Neutrino and Neutrino and Cosmology Cosmology Dept. of Physics - PowerPoint PPT Presentation

Neutrino and Neutrino and Cosmology Cosmology Dept. of Physics and Astrophysics Dept. of Physics and Astrophysics Nagoya University Nagoya University Naoshi SUGIYAMA Naoshi SUGIYAMA

Brief brief review of thermal Brief brief review of thermal history of the Universe history of the Universe � Useful Conversion Useful Conversion � Temperature 1eV ~ 10 4 4 K � Temperature 1eV ~ 10 K � -4 4 eV Present epoch 2.725K~10 - eV Present epoch 2.725K~10 Recombination 3000K~0.1eV Recombination 3000K~0.1eV � Redshift 1+z=T/2.725K Redshift 1+z=T/2.725K �

Thermal History of the Universe Thermal History of the Universe Matter-Radiation Electro-weak Neutrino Equality Epoch Decoupling QCD e + -e - pair Recombination Phase annihilation Transitions Present Big Bang Nucleosynthesis 1TeV 1GeV 1MeV 1KeV 1MeV 1eV 1meV

� After Inflation, the Universe is dominated by After Inflation, the Universe is dominated by � Radiation (Massless Components) Radiation (Massless Components) � At T=1MeV, neutrinos are decupled from thermal At T=1MeV, neutrinos are decupled from thermal � bath bath � At T=500keV, positrons and electrons are pair At T=500keV, positrons and electrons are pair- - � annihilated. annihilated. � Photons are produced, and photon temperature Photons are produced, and photon temperature � increases: Tphoton > Tneutrinos increases: Tphoton > Tneutrinos � At 1MeV~100keV, Primordial Nucleosynthesis At 1MeV~100keV, Primordial Nucleosynthesis � Ω M At 1eV(z=24000 Ω 2 ), radiation and matter h 2 � At 1eV(z=24000 ), radiation and matter M h � densities become equal: equality epoch. Since densities become equal: equality epoch. Since then, the Universe is dominated by Matter. then, the Universe is dominated by Matter. � Recombination takes place at 0.1eV (z=1089) Recombination takes place at 0.1eV (z=1089) �

1. What is the role of Neutrios on 1. What is the role of Neutrios on Observational Cosmology? Observational Cosmology? � Neutrinos were mostly massless through history Neutrinos were mostly massless through history � � Until T ~m Until T ~m ν , massless ν , massless � � e.g., 0.1eV e.g., 0.1eV roughly corresponds to 1000K , roughly corresponds to 1000K , � which is after (yet close) to the recombination which is after (yet close) to the recombination epoch, 3000K. epoch, 3000K. Neutrinos are Radiation Component Neutrinos are Radiation Component

� On top of photons, neutrinos consist of radiation On top of photons, neutrinos consist of radiation � component component � Modify (if change the number of family) Modify (if change the number of family) � ansion Rate of the Universe=Hubble Exp ansion Rate of the Universe=Hubble � Exp � Parameter Parameter Primordial Nucleosynthesis � � Primordial Nucleosynthesis � Matter Radiation Equality Epoch Matter Radiation Equality Epoch � Temperature Anisotropies of Cosmic Microwave � Temperature Anisotropies of Cosmic Microwave � Background (CMB) Background (CMB)

Evolution of the Universe Evolution of the Universe Friedmann Equation: : Friedmann Equation Einstein Equation with homogeneity & isotropy Einstein Equation with homogeneity & isotropy Energy- -Momentum Conservation Momentum Conservation Energy 2  •  π Λ a G K   8 ≡ = ρ − + H 2   a a   2 3 3   ρ = ρ + ρ ρ ≡ ρ + ρ Radiation Matter γ ν Radiation ρ ∝ − + ≡ ρ = w a w p w 3 ( 1 ) : / ( 0 for matter, 1/3 radiation) ρ = π H G H 2 3 / 8 , : Hubble Const. c 0 0 Ω ≡ ρ ρ Ω = − Ω ≡ Λ K H H 2 2 / , / , / 3 Λ c K 0 0

Matter-radiation equality: Radiation log (density) Matter Dominant Matter Radiation Dominant -log T Present epoch

Matter-radiation equality: Increase Increase Radiation Neutrino Neutrino densities densities log (density) Matter Dominant (family) (family) Matter Radiation Dominant -log T Present epoch

Constraints from Big Bang Constraints from Big Bang Nucleosysnthesis Nucleosysnthesis Expansion Rate (Hubble Parameter) depends on Effective Neutrino Number, N eff Change the predicted abundances of light elements Change the predicted abundances of light elements

