Effects of finite coverage on global polarization observables in heavy ion collisions

Abstract

In non-central relativistic heavy ion collisions, the created matter possesses a large initial orbital angular momentum. Particles produced in the collisions could be polarized globally in the direction of the orbital angular momentum due to spin-orbit coupling. Recently, the STAR experiment has presented polarization signals for $\Lambda$ hyperons and possible spin alignment signals for $\varphi$ mesons. Here we discuss the effects of finite coverage on these observables. The results from a multi-phase transport and a toy model both indicate that a pseudorapidity coverage narrower than $|\eta |<\sim 1$ will generate a larger value for the extracted $\varphi$-meson ${\rho }_{00}$ parameter; thus a finite coverage can lead to an artificial deviation of ${\rho }_{00}$ from 1/3. We also show that a finite $\eta$ and $p_T$ coverage affect the extracted $p_H$ parameter for $\Lambda$ hyperons when the real $p_H$ value is non-zero. Therefore proper corrections are necessary to reliably quantify the global polarization with experimental observables.

arXiv commentAccepted by PLB, major revision on simulation results of Lambda global polarization parameter

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Cited by in corpus (14)

• Polarization and Vorticity in the Quark Gluon Plasma
• Pattern of Global Spin Alignment of $\varphi$ and $K^{\ast 0}$ mesons in Heavy-Ion Collisions
• Spin tensor and its role in non-equilibrium thermodynamics
• Further developments of a multi-phase transport model for relativistic nuclear collisions
• Polarization phenomenon in heavy-ion collisions
• Practical considerations for measuring global spin alignment of vector mesons in relativistic heavy ion collisions
• Impact of globally spin-aligned vector mesons on the search for the chiral magnetic effect in heavy-ion collisions
• The effect of hadronic scatterings on the measurement of vector meson spin alignments in heavy-ion collisions
• Rescattering effect on the measurement of K* spin alignment in heavy-ion collisions
• Implication of two-baryon azimuthal correlations in $pp$ collisions at LHC energies on the QGP
• Relativistic hydrodynamics with spin
• Constraining input parameters of AMPT model with $\varphi$ meson production
• Polarization and Chirality: the quantum features of the Quark Gluon Plasma
• Practical considerations for the effect of finite coverage on the azimuthal dependence of global spin alignment