Conveners
Spin in Heavy Ion Collisions: Heavy Ions I
- Aihong Tang (Brookhaven National Laboratory)
Spin in Heavy Ion Collisions: Heavy Ions II
- Takafumi Niida (University of Tsukuba)
Spin in Heavy Ion Collisions: Heavy Ions III
- JINFENG LIAO (INDIANA UNIVERSITY BLOOMINGTON)
In non-central heavy-ion collisions, an initial orbital angular momentum carried by two colliding nuclei is partially transferred to the created medium, resulting in polarization of produced particles on average along the direction of the orbital angular momentum. The observation of global polarization opens new directions in the study of heavy-ion physics. Since the discovery of $\Lambda$...
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...
By measuring the spin polarization of hadrons produced in heavy-ion collisions, it was found that the quark gluon plasma is the most "vorticous" fluid ever observed. This opens the possibility for new phenomenological investigations of spin physics in fluids. Spin polarization is mainly caused by the spin-rotation coupling in relativistic hydrodynamics. In this talk I show how the mean spin...
Standard relativistic hydrodynamics, through the years, has been extremely successful in describing the properties of the strongly-interacting matter produced in heavy-ion collision experiments. Recently, there has been a significant theoretical advancement in this field to explain a new phenomenon of spin polarization of hadrons emitted in these processes. Although current models have...
Taking into account the recent measurements of the spin-polarization of particles produced at RHIC and LHC, the self-consistent formulation of relativistic fluid mechanics for spin-polarized media subjected to a large magnetic field is of great interest to the relativistic heavy-ion collisions community [1]. To meet this need, we formulate a relativistic kinetic theory for spin-polarized...
The polarization of the Λ particle offers the unique opportunity to study the hydrodynamic gradients in the Quark-Gluon Plasma formed in heavy-ion collisions. However, the theoretical formula commonly used to calculate polarization is only a linear order expansion in thermal vorticity and neglects higher-order terms. Here, we present an exact calculation at all orders in (constant) thermal...
The study of strong interaction matter under external conditions (such as high temperatures and/or baryon densities) provides unique insights into its fundamental theory, the Quantum Chromodynamics (QCD). A nonzero angular momentum imposed on a QCD system can bring rich and intriguing phenomena, with the proton spin structure being a perfect example. A much larger QCD system with substantial...
The observation of global vector meson alignment in heavy ion collisions by the STAR collaboration at RHIC has attracted further attention to polarization effects in this filed. In this talk, I would like to make a brief overview of vector meson spin alignment in different high energy reactions and/or different hadronization mechanisms. I will briefly summarize the progresses of different...
Polarization measurements represent an important tool for understanding the particle production mechanisms occurring in proton proton collisions. In particular, for quarkonium states, the very small polarization measured at the LHC represents a serious and a long-lasting challenge for theoretical models. When considering heavy-ion collisions, particle polarization could also be used to...
Under the framework of thermal field theory, we calculate the tensor polarization and the resulted spin alignment of a generic vector meson in local equilibrium up to the first order in the hydrodynamic gradients.
At the zeroth order, the spin alignment of the vector meson emerges mainly due to the degeneracy breaking between the transverse and longitudinal spectral functions.
At the first...
The large scale set by the charm mass means the heavy quark pairs are produced early in heavy-ion collisions and experience the full evolution of the quark-gluon plasma (QGP) created in these collisions. Because of this, $J/\psi$ serves as one of the important probes to study the properties of the QGP. In Ru+Ru and Zr+Zr collisions at $\sqrt{s_{_{\rm NN}}} = 200$ GeV recorded by the STAR...
The search for the Chiral Magnetic Effect (CME) is ongoing in relativistic heavy-ion experiments. It is crucial to scrutinize the CME-sensitive observables to rule out non-CME contributions. Recently STAR has measured an unexpectedly large signal of global spin alignment ($\rho_{00}$) for $\phi$ meson, which is argued to be sensitive to the local fluctuations of the vector meson strong force...
The spins of fermionic constituents of QCD matter created in relativistic heavy ion collisions can be affected by chirality, vorticity and magnetic fields. In recent years, increasingly detailed theories of the mechanisms influencing spin transport in QCD matter have been developed with the goal of understanding the growing number of polarization and spin alignment measurements. In my talk I...
