Neutrino Oscillations in the Universe

1. Neutrino Oscillations in the Universe

2. Universe Constituents from CMB Results WMAP measures the density of baryonic and non-baryonic matter to an accuracy of better than 5%. It is able to determine some of the properties of the non-baryonic matter: the interactions of the non-baryonic matter with itself, its mass and its interactions with ordinary matter all affect the details of the cosmic microwave background fluctuation spectrum. WMAP determined that the universe is flat: the mean energy density is equal to the critical density (within a 2% margin of error), equivalent to a 9.9 x 10-30 g/cm3 (5.9 protons per cubic meter). 4% Atoms, 23% Cold Dark Matter, 73% Dark Energy. Thus 96% of the energy density in the universe is in a form that has never been directly detected in the laboratory. Fast moving neutrinos do not play any major role in the evolution of structure in the universe. They would have prevented the early clumping of gas in the universe, delaying the emergence of the first stars, in conflict with the new WMAP data. The data places new constraints on the Dark Energy. It seems more like a "cosmological constant" than a negative-pressure energy field called "quintessence". But quintessence is not ruled out.

3. Neutrino in the standard cosmological model • According to the standard cosmological model (SCM) our Universe is filled with massless non-oscillating neutrinos (an assumption); • There exist three neutrino flavours- e, m t (confirmed for weakly interacting species by LEP, however sterile neutrino may exist) • The lepton asymmetry is zero (an assumption);; • Neutrino spectra are the equilibrium ones (an assumption);: • After the electron-positron annihilation neutrino temperature becomes lower than the temperature of the photons Tn=(4/11)1/3 Tcmb. The cosmological neutrino phone today is expected with an extremely low temperature ~ 1.9 K, i.e. less than the temperature of the CMB Tcmb~2.7 K. • Today neutrino is the most numerous particle after the CMB photons. Still in contrast to CMB observations the detection of the cosmological neutrino is very difficult: first, because it is an extremely elusive particle due to its very weak interactions and second, because cosmological neutrinos are expected to have today extremely low energy ~Tn4. However, it has been observationally and experimentally proved that neutrinososcillate: i.e. not all neutrino species are massless. LA may be non-zero, and n(E) may differ from the equilibrium ones. A cosmological model accounting for ν oscillations is needed!

4. Positive indications for oscillations of neutrino were obtainedat the greatest neutrinoexperiments. Solar neutrino problem, atmospheric neutrino anomaly and thepositive results of terrestrial experiments can be resolvedby the phenomenon of neutrino oscillations. neutrino oscillations Neutrino oscillations: Mass eigenstates are distinct from the flavor eigenstates. m = Umf f, (f = e, , ) Transitions b/n different flavors are possible - flavor composition changes with time. Neutrino oscillations imply non-zero mass differences and mixing: m2 0, at least 2 neutrino have mn 0. observational evidences for  oscillations: Solar neutrino anomaly:Homestake, Kamiokande, SuperKamioKa,Gallex, SAGE, SNO experiments е   LMA: m27.9.10-5eV2 sin22=0.31 Atmospheric neutrino anomaly: Super-KamioKa, Macro, Soudan 2, IMB  , m22.6.10-3eV2 maximal  Terrestrial experiments: KamLAND, K2K, LSND  e, m2O(1eV2) и sin22=O(0.003) alternative models with s give better agreement with Homestake and explain the variation of the flux with B. We explored a modification of the standard Big Bang Nucleosynthesis with neutrino oscillationsne <->ns.Oscillations effect both expansion rate and the weak interactions rate, leading to He-4 overproduction.

5. Possible cosmological influence of e s: Oscillations a s effective after adecoupling < and Ns<1 may distort e energy spectrum, causing e depletion, neutrino-antineutrino asymmetryand influences the neutrino involved processes in the Universe, like BBN Kinetics, CMB, etc. In case of oscillations effective after decoupling provided that the sterile state is not in equilibrium (Ns<1), the spectrum distortion effect is the major one. Cosmological constraints on oscillations may be derived: From the allowed range of the observables of the early Universe, like baryonic density, light elements abundances, expansion rate, CMB spectrum, structure characteristics of the Universe, etc., it is possible to constrain the parameters of neutrino oscillations.

