E- and B-mode mixing from incomplete knowledge of the shear correlation

Aims. We quantify the mixing of the measured cosmic shear E- and B-mode due to the lack of shear correlation measurements on small and large scales, which arises due to the lack of close projected galaxy pairs and the finite field size, respectively. Methods. We calculate the aperture mass statistics and the E-/B-mode shear correlation functions xi_{E, B +/-} with small- and large-scale cut-offs taken into account. We assess the deviation of the obtained E-mode to the true E-mode, and the introduction of a spurious B-mode. Results. The measured aperture mass dispersion is underestimated by more than 10% on scales smaller than 12 times the lower cut-off. For a precise measurement of the E- and B-mode at the percent level using a combination of xi_{E, B +} and xi_{E, B -}, a field as large as 7 (2.4) degree is necessary for ground-based (space-based) observations