Cosmology and Relic Neutrinos

1. Cosmology and Relic Neutrinos • Expanding Universe • Big Bang • Nucleosynthesis • Cosmic Microwave Background measurements • Relic neutrinos • Informations about neutrino mass • Leptogenesis "From neutrinos ....". DK&ER, lecture12

2. Galaxies Antennae galaxies Andromeda galaxy Galaxy Evolution Explorer Photograph courtesy NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration "From neutrinos ....". DK&ER, lecture12

3. Galaxies "From neutrinos ....". DK&ER, lecture12 The Andromeda galaxy, also known as Messier 31, is the largest neighboring galaxy to the Milky Way. This photo, a mosaic of ten images captured by the Galaxy Evolution Explorer spacecraft in 2003, shows blue-white regions along the galaxy's arms where new stars are forming and a central orange-white area containing older, cooler stars.

4. Expanding Universe In 1929 Hubble observed redshifts of spectral lines from distant gallaxies and ascribed them to velocities: v =Hrwhere r is distance to a gallaxy Hubble constant "From neutrinos ....". DK&ER, lecture12

5. Expanding Universe Expansion of the Universe depends on time. If R(t)is a universal distance scale then: H is time-dependent but today: Universe expansion is described by the solution of Einstein equations: Friedmann equation "From neutrinos ....". DK&ER, lecture12

6. Critical density For k=Λ=0 and nonrelat. constant M one gets: More precisely: Age of the Universe It is then convenient to define: critical density "From neutrinos ....". DK&ER, lecture12

7. Cosmological Parameters For various k and Λ=0 one can define: then i.e. for k=0 Ωtot=1 independent on t "From neutrinos ....". DK&ER, lecture12

8. Cosmological Parameters For various k and Λ=0 one can define: then It is often convenient to separate a contribution from relat. particles Ωγ and from pressureless matter Ωm and introduce : Then "From neutrinos ....". DK&ER, lecture12

9. Radiation dominance in early Universe How various densities evolve with time? Matter density: Radiation energy density: because: = photon density x photon energy because wavelength changes with scale R Therefore while now matter dominates the early Universe was dominated by radiative energy. From Friedmann equation and Stefan-Boltzmann law. one gets : temperature: i.e. at the beginning the Universe was very hot: Big Bang "From neutrinos ....". DK&ER, lecture12

10. Big Bang The earliest moment: We would need quantum gravity (which we do not know) for earlier moments. Planck mass Probably sometimes at this epoch cosmic inflation happened. Cosmic Inflation is necessary in the Big Bang theory to explain the large scale uniformity of the Universe today. In one of the models: early enough the cosmological constant dominates Friedmann equation: giving: Next we’ll describe how the Universe cooled down. We assume, that particles for which: are in thermal equilibrium in comparable abundances and reactions can proceed in both directions eg: "From neutrinos ....". DK&ER, lecture12

11. Big Bang – whole picture http://outreach.web.cern.ch/outreach/public/CERN/PicturePacks/BigBang.html "From neutrinos ....". DK&ER, lecture12

12. Breaking of the symmetry of interactions 1019 GeV 1014 GeV 100 GeV 1 GeV 10 meV "From neutrinos ....". DK&ER, lecture12

13. Big Bang (1) • Wielka Unifikacja – • wszystkie oddz. • nierozróżnialne • bozonów X, Y tyle co np. • kwarków • leptony  kwarki {Δ(B-L)=0} • Plazma kwarkowo-gluonowa • Bozony X, Y znikają • Prawd. pojawia się nadmiar • materii nad antymaterią • wskutek rozpadów ciężkich • neutrin N?? D. Kiełczewska, wykład 14

14. Big Bang (2) • elmgt and weak forces • separate • all W’s and Z’s decayed • not enough energy to • produce them • gamma energy drops enough to allow formation of hadrons • neutrinos do not have enough • energy for • they decouple from matter and move freely "From neutrinos ....". DK&ER, lecture12 Relic neutrinos

15. Big Bang (3) • not enough energy to create e+ e- pairs • positrons disappear • light nuclei are bound • Nucleosynthesis • electrons bound into atoms • photons interact much more • slowly („decouple” from matter) • and move freely Relic gammas or cosmic microwave bkg "From neutrinos ....". DK&ER, lecture12

