LiteBIRD science goals and forecasts: a full-sky measurement of gravitational lensing of the CMB

Lonappan, A. I.; Namikawa, T.; Piccirilli, G.; Diego-Palazuelos, P.; Ruiz-Granda, M.; Migliaccio, M.; Baccigalupi, C.; Bartolo, N.; Beck, D.; Benabed, K.; Challinor, A.; Errard, J.; Farrens, S.; Gruppuso, A.; Krachmalnicoff, N.; Martínez-González, E.; Pettorino, V.; Sherwin, B.; Starck, J.; Vielva, P.; Akizawa, R.; Anand, A.; Aumont, J.; Aurlien, R.; Azzoni, S.; Ballardini, M.; Banday, A. J.; Barreiro, R. B.; Bersanelli, M.; Blinov, D.; Bortolami, M.; Brinckmann, T.; Calabrese, E.; Campeti, P.; Carones, A.; Carralot, F.; Casas, F. J.; Cheung, K.; Clermont, L.; Columbro, F.; Conenna, G.; Coppolecchia, A.; Cuttaia, F.; D'Alessandro, G.; de Bernardis, P.; De Petris, M.; Della Torre, S.; Di Giorgi, E.; Eriksen, H. K.; Finelli, F.; Franceschet, C.; Fuskeland, U.; Galloni, G.; Galloway, M.; Georges, M.; Gerbino, M.; Gervasi, M.; Génova-Santos, R. T.; Ghigna, T.; Giardiello, S.; Gimeno-Amo, C.; Gjerløw, E.; Hazumi, M.; Henrot-Versillé, S.; Hergt, L. T.; Hivon, E.; Kohri, K.; Komatsu, E.; Lamagna, L.; Lattanzi, M.; Leloup, C.; Lembo, M.; López-Caniego, M.; Luzzi, G.; Macias-Perez, J.; Maffei, B.; Masi, S.; Massa, M.; Matarrese, S.; Matsumura, T.; Micheli, S.; Moggi, A.; Monelli, M.; Montier, L.; Morgante, G.; Mot, B.; Mousset, L.; Nagata, R.; Natoli, P.; Novelli, A.; Obata, I.; Occhiuzzi, A.; Pagano, L.; Paiella, A.; Paoletti, D.; Pascual-Cisneros, G.; Pavlidou, V.; Piacentini, F.; Pinchera, M.; Pisano, G. et al.
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Journal of Cosmology and Astroparticle Physics

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We explore the capability of measuring lensing signals in LiteBIRD full-sky polarization maps. With a 30 arcmin beam width and an impressively low polarization noise of 2.16 μK-arcmin, LiteBIRD will be able to measure the full-sky polarization of the cosmic microwave background (CMB) very precisely. This unique sensitivity also enables the reconstruction of a nearly full-sky lensing map using only polarization data, even considering its limited capability to capture small-scale CMB anisotropies. In this paper, we investigate the ability to construct a full-sky lensing measurement in the presence of Galactic foregrounds, finding that several possible biases from Galactic foregrounds should be negligible after component separation by harmonic-space internal linear combination. We find that the signal-to-noise ratio of the lensing is approximately 40 using only polarization data measured over 80% of the sky. This achievement is comparable to Planck's recent lensing measurement with both temperature and polarization and represents a four-fold improvement over Planck's polarization-only lensing measurement. The LiteBIRD lensing map will complement the Planck lensing map and provide several opportunities for cross-correlation science, especially in the northern hemisphere.