Larger Neff → Higher Expansion → Neutrons were decoupled from Chemical Equilibrium Early Large n abundance ↔ + + ν - n p e N eff + ν ↔ + - n p e Time Larger number of Neutrons were left Larger amount of Helium were left

Compare Theoretical Prediction with Compare Theoretical Prediction with 4 He, D, 3 He, 7 Li Observational Abundances of 4 He, D, 3 He, 7 � Observational Abundances of Li � Ω B 2 = 0.023 ± 0.001 from Cosmic Determination of Ω = 0.023 ± h 2 � Determination of 0.001 from Cosmic B h � Microwave Background Anisotropies Microwave Background Anisotropies

N eff =4 N eff =4 N eff =3 N eff =3 N eff =2 N eff =2 CMB Tytler et al. Phys.Scripta (2000)

Life is not so Simple: Life is not so Simple: Some Caveats Some Caveats � Observations were not consistent with each other Observations were not consistent with each other � � Treatments of Systematics are Complicated (Effect of Treatments of Systematics are Complicated (Effect of � stellar absorptions etc.) stellar absorptions etc.) Cheating? Cheating? � Neutron Life Time: Neutron Life Time: � 885.7 ± ± 0.8 Used to be 885.7 0.8, but new measurement: , but new measurement: Used to be ± 0.7(stat) 0.7(stat) ± ± 0.3(sys) 878.5 ± 0.3(sys) ( (Serebrov, et al., (2005)) Serebrov, et al., (2005)) 878.5 Shorter Life time - -> Neutron Decoupling from > Neutron Decoupling from Shorter Life time Chemical equaillibrium becomes later - -> Less > Less Chemical equaillibrium becomes later Neutrons are left - -> Less Hellium Abundance > Less Hellium Abundance Neutrons are left

Life is not so Simple: Life is not so Simple: Some Caveats Some Caveats � Observations were not consistent with each other Observations were not consistent with each other � � Treatments of Systematics are Complicated (Effect of Treatments of Systematics are Complicated (Effect of � stellar absorptions etc.) stellar absorptions etc.) Cheating? Cheating? � Neutron Life Time: Neutron Life Time: � Used to be 885.7 ± ± 0.8, but new measurement: 0.8, but new measurement: Used to be 885.7 ± 0.7(stat) 0.7(stat) ± ± 0.3(sys) ( 878.5 ± 0.3(sys) (Serebrov, et al., (2005)) Serebrov, et al., (2005)) 878.5 Shorter Life time - -> Neutron Decoupling from > Neutron Decoupling from Shorter Life time Chemical equaillibrium becomes later - -> Less > Less Chemical equaillibrium becomes later Neutrons are left - -> Less Hellium Abundance > Less Hellium Abundance Neutrons are left

Helium Abundance History WMAP Observations Courtesy from M. Kawasaki

Life is not so Simple: Life is not so Simple: Some Caveats Some Caveats � Observations were not consistent with each other Observations were not consistent with each other � � Treatments of Systematics are Complicated (Effect of Treatments of Systematics are Complicated (Effect of � stellar absorptions etc.) stellar absorptions etc.) Cheating? Cheating? � Neutron Life Time: Neutron Life Time: � Used to be 885.7 ± ± 0.8, but new measurement: 0.8, but new measurement: Used to be 885.7 ± 0.7(stat) 0.7(stat) ± ± 0.3(sys) ( 878.5 ± 0.3(sys) (Serebrov, et al., (2005)) Serebrov, et al., (2005)) 878.5 Shorter Life time - -> Neutron Decoupling from > Neutron Decoupling from Shorter Life time Chemical equaillibrium becomes later - -> Less > Less Chemical equaillibrium becomes later Neutrons are left - -> Less Hellium Abundance > Less Hellium Abundance Neutrons are left

0.4% Neutron Life Time Dependence Mathews et al (2005)

Constraints from Cosmic Microwave Constraints from Cosmic Microwave Background Anisotropies Background Anisotropies � Increase N Increase N eff , pushes matter- -radiation equality radiation equality eff , pushes matter � at the later epoch, which modifies the peak at the later epoch, which modifies the peak heights and locations of CMB spectrum. heights and locations of CMB spectrum. � Additional neutrino species alters the damping Additional neutrino species alters the damping � l ’ tail on high l ’s. s. tail on high

多重極モーメント

CMB Angular Power Spectrum Theoretical Prediction Measure the family number at z =1000

P. Serpico et al., (2004) A. Cuoco et al., (2004) P. Crotty et al., (2003) S. Hannestad, (2003) V. Barger et al., (2003) R. Cyburt et al. (2005) E. Pierpaoli (2003)