I use two different vertexs to shoot photon with same energy through FMS and FHC, and study the differences between these two cases. The energy of photon is about 30 GeV, and Px=4.8755 GeV, Py=0 GeV, Pz=29.60125 GeV.

   1, vertex (0, 0, 0).

       The particle's pathes are like following,

       But sometimes the pathes are like,

      The energy deposit in FMS

      The energy deposit in FHC

      The energy deposit in both FMS and FHC

      The energy deposit in FMS Vs in FHC

     The energy deposit cell in FHC.

     The energy weighted x, y distribution.

     Then I tried using different x positions but same y and z position of case 1, but the final results are quite similar of case 1, there is not large energy deposit in FMS.

     So I decide to add the y value but with same x and z position of case 1. But the partice will hit some part of EEMC etc., it can't touch FMS. I add the z value and  take the following case as a test.

   2, vertex (0, 20, 400)

      The particle pathes is like

      The energy deposit in FMS

      The energy deposit in FHC

      The energy deposit in both FMS and FHC

      The energy deposit in FMS Vs in FHC

     The energy deposit cell in FHC.

     Case 2 lost some energy before photon pass through FMS and FHC, but it shows good consistency with the behavior of pion0. Most of the energy of photon lost during it passes through FMS.

     The energy weighted x, y distribution.