures the 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) and F(ne + nm + nt )

  11. SNO results • The measured total B neutrino flux is in excellent agreement with the SSM prediction. • Only 1/3 of the B-neutrinos survive as ne • 2/3 of the produced transform into nmor nt SSM & N.P are right All experiments are right Neutrinos are wrong

  12. From Sun to Earth:The KamLAND confirmation • anti-ne from distant (»100 km) nuclear reactors are detected in 1Kton liquid scintillator where: Anti-ne +p -> n + e+ n + p -> d + g • Obs./Expected= 54/ (86+-5.5) -> Oscillation of reactor anti-ne proven - > SNO is confirmed with man made (anti)neutrinos

  13. The impact of SNO and KamLAND Before SNO After SNO-I After KamLAND After SNO-II

  14. BrunoPontecorvo Neutron Well Logging - A New Geological Method Based on Nuclear Physics, Oil and Gas Journal, 1941, vol.40, p.32-33.1942. • An application of Rome celebrated study on slow neutrons, the neutron log is an instrument sensitive to water and hydrocarbons. • It contains a (MeV) neutron source and a (thermal) neutron detector. As hydrogen atoms are by far the most effective in the slowing down of neutrons, the distribution of the neutrons at the time of detection is primarily determined by the hydrogen concentration, i.e. water and hydrocarbons. The Cl-Ar method Neutrino sources (sun, reactors, accelerators) Neutrino oscillations

  15. From neutrons to neutrinos • We have learnt a lot on neutrinos. Their survival/transmutation probabilities in matter are now understood. • We have still a lot to learn for a precise description of the mass matrix (and other neutrino properties…) • Now that we know the fate of neutrinos, we can learn a lot from neutrinos.

  16. Neutrinos and Supernovae Neutrinos and the Earth Neutrino contribution to DM What next? Neutrinos and the Sun

  17. The measured boron flux • The total active FB=F(ne + nm + nt) boron flux is now a measured quantity. By combining all observational data one has: FB= 5.5 (1 ± 7%) 106 cm-2s-1. • The central value is in good agreement with the SSM calculation • Note the present1s error is DFB/FB =7% • In the next few yearsone can expect to reach DFB/FB»3%

  18. FB The Boron Flux, Nuclear Physics and Astrophysics s33s34s17se7spp Nuclear • FB depends on nuclear physics and astrophysics inputs • Scaling laws have been found numerically* and are physically understood FB= FB (SSM)· s33-0.43 s34 0.84 s171 se7-1 spp-2.7 · com1.4 opa2.6 dif 0.34 lum7.2 • These give flux variation with respect to the SSM calculation when the input X is changed by x = X/X(SSM) . • Can learn astrophysics if nuclear physics is known well enough. astro *Scaling laws derived from FRANEC models including diffusion. Coefficients closer to those of Bahcall are obtained if diffusion is neglected.

  19. Uncertainties budget • Nuclear physics uncertainties, particularly on S34 , dominate over the present observational accuracy DFB/FB =7%. • The foreseeable accuracy DFB/FB =3% could illuminate about solar physics if a significant improvement on S34 is obtained. • For fully exploiting the physics potential of a FB measurement with 3% accuracy one has to determine S17 and S34 at the level of 3% or better. *LUNA gift ** See later

  20. Results of direct capture expts**. Progresson S17 • JNB and myself have long been using a conservative uncertainty, however recently high accuracy determinations of S17 have appeared. • Average from low-energy (<425KeV) data of 5 recent determinations yields: S17(0)= 21.4 ± 0.5 with c2/dof=1.2 • A theoretical error of ± 0.5 has to be added. • However all other expts. give somehow smaller S17 than Junghans et al. **See also Gialanella et al EPJ A7, 303 (2001) • Note that indirect methods also give somehow smaller values • In conclusion, it looks that a 5% accuracy has been reached.

  21. Remark on S17 and S34 • For a long time S17 was the main uncertainty. • If S17(0)= 20.5 ± 1 eVba 5% accuracy has been reached. • The 9% error of S34 is the main source of uncertainty for extracting physics from Boron flux. • LUNA measurement of S34 will be extremely important.

