Solar Neutrinos: Solar Neutrinos The Problems They Cause


Outline: Outline Introduction. What are neutrinos? The solar neutrino problem. The solar neutrino solution?


Introduction: Introduction Solar neutrinos provide a useful probe of solar physics. The solar neutrino flux measured at earth shows a neutrino deficit. Experiments continue to provide information about solar neutrinos.


Source of Solar Neutrinos: Source of Solar Neutrinos


Neutrinos: Neutrinos


What is a Neutrino?: What is a Neutrino? Fundamental particle. Electrically neutral, low mass. Three flavors: Electron neutrino Muon neutrino Tau neutrino


More About Neutrinos: More About Neutrinos Wolfgang Pauli 'invented' them to conserve energy and angular momentum in b-decay. (1930) Anti-neutrinos first detected from nuclear reactors. (1956) Produced by nuclear reactions.


Solar Neutrino Production: Solar Neutrino Production Neutrino producing reactions of the p-p fusion chain:


Prediction of the Standard Solar Model: Prediction of the Standard Solar Model


Detecting the Undetectable: Detecting the Undetectable The probability of a neutrino interacting with matter is greater than zero: Neutrino-electron scattering: Removes the electron from an atom. All flavors can scatter in this fashion. Interaction with an atom: Neutrino converted into electron, m-, or t -. Flavor dependent.


Neutrino Detection: Neutrino Detection Inverse b-decay: Neutrino captured by nucleus. Neutron converted to proton and electron. Radioactive nucleus remains to be counted.


The Solar Neutrino Problem: The Solar Neutrino Problem First solar neutrino detector utilized perchloroethylene as detection medium. Only sensitive to electron neutrinos with E andgt; .81 MeV. Neutrino origin not determinable. Measured: 2.56 +/- .23 SNU Theoretical: 7.7 +/- (1.2/1.0) SNU


Experimental versus Theoretical: Experimental versus Theoretical


Gallium Experiments: Gallium Experiments Gallium based experiments confirmed a neutrino deficit in low energy neutrinos. Begun in 1990. They had the same disadvantages of the chlorine based experiments.


Water Based Experiments: Water Based Experiments Sensitive to high energy neutrinos. Able to determine the direction of origin of neutrinos. Originally constructed to observe proton decay.


Kamiokande and Super-K: Kamiokande and Super-K Super-K statistics: Height of 40 m, diameter of 40 m. Filled with 50,000 metric tons of extremely pure water, with optical attenuation length andgt; 70 m. Two regions: 2 m wide outer region, used as shield against low energy particles. Inner region covered by 11,200, 50 cm wide photomultiplier tubes.


Detection Method: Detection Method Experiment is carried out in real time. Cherenkov radiation from neutrino-electron scattering. Only sensitive to high energy neutrinos.


Super-K Detection Threshold: Super-K Detection Threshold


Definitely Solar Neutrinos: Definitely Solar Neutrinos Super-K shows that the observed neutrinos are from the sun. Scattered electrons recoil in direction of sun-earth vector. Scattered electron energies provide information on incident neutrino energy spectrum.


Still a Solar Neutrino Deficit: Still a Solar Neutrino Deficit


Theories for the Deficit: Theories for the Deficit Standard Solar Model (SSM) is incomplete/incorrect. Variations of the SSM have been tried, with little success. Standard Model of particle physics is incomplete/incorrect: Model assumes zero mass for neutrinos. If neutrinos have small mass, solar deficit possibly explained.


Neutrino Oscillations: Neutrino Oscillations If neutrinos have a small mass, they could oscillate between different states. Initial assumption was that solar neutrinos are pure ne. If a ne converts to a nm or a nt in flight, would not be detected by experiments.


Neutrino Oscillations: Neutrino Oscillations MSW effect: An interaction by which neutrinos can change flavor could be enhanced if neutrinos travel through matter. Could become a resonance behavior for certain oscillation and matter density parameters. Effect is only sensitive to (Dm)^2.


Matter Oscillations: Matter Oscillations A neutrino state can be expressed as:


Matter Oscillations: Matter Oscillations Interactions between neutrinos and solar matter must be taken into account. Interaction probability changes with the electron density. All neutrino flavors can have neutral current interactions with atoms. Only electron neutrinos can have charged current interactions with atoms.


Matter Oscillations: Matter Oscillations Maximum probability of an oscillation found to be:


Vacuum Oscillations: Vacuum Oscillations Probability of an electron neutrino remaining an electron neutrino:


Oscillation Diagram: Oscillation Diagram


Super-K Points to Neutrino Mass: Super-K Points to Neutrino Mass Found twice as many atmospheric muon neutrinos from the sky above than from below. The explanation for this was the muon neutrino oscillating to a tau neutrino, or possibly a sterile neutrino flavor.


Super-K Before: Super-K Before


Super-K After: Super-K After


Super-K After: Super-K After


Bibliography: Bibliography J.N. Bachall, The Astrophysical Journal. 467, 475-484 (1996). S.P. Mikheev and A. Yu. Smirnov, Sov. J. Nucl. Phys. 42, 913 (1985). L. Wolfenstein, Phys. Rev. D 17, 2369 (1978).


Graphic Bibliography: Graphic Bibliography Image 1: http://sohowww.nascom.nasa.gov/gallery/EIT/eit027.gif Image 2: http://www.fnal.gov/pub/inquiring/matter/madeof/index.html Image 3,8: http://www.sns.ias.edu/~jnb/ Image 4: http://www.egglescliffe.org.uk/physics/particles/parts/parts1.html Image 5,9: http://www.sns.ias.edu/~jnb/SNviewgraphs/snviewgraphs.html Image 6: http://www-sk.icrr.u-tokyo.ac.jp/sk/photo/sk_build01.jpg Image 7: http://rclsgi.eng.ohio-state.edu/nuclear/ Image 10: http://wwwlapp.in2p3.fr/neutrinos/aoscillanim.html Image 11: http://www-sk.icrr.u-tokyo.ac.jp/doc/sk/photo/sk_build44.jpg Image 12: http://www-sk.icrr.u-tokyo.ac.jp/sk/photo/pmt-damage/dsc00016.jpg Image 13: http://www-sk.icrr.u-tokyo.ac.jp/sk/photo/pmt-damage/11130038.jpg