2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/217569In the Israel-Stewart's theory of 2nd order dissipative hydrodynamics, we have simulated $ϕ$ production in Au+Au and Cu+Cu collisions at $\sqrt{s}_{NN}$=200 GeV. Evolution of QGP fluid with viscosity over the entropy ratio $η/s$=0.25, thermalised at $τ_i$=0.2 fm, with initial energy density $ε_i$=5.1 $GeV/fm^3$ explains the experimental data on $ϕ$ multiplicity, integrated $v_2$, mean $p_T$, $p_T$ spectra and elliptic flow in central and mid-central Au+Au collisions. $η/s$=0.25 is also consistent with centrality dependence of $ϕ$ $p_T$ spectra in Cu+Cu collisions. The central energy density in Cu+Cu collisions is $ε_i$=3.48 $GeV/fm^3$.8 pages, 10 figures. Recent STAR data on $ϕ$ production in Au+Au and Cu+Cu are analysed in viscous hydrodynamicsNuclear Theorytext