Constraints on Neutrino Physics from Cosmology

Transcription

1 Constraints on Neutrino Physics from Cosmology The Future of Neutrino Mass Measurements 4th February 2013, Milano Bicocca Alessandro Melchiorri Universita di Roma, La Sapienza

2 Xmas 2012: a very good one for cosmologists!!! Santa brought us: - Final results from the WMAP experiment! - New results from the ACT experiment! - New results from the SPT experiment! ACT WMAP SPT

3 WMAP

4 WMAP9: final results after nine years of observations Refinement in the data analysis: better treatment of the different frequency channels. Black dots: WMAP9 with improved weighting of frequency channels. Red dots: WMAP9 with previous method. Max change: 5% aroun l=50. Hinshaw et al., astro-ph: Submitted on December 20th, 2012

5 WMAP9: results are consistent with the LCDM six parameter model. Largest change respect to WMAP7: spectral index is now larger by 0.8 sigmas. ns=1 (the HZ spectrum) is consistent in between two sigmas with WMAP9.

6 New ACT results The Atacama Cosmology Telescope (ACT) is a six-meters telescope on Cerro Toco in the Atacama Desert in the north of Chile, at an altitude of 5190 metres. Sievers et al., , 2013

7 New ACT results ACT, thanks to the better angular resolution measures the CMB spectrum at smaller angular scales (high l s). Sievers et al., astro-ph , 2013

8 New ACT results The ACT dataset doesn t improve much on the standard 6 parameters respect to WMAP7. (results appeared just few days after WMAP9) Sievers et al., astro-ph , 2013

9 New SPT results The South Pole Telescope (SPT) is a 10 meters diameter telescope located at the Amundsen- Scott South Pole Station, Antarctica. The data consist of 790 square degrees of sky observed at 90, 150 & 220 GHz.

10 Story et al, astro-ph New SPT results

11 New SPT results SPT dataset slightly improve the constraint on some of the parameters. Again here the WMAP7 dataset is considered. Di Valentino et al, astro-ph , 2013

12 The impact of the new measurements on neutrino physics.

13 Cosmological Neutrinos Neutrinos are in equilibrium with the primeval plasma through weak interaction reactions. They decouple from the plasma at a temperature T dec 1MeV We then have today a Cosmological Neutrino Background at a temperature: T With a density of: n f / 3 4 T 1.945K kt ev 3 (3) g T n, T cm f f k k That, for a relativistic neutrinos translate in a extra radiation component of: 4/ h Neff 4 11 h 2 Standard Model predicts: N eff 3.046

14 Dark Radiation The total amount of relativistic particles in the Universe is therefore parametrized in the following way (see Hannestad talk) : R h 2 4/ Neff h Caveat: Neff can be a function of time (i.e. massive neutrinos). For most of the cases we consider here is assumed to be a constant. A value of Neff > is equivalent to the presence of a new «dark radiation» component : H H 2 M DR a a a a

15 Probing the Neutrino Number with CMB data Changing the Neutrino effective number essentially changes the expansion rate H at recombination. So it changes the sound horizon at recombination: and the damping scale at recombination: s rs D A d rd D A Moreover increases early ISW at Recombination (phase shift) Hou et al, 2011

16 WMAP9 FINAL results on December 20th: N eff th neutrino specie ruled out at 95 % c.l.!!!!

17 Quite an impressive number of press releases! WMAP killed sterile neutrinos! Great achievement, etc See for example:

18 WMAP9 FINAL (again) results on January 30th: N eff The WMAP9 team claims a «slight» correction to Neff (due to a bug in their codes).

19 5. In cosmology, a sudden change of about two sigmas in a key parameter.

20 New results from SPT N eff SPT confirms the presence of extra dark radiation.

21 New results from ACT N eff However ACT is not confirming the presence of extra dark radiation.

22 CMB Temperature Lensing

23 CMB Temperature Lensing unlensed lensed When the luminous source is the CMB, the lensing effect essentially re-maps the temperature field according to :

24 Lensing Effect on Temperature Power Spectrum The effect is a convolution between the lensing potential power spectrum and the unlensed anisotropies power spectrum: The net result is a 3% broadening of the CMB angular power spectrum acustic peaks

25 Parameterizing the Lensing Amplitude The lensing amplitude can be parameterized by introducing the parameter AL that modify the amplitude of the lensing potential. AL =1 means that all is consistent. AL different from one means that we have a systematic or new physics! In the figure CMB models with AL =0,1,3,6,9. Erminia Calabrese, Anze Slosar, Alessandro Melchiorri, George F. Smoot, Oliver Zahn Phys.Rev.D77:123531,2008

26 Scrutinizing the Tension Between SPT and ACT ACT is consistent with 3 neutrinos. But has an anomalous Lensing amplitude (70% higher) SPT is consistent with lensing. But prefers dark Radiation. Systematics? For sure, at least in one of the two. Di Valentino et al, astro-ph , 2013 New Physics? Planck will tell us in two months.

27 Scrutinizing the Tension Between SPT and ACT Discrepancy on the lensing parameter between SPT and ACT at more than 95% c.l.!!! Di Valentino et al, astro-ph , 2013

28 SPT ACT and Neutrino Masses ACT constrain neutrino masses to 0.4 ev at 95 % c.l.!! SPT claim a neutrino masses at 0.4 ev at 95 % c.l.!!! The tension remains but.

29 SPT ACT and Neutrino Masses These results can be explained by the lensing amplitude since a neutrino mass decreases the lensing: ACT measures too much lensing -> strong constraint on neutrino masses SPT measures less lensing -> neutrino mass is favoured. If you let the lensing amplitude too vary: less strong constrain from ACT, no evidence for SPT Di Valentino et al, astro-ph , 2013

30 SPT ACT and Neutrino Masses Di Valentino et al, astro-ph , 2013

31 Planck Satellite launch 14/5/2009

32 Planck in L2 Orbit since 7/2009

33 Planck Status & Future - First complete sky coverage was obtained in June 2010 after 10 months. - A first serie of Early papers (about 25) have been submitted in January 2011 on early results. These papers are now printed in A&A Volume 356, DEC A second bunch of Intermediate papers will be submitted during 2012 (already 11 are in the Arxiv). These papers will focus on astrophysics/foregrounds. - First cosmological analysis and public delivery of temperature data in April expect about 30 cosmology papers on April 1st!!! - Final release (including polarization) in early Currently Planck High Frequency experiment is off (from January). LFI is still working.

34 Constraints on Neutrino Number (forecast!!) Blue: Planck DN=0.18 Red: Planck+ACTpol DN=0.11 Green: CMBPol DN=0.044 Galli, Martinelli, Melchiorri, Pagano, Sherwin, Spergel, Phys.Rev.D82:123504,2010

35 Where Planck will be?

36 Recent CMB measurements fully confirm -CDM. There is no evidence for sterile neutrinos (i.e. at more than 5 sigmas) but there is no evidence either for only 3 neutrinos! Hints for extra relativistic neutrino background (or something new) from WMAP9 and SPT. No extra neutrinos from ACT but anomalous lensing. - Lensing is crucial for neutrino masses! If AL is not one, results are suspicious. Planck experiment working as expected. In two months from Planck we will clarify the ACT vs SPT tension. (I hope!). Lesson from WMAP: Theoretical bias and prejudice may contaminate cosmology releases and papers