diff --git a/compact/definitions.xml b/compact/definitions.xml
index d8dac0d6ad99793791c0f5cd0b34c20371ad463d..ab5d0b01319a708d8c1050cb87605e94fca26b73 100644
--- a/compact/definitions.xml
+++ b/compact/definitions.xml
@@ -284,7 +284,9 @@
<constant name="ForwardRomanPotC_ID" value="157"/>
<constant name="ForwardOffMTracker_ID" value="159"/>
+
<constant name="ffi_ZDC_ID" value="160"/>
+ <constant name="ffi_ZDC_HCAL_ID" value="161"/>
<comment>
=====================================
@@ -654,7 +656,7 @@
<comment> Global parameters </comment>
<constant name="ffi_ZDC_width" value="60.0 * cm"/>
- <constant name="ffi_ZDC_thickness" value="200.0 * cm"/>
+ <constant name="ffi_ZDC_thickness" value="61.0 * cm"/><comment> Changed from 200.0 cm </comment>
<comment> Original Global parameters </comment>
<!--
<constant name="ffi_ZDC_thickness" value="250.0 * cm"/>
@@ -670,6 +672,21 @@
<constant name="ffi_ZDC_ECAL_ntower" value="20"/>
-->
+ <comment> ZDC HCAL parameters </comment>
+ <constant name="ffi_ZDC_HCAL_CrossingAngle" value="0.020*rad"/>
+ <constant name="ffi_ZDC_HCAL_tracker_region_zmax" value="5*m"/>
+ <constant name="ffi_ZDC_HCAL_tracker_region_rmax" value="5*m"/>
+
+ <constant name="ffi_ZDC_HCAL_offset" value="5.0*mm"/>
+ <constant name="ffi_ZDC_HCAL_st_length" value="20.0*mm"/>
+ <constant name="ffi_ZDC_HCAL_lt_length" value="ffi_ZDC_width"/><comment> Changed from 40.0mm </comment>
+ <constant name="ffi_ZDC_HCAL_st_x_pos" value="0.60*m"/>
+ <constant name="ffi_ZDC_HCAL_st_y_pos" value="0.0*m"/>
+ <constant name="ffi_ZDC_HCAL_st_z_pos" value="ffi_ZDC_z_pos + ffi_ZDC_ECAL_thickness + 1*cm"/> <comment> Was 34 m, changed to be placed right after ZDC(The ecal) </comment>
+ <constant name="ffi_ZDC_HCAL_lt_x_pos" value="ffi_ZDC_x_pos"/>
+ <constant name="ffi_ZDC_HCAL_lt_y_pos" value="ffi_ZDC_y_pos"/>
+ <constant name="ffi_ZDC_HCAL_lt_z_pos" value="ffi_ZDC_z_pos + ffi_ZDC_ECAL_thickness + 1*cm"/> <comment> Was 34 m, changed to be placed right after ZDC(The ecal) </comment>
+
<comment>
-----------------------
Gaseous RICH Parameters
diff --git a/compact/ffi_ZDC_HCAL.xml b/compact/ffi_ZDC_HCAL.xml
new file mode 100644
index 0000000000000000000000000000000000000000..682dbd7a988b155876fcc9fa078c6924cbd2ba21
--- /dev/null
+++ b/compact/ffi_ZDC_HCAL.xml
@@ -0,0 +1,93 @@
+<lccdd xmlns:compact="http://www.lcsim.org/schemas/compact/1.0"
+ xmlns:xs="http://www.w3.org/2001/XMLSchema"
+ xs:noNamespaceSchemaLocation="http://www.lcsim.org/schemas/compact/1.0/compact.xsd">
+
+ <!-- Some information about detector -->
+ <info name="ZDC" title="Zero Degree Calorimeter"
+ author="Marshall Scott"
+ url="https://eicweb.phy.anl.gov/EIC/detectors/reference_detector.git"
+ status="development"
+ version="v1 2021-04-20">
+ <comment>Zero Degree Calorimeter detector</comment>
+ <comment>Copied from https://eicweb.phy.anl.gov/EIC/NPDet/-/blob/master/src/detectors/calorimeters/compact/ZDC_example.xml</comment>
+ </info>
+
+ <!-- Use DD4hep elements and materials definitions -->
+ <includes>
+ </includes>
+
+ <define>
+ </define>
+
+ <limits>
+ </limits>
+
+ <regions>
+ </regions>
+
+ <display>
+ </display>
+
+ <!-- Define detector -->
+ <detectors>
+ <detector id="ffi_ZDC_HCAL_ID" name="largeZDC" type="ffi_ZDC_HCAL" readout="ZDCHits" vis="RedVis">
+ <position x="ffi_ZDC_HCAL_lt_x_pos" y="ffi_ZDC_HCAL_lt_y_pos" z="ffi_ZDC_HCAL_lt_z_pos"/>
