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Time modulations and sterile neutrinos
Nuclear Physics B (Proc. Suppl.) 143 (2005) 488 www.elsevierphysics.com
Time modulations and sterile neutrinos Bhag C. Chauhana and Jo˜ ao Pulidoa a
Centro de F´ısica das Interac¸c˜oes Fundamentais (CFIF), Departamento de F´ısica, Instituto Superior T´ecnico, Av. Rovisco Pais, P-1049-001 Lisboa, Portugal
0920-5632/$ – see front matter © 2005 Published by Elsevier B.V. doi:10.1016/j.nuclphysbps.2005.01.153
We assume a field profile concentrated around the bottom of the convective zone. The figure shows the evolution of the three mass eigenvalues: at times of a strong field in the resonance region adiabatic conversion corresponding to a larger separation of eigenvalues will occur, while at times of a weaker field the eigenvalues become closer and less conversion will happen. A time dependent peak field value deep inside the convective zone will hence manifest itself in the time modulation of the neutrino signal. Of all solar neutrino experiments, the Ga one seems to be the most sensitive to these time variations. -10
10
λ2
Radiation Zone
-12
10
Convective Zone
λ1
eV
The BIG QUESTION, now that LMA is generally accepted to be the dominant solution to the Solar Neutrino Problem: is the solar neutrino flux constant in time or is it time modulated in relation to solar activity? Solar neutrino statistical analyses confronting theoretical model predictions with data have been using time averaged event rates or fluxes and could, for this reason, be missing important information. The recent examination of the data on a time basis done by the Stanford Group [1] has in fact provided increasing evidence that the solar neutrino flux is not constant, but varies with well-known solar rotation periods. Such a situation, if confirmed, can in no way be explained by the LMA scenario. It can neither be understood in terms of an SFP transition of νe into ν¯µ or ν¯τ , as this would originate a sizable and unseen ν¯e flux [2]. We propose a magnetic moment driven conversion from active to sterile neutrinos (along with dominant LMA conversion to active neutrinos) which provides an attractive possibility to explain a sizable time modulation in the solar neutrino flux with solar activity. We consider a system of two active neutrinos and a sterile one which mix in the mass eigenstates ν0 , ν1 and ν2 through magnetic moment only. We seek for a model with the simplest departure from the conventional LMA case and able to generate a time dependent transition into a sterile neutrino [3]. We obtain the neutrino survival probability (P (νe → νe )=Pee ) by assuming the propagation inside the sun to be adiabatic except in the region where the adiabaticity parameter reaches its minimum (RSFP resonance). Moreover, the LMA oscillation and the ν2 → ν0 transition are adiabatic in the solar interior.
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λ0
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10
0
0.1
0.2
0.3
0.4
0.5 r/Rs
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0.9
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REFERENCES 1. P.A. Sturrock and J. Scargle, Astrophys. J. 550 (2001) L101. 2. B.C. Chauhan, J. Pulido and E. T-Lujan, Phys. Rev D68 033015 (2003). 3. B.C. Chauhan and J. Pulido, JHEP 0406 (2004) 008.
Time modulations and sterile neutrinos Bhag C. Chauhana and Jo˜ ao Pulidoa a
Centro de F´ısica das Interac¸c˜oes Fundamentais (CFIF), Departamento de F´ısica, Instituto Superior T´ecnico, Av. Rovisco Pais, P-1049-001 Lisboa, Portugal
0920-5632/$ – see front matter © 2005 Published by Elsevier B.V. doi:10.1016/j.nuclphysbps.2005.01.153
We assume a field profile concentrated around the bottom of the convective zone. The figure shows the evolution of the three mass eigenvalues: at times of a strong field in the resonance region adiabatic conversion corresponding to a larger separation of eigenvalues will occur, while at times of a weaker field the eigenvalues become closer and less conversion will happen. A time dependent peak field value deep inside the convective zone will hence manifest itself in the time modulation of the neutrino signal. Of all solar neutrino experiments, the Ga one seems to be the most sensitive to these time variations. -10
10
λ2
Radiation Zone
-12
10
Convective Zone
λ1
eV
The BIG QUESTION, now that LMA is generally accepted to be the dominant solution to the Solar Neutrino Problem: is the solar neutrino flux constant in time or is it time modulated in relation to solar activity? Solar neutrino statistical analyses confronting theoretical model predictions with data have been using time averaged event rates or fluxes and could, for this reason, be missing important information. The recent examination of the data on a time basis done by the Stanford Group [1] has in fact provided increasing evidence that the solar neutrino flux is not constant, but varies with well-known solar rotation periods. Such a situation, if confirmed, can in no way be explained by the LMA scenario. It can neither be understood in terms of an SFP transition of νe into ν¯µ or ν¯τ , as this would originate a sizable and unseen ν¯e flux [2]. We propose a magnetic moment driven conversion from active to sterile neutrinos (along with dominant LMA conversion to active neutrinos) which provides an attractive possibility to explain a sizable time modulation in the solar neutrino flux with solar activity. We consider a system of two active neutrinos and a sterile one which mix in the mass eigenstates ν0 , ν1 and ν2 through magnetic moment only. We seek for a model with the simplest departure from the conventional LMA case and able to generate a time dependent transition into a sterile neutrino [3]. We obtain the neutrino survival probability (P (νe → νe )=Pee ) by assuming the propagation inside the sun to be adiabatic except in the region where the adiabaticity parameter reaches its minimum (RSFP resonance). Moreover, the LMA oscillation and the ν2 → ν0 transition are adiabatic in the solar interior.
-14
10
λ0
-16
10
0
0.1
0.2
0.3
0.4
0.5 r/Rs
0.6
0.7
0.8
0.9
1
REFERENCES 1. P.A. Sturrock and J. Scargle, Astrophys. J. 550 (2001) L101. 2. B.C. Chauhan, J. Pulido and E. T-Lujan, Phys. Rev D68 033015 (2003). 3. B.C. Chauhan and J. Pulido, JHEP 0406 (2004) 008.