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Lagrangian-space Gaussian ansatz for the matter redshift-space power spectrum and correlation function

We study the predictions for the matter redshift-space power spectrum and correlation function of a Lagrangian-space Gaussian ansatz introduced in a previous work. This model is a natural extension of the Zeldovich approximation, where the displacement and velocity power spectra are determined by the equations of motion, instead of being set equal to the linear power spectrum. It does not contain any free parameter. As for the real-space statistics, we find that this Lagrangian-space approach is much more efficient for the correlation functions than for the power spectra. The damping of the BAO oscillations is well recovered but there is a large smooth drift from the simulations in the power spectra. The multipoles of the correlation functions are well recovered on BAO scales, with an accuracy of $2\%$ for $ξ^s_0$ down to $10 h^{-1}$ Mpc, and of $3\%$ for $ξ^s_2$ down to $26 h^{-1}$ Mpc, at $z \geq 0.35$.