Cosmological/phenomenological implications of neutrino oscillations

1. Cosmological/phenomenological implications of neutrino oscillations Steve King S.F.King, NuFact02, London

2. Atmospheric Neutrino Oscillations S.F.King, NuFact02, London

3. Solar Neutrino Oscillations LMA LOW Choubeytalk

4. I. Cosmological Implications See e.g. Kainulainen and Olive, hep-ph/0206163 • Cosmological relic density and dark matter • Galaxy structure limits on neutrino mass • Neutrinos and nucleosynthesis • Neutrinos and supernova • Neutrinos and cosmic rays S.F.King, NuFact02, London

5. Cosmological relic density and dark matter In the early universe neutrinos were in thermal equilibrium with photons, electrons and positrons. When the universe cooled to temperatures of order 1 MeV the neutrinos decoupled, leading to a present day number density similar to photons. If neutrinos have mass they will contribute to mass density of universe, leading to the constraint corresponding to . From the lab limit on the electron-like neutrino mass . together with the atmospheric and solar mass splittings we have a stronger constraint corresponding to the range which implies that neutrinos cannot be the dominant component of dark matter. S.F.King, NuFact02, London

6. Galaxy structure limits neutrino mass Tegmark (opposite), Wang, Zaldarriaga CMB power spectrum 2dF Galaxy Redshift survey astro-ph/0204152 Galaxy power spectrum S.F.King, NuFact02, London

7. Neutrinos and nucleosynthesis The number of light “neutrino species” (or any light species) affects the freeze-out temperature of weak processes which determine n/p, and successful nucleosynthesis gives a constraint S.F.King, NuFact02, London

8. What about sterile neutrinos?The limit on applies to them also, but they need to be produced during the time when nucleosynthesis was taking place, and the only way to produce them is via neutrino oscillations. This leads to strong limits on the sterile-active neutrino mixing angles which disfavour LSND – assuming the primordial lepton asymmetry is not anomalously large (Y.Y.Y.Wong et al) S.F.King, NuFact02, London

9. Neutrinos and Supernovae 99% of a supernova energy is emitted in neutrinos. From SN1987A in Small Magellanic Cloud neutrinos were observed. Studying the spread in arrival times over 10 s leads to LMA affects SN1987A (Valle talk) However SN have their own problems such as how they explode at all, and how the neutron star remnant is kick-started. S.F.King, NuFact02, London

10. Neutrinos and Cosmic Rays GZK cut-off may be exceeded if UHE neutrinos scatter off relic background nu’s to produce Z’s within 50 Mpc – need nu mass But recent data from Fly’s Eye, HiRes and Yakutsk strongly suggest (7 sigma) that GZK cut-off is present after all (Bahcall and Waxman hep-ph/0206217) Z-burst model S.F.King, NuFact02, London

11. II. Phenomenological Implications • Neutrino mass patterns • Neutrino mass matrices • Neutrinoless double beta decay • SUSY and LFV • Highlights of theory talks yesterday in WG1/4 S.F.King, NuFact02, London

12. Possible three neutrino mass patterns: “Normal” “Inverted” S.F.King, NuFact02, London

13. Successful leading order light Majorana matricesBarbieri,Hall,Smith,Strumia,Weiner;Altarelli,Feruglio;SFK hep-ph/0204360;Ross talk Type A (zero in 11) Type B (non-zero 11) Green “natural” Hierarchy Large neutrinoless double beta decay Inverted hierarchy Pseudo-Dirac Degenerate S.F.King, NuFact02, London

14. Neutrinoless double beta decay If the electron neutrino is Majorana, then neutrinoless double beta decay Klapdor-Kleingrothaus et al (2001) have claimed a signal based on re-analysis of Heidelberg-Moscow data: (Criticised by Aalseth et al, Feruglio et al.) GENIUS would resolve this problem with sensitivity down to 0.01 eV Degenerate B: From Pascoli and Petcov (assume LMA) Inverted hierarchy B: Hierarchy and Inverted A: c.f. KATRIN tritium decay sensitivity

15. SUSY and LFV If SUSY is present then neutrino masses inevitably lead to lepton flavour violation due to radiatively generated off-diagonal slepton masses e.g. Blazek, SFK This will lead to large 23 lepton flavour violation and S.F.King, NuFact02, London

16. Blazek,SFK

17. WG1/4 talks yesterday Y. Shimizu MSSM with neutrino masses leads to sizeable LFV. Plots below are for minimal supergravity – in realistic string models even larger rates would be expected due to non-universal A-terms (Ross) S.F.King, NuFact02, London

18. N. Shimoyama In a simplified model where the right-handed neutrino masses are universal the MSSM with neutrino masses leads to too-large rates for with a hierarchical neutrino mass spectrum In such a scheme BR(deg)<BR(inv)~BR(hier) M. Koike He studied . He concluded that Z~30-60 is best for experimental searches, and it is possible to distinguish models of new physics by measurement of several kinds of nuclei. S.F.King, NuFact02, London

19. J. Sato He discussed the possibility that the signal of wrong sign muons in a long baseline experiment may either be due to neutrino oscillations or to some new flavour changing interaction involving neutrinos. Such interactions may be generated in SUSY models, with the mu-tau channel being the most effective leading to an “enhanced oscillation effect” at CNGS. K. Babu Proposed an explanation of LSND involving three active neutrinos, but with lepton number violating decay . Predicts that MiniBoone sees no oscillation signal since it uses neutrinos from pion decay. Michel parameter rho=0.7485 (not ¾). Fermi constant from muon decay differs by 0.2%. S.F.King, NuFact02, London

20. Final Remarks • Neutrino mass and mixing angles as inferred from oscillations plays a crucial role in cosmology in particular dark matter, galaxy structure, nucleosynthesis, supernovae and cosmic rays. • Superbeams in medium term, and neutrino factory in longer term are required to determine the 13 mixing angle, the CP phase and the pattern of neutrino masses to really pin down our universe. • We also need to know the absolute scale of neutrino mass from neutrinoless double beta decay or tritium beta decay – present best limit is from galaxy structure. GRBs could also provide strong limits in future (Choubey,SFK). • If SUSY is present neutrino masses (via the see-saw mechanism) lead to lepton flavour violation which according to talks at this workshop could be observed soon. • In summary neutrino oscillations not only are the most important discovery in particle physics for 20 years but also have profound cosmological and phenomenological implications. S.F.King, NuFact02, London