Conveners
Spin in heavy ion collisions: 02
- Xiaozhi Bai (University of Science and Technology of China)
- Francesco Becattini (Università di Firenze)
Spin in heavy ion collisions: 02
- Xu-Guang Huang (Fudan University)
- Zhenyu Chen (Shandong University)
Spin in heavy ion collisions
- Jinfeng Liao (INDIANA UNIVERSITY & RBRC)
- Qun Wang (University of Science and Technology of China)
Description
Conveners: Enrico Speranza, Jinhui Chen, Takafumi Niida
We present an analytically solvable model based on the blast-wave picture of heavy-ion collisions with flow-momentum correspondence. It can describe the key features of spin polarizations in heavy-ion collisions. With the analytical solution, we can clearly show that the spin polarization with respect to the reaction plane is governed by the directed flow, while the spin polarization along the...
Particles of non-zero spin produced in non-central heavy-ion collisions are expected to be polarized along the direction perpendicular to the reaction plane because of their spin-orbit interactions in the produced matter. In this talk, I will show that the hypertriton, which is the lightest hypernucleus, is also polarized in these collisions. I will demonstrate that the polarization and decay...
Measurements by the STAR Collaboration of global Λ hyperon polarization and 𝜙,𝐾∗0 meson spin alignment in heavy-ion collisions [1, 2] have confirmed the global polarization of quark matter [3, 4] and indicated strong quark–antiquark spin correlations. Quark spin correlations have emerged as a new frontier and a rapidly developing research hotspot.
In Ref. [5], we propose a systematic method...
The observation of hyperon global polarization along the system's angular momentum has revealed the existence of large vorticities in the medium created by heavy-ion collisions. In this talk, we present measurements of global polarization for $\Lambda$, $\Xi$, and $\Omega$ hyperons in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 9.2, 11.5, 14.6, 17.3, 19.6, and 27 GeV, based on high-statistics...
In this talk, we have implemented the quantum kinetic theory combined the relativistic hydrodynamics to study the spin polarization of Lambda hyperons in the relativistic AA and pA collisions. The global polarization can be well described by the current theoretical frameworks. The local polarization in low energies AA collisions and pA collisions cannot be fully understood.
In this talk, we will demonstrate how quantum kinetic theory determines spin effects in global equilibrium. We show that by generalizing from constant to varying electromagnetic fields, previously indeterminate spin effects induced by vorticity and electromagnetic fields can now be further pinned down.
Heavy quarks, i.e. charm and beauty, are produced in the initial stage of the heavy-ion collisions, and can inherit a polarisation that is preserved through hadronisation and manifested in the spin state of the final hadron. This polarisation can be quantified via the spin density matrix element ρ₀₀, where deviations from 1/3 signal spin alignment. Measuring the spin alignment of vector mesons...
The observation of hyperon polarization along beam direction ($P_z$) in nucleus-nucleus collisions has opened a new way to study the complex vortical structures of the QGP. With the high-statistics data collected by the CMS experiment, we present the first $P_z$ results for $\Lambda$ and $\bar{\Lambda}$ particles in pPb collision at $\sqrt{s_{NN}}= 8.16$ TeV over a wide transverse momentum...
We have implemented the 3+1 dimensional CLVisc hydrodynamics model with \trento-3D initial conditions to investigate the spin polarization of $\Lambda$ hyperons along the beam direction in p+Pb collisions at $\sqrt{s_{NN}} = 8.16$ TeV. Following our previous theoretical framework based on quantum kinetic theory, we consider three different scenarios: $\Lambda$ equilibrium, $s$ quark...
In this talk, I present our recent investigation of charmonium systems in strong external magnetic fields using a relativistic light-front Hamiltonian approach within the basis light-front quantization (BLFQ) framework. By solving the eigenvalue problem for the invariant mass squared operator — incorporating confinement potentials and one-gluon-exchange interactions — we compute the mass...