6. Evolution of neutrinos in the presence of oscillationsApproach: follow the evolution of neutrino for each momentum; account for oscillations, expansion and interactions with the medium simultaneously Analytical solution for vacuum neutrino oscillations (post BBN epoch):

7. Numerical solutions for matter neutrino oscillations The distortion concerns first the low energetic part of the spectrum because the oscillations become effective first to low energy neutrinos. Soon after, the whole spectrum is distorted from its equilibrium Fermi-Dirac form. The non-equilibrium initial condition leads to considerable and continuous deviations from the equilibrium The spectrum distortion of the active neutrino for a wide range of oscillation parameters persists during BBN

8. Dependence of neutrino evolution on the initial popuation of s Ns Sterile neutrinos may be present at the onset of BBN epoch -- may be produced in GUT models, in models with large extra dimensions, Manyfold Universe models, mirror matter models, or by oscillations in 4-neutrino mixing schemes, etc. The degree of population may be different depending on the production model. The distortion of the neutrino spectrum due to active-sterile oscillations and the kinetic effect caused Nk depends on the degree of initial population of s. The biggest effect is Nk,0 at Ns=0, the effect decreases with Ns. DK,Int.J.M.P.D,2004, 2007 Nk~ Nk,0- Nk,0 Ns Spectrum distortion for different initial population of s.: Ns=0 – the lowest curve, Ns=0,5 andNs=0,8 – the upper curve. The dashed curve shows the equilibrium spectrum.

9. BBN with oscillations He-4 mass fraction is a strong function of the effective number of light stable particles at BBN epoch It depends also on the echaracteristics decreasen/pfreezes earlier4Неis overproduced BBN with fasta s : increase effective before adecoupling BBN with a s e spectrum effective after adecoupling and Ns<1distortions

10. Evolution of nucleons in the presence of е  sthe numerical approach

11. total effect decreases kinetic effect decreases dynamic effect increases The interplay b/n effects Nk,0 >1 N= Nk,0- Nk,0 Ns +Ns Nk,0 Ns >Ns m2=10-7 eV2sin22=1

12. total effect decreases kinetic effect decreases dynamic effect increases The interplay b/n effects Nk,0 >1 N= Nk,0- Nk,0 Ns +Ns Nk,0 Ns >Ns m2=10-7 eV2sin22=1

13. Maximum He-4 overproduction in BBN with oscillations due to spectrum distortion Dependence of maximum overproduction on the mixing 0Y/Y32%for resonant case 0Y/Y14 %for non-resonant Expressed in terms of effective number of neutrinos the kinetic effect due to espectrum distortion: Nk,0 6for resonant osc Nk,0 3for non-resonant osc DK , Astrop.Phys.,2003

14. Maximum He-4 overproduction in BBN with oscillations due to spectrum distortion Maximal overproduction dependence on mass difference BBN constraints doexist if He-4 uncertainty is over 5% but for non-equilibrium oscillations. BBN with nonequilibrium es allows to constrain  oscillation parameters for He-4 uncertainty up to32% (14%) in resonant (non-resonant) case. DK , Astrop.Phys.,2003

15. 4Не – the preferred element BBN - the most early and precision probe for physical conditions in the early Universe, and for constraining new physics, relevant at this E. For a precise analysis of the oscillations effect on BBN, He-4 is used because the most reliable and abundant data now available are for that element. • Observed in НІІ low metalicity regions of dwarf galaxies • Extrapolated towards zero metalicity Yp=0,24210,0021Izotov, Thuan 2000 Yp=0,24290,009Izotov, Thuan 2004 dispersion of the determinations Yp=0,2450,013Olive, Skillman 2004 Yp=0,24910,0091Olive, Skillman 2004 Determinations indicate 3-5% uncertainty (systematic errors). Sasselov, 95 Possibly it is related with the evaluation of ionization level, stellar absorption, .. Luridiana, 2002 For a precise analysis of the oscillations effect on BBN, He-4 is used because the most reliable and abundant data now available are for that element. The primordial abundance Yp, predicted from SBBN, is calculated with great precision: the theoretical uncertainty is less than 0.1% within a wide range of baryon density.

