Spin alignment of vector mesons induced by local spin density fluctuations

We propose a novel mechanism that the spin alignment of vector meson phi and K-*0 in most central heavy ion collisions is induced by intrinsic quantum chromo dynamics (QCD) without external vortical/magnetic fields. The local spin density fluctuation of quarks due to the axial-vector and tensor interactions between quarks can induce the spin alignments of vector meson. It is found that axial-vector interaction results in rho(00) < 1/3 for the spin alignment of phi meson, while tensor interaction results in rho(00) > 1/3. We argue that the spin alignment of K-*0 due to the spin density fluctuation from flavor-mixing would be a signature or hint of instanton.