1. Detecting the CMB Polarization Ziang Yan

2. How do we know about the universe by studying CMB?

3. By blackbody spectrum(1965): Fig.1 Blackbody spectrum of CMB measured by COBE

4. By temperature power spectrum(1992,COBE): Fig.2 Temperature power spectrum taken by Planck

5. By polarization power spectrum: Fig.3 Polarization power spectrum under certain cosmological model

6. What can polarization power spectrum tell us? EE signals: test the polarization and fluctuation nature of CMB TE signals: degree scales:generation of CMB fluctuation. large scales:reionization at large redshift. EE and TE signals can be analyzed combining with TT signals which is relatively easy to be detected.

7. What can polarization power spectrum tell us? BB signals: degree scales:detecting the information on CMB printed by primordial gravitational waves. small scales:Probe lage- scale structure to z 1000 by detecting the gravitational lensing effects on polarization spectrum. BB signals at degree scales is believed to be an effective way to detect primordial gravitational wave such as to bolster the inflation model.

8. Why polarization signals so difficult to be detected?

9. Fig.4 Pre-DASI experiments set up limit to polarization signals before finally detect it.

10. DASI reported their first data in 2002 claiming E-mode polarization signals Fig.5 Detections of CMB polarization with DASI and WMAP. Panels show experimental bandpowers of temperature T, TE correlation, E-mode, and B-mode polarization.

11. Fig.6 DASI experiment

12. Other Experiments Ground Based:BICEP (Keating et al. (2003)), QUEST (Church et al. (2003)), POLARBEAR (Kermish et.al (2012)),QUIET(Bischo et.al(2012)),QUBIC(Battistelli et.al(2010))… Balloon-Borne:Boomerang (Montroy et al. 2003), MAXIPOL (Johnson et al. 2003)... Satellite:WMAP,Planck...

13. Fig.7 BICEP2 BB auto spectra and 95% upper limits from several previous experiments

14. Fig.8 E and B signal detected by BICEP2

16. Digression:why not low l? Low l hump generated by GW and reionization The signal at l~100 is easy to be contaminated lensing hump. Why don’t we detect low-l signals? -Cosmic variance:

17. Challenge from Planck Satellite Dust may also produce B-mode polarization signal (1405.5857) (1405.7351)

18. Fig.10 Spectrum of different models(1405.7351)

19. Fig11 Left: Joint constraints (68% and 95% c.l.) on r and the amplitude of the dust polarization spectrum at l = 100 from Planck+WP+BICEP2, assuming a flat prior on the dust amplitude. Right:Constraints from the same combination of data in the r–ns plane (blue contours), compared with constraints from Planck+WP alone (yellow contours).

20. Other source of B-modes:magnetic field? 1403.6768

21. Challenges call for more experiment results. Ongoing experiments:BICEP3,Keck Array,Litebird,QUBIC,etc… More independent experiment results is needed to test the result of BICEP2. A more accurate dust mapping is need to eliminate its influence on the BB spectrum.

22. Reference Bonvin C, Durrer R, Maartens R. Can PrimordialMagnetic Fields be the Origin of the BICEP2 Data?[J]. 2014. Carlstrom J E, Kovac J, Leitch E M, et al. Status of CMB polarization measurements from DASI and other experiments[J]. 2003. Collaboration B, Ade P A R, Aikin R W, et al. BICEP2 I: Detection Of B-mode Polarization at Degree Angular Scales[J]. 2014:19. Dodelson S. Modern cosmology[M]. Academic Press,2003. Flauger R, Hill J C, Spergel D N. Toward an Understanding of Foreground Emission in the BICEP2 Region[J]. arXiv preprint arXiv:1405.7351, 2014. Hu W. CMB temperature and polarization anisotropy fundamentals[J]. 2003. Mortonson M J, Seljak U. A joint analysis of Planck and BICEP2 B modes including dust polarization uncertainty[J]. 2014:12. Petet P, Uzan J. Primordial Cosmology[M]. Great Britian: Oxford University Press, 2009.

23. Thank you for attention!