Global Lambda hyperon polarization in nuclear collisions

Kód výsledku v 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>

Nalezeny alternativní kódy

RIV/68407700:21340/17:00318511

Výsledek na webu

<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>

Jazyk výsledku

angličtina

Název v původním jazyce

Global Lambda hyperon polarization in nuclear collisions

Popis výsledku v původním jazyce

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.

Název v anglickém jazyce

Global Lambda hyperon polarization in nuclear collisions

Popis výsledku anglicky

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.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10304 - Nuclear physics

Projekt

Výsledek vznikl pri realizaci vícero projektů. Více informací v záložce Projekty.

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2017

Kód důvěrnosti údajů

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

Název periodika

Nature

ISSN

0028-0836

e-ISSN

—

Svazek periodika

548

Číslo periodika v rámci svazku

7665

Stát vydavatele periodika

GB - Spojené království Velké Británie a Severního Irska

Počet stran výsledku

5

Strana od-do

—

Kód UT WoS článku

000406831700036

EID výsledku v databázi Scopus

2-s2.0-85026899072