We argue that a detailed analysis of the spin aligement of vector mesons can serve as a probe of some aspects of spin dynamics in the vortical fluid for which there have been quite a few theoretical developments but relatively little phenomenology:
The degree of relaxation between vorticity and parton spin polarization, and the degree of coherence of the hadron wavefunction at...
NA61/SHINE is a fixed-target experiment at the CERN SPS. Its spectrometer has unique properties including large particle acceptance and precise momentum measurement. These properties together with high statistics of collected proton-proton collisions at beam momentum 158 GeV/c allow analyzing the transverse polarization of $\Lambda$ hyperons produced in the primary vertex.
The opportunities...
Spin is an intrinsic quantum degree of freedom for various elementary particles that together make all of matter in our Universe. A salient feature of spin is its polarizability when subject to external conditions such as chirality, vorticity and magnetic fields. In recent years, there have been significant interests and considerable progress in understanding novel transport effects arising...
Lattice calculations indicate that the chiral systems such as Quark Gluon Plasma posses domains of finite topological charge density. The scattering processes are significantly modified in these domains. In particular, the transport cross section acquires a resonance at the scattering angle proportional to the chiral conductivity. As a result, the transport coefficients such as the electrical...
High-energy heavy-ion collisions generate an extremely strong magnetic field which plays a key role in a number of novel quantum phenomena in quark-gluon plasma (QGP), such as the chiral magnetic effect (CME). However, due to the complexity in theoretical modelings of the coupled electromagnetic fields and the QGP system, especially in the pre-equilibrium stages, the lifetime of the magnetic...
Non-central heavy-ion collisions produce a large angular momentum that leads to vorticity of the created system.Due to the spin-orbit coupling, spin directions of particles are aligned with the orbital angular momentum of the system. Global polarization of $\Lambda$ and $\overline{\Lambda}$ hyperons has been measured in Au+Au collisions from $\sqrt{\rm{s_{NN}}}$ = 7.7 GeV to 5.02 TeV [1-3]....
We present a theoretical framework to describe spin transport phenomena in quark-gluon plasma based on a hydrodynamical picture. We discuss how different power counting schemes lead to different spin hydrodynamic equations. We also discuss the role played by chiral anomaly in spin transport. Finally, the possible implications to hyperon spin polarization will also be discussed.
We have derived the chiral kinetic theory (CKT) with collisions in a QED matter. We have discussed the global equilibrium conditions in the presence of collisions. Then, we implement the CKT with effective collision term in the moment expansion and derive the off-equilibrium corrections to the axial currents and spin polarization vector.
In heavy-ion collisions, the observation of the global and local polarization of hyperons has revealed the existence of large vorticities perpendicular to reaction plane due to systems's orbital angular momentum and along beam direction due to collective velocity field, respectively. With the high-statistics data from isobar collisions of Ru+Ru and Zr+Zr at $\sqrt{s_{NN}}= 200$ GeV collected...
We present a systematic study of $\Lambda$ hyperon polarization in heavy-ion collisions at HADES energies within the framework of microscopic transport model UrQMD combined with the hadron-resonance gas statistical model. This study demands a complex analysis of the fireball evolution including time slices, extraction of temperature and baryonic chemical potentials, as well as freeze-out...
We predict a new effect due to the presence of the global vorticity in non-central relativistic heavy-ion collisions, namely a splitting of the elliptic flow parameter $v_2$ at non-zero rapidity. The size of the splitting is proposed as a new observable that can be used to constrain the initial vortical configuration of the produced QCD matter in experiments. The new findings are demonstrated...
QCD vacuum fluctuations can lead to chirality anomaly and parity violation in metastable local domains. This would result in a charge separation along the strong magnetic field produced in off-center relativistic heavy-ion collisons, a phenomenon called the chiral magnetic effect (CME). A widely used observable to search for the CME is the charge-dependent three-point correlator,...
Recent measurements on $\Lambda$ hyperon's polarization suggest a strong correlation with the local fluid vorticity in hydrodynamic models. Jet-medium interactions induce a generic vortex ring structure of the fluid kinematic vorticity along the quenched jet axis. In this talk, we propose a novel ring observable R^J to capture such a ring excitation in the fluid's flow field by high-energy...
We present a systematic study of the hyperon global polarization's sensitivity to the collision systems' initial longitudinal flow velocity, by extending our previous work [1] to event-by-event 3+1D hydrodynamic simulations. By explicitly imposing local energy-momentum conservation when mapping the initial collision geometry to macroscopic hydrodynamic fields, the evolution of systems' orbital...
