SOLAR ATMOSPHERE NEUTRINOS TAUP 2007 – International Conference on Topics in Astroparticle and Underground Physics Sendai, 11-15 September 2007 SOLAR ATMOSPHERE NEUTRINOS Alessandro MIRIZZI (MPI, Munich, Germany) Based on: G.L. Fogli, E. Lisi, A.M., D. Montanino, P.D. Serpico, PRD 74, 093004 (2006) [hep-ph/0608321].

OUTILNE Solar atmosphere neutrino (SAn) fluxes Sun as high energy neutrino source Solar atmosphere neutrino (SAn) fluxes SAn oscillations in Sun and in vacuum Event rate in HE neutrino telescopes Conclusions Alessandro Mirizzi TAUP 2007 Sendai, 13/09/2007

MeV SOLAR NEUTRINOS Sun is a well-known source of low-energy O(MeV) ne, produced in its core by nuclear reactions Solar neutrinos provide us with solid evidence for  mass & mixing, and with a beautiful synthesis of physics and astrophysics. Alessandro Mirizzi TAUP 2007 Sendai, 13/09/2007

HIGH ENERGY SOLAR NEUTRINOS Solar flares (E~ 50 MeV) WIMP annihilation in the Sun (E~ GeV) Alessandro Mirizzi TAUP 2007 Sendai, 13/09/2007

SOLAR ATMOSPHERE NEUTRINOS (SAn) Cosmic rays hitting the solar atmosphere lead to the production of secondary particles via high-energy pp interaction, the decay of which produces a flux of ne and nm. ( ) ( ) (at production)

SAn ORIGINAL FLUXES [G.Ingelman & M.Thunman, hep-ph/9604288 ] SAn flux calculated basing on Montecarlo models (PHYTIA & JETSET) for high energy particle interactions at different impact parameter 0<b<R. . b The original fluxes are almost b-independent below the TeV scale Alessandro Mirizzi TAUP 2007 Sendai, 13/09/2007

SAn ATTENUATION IN THE SUN While propagating in Sun, SAn are affected by oscillations in matter attenuations through weak interactions with nucleons of the solar medium. Interaction cross sections approximatively the same: oscillations and absorptions can be factorized [V.Naumov, hep-ph/0112249] Absorptions taken into account multiplying the original n fluxes by an overall attenuation function A(E,b) Attenuation function For E~102-103 GeV, a flux attenuation of O(10%) or less is expected only for case with b~0 (which have little geometrical weight)

UNOSCILLATED SAn FLUXES The factorization of oscillations and absorptions allows to take as unoscillated input the attenuated fluxes, integrated over the solar disk. For E<100 GeV, no simulation We assume as in [C.Hettlage, K.Mannheim, J. Learned, astro-ph/9910208] with 1.75<g<2.45 to take into account uncertainties related to heliomagnetic effects [D.Seckel, T.Stanev, T.K. Gaisser, Astrophys. J. 382, 652 (1991)]

The neutrino event rates above 1 TeV can be ignored in practice. The rapid decrease of the SAn fluxes with energy is only partially compensated by the increase of the (charged current) neutrino cross sections s. The neutrino event rates above 1 TeV can be ignored in practice. Relatively low experimental threshold will be crucial for future SAn detection. Alessandro Mirizzi TAUP 2007 Sendai, 13/09/2007

Dynamical MSW term (in matter) Kinematical mass-mixing term SAn OSCILLATIONS SAn fluxes are affected by oscillation effects in Sun and then in vacuum. We have solved numerically MSW neutrino equations considering the standard 3n oscillation framework Dynamical MSW term (in matter) Kinematical mass-mixing term Alessandro Mirizzi TAUP 2007 Sendai, 13/09/2007

