"$a \to \pi^+\pi^-\eta$ (Primakoff production)" of "Search for hadronic decays of feebly-interacting particles at NA62"

Number of expected $a \to \pi^+\pi^-\eta$ events for BR = 1 in the plane (mass, width) after full selection, for Primakoff production assuming production coupling $C_{\gamma\gamma}/\Lambda=1\,\mathrm{GeV}^{-1}$. Acceptance for particles that reach the FV and decay therein and mass resolution.

在完成全部筛选步骤后，针对普里马科夫产生（Primakoff production）过程，假设其产生耦合$C_{gammagamma}/Lambda=1,mathrm{GeV}^{-1}$且分支比（Branching Ratio，BR）为1时，（质量，宽度）平面内预期的$a o pi^+pi^-eta$ 事例数；该结果已计入抵达 fiducial体积（fiducial volume，FV）并在其中衰变的粒子的接收度，以及质量分辨率。