Testing CPT Symmetry with Current and Future CMB. Jun-Qing Xia (IHEP, Beijing) On Behalf of IHEP Cosmology Group

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1 Testing CPT Symmetry with Current and Future CMB Jun-Qing Xia (IHEP, Beijing) On Behalf of IHEP Cosmology Group Florence, September 8, 2015

2 Outline 2 History of the CPT-testing project in IHEP group Isotropic Polarization Rotation Angle Anisotropic Polarization Rotation Angle Potential CMB Observation Site Ali, Tibet, China

3 Working History Now

4 Working History Now Inspired by A. Lue, L. M. Wang, M. Kamionkowski, PRL (1999), we started CPT-testing project and found that the CMB EB spectrum is more sensitive to the polarization rotation angle (CPR) than the CMB TB. Feng, Li, Li, Zhang, PLB 620, 27 (2005)

5 Working History Now The BOOMERanG experiment published the CMB polarization data which include the TB and EB information. We used this CMB data, together with the WMAP1/WMAP3 data, to measure the CPR for the first time and found the interesting hint for nonzero CPR. Feng, Li, XIA, Chen, Zhang, PRL 96, (2006)

6 Working History Now We discussed with E. Komatsu about this CPT symmetry testing and WMAP published TB and EB information to measure CPR in 5yr, 7yr, 9yr data. WMAP5, WMAP7, WMAP9 Papers

7 Working History Now We firstly considered effects on CMB polarization power spectra from the anisotropic CPR. Li, Zhang, PRD 78, (2008)

8 Working History Now BICEP experiment published the first three year data and we found that this data strongly favor a negative CPR at more than 2\sigma level. BICEP group improved their calibration method and used self-calibration to remove this CPR. XIA, Li, Zhang, PLB 687, 129 (2010)

9 Working History Now We also realized that this new CMB BB-generating mechanism could affect the measurement of CMB primordial BB signal, if the tensor-to-scalar ratio r is not very large. XIA, Li, Zhang, PLB 687, 129 (2010)

10 Working History Now We mainly focus on constraints on CPR from CMB current and future data and are more interested in how large bias results on the measurement of primordial BB signal when we ignore the effect of CPR. Li, XIA, Li, Li, Zhang, ApJ 799, 211 (2015)

11 Isotropic CPR

12 Chern-Simons Term 12 In the standard CMB theory, TB/EB are zero, due to the parity conservation. However, if there is an interaction between CMB photons and the other field, like Chern-Simons term which violates Lorentz and CPT symmetries: The vacuum Maxwell equations are different: The polarization plane of CMB photons is rotated. The non-zero CPR will be induced

13 Chern-Simons Term 13 Stokes parameters Q & U are changed. CMB polarization spectra are modified.

14 Current Constraints on Isotropic CPR 14 Systematic errors of CMB experiments are included.

15 Effect on BB spectrum (Xia et al., PLB 2010) 15 Only few degrees of rotation angle will mimic the effect of r on large scales. Therefore, the BB spectrum induced by the nonzero rotation angle will affect the measurement of the CMB primordial BB signal.

16 BICEP2 & CPR (Li, Xia & Zhang, ) 16 The non-zero rotation angle with few degrees could give similar order of CMB BB spectrum with the BICEP2 measurement.

17 Future Mock Data 17 Using the mock data with Planck-like sensitivity, the standard deviation of CPR shrinks by a factor of 10,

18 Recent Planck to constrain CPR 18 Planck 2015 released the polarization data: Highl TE/EE: 30 < \ell < 1996 Lowl TEB: 2 < \ell < 30 We use Planck polarization and BKP data to constrain isotropic CPR The Planck polarization is much weaker than we expected on CPR constraints.

19 Future Mock Data 19 Fiducial model: NO GWs, NON-ZERO CPR If the CPR is forced to be ZERO in the analysis, the constraint on r will be biased obviously. We might obtain the false signal of GWs.