  22. pp Be Fi/FiSSM B T/TSSM Sensitivity to the central temperature Castellani et al. ‘97 Bahcall and Ulmer. ‘96 • Boron neutrinos are mainly determined by the central temperature, almost in the way we vary it. • (The same holds for pp and Be neutrinos)

  23. The central solar temperature • The various inputs to FB can be grouped according to their effect on the solar temperature. • All nuclear inputs (but S11) only determine branches ppI/ppII/ppIII without changing solar structure. • The effect of the others can (largely) be reabsorbed into a variation of the “central” solar temperature: • FB =FB(SSM) [T /T(SSM) ]20. .S33-0.43 s340.84 s17 se7-1 Boron neutrinos are excellent solar thermometers due to their high (»20) power dependence.

  24. Present and future for measuring T with B-neutrinos • At present, DFB/FB =7% and DSnuc/ Snuc= 10% (cons.) translate into DT/T= 0.6 % the main error being due to S17 and S34. • If nuclear physics were perfect (DSnuc/Snuc =0) already now we could have: DT/T= 0.3 % • When DFB/FB =3% one can hope to reach (for DSnuc/Snuc =0) : DT/T= 0.15 %

  25. Du/u 1s3s The central solar temperature and helioseismology • Helioseismology determines sound speed. • The accuracy on its square is Du/u 0.15% inside the sun. • Accuracy of the helioseismic method degrades to 1% near the centre. • Boron neutrinos provide a complementary information, as they measure T. present DT/T future • For the innermost part, neutrinos are now (DT/T = 0.6%) almost as accurate as helioseismology • They can become more accurate than helioseismology in the future.

  26. The Sun as a laboratory for astrophysics and fundamental physics • A measurement of the solar temperature near the center with 0.15% accuracy can be relevant for many purposes • It provides a new challenge to SSM calculations • It allows a determination of the metal content in the solar interior, which has important consequences on the history of the solar system (and on exo-solar systems) • One can find constraints (surprises, or discoveries) on: • Axion emission from the Sun • The physics of extra dimensions (through Kaluza-Klein axion emission) • Dark matter (if trapped in the Sun it could change the solar temperature very near the center) • …

  27. CNO neutrinos, LUNA and the solar interior Solar model predictions for CNO neutrino fluxes are not precise because the CNO fusion reactions are not as well studied as the pp reactions. Also, the Coulomb barrier is higher for the CNO reactions, implying a greater sensitivity to details of the solar model. • The principal error source is S1,14. The new measurement by LUNA is obviously welcome. • A measurement of the CNO neutrino fluxes would provide a stringent test of the theory of stellar evolution and unique information about the solar interior.

  28. Solar neutrino experiments and CNO cycle Bahcall, Garcia & Pena-Garay Astro-ph 0212331 • Solar neutrino experiments set an upper limit (3s) of 7.8% to the fraction of energy that the Sun produces via the CNO fusion cycle. • An order of magnitude improvement upon the previous limit. • New experiments are required to detect CNO neutrinos and to proof that some 1% of the solar luminosity is generated by the CNO cycle.

  29. Is the Sun fully powered by nuclear reactions? • Are there additional energy sources beyond 4H->He?: • Are there additional energy losses, beyond photons and neutrinos? • One can determine the “nuclear luminosity” from measured neutrino fluxes , Knuc = Ftot Q/2 , and compare with the observed luminosity K: Knuc/K= 1.4 (1 +- 25%) (1s) • This means that, within 25%, the Sun is actually powered by 4H->He fusion…

  30. Summary • Solar neutrinos are becoming an important tool for studying the solar interior and fundamental physics. • Better determinations of S34 and S1,14 are needed for fully exploiting the physics potential of solar neutrinos. • All this brings towards answering fundamental questions: • Is the Sun fully powered by nuclear reactions? • Is the Sun emitting something else, beyond photons and neutrinos?

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