A crucial problem for partial sky analysis of CMB polarization is the E-B leakage problem. Such leakage arises from the presence of `ambiguous' modes that satisfy properties of both E and B modes. Solving this problem is critical for primordial polarization B mode detection in partial sky CMB polarization experiments. In this work we introduce a new method for reducing the leakage. We demonstrate that if we complement the E-mode information outside the observation patch with ancillary data from full-sky CMB observations, we can reduce and even effectively remove the E-to-B leakage. For this objective, we produce E-mode Stokes QU maps from Wiener filtered full-sky intensity and polarization CMB observations. We use these maps to fill the sky region that is not observed by the ground-based experiment of interest, and thus complement the partial sky Stokes QU maps. Since the E-mode information is now available on the full sky we see a significant reduction in the E-to-B leakage. We evaluate on simulated data sets the performance of our method for a `shallow' f_sky = 8%, and a `deep' f_sky = 2% northern hemisphere sky patch, with AliCPT-like properties, and a LSPE-like f_sky = 30% sky patch, by combining those observations with Planck-like full sky polarization maps. We find that our method outperforms the standard and the pure-B method pseudo-C_ℓ estimators for all of our simulations. Our new method gives unbiased estimates of the B-mode power spectrum through-out the entire multipole range with near-optimal pseudo-C_ℓ errors for ℓ > 20. We also study the application of our method to the CMB-S4 experiment combined with LiteBIRD-like full sky data, and show that using signal-dominated full sky E-mode data we can eliminate the E-to-B leakage problem.

对CMB极化进行部分天空分析的关键问题是 E--乙泄漏问题。这种泄漏是由于同时存在“模棱两可”的模态而引起的。E 和 乙模式。解决这个问题对于原始极化至关重要乙天空CMB极化实验中的模式检测。在这项工作中，我们介绍了一种减少泄漏的新方法。我们证明，如果我们补充E包含来自全天候CMB观测的辅助数据的观测补丁以外的模式信息，我们可以减少甚至有效地去除 E-到-乙泄漏。为了这个目标，我们产生E模式斯托克斯 曲来自维纳的地图对全天空强度和极化CMB观测值进行了滤波。我们使用这些地图来填充感兴趣的基于地面的实验未观察到的天空区域，从而补充了部分天空斯托克斯曲地图。自从E-模式信息现在可以在全天候使用，我们发现 E-到-乙泄漏。我们在模拟数据集上评估我们的方法在“浅”情况下的性能˚F_天空 = 8％和“深层” ˚F_天空 = 2％ 北半球的天空斑块，具有类似AliCPT的特性和类似LSPE的特性 ˚F_天空 = 30％通过将这些观测值与类似普朗克的全天空极化图相结合来获得天空补丁。我们发现我们的方法优于标准方法和纯乙 方法伪C _＆ell;我们所有模拟的估计量。我们的新方法给出了无偏估计乙模功率谱遍及整个多极范围，具有接近最佳的伪C _＆ell; 错误 ＆ell; > 20。我们还研究了我们的方法与类似LiteBIRD的满天数据结合在CMB-S4实验中的应用，并表明使用信号主导的满天E模式数据我们可以消除 E-到-乙 泄漏问题。