20 Anisotropic CPR

21 Anisotropies of Rotation Angle 21 (Li & Zhang, PRD, 2008) In the linear perturbation theory, the rotation angle is decomposed into the isotropic part and the fluctuations The self-calibration method can only remove the effect of Isotropic Rotation. The anisotropies can be decomposed as: Then can define the angular power spectrum and correlation function of rotation angle

22 Modified CMB Polarization Spectra 22 To fit CMB data, we use 7 more parameters to describe the effect of anisotropic CPR: Variance of the two point correlation functions 6 parameters for the binned power spectrum of CPR, which are the average values in the multipole regions (Li & Yu, JCAP, 2013, Li et al., ApJ, 2015)

23 Current & Future Constraints 23

24 Generating non-zero BB 24 In the model with ZERO isotropic CPR and NON- ZERO anisotropic CPR: TB and EB are ZERO to satisfy the self-calibration Still generate the NON-ZERO BB power spectrum, which could contaminate the CMB primordial B-modes signal. (Li et al., ApJ, 2015)

25 Future Mock Data 25 Fiducial model: NON-ZERO GWs, ZERO CPR Due to the degeneracy between anisotropic CPR and r, when including anisotropic CPR into the calculation, the constraint on r is weakened. The significance of GWs detection becomes lower. without CPR with CPR

26 Future Mock Data 26 Fiducial model: ZERO GWs, NON-ZERO CPR If the anisotropic CPR is forced to be ZERO in the analysis, the constraint on r will be biased obviously. We might obtain the false signal of Primordial GWs

27 27 Potential CMB Observation Site Ali, Tibet, China

28 Atmosphere Transmission 28

29 Atmosphere Transmission 29

30 Atmosphere Transmission 30

31 Ali Observatory, Tibet 31 N32, E80, 5100m Altitude

32 Ali Observatory, Tibet Km south of Shiquanhe Town 25 Km to Kunsha Airport With a 25 KW solar power station Power transmission tower & line prepared

33 Ali Observatory, Tibet 33

34 Precipitable Water Vapor (PWV) 34 PWV measurement at Oma, Tibet. PWV at Ali should be better than that at Oma.

35 PWV of Ali from Weather Data 35 Using the Weather Research & Forecasting (WRF) model to estimate the PWV at Ali from the annual weather data in 2014.

36 Preliminary PWV data at Ali 36

37 Advantages of Ali site 37 In Northern Hemisphere, large sky coverage Easy access and less cost: airport, paved road Well-developed infrastructure Good observation conditions in winter Significant support from both the science community and government Experiences with large international collaboration in Tibet NAOC, CAS owns the Ali site, less limitation Surrounding higher sites are possible

38 Sky Coverage 38 Here, we ignore the foreground and use the Celestial coordinates. For Greenland, the sky coverage is about 30%. For Ali, the sky coverage is more than 60%, due to its low latitude.

39 Advantages of Ali site 39 In Northern Hemisphere, large sky coverage Easy access and less cost: airport, paved road Well-developed infrastructure Good observation conditions in winter Significant support from both the science community and government Experiences with large international collaboration in Tibet NAOC, CAS owns the Ali site, less limitation Surrounding higher sites are possible

40 Small ZiDaBan Site Km south of Ali site 6000m altitude with very long and wide mountain ridge with road nearby

41 Capability 41 Using BICEP3-like sensitivity, a very simple and optimistic simulation shows that Ali site could measure the primordial BB signal and CPR very well. r < (95%)

42 3 rd Beijing-Chicago Workshop 42 In March we discussed this Ali site with Prof. John Carlstrom on this workshop. He and Prof. John Kovac will visit the Ali site in the end of September.

43 Conclusions 43 We use the current and future CMB data to study the isotropic and anisotropic CPR. For the future accurate CMB data, if we do not take the CPR into account properly, we might obtain some bias results, even the false signal of primordial gravitational waves. Ali site in Tibet is a potential CMB observation place. It has a lot of advantages and could be an important CMB experiment in northern hemisphere. Any suggestions or comments are welcome. Thanks!

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