Mixing parameters: U = U (q12, q13, q23) as for CKM matrix 3n FRAMEWORK Mixing parameters: U = U (q12, q13, q23) as for CKM matrix M2 = - , + , ± Dm2 dm2 2 “solar” “atmospheric” Mass-gap parameters: n3 Dm2 dm2 ≈ 7.92 (1±0.09)  10-5 eV2 sin2q12 ≈ 0.314 (1+0.18-0.15) Dm2 ≈ 2.6 (1+0.14-0.15)  10-3 eV2 sin2q23 ≈ 0.45(1+0.35-0.20) sin2q13 = 0.8+2.3-0.8  10-2 inverted hierarchy n1 dm2/2 n1 dm2/2 n2 -dm2/2 n2 -dm2/2 n3 -Dm2 normal hierarchy [Fogli et al., hep-ph/0608060] In the following we will assume normal hierarchy Alessandro Mirizzi TAUP 2007 Sendai, 13/09/2007

NEUTRINO POTENTIAL Matter effects on n oscillations crucially depend on neutrino potential in Sun: + ( n ) ; - ( n ) Potentially large matter effects are expected at resonance when or In normal hierarchy the resonance condition can be fulfilled only by n

OSCILLATED n FLUXES SAn fluxes at Earth expressed in terms of the oscillation probabilities appearence ! …. But, challenging to be detected at E~ 102 GeV Alessandro Mirizzi TAUP 2007 Sendai, 13/09/2007

VACUUM APPROXIMATION (V=0) [C.Hettlage, K.Mannheim, J. Learned, astro-ph/9910208] (at the production) VACUUM OSCILLATIONS Many oscillation cycles in vacuum + n decoherence at Earth (energy resolution) (at Earth) [for q23=p/4] Alessandro Mirizzi TAUP 2007 Sendai, 13/09/2007

MATTER EFFECTS Matter effects High energy vacuum limit (l»R) Resonance condition never realized in n channel. Matter effects negligible. Matter effects suppressed after averaging over n+n Alessandro Mirizzi TAUP 2007 Sendai, 13/09/2007

AVERAGING OVER THE IMPACT PARAMETER Given the limited angular resolution of the detector (dq>1°), one has to integrate over the solar disk (qsun~0.26°). Matter effects strongly suppressed after the averaging. Oscillation probabilities very similar to the phase-averaged vacuum case Alessandro Mirizzi TAUP 2007 Sendai, 13/09/2007

VARIATIONS OF OSCILLATION PARAMETERS The spread of the curves due to sin2q23 uncertainties amounts to about ±15%, while the variations due to sin2q13 and d are roughly a factor of three smaller. The ± 2s errors on the other oscillations parameters (Dm2, dm2, sin2q12), as well as the change from normal to inverted hierarchy, would produce even smaller variations in these curves. In practice, one can currently evaluate the effects of oscillation parameters uncertainties in terms of sin2q23 only. Alessandro Mirizzi TAUP 2007 Sendai, 13/09/2007

OSCILLATED SAn FLUXES AT EARTH Uncertainty associated to 2s range of q23 Uncertainty associated to the initial fluxes OSCILLATIONS Alessandro Mirizzi TAUP 2007 Sendai, 13/09/2007

SAn EVENT RATE Events rate in a km3 detector (e.g., Icecube) [A= 1 km2] SAn signal dominates over the atmospheric bkg in the solar angular bin. Mismatch between the produced m and the original n: in the observable angular bin S/N ~ 1 for E > 100 GeV Huge cosmic ray bkg: only upgoing n useful ~ 4 useful m events/year above 100 GeV In ~10 years it would allow a “SAn check” of q23 Alessandro Mirizzi TAUP 2007 Sendai, 13/09/2007

CONCLUSIONS The Sun is a valuable source of high-energy neutrinos, produced by cosmic ray interactions in solar atmosphere (“solar atmosphere neutrinos”, SAn) We have performed a detailed study of SAn oscillations, including matter effects in the Sun: SAn are affected by peculiar matter effects (in principle, sensitive to q13 and to mass hierarchy). However, (i) the averaging over the impact parameter; (ii) the indistinguishability between n and n strongly contribute to suppress them. “Vacuum” approximation is accurate enough to characterize SAn oscillation effects. The detection of SAn in large telescope detectors would: test n vacuum oscillation at high energy scale provide information on solar astrophysics perhaps provide signature of new neutrino physics and eventually of dark matter Alessandro Mirizzi TAUP 2007 Sendai, 13/09/2007