Evidence of Spin-Orbital Angular Momentum Interactions in Relativistic Heavy-Ion Collisions.
Evidence of Spin-Orbital Angular Momentum Interactions in Relativistic Heavy-Ion Collisions.
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DOI：
10.1103/physrevlett.125.012301
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发表时间：
2019-10
影响因子：
8.6
通讯作者：
S. Acharya;D. Adamová;A. Adler;J. Adolfsson;M. Aggarwal;G. Aglieri Rinella;M. Agnello;N. Agrawal-N.-Agra
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文献类型：
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作者：
S. Acharya;D. Adamová;A. Adler;J. Adolfsson;M. Aggarwal;G. Aglieri Rinella;M. Agnello;N. Agrawal-N.-Agra
报道了大型强子对撞机（LHC）重离子碰撞中矢量介子（K^{*0}和φ）自旋对准的第一个证据。利用ALICE探测器测量了质心能量（sqrt[s_{NN}]）为2.76 TeV的Pb-Pb碰撞中速（|y|<0.5）下的自旋密度矩阵元ρ_{00}。在K^{*0}和φ分别为3σ和2σ的低横动量（p_{T}<2 GeV/c）下，ρ_{00}值小于1/3（1/3表示没有自旋取向）。对于Pb-Pb碰撞中的K_{S}^{0}介子（自旋=0）和pp碰撞中的矢量介子，没有观察到明显的自旋对准。测量到的自旋排列出乎意料地大，但在质量上与模型的预期一致，该模型将其归因于重离子碰撞中角动量存在的夸克极化和随后的重组过程中的强子化。
The first evidence of spin alignment of vector mesons (K^{*0} and ϕ) in heavy-ion collisions at the Large Hadron Collider (LHC) is reported. The spin density matrix element ρ_{00} is measured at midrapidity (|y|<0.5) in Pb-Pb collisions at a center-of-mass energy (sqrt[s_{NN}]) of 2.76 TeV with the ALICE detector. ρ_{00} values are found to be less than 1/3 (1/3 implies no spin alignment) at low transverse momentum (p_{T}<2 GeV/c) for K^{*0} and ϕ at a level of 3σ and 2σ, respectively. No significant spin alignment is observed for the K_{S}^{0} meson (spin=0) in Pb-Pb collisions and for the vector mesons in pp collisions. The measured spin alignment is unexpectedly large but qualitatively consistent with the expectation from models which attribute it to a polarization of quarks in the presence of angular momentum in heavy-ion collisions and a subsequent hadronization by the process of recombination.