论文标题
低 - $ p _ {\ rm t} $ j/$ψ$从外围到中央pb $ - $ $ pb碰撞的光生效
Photoproduction of low-$p_{\rm T}$ J/$ψ$ from peripheral to central Pb$-$Pb collisions at 5.02 TeV
论文作者
论文摘要
在非常低的横向动量下（$ p _ {\ rm t} <0.3 $ gev/$ c $）的j/$ψ$产量超过了，源自相干光增生，在外围和半肠HADRONIC PB $ - $ pb $ -pb $ -PB碰撞中，在每核中心的能量collisions $ \ ssqrt n n n of pb $ -pb collisions中5.02 $ TEV。该测量是通过Alice探测器通过Dimuon衰减通道以前快速度（$ 2.5 <y <4 $）进行的。 $ P _ {\ rm t} $和相干光增生性横截面的核修饰因子是作为中心性的函数测量到10％的最中心碰撞的。这些结果将先前的研究扩展到$ \ sqrt {s _ {\ rm nn}} = 2.76 $ tev，证实了在$ p _ {\ rm t} $范围0 $ - $ 0.3 gev/$ c $和中心范围70 $ - $ 90％的$ 0.3 $ 0.3 $ 0.3 50 $ - $ 70％和30美元 - $ 50％的中心范围。将结果与$ \ sqrt {s _ {\ rm nn}} = 2.76 $ TEV的早期测量值进行了比较，并具有不同的理论预测，旨在描述与核重叠的规基相互作用中的相干光增生。
An excess of J/$ψ$ yield at very low transverse momentum ($p_{\rm T} < 0.3$ GeV/$c$), originating from coherent photoproduction, is observed in peripheral and semicentral hadronic Pb$-$Pb collisions at a center-of-mass energy per nucleon pair of $\sqrt{s_{\rm NN}} = 5.02$ TeV. The measurement is performed with the ALICE detector via the dimuon decay channel at forward rapidity ($2.5<y<4$). The nuclear modification factor at very low $p_{\rm T}$ and the coherent photoproduction cross section are measured as a function of centrality down to the 10% most central collisions. These results extend the previous study at $\sqrt{s_{\rm NN}} = 2.76$ TeV, confirming the clear excess over hadronic production in the $p_{\rm T}$ range 0$-$0.3 GeV/$c$ and the centrality range 70$-$90%, and establishing an excess with a significance greater than 5$σ$ also in the 50$-$70% and 30$-$50% centrality ranges. The results are compared with earlier measurements at $\sqrt{s_{\rm NN}} = 2.76$ TeV and with different theoretical predictions aiming at describing how coherent photoproduction occurs in hadronic interactions with nuclear overlap.