16. Constraints on neutrino oscillation parameters BBN with electron-sterile neutrino oscillations: 4Не depends on the echaracteristics : e decrease n/pfreezes earlier 4Не is overproduced. DK, 88; Chizhov, DK, ‘97,’00 4Не depends on the dynamics of the Universe: g increase n/pfreezes earlier 4Не is overproduced. Dolgov ’81, Barbieri, Dolgov 90

17. BBN constraints on oscillationsBBN with neutrino oscillations between initially empty ns and ne Observational data on primordial He- 4 was used toputstringent limitson the allowed oscillation parameters. BBN constraints on е  s : Barbieri, Dolgov 91 – depletionaccount Dolgov 2000 – dashed curve; DK, Enqvist et al. 92 – one p approx. DK.,Chizhov 2001 – distortionand asymmetry growth account Dolgov, Villante, 2003 - spectrum distortion

18. Spectrum distortion reflected in neutrino oscillations constraints from BBN The distortion leads to a decrease of the weak rates to an increase of the n/p freezing T and He overproduction. Correspondingly the account of spectrum distortion leads to strengthening of BBN constraints at large mixings. The account of the neutrino-antineutrino asymmetry growth caused by resonant oscillations leads to relaxation of the constraints for small mixings. Ns=0

19. Spectrum distortion and BBN constraintsFor nonequilibrium oscillations the constraints are strengthened by orders of magnitude: Dolgov A., F.Villante ,2003 m2>10-6 eV2, i.e. kinetic equilibrium constraints for non-resonant case: At smaller m2re-population of active neutrino becomes slow, spectrum distortion is considerable. Chizhov M., DK, 2001; D.K. 2005

20. Antimatter in the UniverseBaryogenesis

21. Antimatter in the Universe Missions for search of cosmic/galactic antimatter: PAMELA, BESS, AMS, AMS-2(2009),PEBS(2010), etc • The cosmic ray results from search of antiprotons, positrons and antinuclei indicate that there is not significant quantity ofantimatter objects within a radius 1 Mpc. BESS 98 AMS 01 • Gama ray flux measurements exclude significant amounts of antimatter up to the distance of galaxy cluster scales ~ 10 -20 Mpc. Steigman 79, Stecker 85, Dolgov 99 Cosmic ray and gama ray data do not rule out large antimatter domains on scales larger than 10 -20 Mpc, or small ratios of antimatter/matter objects on small scales (stars, globular clusters). Large but subdominant domains of antimatter allowed within the Galaxy as well. Both ‘natural’ theory and observations allow the presence of antimatter in astronomically significant quantities.

25. Antimatter signatures We have analyzed all experimental data, available from experiments on balloons and on spacecraft , for antinuclei and antiprotons in cosmic rays. The figure presents the antiproton data from BESS, MASS and CAPRICE experiments compared with different models predictions for secondary antiprotons. The comparison with theoretical predictions for secondary antiprotons does not exclude the possibility for a small fraction of primordial antiprotons. Kirilova,Panayotova, 2002

28. B Asymmetric Universe

29. General conditions for successful BA generation Due to considerations based on theexistance of an inflationary period: BA may not be postulated as an initial condition BA should be generated in the Early Universe before BBN epoch Sacharov's conditions for BA generation: • Baryon number violation (BV). • C and CP violation. • Departure from thermal equilibrium.

31. AD Baryogenesis • We analyzed numerically a baryogenesis model, based on the Afleck-Dine baryogenesis scenario. Dolgov, DK 89; DK, Chizhov 95; • We have provided more precise account for the particle creation processes, which were proved to play an essential role for baryogenesis. 2000DK, Valchanov, Panayotova 2005,2007 The model allows natural production of large antimatter domains in the Universe.

36. Благодаря за вниманието!