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| CMS-PAS-HIN-24-002 | ||
| Azimuthal dependence of hyperon polarization along the beam direction in pPb collisions at $ \sqrt{\smash[b]{s_{_{\mathrm{NN}}}}} = $ 8.16 TeV | ||
| CMS Collaboration | ||
| 3 June 2024 | ||
| Abstract: The polarization of the $ \Lambda $ and $ \overline{\Lambda} $ hyperons along the beam ($ z $) direction, $ P_z $, has been measured for the first time in pPb collisions at the LHC with $ \sqrt{\smash[b]{s_{_{\mathrm{NN}}}}}= $ 8.16 TeV data collected by the CMS experiment. Assuming the largest contributions to $ P_z $ come from collective flow, this polarization can be characterized by the Fourier sine coefficients $ P_{z,sn} = \langle P_{z}\sin(n\phi - n\Psi_{n}) \rangle $, where $ \phi $ is the hyperon azimuthal emission angle and $ \Psi_{n} $ is the $ n $-th order flow plane angle. The second order Fourier sine coefficient $ P_{z,s2} $ is reported for $ \Lambda $ and $ \overline{\Lambda} $ particles as a function of transverse momentum and event multiplicity. A significant positive $ P_{z,s2} $ signal is observed for 0.8 $ < p_{\mathrm{T}} < $ 6.0 GeV/$c$ over the entire multiplicity range (from 3 to 250 charged particles). The measured $ P_{z,s2} $ values increase as a function of $ p_{\mathrm{T}} $ and decrease as a function of multiplicity. These results can provide new constraints on the potential creation of quark-gluon plasma droplets and the spin polarization mechanism in pp and pA systems. | ||
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Links:
CDS record (PDF) ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, Submitted to PRL. The superseded preliminary plots can be found here. |
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Compact Muon Solenoid LHC, CERN |
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