Zero Degree Calorimeter detector

Zero Degree Calorimeter using existing RHICf and LHCf technology.

src/GenericDetectors/calorimeters/compact/macro/gps_zdc.mac

+/run/beamOn 1
+/control/verbose 2
+/run/initialize
+
+/gps/verbose 2
+/gps/particle neutron 
+/gps/number 1
+
+/gps/ene/type Gauss
+/gps/ene/mono  2.5 GeV
+/gps/ene/sigma 2.0 GeV
+
+/gps/pos/type Volume
+/gps/pos/shape Cylinder
+/gps/pos/centre 0.0 0.0 0.0 cm
+/gps/pos/radius 0.01 cm
+/gps/pos/halfz  0.01 cm
+/gps/position 0 0 -1.0 cm
+
+/gps/direction 0.0 0.5 1.0 
+#/gps/ang/type iso
+
+
+/control/execute macro/vis_zdc.mac
+
+/run/beamOn 1