Polarization of Lambda and (Lambda)over-bar Hyperons along the Beam Direction in Pb-Pb Collisions at root s(NN)=5.02 TeV

Result code in IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F68407700%3A21340%2F22%3A00363954" target="_blank" >RIV/68407700:21340/22:00363954 - isvavai.cz</a>
Result on the web
<a href="https://doi.org/10.1103/PhysRevLett.128.172005" target="_blank" >https://doi.org/10.1103/PhysRevLett.128.172005</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.1103/PhysRevLett.128.172005" target="_blank" >10.1103/PhysRevLett.128.172005</a>

Result language
angličtina
Original language name
Polarization of Lambda and (Lambda)over-bar Hyperons along the Beam Direction in Pb-Pb Collisions at root s(NN)=5.02 TeV
Original language description
The polarization of the Lambda and (Lambda) over bar hyperons along the beam (z) direction, P-z, has been measured in Pb-Pb collisions at root s(NN) = 5.02 TeV recorded with ALICE at the Large Hadron Collider (LHC). The main contribution to P-z comes from elliptic flow-induced vorticity and can be characterized by the second Fourier sine coefficient P-z,P-s2 = < P-z sin(2 phi - 2 Psi(2))>, where phi is the hyperon azimuthal emission angle and Psi(2) is the elliptic flow plane angle. We report the measurement of P-z,P-s2 for different collision centralities and in the 30%-50% centrality interval as a function of the hyperon transverse momentum and rapidity. The P-z,P-s2 is positive similarly as measured by the STAR Collaboration in Au-Au collisions at root s(NN) = 200 GeV, with somewhat smaller amplitude in the semicentral collisions. This is the first experimental evidence of a nonzero hyperon P-z in Pb-Pb collisions at the LHC. The comparison of the measured P-z,P-s2 with the hydrodynamic model calculations shows sensitivity to the competing contributions from thermal and the recently found shear-induced vorticity, as well as to whether the polarization is acquired at the quark-gluon plasma or the hadronic phase.
Czech name
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Czech description
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Type
J<sub>imp</sub> - Article in a specialist periodical, which is included in the Web of Science database
CEP classification
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OECD FORD branch
10303 - Particles and field physics

Project
Result was created during the realization of more than one project. More information in the Projects tab.
Continuities
P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Publication year
2022
Confidentiality
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

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