16. "From neutrinos ....". DK&ER, lecture12

17. Nucleosynthesis • Let’s take Universe ~1 sec old • By now most of heavier particles annihilated with their antiparticles • What is left is: 109 times more ν and γ than baryons • The following processes take place: But: Also a part of neutrons is bound in nuclei and they don’t decay anymore. Moreover neutrons decay with Effectively after 400 sec one gets: "From neutrinos ....". DK&ER, lecture12

18. Nucleosynthesis Nuclei are produced in elmgt processes: Atoms appear only 300 000 years later. Production of various nuclei strongly depends on the relative density of baryons to photons. It appears, that observed abundances of various isotopes agree with expectations if: Experimental confirmation of BB "From neutrinos ....". DK&ER, lecture12

19. Number of neutrino species in BB nucleosynthesis range acceptable for other nuclei Expansion rate depends on energy density, which in turn depends on the number of neutrino flavors: Nν For faster expansion less neutrons manage to decay and more helium nuclei can be bound. consistent wit LEP measurements "From neutrinos ....". DK&ER, lecture12

20. Cosmic microwave background CMB CMB photon energy spectrum agrees with the black body frequency distribution. According to: we may expect that today the temperature of CMB is a few K. COBE satellite (1999) In 1965 r Penzias i Wilson discovered CMB. Its temp.: Another observation consistent with BB model. Remnant of the hot cosmic plasma "From neutrinos ....". DK&ER, lecture12

21. CMB anisotropy measured by WMAP Satellite experiment „Wilkinson Microwave Anisotropy Probe.” has collected data since 2001. It studies temp. fluctuations with precision of 10-5. Images Universe 300 000 years old. Fluctuations may come from inflation era. If eg. inflation was when: then according to Heisenberg principle we may expect „quantum fluctuations” Quantum fluctuations could give rise to matter condensation seeds, from which gallaxies evolved "From neutrinos ....". DK&ER, lecture12

22. Cosmic Microwave Background- anisotropy measurements (WMAP) Autocorrelation function: measures temp. fluctuations around a mean temp. T0 in the directions m and n. For small angles: curve: LCDM model By fitting the model to the data a surprising number of parameters can be determined. WMAP & 2dfGRS,astro-ph/0302209 "From neutrinos ....". DK&ER, lecture12

23. Models fitted to the data • A baryon-photon liquid in a gravitation potential well. • Radiative pressure of photons competes with the gravitation which compresses the liquid. • Acoustic oscillations appear in liquid.. • WMAP measures maxima and minima of acoustic oscillations and consequently properties of the liquid as well as the potential well. • Springs represent photon pressure and balls represent the effective mass of the fluid. • Regions of compression (maxima) represent hot regions and rarefaction (minima) cold regions "From neutrinos ....". DK&ER, lecture12

24. Baryon-photon ratio in the CMB Baryons increase the effective mass of the fluid. This changes the balance between pressure and gravity in the fluid. Gravitational infall now leads to greater compression of the fluid in the potential well. This increases the amplitude of the oscillation.Thus the relative heights of the peaks present one way of measuring the baryon content of the universe. "From neutrinos ....". DK&ER, lecture12

25. Curvature of the Universe E.g. in the case of positive curvature A spatial temperature fluctuation on the last scattering surface appears to us as an anisotropy on the sky. The conversion from physical scale into angular scale depends on the curvature of the universe and the distance to the last scattering surface. Photons free stream to the observer on geodesics analogous to lines of longitude to the pole. Thus the same angular scale represents a smaller physical scale in a closed universe. "From neutrinos ....". DK&ER, lecture12

26. Curvature and cosmol. constant From WMAP measurements: The spacing between the peaks provides the most robust test of the curvature. "From neutrinos ....". DK&ER, lecture12

27. Summary of recent measurements http://pdg.lbl.gov/2008/ Particle Data Group "From neutrinos ....". DK&ER, lecture12

28. Summary of recent results (PDG2008) "From neutrinos ....". DK&ER, lecture12

29. Measurements of distant supernovae Supernovae Ia have known luminosity as a function of time so they may serve as „standard candles”. Comparing the expected luminosity with the observed one can determine the SN distance. Measurement of the „redshift” allows to determine the recession velocity "From neutrinos ....". DK&ER, lecture12

