Speaker
Description
The medium modification to particle spectra and the origin of collectivity in small collision systems are widely debated topics in our community.
To address these open questions we propose the study of particle production and collectivity for varying system sizes, presented in decreasing order (Au+Au $>$ Ru+Ru/Zr+Zr $>$ $^{3}$He+Au $>$ d+Au $>$ p+Au $>$ p+p $>$ $\gamma$+Au), available at RHIC using the STAR detector.
We present the first measurements of charged hadron yields in isobar (Ru+Ru and Zr+Zr) collisions. We perform measurements of identified particle spectra at low transverse momenta ($p_\mathrm{T}$) as a function of rapidity and event centrality. We also perform the centrality dependent measurements of nuclear modification factors ($R_\mathrm{AA}$) at high $p_\mathrm{T}$. Combined with the existing results in smaller systems (p/d+Au), these results provide an additional handle in studying system size and collision geometry dependences of the medium modification to particle production.
We also revisit the measurements of elliptic ($v_2$) and triangular ($v_3$) anisotropies in p+Au, d+Au and $^{3}$He+Au collisions at 200 GeV including a comprehensive evaluation of the non-flow effects using different subtraction methods.
In addition to the results obtained from the mid-rapidity ($|\eta|<$1), we also use the Event Plane Detectors that span over 2.1$<|\eta|<$5.1 to investigate the potential influence of longitudinal flow de-correlations in $v_n$ measurements using peripheral Ru+Ru and Zr+Zr collisions.
Our study of photonuclear ($\gamma$+Au) processes using ultra-peripheral Au+Au data can push the boundaries of small system scan at RHIC. We lastly present measurements on particle production and long-range di-hadron correlations in inclusive $\gamma$+Au-rich events that are not dominated by hadronic interactions.
