Neutrinos and observations of the CMB and Large
Neutrinos and observations of the CMB and Large Scale Structure
Descriptive account of structure growth • Inflation leads to the early Universe having tiny random fluctuations in density • Fluctuations only start evolving when they are within the horizon
Descriptive account of structure growth • When photons and baryons are coupled, competition between gravitational attraction and radiation pressure leads to acoustic oscillations
After decoupling • Baryons fall into dark matter potential wells • Density contrast grows by gravitational instability
Temperature fluctuations • Denser regions hotter • Photons climbing out of potential wells are redshifted (non-integrated Sachs Wolfe) • Doppler shift for photons scattered from moving electrons • Integrated Sachs Wolfe • Gravitational Lensing • . . .
Sachs-Wolfe Effect • The Sachs Wolfe effect refers to the temperature difference in the CMB due to gravitational redshift – Non-integrated Sachs-Wolfe is the redshift due to the gravitational potential wells at the time of last scattering – Integrated Sachs-Wolfe occurs between the surface of last scattering and observation and only occurs when the Universe is not dominated by matter. When the Universe is matter dominated gravitational potential wells do not evolve much in the time that photons traverse them (so blueshift as falling in and redshift climbing out cancel) • Early Integrated Sachs-Wolfe occurs soon after last scattering when the radiation density of the Universe is non-negligible • Late-time Integrated Sachs Wolfe occurs when the cosmological constant is dominant
Neutrino effects • Neutrinos free stream – they fly out of overdensities. This damps small scale structure
Neutrino effects • Neutrino component affects matter-radiation equality epoch
Slide from Yvonne Wong
Slide from Yvonne Wong
Neutrino effects • Prior to Planck the dominant effect from neutrino mass on the CMB was on the early integrated Sachs Wolfe effect. “The Planck data move us into a new regime where the dominant effect is from gravitational lensing. ”
Planck 2013 Results • Planck Collaboration, Planck 2013 results. XVI Cosmological parameters arxiv: 1303. 507
Planck 2013 Neutrino mass
Planck 2013 Neff
References • A. D. Dolgov, Neutrinos in Cosmology, Phys Rept. 370 (2002) 333 [hep=ph/0202122] • J. Lesgourges and S. Pastor, Massive neutrinos and cosmology, Phys. Rep. 429 (2006) [astro-ph/0603494] • S. Hannestad, Primordial neutrinos, Ann. Rev. Nucl. Part. Sci. 56 (2006) 17 [hep-ph/0602058] • Y. Y. Y. Wong, Neutrino mass in cosmology: status and prospects, Ann. Rev. Nul. Part. Sci. 56 (2006) 137 [hepph/0602058]
Neutrinos as probes of ultra-high energy astrophysical phenomena
Neutrino sources 10 -40 Me. V Ge. V – 10 s. Te. V up to 10 Me. V J. Becker Phys. Rep. 458
How do we know there are high energy astrophysical phenomena? • Observe high energy cosmic ray particles • Observe radiation that is indicative of high energy processes • And as well there might be hidden sources…
Cosmic messengers
Origin of the ultra-high energy cosmic rays? ? 1012 e. V = Te. V 1015 e. V=Pe. V 1018 e. V = Ee. V
Why detect neutrinos? Figure: Wolfgang Wagner, Ph. D thesis
Auger sky map • At energies > 6 X 1019 e. V may be able to get indications of origin. • significance reduced in larger data set
Nature’s accelerators
Information from Gamma-Rays • Lots of gamma ray sources identified • Most sources can be described by leptonic models as well as/better than hadronic
BL Lac Object Krawczynski et al. , Ap. J 601 (2004)
Why detect neutrinos? To identify the source of the highest energy cosmic rays
How do we accelerate a particle? • Fermi Acceleration
How do we accelerate a tennis ball? Bounce=unchanged speed • Not with a steady tennis racket!
Need a moving racket Speed unchanged with respect to the racket but in the frame of the court the speed is changed
Back to particles… ball ↔ charged particle racket ↔ magnetic mirror
Fermi Acceleration • 2 nd Order: randomly distributed magnetic mirrors slow and inefficient • 1 st Order: acceleration in strong shock waves
Hillas Plot The highest energy that a particular site can accelerate particles to can be estimated through the gyroradius. The gyroradius is less than the linear size of the accelerator E~G ZBR
Why do we think neutrinos will be produced where cosmic rays are produced?
Neutrino production • p + p or p + give pions which give neutrinos eg. p + + n/ 0 p – + + e – 0 (E ~Te. V) Animation generated with povray
How do we detect astrophysical neutrinos?
Neutrino sources 10 -40 Me. V Ge. V – 10 s. Te. V up to 10 Me. V J. Becker Phys. Rep. 458
How do we detect astrophysical neutrinos? With a very big detector. . .
Neutrino telescopes around the globe ANTARES Lake Baikal NEMO NESTOR KM 3 NET Ice. Cube, ANITA, ARA
Ice. Cube is a LARGE neutrino detector. . .
Ice. Cube is a LARGE neutrino detector. . . Super Kamiokande SNO
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