Recently, STAR reported the isobar (${^{96}_{44}\text{Ru}}+{^{96}_{44}\text{Ru}}$, ${^{96}_{40}\text{Zr}}+{^{96}_{40}\text{Zr}}$) results for chiral magnetic effect (CME) search [1]. The Ru+Ru to Zr+Zr ratio of the CME-sensitive observable $\Delta\gamma$, normalized by elliptic anisotropy ($v_{2}$), is close to the inverse multiplicity ($N$) ratio. In other words, the ratio of the...
We investigate the angular momentum in heavy-ion collisions applying the hadronic transport approach SMASH. In contrast to geometrical models (e.g. a Glauber approach) our transport approach allows to access the full phase-space information of every particle at any time. The importance of understanding the non-equilibrium angular momentum transferred to the fireball and in turn the quark-gluon...
Recent relativistic heavy-ion collision experiments have found evidence for the generation of strong magnetic field and global angular momentum. The numerical simulation of evolution of the QCD medium is based on either magnetohydrodynamics or spin-hydrodynamics for calculation of observables pertaining to magnetic field or global angular momentum, respectively. However, these two effects are...
The study of the production of $\phi$ meson has always been of great interest both in elementary and heavy-ion collisions. As observed by ALICE, strangeness enhancement in high-multiplicity pp collisions is one of the potential manifestations of QGP formation. Recent results at LHC suggest that $\phi$ behaves like a particle with net strangeness between 1 and 2 in small systems. These...
The proton spin decomposition provides key information about the structure of the nucleons. Since the late 1980s, experiments showed that the quark spin contributes only $\sim$30\% to the proton spin, with the remaining part coming from the gluon spin as well as the quark and gluon orbital angular momentum. While the quark spin contribution was better constrained by polarized deep inelastic...
Non-trivial collective velocity field due to anisotropic flow leads to vorticity along the beam direction in heavy-ion collisions. Polarization of $\Lambda$ and $\bar{\Lambda}$ hyperons along the beam direction relative to the elliptic flow plane has been observed in Au+Au collisions at RHIC and Pb+Pb collisions at the LHC. However, unlike for the case of the global polarization originating...
We have studied local spin polarization and helicity polarization in the relativistic hydrodynamic model. Generalizing the Wigner functions previously obtained from chiral kinetic theory to the massive case, we present the possible contributions up to the order of hbar from thermal vorticity, shear viscous tensor, other terms associated with the temperature and chemical-potential gradients,...
Semi-classical evolution equations for the scalar and axial-vector components of the Wigner function are treated in the relaxation time approximation to introduce a framework of relativistic dissipative hydrodynamics of particles with spin 1/2. We show that a classical treatment of spin is consistent with earlier calculations using the Wigner function approach with a quantum description of...
In non-central heavy-ion collisions, a large orbital angular momentum is created along the direction opposite to the reaction plane, which will be transferred to the spin of quarks through the spin-orbit coupling in parton scatterings. In our recent work, we formulate an improved coalescence model through spin density matrix with phase space dependence, which provides a uniform way to compute...
We derive Boltzmann equations for massive spin-1/2 fermions with local and nonlocal collision terms from the Kadanoff--Baym equation in the Schwinger--Keldysh formalism, properly accounting for the spin degrees of freedom. The Boltzmann equations are expressed in terms of matrix-valued spin distribution functions, which are the building blocks for the quasi-classical parts of the Wigner...
No chiral-magnetic effect signature has been observed in the experimental analysis of the isobar run at RHIC [1]. In this talk, based on [2], we highlight the influence of the nuclear structure of the isobar systems on the CME search within a relativistic hadronic transport approach (SMASH). We show that the quadrupole deformation of Ru enhances the eccentricity ratio between the isobars in...
The interplay of the chiral anomaly and the strong magnetic field (~10$^{15}$ T) created in the off-central heavy-ion collisions could give rise to a collective excitation in the quark-gluon plasma called the Chiral Magnetic Wave (CMW), which can be experimentally sought by the charge asymmetry ($A_{\rm ch}$) dependence of elliptic flow $v_2$ of positively and negatively charged hadrons....
This talk presents a novel instability in the Chern-Simons (or axionic) magnetohydrodynamics (MHD), arising from the spatial inhomogeneity of the axion-like field. In particular, this instability amplifies the Alfven waves in certain regions of spacetime in a way that is clearly parity-violating. The Aflven velocity reaches the speed of light in such regions, but it never exceeds it.
Recent observations of the spin polarization of weakly decaying Lambda hyperons have opened up a new direction to explore non-trivial vortical structures of strongly interacting matter produced in the heavy-ion experiments. A consistent framework of relativistic hydrodynamics with spin degrees of freedom (spin hydrodynamics) is under construction now to allow for future dynamic simulations of...
Since the first positive measurement of the Λ-hyperon global spin polarization in heavy-ion collisions by STAR collaboration in 2017, the understanding of the nature of this phenomenon is one of the most intriguing challenges for the heavy-ion physics community. As relativistic fluid dynamics celebrates multiple successes in describing collective dynamics of the QCD matter in such reactions,...
