Measurements of azimuthal anisotropy and charged-particle multiplicity in $d$$+$Au collisions at $\sqrt{s_{{}_{NN}}}=$200, 62.4, 39, and 19.6 GeV

Abstract

We present measurements of the elliptic flow, $v_2$, as a function of transverse momentum ($p_T$), pseudorapidity ($\eta$), and centrality in $d$$+$Au collisions at $\sqrt{s_{{}_{NN}}}=$200, 62.4, 39, and 19.6 GeV. The beam-energy scan of $d$$+$Au collisions provides a testing ground for the onset of flow signatures in small collision systems. We measure a nonzero $v_2$ signal at all four collision energies, which, at midrapidity and low $p_T$, is consistent with predictions from viscous hydrodynamic models. Comparisons with calculations from parton transport models (based on the {\sc ampt} Monte Carlo generator) show good agreement with the data at midrapidity to forward ($d$-going) rapidities and low $p_T$. At backward (Au-going) rapidities and $p_T>1.5$ GeV/$c$, the data diverges from {\sc ampt} calculations of $v_2$ relative to the initial geometry, indicating the possible dominance of nongeometry related correlations, referred to as nonflow. We also present measurements of the charged-particle multiplicity ($d{N}_{\mathrm{ch}}/d\eta$) as a function of $\eta$ in central $d$$+$Au collisions at the same energies. We find that in $d$$+$Au collisions at $\sqrt{s_{{}_{NN}}}=$200 GeV the $v_2$ scales with $d{N}_{\mathrm{ch}}/d\eta$ over all $\eta$ in the PHENIX acceptance. At $\sqrt{s_{{}_{NN}}}=$62.4, and 39 GeV, $v_2$ scales with $d{N}_{\mathrm{ch}}/d\eta$ at midrapidity and forward rapidity, but falls off at backward rapidity. This departure from the $d{N}_{\mathrm{ch}}/d\eta$ scaling may be a further indication of nonflow effects dominating at backward rapidity.

246 authors, 20 pages, 16 figures, 6 tables. v2 is version accepted for publication in Phys. Rev. C Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.html

References in corpus (6)

• Observation of long-range near-side angular correlations in proton-lead collisions at the LHC
• Evidence for collective multi-particle correlations in pPb collisions
• Multi-particle azimuthal correlations in p-Pb and Pb-Pb collisions at the CERN Large Hadron Collider
• Effect of flow fluctuations and nonflow on elliptic flow methods
• Particle spectra and HBT radii for simulated central nuclear collisions of C+C, Al+Al, Cu+Cu, Au+Au, and Pb+Pb from Sqrt(s)=62.4-2760 GeV
• Collective flow in ultrarelativistic ${}^3$He-Au collisions

Cited by in corpus (12)

• A collision geometry-based 3D initial condition for relativistic heavy-ion collisions
• The smallest fluid on earth
• Longitudinal dynamics and particle production in relativistic nuclear collisions
• ${}^{16}{\mathrm{O}}^{16}\mathrm{O}$ at RHIC and the LHC comparing $\alpha$ clustering vs substructure
• The 3D structure of anisotropic flow in small collision systems at the Relativistic Heavy Ion Collider
• Overview of high-density QCD studies with the CMS experiment at the LHC
• Kinematic dependence of azimuthal anisotropies in $p$$+$Au, $d$$+$Au, ${}^3$He+Au at $\sqrt{s_{{}_{NN}}}$ = 200 GeV
• Searching for QGP droplets with high-$p_T$ hadrons and heavy flavor
• Pseudorapidity distributions of charged hadrons in lead-lead collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.36 TeV
• Ultracentral Collisions of Small and Deformed Systems at RHIC: $UU$, $dAu$, ${}^{9}BeAu$, ${}^{9}Be{}^{9}Be$, ${}^{3}He{}^{3}He$, and ${}^{3}HeAu$ Collisions
• Effect of $\alpha$-clusters on particle production in O$-$O and p$-$O collisions at LHC energies
• Elliptic flow of charged hadrons in d+Au collisions at $\sqrt{s_{NN}}=$ 200 GeV using a multi-phase transport model