Spin alignments of vector mesons and hyperons in relativistic heavy-ion collisions have been proposed as signals of global polarization.The STAR experiment first observed the ∧ polarization.Recently,the ALICE collabo...Spin alignments of vector mesons and hyperons in relativistic heavy-ion collisions have been proposed as signals of global polarization.The STAR experiment first observed the ∧ polarization.Recently,the ALICE collaboration measured the transverse momentum {PT) and the collision centrality dependence of K*,and Φ spin alignments during Pb-Pb collisions at 1/2sNN=2.76 TeV.A large signal is observed in the low pT region of mid-central collisions for K*,while the signal is much smaller for Φ,and these have not been understood yet.Since vector mesons have different lifetimes and their decay products have different scattering cross sections,they suffer from different hadronic effects.In this paper,we study the effect of hadronic interactions on the spin alignment of K*,Φ,and p mesons in relativistic heavy-ion collisions with a multi-phase transport model.We find that hadronic scatterings lead to a deviation of the observed spin alignment matrix element p00 away from the true value for p and K*mesons(with a bigger effect on p) while the effect is negligible for the Φ meson.The effect depends on the kinematic acceptance:the observed p00 value is lower than the true value when the pseudorapidity(η) coverage is small,while there is little effect when the η coverage is large.Hence,this study provides valuable information to understand the vector meson spin alignment signals observed during the experiments.展开更多
Vorticities in heavy-ion collisions(HICs)are supposed to induce spin alignment and polarization phenomena of quarks and mesons.In this work,we analyze the spin alignment of vector mesonsϕandρinduced by rotation from ...Vorticities in heavy-ion collisions(HICs)are supposed to induce spin alignment and polarization phenomena of quarks and mesons.In this work,we analyze the spin alignment of vector mesonsϕandρinduced by rotation from quark dynamics in the framework of the Nambu-Jona-Lasinio(NJL)model.The rotating angular velocity induces mass splitting of spin components for vectorϕ,ρmesons M_(ϕ,ρ)(Ω)≃M_(ϕ,ρ)(Ω=0)−szΩ.This behavior contributes to the spin alignment of vector mesonsϕ,ρin an equilibrium medium and naturally explains the negative deviation ofρ00−1/3 for vector mesons.Incidentally,the positive deviation ofρ00−1/3 under the magnetic field can also be easily understood from quark dynamics.展开更多
The global spin alignment of vector mesons has been observed by the STAR collaboration at the Relativistic Heavy Ion Collider(RHIC)at Brookhaven National Laboratory(BNL).It provides a unique opportunity to probe the c...The global spin alignment of vector mesons has been observed by the STAR collaboration at the Relativistic Heavy Ion Collider(RHIC)at Brookhaven National Laboratory(BNL).It provides a unique opportunity to probe the correlation between the po-larized quark and antiquark in the strongly coupled quark-gluon plasma(sQGP)produced in relativistic heavy ion collisions,opening a new window to explore the properties of sQGP.In addition,spin alignments of vector mesons have also been observed in other high-energy particle collisions such as e^(+)e^(−)annihilations at high energies where hadron production is dominated by quark fragmentation mechanism.The results obtained are quite different from those obtained in heavy ion collisions where quark coalescence/combination mechanism dominates suggesting strong dependence on hadronization mechanisms.So comprehensive studies in different hadronization processes are needed.In this article,we present a brief review of theoretical and experimen-tal advances in the study of vector meson’s spin alignments in a variety of high-energy particle collisions,with emphasis on hadronization mechanisms.展开更多
基金the Strategic Priority Research Program of Chinese Academy of Sciences(XDB34030000)the Guangdong Major Project of Basic and Applied Basic Research(2020B0301030008)the National Natural Science Foundation of China(12025501,11890710,11890714,11775288)。
文摘Spin alignments of vector mesons and hyperons in relativistic heavy-ion collisions have been proposed as signals of global polarization.The STAR experiment first observed the ∧ polarization.Recently,the ALICE collaboration measured the transverse momentum {PT) and the collision centrality dependence of K*,and Φ spin alignments during Pb-Pb collisions at 1/2sNN=2.76 TeV.A large signal is observed in the low pT region of mid-central collisions for K*,while the signal is much smaller for Φ,and these have not been understood yet.Since vector mesons have different lifetimes and their decay products have different scattering cross sections,they suffer from different hadronic effects.In this paper,we study the effect of hadronic interactions on the spin alignment of K*,Φ,and p mesons in relativistic heavy-ion collisions with a multi-phase transport model.We find that hadronic scatterings lead to a deviation of the observed spin alignment matrix element p00 away from the true value for p and K*mesons(with a bigger effect on p) while the effect is negligible for the Φ meson.The effect depends on the kinematic acceptance:the observed p00 value is lower than the true value when the pseudorapidity(η) coverage is small,while there is little effect when the η coverage is large.Hence,this study provides valuable information to understand the vector meson spin alignment signals observed during the experiments.
基金the National Natural Science Foundation of China(NSFC)(12235016,12221005)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB34030000)+1 种基金the start-up funding from the University of Chinese Academy of Sciences(UCAS)the Fundamental Research Funds for the Central Universities。
文摘Vorticities in heavy-ion collisions(HICs)are supposed to induce spin alignment and polarization phenomena of quarks and mesons.In this work,we analyze the spin alignment of vector mesonsϕandρinduced by rotation from quark dynamics in the framework of the Nambu-Jona-Lasinio(NJL)model.The rotating angular velocity induces mass splitting of spin components for vectorϕ,ρmesons M_(ϕ,ρ)(Ω)≃M_(ϕ,ρ)(Ω=0)−szΩ.This behavior contributes to the spin alignment of vector mesonsϕ,ρin an equilibrium medium and naturally explains the negative deviation ofρ00−1/3 for vector mesons.Incidentally,the positive deviation ofρ00−1/3 under the magnetic field can also be easily understood from quark dynamics.
基金supported in part by the National Key Research and Development Program of China(Grant No.2022YFA1604900)the National Natural Science Foundation of China(Grant Nos.12025501,11890710,11890713,11890714,12147101,and 12135011)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(CAS)(Grant No.XDB34030102)the Natural Science Foundation of Shandong Province。
文摘The global spin alignment of vector mesons has been observed by the STAR collaboration at the Relativistic Heavy Ion Collider(RHIC)at Brookhaven National Laboratory(BNL).It provides a unique opportunity to probe the correlation between the po-larized quark and antiquark in the strongly coupled quark-gluon plasma(sQGP)produced in relativistic heavy ion collisions,opening a new window to explore the properties of sQGP.In addition,spin alignments of vector mesons have also been observed in other high-energy particle collisions such as e^(+)e^(−)annihilations at high energies where hadron production is dominated by quark fragmentation mechanism.The results obtained are quite different from those obtained in heavy ion collisions where quark coalescence/combination mechanism dominates suggesting strong dependence on hadronization mechanisms.So comprehensive studies in different hadronization processes are needed.In this article,we present a brief review of theoretical and experimen-tal advances in the study of vector meson’s spin alignments in a variety of high-energy particle collisions,with emphasis on hadronization mechanisms.
