Abstract
The journal Nature recently published a letter titled "Creating small circular, elliptical, and triangular droplets of quark-gluon plasma" [1]. The basis for that claim is a combination of measured Fourier amplitudes v2 and v3 from collision systems p-Au, d-Au and h-Au (helion h is the nucleus of atom 3He), Glauber Monte Carlo estimates of initial-state transverse collision geometries for those systems and hydrodynamic Monte Carlo descriptions of the vn data. Apparent correspondence between hydrodynamic model vn trends and data trends is interpreted as confirmation of “collectivity” occurring in the small collision systems, further interpreted to indicate QGP formation. QGP formation in small systems runs counter to pre-RHIC theoretical assumptions that QGP formation should require large collision systems (e.g. central A-A collisions). There is currently available a broad context of experimental data from p-p, A-A and p-Pb collisions at the RHIC and LHC against which the validity of the Nature letter claims may be evaluated. This talk provides a summary of such results and their implications.
[1] Nature Phys. 15, no. 3, 214 (2019).