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.

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

References in corpus (5)

• An Introduction to PYTHIA 8.2
• Big-Bang Nucleosynthesis
• Angular momentum conservation in heavy ion collisions at very high energy
• Global polarization measurement in Au+Au collisions
• Evolution of transverse flow and effective temperatures in the parton phase from a multi-phase transport model

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