论文标题
在大型强子对撞机的连贯$ j/ψ$光生生效中抑制核抑制
Nuclear suppression from coherent $J/ψ$ photoproduction at the Large Hadron Collider
论文作者
论文摘要
使用有关在大型强生对撞机（LHC）中运行1和2获得的PB-PB超剂量碰撞（UPC）中相干$ J/ψ$光增生的数据，我们以$ s_ {pb}（pb}（x）$的核抑制因子的核抑制因子的核抑制因子良好确定。 In the small-$x$ region $x < 10^{-3}$, our $χ^2$ fit favors a flat form of $S_{Pb}(x) \approx 0.6$ with approximately a 5% accuracy for $x=6 \times 10^{-4} - 10^{-3} $ and a 25% error at $x=10^{-4}$.同时，拟合的不确定性并不排除在小$ x $限制中的$ s_ {pb}（x）$的缓慢降低。 At large $x$, $S_{Pb}(x)$ is constrained to better than 10% precision up to $x=0.04$ and is also consistent with the value of $S_{Pb}(x)$ at $\langle x \rangle =0.042$, which we extract from the Fermilab data on the $A$ dependence of the cross section of coherent $J/ψ$ photoproduction on fixed nuclear目标。 $ s_ {pb}（x）$上的结果不确定性很小，这表明LHC在PB-PB UPC中相干charmon Phopodulaugtion的LHC数据潜力提供了对小$ x $ npdfs的其他约束。我们以示例为例EPPS16和NCTEQ16核部分分布函数，明确证明了这一点，在讨论的UPC数据的贝叶斯重新加权后，其不确定性减少了几倍。
Using the data on coherent $J/ψ$ photoproduction in Pb-Pb ultraperipheral collisions (UPCs) obtained in Runs 1 and 2 at the Large Hadron Collider (LHC), we determined with a good accuracy the nuclear suppression factor of $S_{Pb}(x)$ in a wide range of the momentum fraction $x$, $10^{-5} \leq x \leq 0.04$. In the small-$x$ region $x < 10^{-3}$, our $χ^2$ fit favors a flat form of $S_{Pb}(x) \approx 0.6$ with approximately a 5% accuracy for $x=6 \times 10^{-4} - 10^{-3} $ and a 25% error at $x=10^{-4}$. At the same time, uncertainties of the fit do not exclude a slow decrease of $S_{Pb}(x)$ in the small-$x$ limit. At large $x$, $S_{Pb}(x)$ is constrained to better than 10% precision up to $x=0.04$ and is also consistent with the value of $S_{Pb}(x)$ at $\langle x \rangle =0.042$, which we extract from the Fermilab data on the $A$ dependence of the cross section of coherent $J/ψ$ photoproduction on fixed nuclear targets. The resulting uncertainties on $S_{Pb}(x)$ are small, which indicates the potential of the LHC data on coherent charmonium photoproduction in Pb-Pb UPCs to provide additional constraints on small-$x$ nPDFs. We explicitly demonstrate this using as an example the EPPS16 and nCTEQ16 nuclear parton distribution functions, whose uncertainties decrease severalfold after the Bayesian reweighting of the discussed UPC data.