+ <dimensions x = "ffi_ZDC_HCAL_lt_length" y = "ffi_ZDC_HCAL_lt_length"/>
+ <layer repeat="2">
+ <slice name="Tungsten_slice" material="TungstenDens24" thickness="7*mm" vis = "GrayVis"/>
+ <slice name="Scint_slice" material="PlasticScint" thickness="3*mm" vis = "BlueVis" sensitive = "true"/>
+ </layer>
+ <layer repeat="1">
+ <slice name="Tungsten_slice" material="TungstenDens24" thickness="7*mm" vis = "GrayVis"/>
+ <slice name="SciFi_belt" material="PlasticScint" thickness="1*mm" vis = "RedVis" sensitive = "true"/>
+ <slice name="SciFi_belt" material="PlasticScint" thickness="1*mm" vis = "RedVis" sensitive = "true"/>
+ </layer>
+ <layer repeat="2">
+ <slice name="Scint_slice" material="PlasticScint" thickness="3*mm" vis = "BlueVis" sensitive = "true"/>
+ <slice name="Tungsten_slice" material="TungstenDens24" thickness="7*mm" vis = "GrayVis"/>
+ </layer>
+ <layer repeat="2">
+ <slice name="SciFi_belt" material="PlasticScint" thickness="1*mm" vis = "RedVis" sensitive = "true"/>
+ </layer>
+ <layer repeat="7">
+ <slice name="Scint_slice" material="PlasticScint" thickness="3*mm" vis = "BlueVis" sensitive = "true"/>
+ <slice name="Tungsten_slice" material="TungstenDens24" thickness="7*mm" vis = "GrayVis"/>
+ </layer>
+ <layer repeat="1">
+ <slice name="Tungsten_slice" material="TungstenDens24" thickness="7*mm" vis = "GrayVis"/>
+ <slice name="Scint_slice" material="PlasticScint" thickness="3*mm" vis = "BlueVis" sensitive = "true"/>
+ <slice name="Tungsten_slice" material="TungstenDens24" thickness="7*mm" vis = "GrayVis"/>
+ <slice name="Tungsten_slice" material="TungstenDens24" thickness="7*mm" vis = "GrayVis"/>
+ </layer>
+ <layer repeat="2">
+ <slice name="SciFi_belt" material="PlasticScint" thickness="1*mm" vis = "RedVis" sensitive = "true"/>
+ </layer>
+ <layer repeat="3">
+ <slice name="Scint_slice" material="PlasticScint" thickness="3*mm" vis = "BlueVis" sensitive = "true"/>
+ <slice name="Tungsten_slice" material="TungstenDens24" thickness="7*mm" vis = "GrayVis"/>
+ <slice name="Tungsten_slice" material="TungstenDens24" thickness="7*mm" vis = "GrayVis"/>
+ </layer>
+ <layer repeat="2">
+ <slice name="SciFi_belt" material="PlasticScint" thickness="1*mm" vis = "RedVis" sensitive = "true"/>
+ </layer>
+ <layer repeat="1">
+ <slice name="Scint_slice" material="PlasticScint" thickness="3*mm" vis = "BlueVis" sensitive = "true"/>
+ <slice name="Tungsten_slice" material="TungstenDens24" thickness="7*mm" vis = "GrayVis"/>
+ </layer>
+ </detector>
+ </detectors>
+
+ <!-- Definition of the readout segmentation/definition -->
+ <readouts>
+ <readout name="ZDCHits">
+ <segmentation type="CartesianGridXY" grid_size_x="1.0*mm" grid_size_y="1.0*mm" />
+ <id>system:8,layer:12,slice:12,x:48:-8,y:-8</id>
+ </readout>
+ </readouts>
+
+ <plugins>
+ </plugins>
+
+ <fields>
+ </fields>
+</lccdd>
diff --git a/reference_detector.xml b/reference_detector.xml
index f1443893f7021c5abdc39c721dc94eef5c77388e..b84e4bf7f9d194f9db07ae3a4abf23d1634e6274 100644
--- a/reference_detector.xml
+++ b/reference_detector.xml
@@ -131,6 +131,10 @@
<include ref="compact/far_forward_romanpots.xml"/>
<include ref="compact/far_forward_detectors.xml"/>
+
+ <include ref="compact/ffi_ZDC_HCAL.xml"/>
+
+
<!--
<include ref="compact/mm_tracker_barrel.xml"/>
<include ref="compact/cb_VTX_Barrel.xml"/>
diff --git a/src/ffi_ZDC_HCAL.cpp b/src/ffi_ZDC_HCAL.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..d4cbf641dd868859b5d37352f259d2be88f57352