Despite the successful description of global polarization of $\Lambda$ hyperons in heavy ion collisions through thermal voricity, the follow-up observations of local spin polarization and spin alignment of vector mesons further indicate the presence of additional mechanisms upon spin transport of quarks in the QCD medium. In high-energy nuclear collisions, the soft thermal gluons in the quark...
We present an upgraded formula for Wigner function and spin polarization of fermions emitted by a relativistic fluid at local thermodynamic equilibrium at the freeze-out which improves the one obtained in literatures and used in numerical simulations of relativistic nuclear collisions. By using a
new expansion method applicable to freeze-out hypersurfaces with arbitrary geometry, we reproduce...
Quarkonia production in high-energy proton-proton (pp) collisions serves as an important probe for studying quantum chromodynamics (QCD) in vacuum. Understanding the production mechanism of the J/$\psi$, a bound state of a charm and anticharm quark, is essential for constraining both perturbative and non-perturbative aspects of QCD calculations. The polarization of quarkonia in pp collisions...
The observation of hyperon global polarization and vector meson spin alignment in heavy-ion collisions has revealed that spin phenomena are important probes of quark matter properties. These findings point toward possible spin correlations between quarks and antiquarks in the quark-gluon plasma. Such correlations are sensitive to production mechanism and evolution dynamics of spin...
We study the two-flavor Nambu-Jona-Lasinio model under the rotation and chiral chemical potential μ5. First, the influence of chiral imbalance on the chiral phase transition in the Tpc − ω plane is investigated. Research manifests that, as μ5 increases, the critical point of the Tpc − ω plane chiral phase transition will move closer to the T axis. This means that the chiral chemical potential...
In recent years, spin polarization of hyperons and the spin alignment of vector mesons were observed by STAR in 20%-60% centrality collision, where the large angular momentum and the magnetic field were supposed to be the main reasons. However, in the most central collision with collision energy 200GeV, the rotation, magnetic field as well as the baryon number should vanish, spin alignment...
Recent experimental success of detecting the spin polarization of Lambda hyperons in heavy-ion collisions enables us to extract the novel properties of fluid vorticity and spin transport of quark gluon plasma (QGP). These findings motivated the development of a hydrodynamics-like theory for spin polarization and transport. We will discuss the construction of such a theory (the relativistic...
The “local Lambda polarization puzzle” in relativistic heavy-ion collisions has challenged conventional models based solely on thermal vorticity, which fail to reproduce the observed sign of local polarization. Recently, incorporating shear-induced polarization (SIP) successfully reproduces the sign and opens the path toward a quantitative description of spin polarization.
Using 3+1D MUSIC...
Theoretical developments in relativistic spin hydrodynamics, which explicitly describes the internal angular momentum of a fluid element as spin, have progressed rapidly since the experimental observation of the global spin polarization of Λ hyperons in relativistic heavy-ion collisions. However, numerical simulations of relativistic spin hydrodynamics remain underdeveloped due to significant...
We derive a formulation of relativistic spin hydrodynamics with totally antisymmetric spin tensors that satisfy the Frenkel-Mathisson-Pirani condition. In our proposed spin hydrodynamics, the second law of thermodynamics is fulfilled by the spin-induced corrections in the heat flow, the viscous tensor, and the antisymmetric part of the energy-momentum tensor. These corrections are interpreted...
The shear-induced polarization plays a crucial role in understanding the local polarization of Λ and Λ⎯⎯⎯⎯ hyperons. A key puzzle is whether the shear-induced polarization is non-dissipative or not. In this work, we analyzed the shear-induced polarization and the anomalous Hall effects using the entropy flow and H-theorem introduced from quantum (chiral) kinetic theory. While the shear-induced...
We study the influence of a rotation on the string tension and the temperature of the confinement-deconfinement phase transition of gluodynamics by gauge/gravity duality. We explore two distinct approaches, global transformation and local transformation, to introduce rotation and compare the results. It is shown that the string tension extracted from the free energy in the presence of a heavy...