30. Supernova measurements (SNIa) Strong indication of Dark Energy

31. Cosmological parameters However we do not understand the nature of energy represented by Λ We call it Dark Energy PDG 2008 "From neutrinos ....". DK&ER, lecture12

32. Flat geometry Matter density slows down expansion

33. History of the Universe http://map.gsfc.nasa.gov/m_mm.html

34. Neutrino and photon decoupling At decoupling the neutrino temperature is slightly lower than that of photons Because of an effect of „reheating” when slow electr. annihilate +1 for neutrinos -1 for photons Then both temperatures decrease with the increasing scale of the Universe as 1/R so eventually now: For nonrelativistic case: Maxwell distribution "From neutrinos ....". DK&ER, lecture12

35. What do we know about ? „Visible” matter i.e. stars, gas etc: Baryons visible or invisible calculated from nucleosynthesis: Total matter deduced from gravitational potential energy of gallaxies and gal. clusters: Dark matter: Ciemna energia „flat geometry” k=0 "From neutrinos ....". DK&ER, lecture12

36. The most recent WMAP results (04/2008) Energiy balance of the Universe Today 380 000 years after BB Dark energy contribution rises with time "From neutrinos ....". DK&ER, lecture12

37. Relic neutrinos Number density from thermodynamic equilibrium for 3 flavors Neutrino Dark Matter: • neutrino fraction of the • total energy of the • Universe "From neutrinos ....". DK&ER, lecture12

38. Weighing Neutrinos with Galaxy Surveys Large scale cluster formation is prevented by relativistic neutrinos which stream out of the clusters. This sets a limit on a fraction of energy carried by neutrinos. The line is for ΛCDM model Recent results from experiments: PDG2008 "From neutrinos ....". DK&ER, lecture12

39. Neutrino contribution to the Universe energy From oscillations: With that one can calculate the neutrino contribution to the total energy in the Universe: which is much more than all the visible matter: On the other hand we have the limit (from tritium decays): From ΛCDM cosmology: which gives for a heaviest state: "From neutrinos ....". DK&ER, lecture12

40. Currentbounds on neutrino masses from cosmol. "From neutrinos ....". DK&ER, lecture12

41. Matter-antimatter asymmetry One would expect that BB produced the same amount of matter and antimatter. However one observes an excess of matter over antimatter We therefore expect that some processes violating CP symmetry gave rise to this matter excess. The observed CP violation in quark sector is not enough to explain the above ratio. A question: maybe CP violation in lepton sector may explain this excess? "From neutrinos ....". DK&ER, lecture12

42. Leptogenesis The most attractive explanation of matter-antimatter asymmetry is by Leptogenesis If neutrinos are Majorana particles, then an elegant way to get their masses is via interactions with Higgs of both: known light LH neutrinos ν as well as very heavy RH neutrinos N with masses of 10(9-15) GeV. N should be produced in the very early moments of BB. Because: so the following decays are possible: where l+, l- are charged leptons If: then: we get excess of leptons over antileptons” Leptogenesis. Then a baryon excess can be obtained via so called sphalerons. "From neutrinos ....". DK&ER, lecture12

43. CP violation for Majorana neutrinos So the clue to understand matter asymmetry is to look for differences in oscillations:and One can ask: if then what is the difference between: The difference is that in π+ decays neutrinos are mostly LH and consequently after oscillations they produce e-: while the opposite happens for π- decays: If Leptogenesis hypothesis is true then we all come from heavy neutrinos. "From neutrinos ....". DK&ER, lecture12

44. Summary • Cosmology and particle physcics are closely connected • Cosmology has become an experimental science • Big Bang Model confirmed by: • measurements of cosmic microwave background CMB • abundances of light nuclei in Universe BUT • We don’t know what constitutes more than 90% of Universe energy • Dark Matter ? • Dark Energy ? • We don’t understand how the matter-antimatter symmetry has been broken during the Universe D. Kiełczewska, wykład 14