Transcript 3. Solar Neutrinos

STELLAR EVOLUTION
– THE STANDARD SOLAR MODEL AND SOLAR NEUTRINOS –
MARIE ZECH
Content:
1. Our sun – basic facts
2. SSM – the Standard Solar Model
1.
2.
3.
What is the SSM?
Helioseismology
The solar abundance problem
3. Solar Neutrinos
1.
2.
3.
4.
What is a neutrino/ solar neutrino?
Detection of neutrinos
Solar neutrino problem
Neutrino oscillation
4. Summary
5. Sources
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1. Our Sun - Basic Facts
 G –type main sequence star  yellow dwarf
 diameter: 109 x Earth
 mass: 330,000 x Earth
 Population I: heavy element rich star
 temperature
 in the core: up to 15.7 million K
 on the surface: ≈ 5,800K
Marie Zech
composition of our sun:
Hydrogen
Helium
Oxygen
Carbon
Iron
Neon
Nitrogen
Silicon
Magnesium
Sulfur
73.46%
24.85%
0.77%
0.29%
0.16%
0.12%
0.09%
0.07%
0.05%
0.04%
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1. Our Sun – Basic Facts
 formed ~4.567 billion years ago
 formation may have been
triggered by nearby supernovae
 NOW:
 roughly middle aged
 will remain fairly stable
 FUTURE:
 red giant
 becomes very large
http://www.nasa.gov/images/content/171926main
_heliolayers_label_lg.jpg
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2. The Standard Solar Model
2.1 What is the SSM?
 mathematical treatment of the sun as a spherical ball of gas
 principal approximations:
 hydrostatic equilibrium
 energy transport by photons or convective motion
 energy generation by nuclear reaction:
4𝑝 → 4𝐻𝑒 + 2𝑒 + + 2ν𝑒 + 26.73𝑀𝑒𝑉
 abundance changes caused solely by nuclear reactions
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2. The Standard Solar Model
 major input parameters/ functions:
 relative chemical abundances: hydrogen(X), helium(Y), heavy elements(Z)
𝑋 + 𝑌 + 𝑍 = 1.0
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radiative opacity
equation of state
luminosity
age
nuclear parameters
 used to test validity of stellar evolution theory
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2. The Standard Solar Model
figure d: dependence of
electron number density
upon solar radius
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2. The Standard Solar Model
Properties of the solar model as a function of time
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2. The Standard Solar Model
2.2 Helioseismology:
 study of solar seismology
 provides information about the interior
of the body
 the surface of the sun is filled with
patches that oscillate
 the sun oscillates in three dimensions 
rich spectrum of frequencies
 these frequencies provide information
about temperature and density
distribution within the sun and it´s
chemical composition
Marie Zech
https://www.spaceinn.eu/project
/science/helioseismology/
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2. The Standard Solar Model
2.3 The solar abundance problem
 inconsistency between the SSM and the helioseismic data
 connection to neutrinos:
 Temperature dependent 8𝐵 and 7𝐵𝑒 neutrino fluxes are sensitive to
metallicty
→ cross – check conclusions from helioseismology
 measurements of CN solar neutrino flux potential to directly measure solar
core abundance of C+N
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2. The Standard Solar Model
GS98 – high metallicity
AGSS09 – low metallicity
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2. The Standard Solar Model
SSM characteristics compared to helioseismic values
𝑅𝐶𝑍 is the radius to the convective zone
δ𝑐/𝑐 is the average fractional discrepancy in the sound speed, relative to helioseismic values
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3. Solar Neutrinos
3.1 What is a neutrino?
 lepton, charged neutral
 3 flavours:
 electron neutrinos
 muon neutrinos
 tau neutrinos
 solar neutrinos are created in the core by nuclear reactions
 neutrino fluxes are sensitive to the core temperature
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3. Solar Neutrinos
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3. Solar Neutrinos
estimated neutrino fluxes of different SSMs
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3. Solar Neutrinos
3.2 Detection of neutrinos
 cannot be detected directly
 detector are often build underground for protection from cosmic rays
and background radiation
 90ies: Super Kamiokande in Japan
 50,000 t Water – Cherenkov – detector
 can´t distinguish between different neutrino flavours
 1999 – 2006 Sudbury Neutrino Observatory in Canada
 heavy water
 possible to differ between muon and tau / electron neutrinos via statistics
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3. Solar Neutrinos
Super Kamiokande
Fish-eye photo of the SNO Detector
http://www-sk.icrr.u-tokyo.ac.jp/sk/gallery/wme/sk_01hwm.jpg
https://www.snolab.ca/sites/default/file
s/images/SNO-hi%20res.preview.jpg
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3. Solar Neutrinos
3.3 Solar neutrino problem
 pattern of fluxes in contrast
to SSM predictions
 significant deficit of electron
neutrinos and muon
neutrinos
 day/ night differences
(upward going Neutrinos in
detector)
http://www-sk.icrr.u-tokyo.ac.jp/sk/sk/neutrino-e.html
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3. Solar Neutrinos
superposition of neutrino eigenstates
3.4 Neutrino Oscillation
 quantum mechanical interference
phenomenom
 flavour of neutrino can change while „flying“
 probability of this change can be calculated
 solution to solar neutrino problem: missing
neutrinos changed e.g. into not with
Kamiokande or SNO detectable tau neutrinos
 NEW: neutrinos are not without a mass  new
physics aside from standard model of
astrophysics needed
Marie Zech
http://www-sk.icrr.utokyo.ac.jp/sk/sk/neutrino-e.html
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3. Solar Neutrinos
Winners of the Nobel Prize 2015 in Physics
Takaaki Kajita
Arthur B. McDonald
https://www.snolab.ca/news/2015-10-15-canadianscientist-shares-nobel-prize-win-physics-snoexperiment
http://www.nobelprize.org/nobel_pr
izes/physics/laureates/2015/images/
kajita-photogallery.jpg
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4. Summary
 data from low Z abundance SSM showd in comparison to helioseismic
data inconsistencies
 to check data: neutrino fluxes
 not as much neutrinos were detected as calculated
→ solved by neutrino oscillation (change of neutrino flavour is possible)
→ new kind of physics is needed, standard model of
astrophysics is not entirely correct
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5. Sources:
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Annu. Rev. Astron. Astrophys. 2013.51:21-61
Bahcall, John N: Neutrino Astrophysics, Cambridge University Press, 1989
Physik Journal 14 (12), WILEY-VCH Verlag GmbH&Co.KGaA, Dezember 2015
https://www.snolab.ca/
http://www-sk.icrr.u-tokyo.ac.jp
https://en.wikipedia.org/wiki/Sun
https://en.wikipedia.org/wiki/Solar_neutrino
https://en.wikipedia.org/wiki/Neutrino
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