--- /dev/null
+++ b/src/ffi_ZDC_HCAL.cpp
@@ -0,0 +1,97 @@
+#include "DD4hep/DetFactoryHelper.h"
+#include "DD4hep/Printout.h"
+#include <XML/Helper.h>
+#include "TMath.h"
+#include "DDRec/Surface.h"
+#include "DDRec/DetectorData.h"
+#include "XML/Layering.h"
+#include "Math/Transform3D.h"
+
+///////////////////////////
+// Zero Degree Hadron Calorimeter
+///////////////////////////
+
+using namespace std;
+using namespace dd4hep;
+using namespace dd4hep::rec;
+using namespace dd4hep::detail;
+
+
+static Ref_t createDetector(Detector& lcdd, xml_h e, SensitiveDetector sens) {
+ xml_det_t x_det = e;
+ int det_id = x_det.id();
+ string det_name = x_det.nameStr();
+ xml_dim_t pos = x_det.position();
+ double x_pos = dd4hep::getAttrOrDefault(pos, _Unicode(x),0.0);
+ double y_pos = dd4hep::getAttrOrDefault(pos, _Unicode(y),0.0);
+ double z_pos = dd4hep::getAttrOrDefault(pos, _Unicode(z),0.0);
+ xml_dim_t dim = x_det.dimensions();
+ double pixel_x = dim.x();
+ double pixel_y = dim.y();
+ Material air = lcdd.material("Air");
+ double z = z_pos;
+ double zmin = z_pos;
+ DetElement det(det_name, det_id);
+
+ int layer_num = 1;
+ int slice_num = 1;
+ double totWidth = Layering(x_det).totalThickness();
+ Box envelope (pixel_x/2.0, pixel_y/2.0, totWidth/2.0);
+ Volume envelopeVol(det_name+"_envelope", envelope, air);
+ PlacedVolume pv;
+
+ xml_comp_t x_layer = x_det.child(_U(layer));
+
+ // Read layers
+ for(xml_coll_t c(x_det,_U(layer)); c; ++c)
+ {
+ xml_comp_t x_layer = c;
+ int repeat = x_layer.repeat();
+ double layerWidth = 0;
+ for(xml_coll_t l(x_layer,_U(slice)); l; ++l)
+ layerWidth += xml_comp_t(l).thickness();
+
+ // Loop over repeat#
+ for(int i=0; i< repeat; i++)
+ {
+ double zlayer = z;
+ string layer_name = det_name + _toString(layer_num,"_layer%d");
+ Volume layer_vol(layer_name,Box(pixel_x/2.0, pixel_y/2.0,layerWidth/2.0),air);
+
+ // Loop over slices
+ for(xml_coll_t l(x_layer,_U(slice)); l; ++l)
+ {
+ xml_comp_t x_slice = l;
+ double w = x_slice.thickness();
+ string slice_name = layer_name + _toString(slice_num,"slice%d");
+ Material slice_mat = lcdd.material(x_slice.materialStr());
+ Volume slice_vol (slice_name,Box(pixel_x/2.0, pixel_y/2.0,w/2.0),slice_mat);
+ if(x_slice.isSensitive())
+ {
+ sens.setType("calorimeter");
+ slice_vol.setSensitiveDetector(sens);
+ }
+ slice_vol.setAttributes(lcdd,x_slice.regionStr(), x_slice.limitsStr(), x_slice.visStr());
+ pv = layer_vol.placeVolume(slice_vol, Transform3D(RotationZYX(0, 0, 0),Position(0.0,0.0,z-zlayer-layerWidth/2.0+w/2.0)));
+ pv.addPhysVolID("slice", slice_num);
+ z += w;
+ ++slice_num;
+ }
+ string layer_vis = dd4hep::getAttrOrDefault(x_layer, _Unicode(vis), "InvisibleWithDaughters");
+ layer_vol.setAttributes(lcdd, x_layer.regionStr(), x_layer.limitsStr(), layer_vis);
+ pv = envelopeVol.placeVolume(layer_vol, Transform3D(RotationZYX(0, 0, 0), Position(0,0,zlayer-zmin-totWidth/2.0+layerWidth/2.0)));
+ pv.addPhysVolID("layer", layer_num);
+ ++layer_num;
+ }
+ }
+ envelopeVol.setAttributes(lcdd, x_det.regionStr(), x_det.limitsStr(), "InvisibleWithDaughters");
+
+ Volume motherVol = lcdd.pickMotherVolume(det);
+ PlacedVolume phv = motherVol.placeVolume(envelopeVol, Position(x_pos,y_pos,z_pos+totWidth/2.0));
+ phv.addPhysVolID("system", det.id());
+ det.setPlacement(phv);
+
+ return det;
+}
+
+DECLARE_DETELEMENT(ffi_ZDC_HCAL, createDetector)