Diapositiva 1

1
NOW 2006 Neutrino Oscillation Workshop Conca
Specchiulla, 9-16 September 2006
SOLAR ATMOSPHERE NEUTRINOS
Alessandro MIRIZZI (Dip. di Fisica INFN, BARI,
Italy)
Based on G.L. Fogli, E. Lisi, A.M., D.
Montanino, P.D. Serpico, hep-ph/0608321
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OUTILNE

• 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
NOW 2006
Conca Specchiulla, 14/09/2006
3
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
NOW 2006
Conca Specchiulla, 14/09/2006
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HIGH ENERGY SOLAR NEUTRINOS

• Solar flares (E 50 MeV)

• WIMP annihilation in the Sun (E GeV)

Alessandro Mirizzi
NOW 2006
Conca Specchiulla, 14/09/2006
5
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)
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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
0ltbltR?.
b
The original fluxes are almost b-independent
below the TeV scale
Alessandro Mirizzi
NOW 2006
Conca Specchiulla, 14/09/2006
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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)
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UNOSCILLATED SAn FLUXES
The factorization of oscillations and absorptions
allows to take as unoscillated input the
attenuated fluxes, integrated over the solar
disk.
For Elt100 GeV, no simulation We assume
as in C.Hettlage, K.Mannheim, J. Learned,
astro-ph/9910208
with 1.75ltglt2.45 to take into account
uncertainties related to heliomagnetic effects
D.Seckel, T.Stanev, T.K. Gaisser, Astrophys. J.
382, 652 (1991)
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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
NOW 2006
Conca Specchiulla, 14/09/2006
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3n FRAMEWORK
Mixing parameters U U (q12, q13, q23)
as for CKM matrix
Mass-gap parameters

• Dm2

n3
dm2 7.92 (10.09) ? 10-5 eV2 sin2q12
0.314 (10.18-0.15) Dm2 2.6
(10.14-0.15) ? 10-3 eV2 sin2q23
0.45(10.35-0.20) sin2q13 0.82.3-0.8 ? 10-2
inverted hierarchy

• dm2/2

• dm2/2

n1
n1
-dm2/2
n2
n2
-dm2/2
-Dm2
n3
normal hierarchy
Fogli et al., hep-ph/0608060
In the following we will assume normal hierarchy
Alessandro Mirizzi
NOW 2006
Conca Specchiulla, 14/09/2006
11
NEUTRINO POTENTIAL
Matter effects on n oscillations crucially depend
on neutrino potential in Sun
Potentially large matter effects are expected at
resonance when
or
In normal hierarchy the resonance condition can
be fulfilled only by n
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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
NOW 2006
Conca Specchiulla, 14/09/2006
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VACUUM APPROXIMATION (V0)
C.Hettlage, K.Mannheim, J. Learned,
astro-ph/9910208
(at the production)
Many oscillation cycles in vacuum
n decoherence at Earth (energy resolution)
Alessandro Mirizzi
NOW 2006
Conca Specchiulla, 14/09/2006
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MATTER EFFECTS
Alessandro Mirizzi
NOW 2006
Conca Specchiulla, 14/09/2006
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AVERAGING OVER THE IMPACT PARAMETER
Given the limited angular resolution of the
detector (dqgt1), one has to integrate over the
solar disk (qsun0.26).
Matter effects strongly suppressed after the
averaging.
Oscillation probabilities very similar to the
phase-averaged vacuum case
Alessandro Mirizzi
NOW 2006
Conca Specchiulla, 14/09/2006
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OSCILLATED SAn FLUXES AT EARTH
OSCILLATIONS
Alessandro Mirizzi
NOW 2006
Conca Specchiulla, 14/09/2006
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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 gt
  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
NOW 2006
Conca Specchiulla, 14/09/2006
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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
Alessandro Mirizzi
NOW 2006
Conca Specchiulla, 14/09/2006