SPT-3G D1: Foreground-Robust Lensing Templates for Primordial Gravitational Wave Searches

@misc{nakato2026spt3g,
  title = {{SPT-3G D1: Foreground-Robust Lensing Templates for Primordial Gravitational Wave Searches}},
  author = {Y Nakato and W.L.K Wu and Y Omori and E Anderes and A.J Anderson and B Ansarinejad and M Archipley and L Balkenhol and D.R Barron and P.S Barry and K Benabed and A.N Bender and B.A Benson and F Bianchini and L.E Bleem and S Bocquet and F.R Bouchet and E Camphuis and M.G Campitiello and J.E Carlstrom and J Carron and C.L Chang and P.M Chichura and A Chokshi and T.-L Chou and A Coerver and T.M Crawford and C Daley and T de Haan and K.R Dibert and M.A Dobbs and M Doohan and D Dutcher and C Feng and K.R Ferguson and N.C Ferree and K Fichman and A Foster and S Galli and A.E Gambrel and A.K Gao and F Ge and F Guidi and S Guns and N.W Halverson and E Hivon and G.P Holder and W.L Holzapfel and J.C Hood and A Hryciuk and N Huang and T Jhaveri and F Kéruzoré and A.R Khalife and L Knox and K Kornoelje and C.-L Kuo and K Levy and Y Li and A.E Lowitz},
  howpublished = {HAL},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2608.06343},
  eprint = {2608.06343},
  archivePrefix = {arXiv},
  url = {https://hal.science/hal-05736061v1},
}

TY  - UNPB
TI  - SPT-3G D1: Foreground-Robust Lensing Templates for Primordial Gravitational Wave Searches
AU  - Y Nakato
AU  - W.L.K Wu
AU  - Y Omori
AU  - E Anderes
AU  - A.J Anderson
AU  - B Ansarinejad
AU  - M Archipley
AU  - L Balkenhol
AU  - D.R Barron
AU  - P.S Barry
AU  - K Benabed
AU  - A.N Bender
AU  - B.A Benson
AU  - F Bianchini
AU  - L.E Bleem
AU  - S Bocquet
AU  - F.R Bouchet
AU  - E Camphuis
AU  - M.G Campitiello
AU  - J.E Carlstrom
AU  - J Carron
AU  - C.L Chang
AU  - P.M Chichura
AU  - A Chokshi
AU  - T.-L Chou
AU  - A Coerver
AU  - T.M Crawford
AU  - C Daley
AU  - T de Haan
AU  - K.R Dibert
AU  - M.A Dobbs
AU  - M Doohan
AU  - D Dutcher
AU  - C Feng
AU  - K.R Ferguson
AU  - N.C Ferree
AU  - K Fichman
AU  - A Foster
AU  - S Galli
AU  - A.E Gambrel
AU  - A.K Gao
AU  - F Ge
AU  - F Guidi
AU  - S Guns
AU  - N.W Halverson
AU  - E Hivon
AU  - G.P Holder
AU  - W.L Holzapfel
AU  - J.C Hood
AU  - A Hryciuk
AU  - N Huang
AU  - T Jhaveri
AU  - F Kéruzoré
AU  - A.R Khalife
AU  - L Knox
AU  - K Kornoelje
AU  - C.-L Kuo
AU  - K Levy
AU  - Y Li
AU  - A.E Lowitz
PY  - 2026
DA  - 2026/09/02
PB  - HAL
DO  - 10.48550/arxiv.2608.06343
UR  - https://hal.science/hal-05736061v1
AB  - Gravitational lensing of the cosmic microwave background (CMB) generates B-mode polarization that acts as a source of contamination to searches for B modes generated by primordial gravitational waves (PGWs). The strongest constraint on PGW B modes is already significantly limited by lensing B modes, as shown in the most recent BICEP result. In this work, we present CMB lensing B-mode templates constructed using SPT-3G and Planck data, which characterize the lensing B modes and can be used to improve PGW B-mode searches. We use SPT-3G data from the 2019 and 2020 observing seasons for the E modes and the CMB-reconstructed lensing potential, and a cosmic infrared background (CIB) map from Planck as an external lensing tracer. To test for extragalactic foreground biases in the lensing template, we consider CMB lensing reconstruction variants with different levels of foreground immunity: the standard and profile-hardened global minimum variance (GMV) quadratic estimators, and a polarization-only quadratic estimator. We validate the template construction using Gaussian simulations and Agora simulations with realistic non-Gaussian foregrounds. From simulations, we find that foreground-induced biases are strongly suppressed for the template constructed with the profile-hardened GMV + CIB tracer, with residual bias below 10% of the statistical uncertainty on the template power spectrum. Data difference tests on this template similarly show no evidence for significant foreground contamination. This foreground-immune lensing template achieves delensed residual BB power of A_lens^res ≃ 0.48 averaged over 20 ≤ ℓ ≤ 200, the highest delensing efficiency lensing template to date. These results demonstrate and validate a method to construct foreground-robust lensing templates which will be used in upcoming delensed PGW B-mode analyses of BICEP data.
ER  -