Global Lambda hyperon polarization in nuclear collisions

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61389005%3A_____%2F17%3A00477471" target="_blank" >RIV/61389005:_____/17:00477471 - isvavai.cz</a>

Alternative codes found

RIV/68407700:21340/17:00318511

Result on the web

<a href="http://dx.doi.org/10.1038/nature23004" target="_blank" >http://dx.doi.org/10.1038/nature23004</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1038/nature23004" target="_blank" >10.1038/nature23004</a>

Result language

angličtina

Original language name

Global Lambda hyperon polarization in nuclear collisions

Original language description

The extreme energy densities generated by ultra-relativistic collisions between heavy atomic nuclei produce a state of matter that behaves surprisingly like a fluid, with exceptionally high temperature and low viscosity. Non-central collisions have angular momenta of the order of 1,000., and the resulting fluid may have a strong vortical structure that must be understood to describe the fluid properly. The vortical structure is also of particular interest because the restoration of fundamental symmetries of quantum chromodynamics is expected to produce novel physical effects in the presence of strong vorticity. However, no experimental indications of fluid vorticity in heavy ion collisions have yet been found. Since vorticity represents a local rotational structure of the fluid, spin-orbit coupling can lead to preferential orientation of particle spins along the direction of rotation. Here we present measurements of an alignment between the global angular momentum of a non-central collision and the spin of emitted particles (in this case the collision occurs between gold nuclei and produces Lambda baryons), revealing that the fluid produced in heavy ion collisions is the most vortical system so far observed. We find that Lambda and (Lambda) over bar hyperons show a positive polarization of the order of a few per cent, consistent with some hydrodynamic predictions. A previous measurement that reported a null result, that is, zero polarization, at higher collision energies is seen to be consistent with the trend of our observations, though with larger statistical uncertainties. These data provide experimental access to the vortical structure of the nearly ideal liquid(8) created in a heavy ion collision and should prove valuable in the development of hydrodynamic models that quantitatively connect observations to the theory of the strong force.

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

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OECD FORD branch

10304 - Nuclear physics

Project

Result was created during the realization of more than one project. More information in the Projects tab.

Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2017

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Nature

ISSN

0028-0836

e-ISSN

—

Volume of the periodical

548

Issue of the periodical within the volume

7665

Country of publishing house

GB - UNITED KINGDOM

Number of pages

5

Pages from-to

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UT code for WoS article

000406831700036

EID of the result in the Scopus database

2-s2.0-85026899072