Holographic spin alignment of J/ψ meson in magnetized plasma

We study the mass spectra and spin alignment of vector meson J/psi in a thermal magnetized background using a generalized theoretical framework based on gauge/gravity duality. Utilizing a soft wall model for the QGP background and a massive vector field for the J/psi meson, we delve into the meson's spectral function and spin parameters(lambda(theta), lambda(phi), lambda(theta phi))for different cases, assessing their response to variations in magnetic field strength, momentum, and temperature. We initially examine scenarios where a meson's momentum aligns parallel to the magnetic field in helicity frame. Our results reveal a magnetic field-induced positive lambda(H)(theta) for low meson momentum, transitioning to negative with increased momentum. Asa comparison, we also study the case of momentum perpendicular to the magnetic field and find the direction of magnetic field does not affect the qualitative behavior for thee B-dependence of lambda(H)(theta). Moreover, we apply our model to real heavy-ion collisions for three different spin quantization directions. Further comparisons with experimental data show qualitative agreement for spin parameters lambda theta and lambda(phi) in the helicity and Collins-Soper frames