"Figure 11 (bottom, middle)" of "Measurement of the central exclusive production of charged particle pairs in proton-proton collisions at $\sqrt{s} = 200$ GeV with the STAR detector at RHIC"

Differential fiducial cross section for CEP of $K^+K^-$ pairs as a function of the sum of the squares of the four-momenta losses in the proton vertices.

Systematic uncertainties assigned to data points are strongly correlated between bins and should be treated as allowed collective variation of all data points. There are two components of the total systematic uncertainty. The systematic uncertainty related to the experimental tools and analysis method is labeled "syst. (experimental)". The systematic uncertainty related to the integrated luminosity (fully correlated between all data points) is labeled "syst. (luminosity)".

Fiducial region definition:
* central state $K^+$, $K^-$
- $p_{\mathrm{T}} > 0.3~\mathrm{GeV}$
- $min(p_{\mathrm{T}}(K^+), p_{\mathrm{T}}(K^-)) < 0.7~\mathrm{GeV}$
- $|\eta| < 0.7$
* intact forward-scattered beam protons $p'$
- $p_x > -0.2~\mathrm{GeV}$
- $0.2~\mathrm{GeV} < |p_{y}| < 0.4~\mathrm{GeV}$
- $(p_x+0.3~\mathrm{GeV})^2 + p_y^2 < 0.25~\mathrm{GeV}^2$

$K^+K^-$对的中心排他性产生（Central Exclusive Production，CEP）过程的差分 fiducial 截面（fiducial cross section），其以质子顶点处四动量损失的平方和作为自变量。
各数据点所对应的系统误差在不同分箱（bins）间存在强相关性，因此应将其视为所有数据点的整体允许涨落进行处理。总系统误差包含两个分量：与实验装置及分析方法相关的系统误差标记为"syst. (experimental)"；与积分亮度相关的系统误差（在所有数据点间完全相关）标记为"syst. (luminosity)"。

fiducial 区域定义（fiducial region）：
* 中心态$K^+$、$K^-$
- 横向动量$p_mathrm{T} > 0.3 mathrm{GeV}$
- $K^+$与$K^-$的横向动量最小值小于$0.7 mathrm{GeV}$
- 赝快度$|eta| < 0.7$
* 未碎裂的前向散射束流质子$p'$
- 横向动量分量$p_x > -0.2 mathrm{GeV}$
- $0.2 mathrm{GeV} < |p_y| < 0.4 mathrm{GeV}$
- $(p_x + 0.3 mathrm{GeV})^2 + p_y^2 < 0.25 mathrm{GeV}^2$