  Using angle-resolved photoemission spectroscopy it is revealed that in the
vicinity of optimal doping the electronic structure of La2-xSrxCuO4 cuprate
undergoes an electronic reconstruction associated with a wave vector q_a=(pi,
0). The reconstructed Fermi surface and folded band are distinct to the shadow
bands observed in BSCCO cuprates and in underdoped La2-xSrxCuO4 with x <= 0.12,
which shift the primary band along the zone diagonal direction. Furthermore the
folded bands appear only with q_a=(pi, 0) vector, but not with q_b= (0, pi). We
demonstrate that the absence of q_b reconstruction is not due to the
matrix-element effects in the photoemission process, which indicates the
four-fold symmetry is broken in the system.
