论文标题
在LHC处的PB-PB碰撞中的事件平面的J/$ψ$极化的测量
Measurement of the J/$ψ$ polarization with respect to the event plane in Pb-Pb collisions at the LHC
论文作者
论文摘要
我们研究了$ \ sqrt {s _ {\ rm nn}} = 5.02 $ tev在Dimuon通道的LHC中，通过$ \ sqrt {s _ {s _ {s _ {s _ {s _ {s _ {s _ {s _ {s _ {s _ {s _ {s _ {我们在快速区域进行研究$ 2.5 <y <4 $，用于三个横向动量间隔（$ 2 <p _ {\ rm t} <4 $，$ 4 <p _ {\ rm t} <6 $，$ 6 <p _ {\ rm t} t} <6 $ gev/c。通过考虑J/$ψ$休息框架中的正电荷衰减锥与垂直于实验室系统中事件平面矢量垂直的轴线之间的正递减元音之间的角度，对碰撞的事件平面进行了首次衡量。测量一个小的横向极化，在低$ p _ {\ rm t} $时，其显着性达到3.9 $σ$，对于中心价值。极化可以与Quark $ - $ gluon等离子体的行为相关联，该等离子在PB $ -PB碰撞中形成，作为具有巨大涡度的旋转流体，以及在形成的早期阶段存在强磁场。
We study the polarization of inclusive J/$ψ$ produced in Pb$-$Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV at the LHC in the dimuon channel, via the measurement of the angular distribution of its decay products. We perform the study in the rapidity region $2.5<y<4$, for three transverse momentum intervals ($2<p_{\rm T}<4$, $4<p_{\rm T}<6$, $6<p_{\rm T}<10$ GeV/$c$) and as a function of the centrality of the collision for $2<p_{\rm T}<6$ GeV/c. For the first time, the polarization is measured with respect to the event plane of the collision, by considering the angle between the positive-charge decay muon in the J/$ψ$ rest frame and the axis perpendicular to the event-plane vector in the laboratory system. A small transverse polarization is measured, with a significance reaching 3.9$σ$ at low $p_{\rm T}$ and for intermediate centrality values. The polarization could be connected with the behaviour of the quark$-$gluon plasma, formed in Pb$-$Pb collisions, as a rotating fluid with large vorticity, as well as with the existence of a strong magnetic field in the early stage of its formation.
