Measurements of $v_2$ and $v_3$ in $p$Au, $d$Au and $^3$HeAu collisions at RHIC energy from STAR

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In this presentation, measurements of $v_2$ and $v_3$, in the p/d/$^3$He+Au collisions at 200 GeV will be shown as a function of $p_{T}$ and multiplicity from STAR. The non-flow is studied with several different methods using p+p collision as a reference. It has been found that non-flow subtracted $v_{n}$ signals are not sensitive to these methods. The $v_2$ signals are also extracted using four-particle azimuthal correlations for comparison. A system independence of $v_{3}$ has been observed for three small systems as a function of $p_{T}$. Comparison with hydro-calculations with different assumptions on the initial conditions indicates that the initial geometry in small system may be dominated by sub-nulceon fluctuations. Similar to large systems, at comparable centralities, $v_{n}$ in p+Au at RHIC has also been found to be similar to those in p+Pb at the LHC. In the context of our measurement we will also discuss the prospects of the proposed O+O run at RHIC. It will facilitate a direct comparison with the results from an anticipated O+O run at the LHC, and further help us to address the underlying physics for the anisotropic behavior and initial geometry in small system..

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