Vorticity in low-energy heavy-ion collisions

Deng, Xian-Gai; Huang, Xu-Guang; Ma, Yugang; Zhang, Song

doi:10.1103/physrevc.101.064908

Cited by 71 publications

(29 citation statements)

References 57 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In noncentral heavy-ion collisions, a large orbital angular momentum (OAM) [1][2][3] as well as a very strong electromagnetic field [4][5][6][7][8][9][10] are generated. Part of the OAM is transferred to the hot and dense matter or the quark-gluon plasma in the form of vorticity fields [11][12][13][14] and leads to a global spin polarization perpendicular to the reaction plane [1,[15][16][17][18][19][20]. The global spin polarization of Λ hyperons has been observed by the STAR Collaboration in Au þ Au collisions at ffiffiffiffiffiffiffi ffi s NN p ¼ 7.7-200 GeV [21,22]; see, e.g., Refs.…”

Section: Introductionmentioning

confidence: 97%

Kinetic theory with spin: From massive to massless fermions

2020

Self Cite

View full text Add to dashboard Cite

We find that the recently developed kinetic theories with spin for massive and massless fermions are smoothly connected. By introducing a reference-frame vector, we decompose the dipole-moment tensor into electric and magnetic dipole moments. We show that the axial-vector component of the Wigner function contains a contribution from the transverse magnetic dipole moment, which accounts for the transverse spin degree of freedom (d.o.f.) and vanishes smoothly in the massless limit. As a result, the kinetic equations, describing 4 d.o.f. for massive fermions, smoothly becomes the chiral kinetic equations describing 2 d.o.f. in the massless limit. We also confirm the small-mass behavior of the Wigner function by an explicit calculation using a Gaussian wave packet.

show abstract

Section: Introductionmentioning

confidence: 97%

Kinetic theory with spin: From massive to massless fermions

2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…Following the method outlined in Ref. [30], the initial angular velocity ω (i.e., after full nuclei overlap) produced in Au þ Au collisions is hereby computed as follows: For every event generated with UrQMD [31], a smearing function is used to smooth the position profile of the participating nucleons, which then can be used to obtain a continuous velocity field. With this information, the angular velocity can be computed as the usual spatial derivative of the velocity field.…”

Section: Quark Interaction Rate At Finite Density and Temperaturementioning

confidence: 99%

“…Notice that, as explored in Ref. [30], different choices of smearing functions for the calculation of the velocity profile, or the definition of the velocity of the produced particles itself, can lead to a variation on the values resulting for the angular velocity; for a more detailed study, see Refs. [32,33].…”

Section: Quark Interaction Rate At Finite Density and Temperaturementioning

confidence: 99%

Relaxation time for the alignment between the spin of a finite-mass quark or antiquark and the thermal vorticity in relativistic heavy-ion collisions

et al. 2020

View full text Add to dashboard Cite

We study the relaxation time required for the alignment between the spin of a finite-mass quark or antiquark and the thermal vorticity, at finite temperature and baryon chemical potential, in the context of relativistic heavy-ion collisions. The relaxation time is computed as the inverse of the total reaction rate that in turn is obtained from the imaginary part of the quark or antiquark self-energy. We model the interaction between spin and thermal vorticity within the medium by means of a vertex coupling quarks and thermal gluons that, for a uniform temperature, is proportional to the global angular velocity and inversely proportional to the temperature. We use realistic estimates for the angular velocities for different collision energies and show that the effect of the quark mass is to reduce the relaxation times as compared to the massless quark case. Using these relaxation times we estimate the intrinsic quark and antiquark polarizations produced by the thermal vorticity. We conclude by pointing out that, although the intrinsic global polarization of the s-quark turns out to be larger than that of thes-quark, there is room to explain recent STAR results which show that the global polarization ofΛ is larger than that of Λ when considering that these hyperons can be produced from different density regions in a core-corona model.

show abstract

“…The purpose of the this paper is to extend the previous calculations for kinematic and thermal vorticities in Ref. [42] to extract the spin polarization of Λ hyperons at energies √ s NN = 2.42 − 7.7 GeV with two different methods to connect the spin polarization to the vorticities or angular momentum of the medium. We will also compare our results with the recent calculations in Refs.…”

Section: Introductionmentioning

confidence: 98%

Lambda polarization in $^{108}$Ag +$^{108}$Ag and $^{197}$Au +$^{197}$Au collisions around a few GeV

Deng,

Huang,

2021

Preprint

Self Cite

View full text Add to dashboard Cite

Within the framework of Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, we extract the global spin polarization of Λ hyperon in 108 Ag + 108 Ag and 197 Au + 197 Au collisions at √ sNN = 2.42 − 7.7 GeV. We use two different methods to calculate the Λ polarization Py: one is based on equilibrium assumption so that Py is determined by thermal vorticity and another assumes a proportional relation between Py and the system's angular momentum in Λ's rest frame. We find that both methods can describe the experimental data suggesting that the global spin polarization is a result of global angular momentum and is thus insensitive to the intermediate prescription to extracting it.

show abstract

Vorticity in low-energy heavy-ion collisions

Cited by 71 publications

References 57 publications

Kinetic theory with spin: From massive to massless fermions

Kinetic theory with spin: From massive to massless fermions

Relaxation time for the alignment between the spin of a finite-mass quark or antiquark and the thermal vorticity in relativistic heavy-ion collisions

Lambda polarization in $^{108}$Ag +$^{108}$Ag and $^{197}$Au +$^{197}$Au collisions around a few GeV

Contact Info

Product

Resources

About