We present a novel framework for parameterizing Lorentz spacetime coordinates using coupled rapidity parameters, extending classical special relativity with new insights into rapidity symmetries and spin effects. Building upon the Euler–Hamilton formalism, we introduce angular and transverse rapidities, enabling spectral decompositions of relativistic dynamics into elementary functions even...
The STAR Collaboration results on global spin alignment of vector mesons in heavy-ion collisions [1] reveal that quarks in the quark-gluon plasma (QGP) exhibit not only global polarization[2, 3] but also spin correlations, leading the study on spin effects in heavy-ion collisions to a new climax.
A systematic formalism for describing spin correlations in a system of spin-1/2 particles and...
We present an analytically solvable model based on the blast-wave picture of heavy-ion collisions with flow-momentum correspondence. It can describe the key features of spin polarizations in heavy-ion collisions. With the analytical solution, we can clearly show that the spin polarization with respect to the reaction plane is governed by the directed flow, while the spin polarization along the...
Measurements by the STAR Collaboration of global $\Lambda$ hyperon polarization and $\phi,K^{*0}$ meson spin alignment in heavy-ion collisions [1, 2] have confirmed the global polarization of quark matter [3, 4] and indicated strong quark–antiquark spin correlations. Quark spin correlations have emerged as a new frontier and a rapidly developing research hotspot.
In Ref. [5], we propose a...
Non-central heavy-ion collisions produce hot and dense nuclear matter with significant fluid vorticity, which induces global polarizations of particles with non-zero spins along the direction of the total orbital angular momentum. This phenomenon has been observed for hyperons and vector mesons in experiments. In the present study, we demonstrate that polarized nucleons lead to global spin...
The STAR Collaboration results on global spin alignment of vector mesons in heavy-ion collisions [1] reveal that quarks in the quark-gluon plasma (QGP) exhibit not only global polarization[2, 3] but also spin correlations, leading the study on spin effects in heavy-ion collisions to a new climax.
A systematic formalism for describing spin correlations in a system of spin-1/2 particles and...
We establish a holographic framework for investigating spin alignment (ρ₀₀) of flavorless vector mesons using gauge/gravity duality. By analyzing dilepton production via meson decay, we derive a universal relation between production rates per spin channel and the in-medium spectral function—computable holographically for strongly coupled systems. Applying this to J/ψ and ϕ mesons in a moving...
The “local Lambda polarization puzzle” in relativistic heavy-ion collisions has challenged conventional models based solely on thermal vorticity, which fail to reproduce the observed sign of local polarization. Recently, incorporating shear-induced polarization (SIP) successfully reproduces the sign and opens the path toward a quantitative description of spin polarization.
Using 3+1D MUSIC...
The shear-induced polarization plays a crucial role in understanding the local polarization of $\Lambda$ and $\overline{\Lambda}$ hyperons. A key puzzle is whether the shear-induced polarization is non-dissipative or not. In this work, we analyzed the shear-induced polarization and the anomalous Hall effects using the entropy flow and H-theorem introduced from quantum (chiral) kinetic theory....
Ultra-relativistic heavy-ion collisions create a hot and dense state of strongly interacting matter — the quark–gluon plasma (QGP). Its space–time evolution is dominated by strong collective expansion, which generates anisotropic flow and demonstrates the nearly perfect fluid nature of the QGP. This anisotropic expansion, in particular the elliptic flow coefficient $v_{2}$, gives rise to local...
Theoretical developments in relativistic spin hydrodynamics, which explicitly describes the internal angular momentum of a fluid element as spin, have progressed rapidly since the experimental observation of the global spin polarization of $\Lambda$ hyperons in relativistic heavy-ion collisions. However, numerical simulations of relativistic spin hydrodynamics remain underdeveloped due to...
We study the influence of a rotation on the string tension and the temperature of the confinement-deconfinement phase transition of gluodynamics by gauge/gravity duality. We explore two distinct approaches, global transformation and local transformation, to introduce rotation and compare the results. It is shown that the string tension extracted from the free energy in the presence of a heavy...
