# Creation of quark–gluon plasma droplets with three distinct geometries

Abstract : Experimental studies of the collisions of heavy nuclei at relativistic energies have established the properties of the quark–gluon plasma (QGP), a state of hot, dense nuclear matter in which quarks and gluons are not bound into hadrons1–4. In this state, matter behaves as a nearly inviscid fluid5 that efficiently translates initial spatial anisotropies into correlated momentum anisotropies among the particles produced, creating a common velocity field pattern known as collective flow. In recent years, comparable momentum anisotropies have been measured in small-system proton–proton (p+p) and proton–nucleus (p+A) collisions, despite expectations that the volume and lifetime of the medium produced would be too small to form a QGP. Here we report on the observation of elliptic and triangular flow patterns of charged particles produced in proton–gold (p+Au), deuteron–gold (d+Au) and helium–gold (3He+Au) collisions at a nucleon–nucleon centre-of-mass energy $\sqrt {s_{{\mathrm{NN}}}} = 200$ GeV. The unique combination of three distinct initial geometries and two flow patterns provides unprecedented model discrimination. Hydrodynamical models, which include the formation of a short-lived QGP droplet, provide the best simultaneous description of these measurements.
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https://hal.archives-ouvertes.fr/hal-01802043
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Submitted on : Monday, May 28, 2018 - 10:31:59 PM
Last modification on : Wednesday, June 26, 2019 - 12:47:56 AM

### Citation

C. Aidala, Y. Akiba, M. Alfred, V. Andrieux, K. Aoki, et al.. Creation of quark–gluon plasma droplets with three distinct geometries. Nature Phys., 2019, 15 (3), pp.214-220. ⟨10.1038/s41567-018-0360-0⟩. ⟨hal-01802043⟩

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