Local spin polarization in high energy heavy ion collisions

Wu, Haohao; Pang, Long-Gang; Huang, Xu-Guang; Wang, Qun

doi:10.1103/physrevresearch.1.033058

Cited by 107 publications

(59 citation statements)

References 103 publications

(153 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…A similar, more recent calculation (145) finds that the rapidity dependence of vorticity itself depends on √ s NN at RHIC energies and that it is sensitive to important physical parameters of the model itself. Numerical calculations with transport-hybrid codes (96,99,102) also indicate a forward migration of vorticity, especially as the collision energy increases (99). Finally, hydrodynamic models predict much higher vorticity in the beam fragmentation region at both NICA (97, 146) and RHIC (92,147) energies.…”

Section: 43mentioning

confidence: 82%

“…Clearly, |J sys | increases with increasing √ s NN , and transport calculations (96,97) predict that about 20% of this angular momentum is transferred to the QGP fireball. While some early calculations ( 25) predicted an increased polarization at high collision energies, a strongly decreasing trend is produced by most hydrodynamic (50,98) and transport-hybrid codes in which the thermal vorticity field is obtained through a coarse-graining procedure (96,(99)(100)(101)(102).…”

Section: Global Hyperon Polarization: Observationmentioning

confidence: 99%

See 1 more Smart Citation

Polarization and Vorticity in the Quark–Gluon Plasma

Becattini

Lisa

2020

Annu. Rev. Nucl. Part. Sci.

213

128

View full text Add to dashboard Cite

The quark–gluon plasma (QGP) produced by collisions between ultrarelativistic heavy nuclei is well described in the language of hydrodynamics. Noncentral collisions are characterized by very large angular momentum, which in a fluid system manifests as flow vorticity. This rotational structure can lead to a spin polarization of the hadrons that eventually emerge from the plasma, and thus these collisions provide experimental access to flow substructure at unprecedented detail. Recently, the first observations of Λ hyperon polarization along the direction of collisional angular momentum were reported. These measurements are in broad agreement with hydrodynamic and transport-based calculations and reveal that the QGP is the most vortical fluid ever observed. However, there remain important tensions between theory and observation that might be fundamental in nature. In the relatively mature field of heavy-ion physics, the discovery of global hyperon polarization and 3D simulations of the collision have opened an entirely new direction of research. We discuss the current status of this rapidly developing area and directions for future research.

show abstract

Section: 43mentioning

confidence: 82%

Section: Global Hyperon Polarization: Observationmentioning

confidence: 99%

Polarization and Vorticity in the Quark–Gluon Plasma

Becattini

Lisa

2020

Annu. Rev. Nucl. Part. Sci.

213

128

View full text Add to dashboard Cite

show abstract

“…Although the simulations based on the modified Cooper-Frye formula for spin polarization [5,6] have shown remarkable agreements with global polarization of Λ [7,8], more recent observations for local polarization caused the new tension between experiments and theories [9,10]. Further phenomenological studies have alluded to an essential role for non-equilibrium corrections [11,12], where the spin polarization is no longer just dictated by thermal vorticity and equilibrium distribution functions for Λ. Also, the feed-down effects are analyzed in refs.…”

Section: Jhep07(2020)070 Introductionmentioning

confidence: 99%

Effective quantum kinetic theory for spin transport of fermions with collsional effects

Yang

Hattori

Hidaka

2020

J. High Energ. Phys.

109

View full text Add to dashboard Cite

We systematically derive the collision term for the axial kinetic theory, a quantum kinetic theory delineating the coupled dynamics of the vector/axial charges and spin transport carried by the massive spin-1/2 fermions traversing a medium. We employ the Wigner-function approach and propose a consistent power-counting scheme where the axial-charge distribution function, a non-conserved quantity for massive particles, is accounted as the first-order quantity in the expansion, while the vector-charge distribution function the zeroth-order quantity. This specific power-counting scheme allows us to organize a reduced expansion for the collision term and to formally identity the spindiffusion effect and the spin-polarization effect at the same order. We confirm that the obtained collisional axial kinetic theory smoothly reduces to the chiral kinetic theory in the massless limit, serving as a consistency check. In the absence of electromagnetic fields, we further present the simplified axial kinetic equations suitable for tracking dynamical spin polarization of heavy and light fermions, respectively. As an application to the weakly coupled quark-gluon plasma at high temperature, we compute the spin-diffusion term for massive quarks within the leading-log approximation. The formal expression for the firstorder terms provides a path toward evaluation of the spin polarization effect in quantum chromodynamics.

show abstract

“…Also, we would like to note here that during the final preparation of this manuscript another paper following the idea of spin polarization being given by a definition of vorticity different from thermal vorticity appeared [42]. In fact the conclusions of this study show that the correct sign of the longitudinal spin polarization may be obtained using the so-called T -vorticity [43].…”

Section: Resultsmentioning

confidence: 73%

Longitudinal spin polarization in a thermal model

et al. 2019

View full text Add to dashboard Cite

We use a thermal model with single freeze-out to determine longitudinal polarization of Λ hyperons emitted from a hot and rotating hadronic medium. We consider the top RHIC energies and use the model parameters determined in the previous analyses of particle spectra and elliptic flow. Using a direct connection between the spin polarization tensor and thermal vorticity, we reproduce earlier results which indicate a quadrupole structure of the longitudinal component of the polarization three-vector with an opposite sign compared to that found in the experiment. We further use only the spatial components of the thermal vorticity in the laboratory system to define polarization and show that this leads to the correct sign and magnitude of the quadrupole structure. This procedure resembles a non-relativistic connection between the polarization three-vector and vorticity employed in other works. In general, our results bring further evidence that the spin polarization dynamics in heavy-ion collisions may be not directly related to the thermal vorticity. The additional material explains the construction of the hydrodynamicaly consistent gradients of fluid velocity and temperature in thermal models with the help of the perfect-fluid equations of motion.

show abstract

Local spin polarization in high energy heavy ion collisions

Cited by 107 publications

References 103 publications

Polarization and Vorticity in the Quark–Gluon Plasma

Polarization and Vorticity in the Quark–Gluon Plasma

Effective quantum kinetic theory for spin transport of fermions with collsional effects

Longitudinal spin polarization in a thermal model

Contact Info

Product

Resources

About