  The on-site Coulomb potential, U, and the covalent state of electronic
orbitals play key roles for the Cooper pair symmetry and exotic electromagnetic
properties of high-Tc superconducting cuprates. In this paper, we demonstrate a
way to determine the value of U and present the whole picture of the covalent
state of Cu spins in the mother system of the La-based high-Tc superconducting
cuprate, La2CuO4, by combining the muon spin rotation ({\mu}SR) and the density
functional theory (DFT) calculation. We reveal local deformations of the CuO6
octahedron followed by changes in Cu-spin distributions caused by the injected
muon. Adjusting the DFT and muSR results, U and the minimum charge-transfer
energy between the upper Hubbard band and the O 2p band were optimized to be
4.87(4) and 1.24(1) eV, respectively.
