It was discovered that the layerON bit mask of the TkID class in the GISMO code was not consistent with the placement of the fields in the binary tag for the Tracker and VXD sub-systems. Also, the TkID class in the RootApps/Event/ space does not place the fields in the same spot as the GISMO TkID class. First off, don't go and delete all of your simulated events. They're still good. This is because even when put in the wrong spot, the fields don't over-write each other. To do reconstruction you will have to make some changes to the TkID class in RpptApps/Event/V1.0/src/TkID.cxx. Find the method TkID::layer(). This method and the setLayer method,right below it will need to be changed. Currently, the methods should look like this: Int_t TkID::layer() const { // This returns the layer number from the first 8 bits of m_tag Int_t layer = (TkID::layerOn & m_tag); return layer; } //____________________________________________________________ void TkID::setLayer(Int_t tag) { // setLayer sets the first 8 bits of m_tag to the layer number Int_t layerShift = tag; Int_t layer = (TkID::layerOff & m_tag) | layerShift; m_tag = layer; } To be able to do reconstruction dealing with the Tracker and VXD you will need to change these methods to look like this: int TkID::layer() const { int layer = (TkID::layerOn & m_tag) >> 21; return layer; }; void TkID::setLayer(int tag) { int layerShift = tag << 21; int layer = (TkID::layerOff & m_tag) | layerShift; m_tag = layer; }; You will also need to change the layerOn mask which is defined at the bottom of TkID.cxx. You will need to change it from 0x000000FF to 0x1FE00000. After doing all of this, remake the Event shared library. All the RootApps packages link to this library so they will need to be relinked as well. Confused yet? These changes will allow you to process all of the events that you have already generated. We are planning on releasing a new version of the package sometime early next week. The inconsistencies with the TkID class will be fixed in the simulator and the reconstruction code but this fix will probably mean that the files you generated previously will not produce accurate reconstruction's of the VXD and Tracker if they are used with the new version of the code. So you may want to copy TkID to another space before you install the new version of the reconstruction code just so you have a version of TkID that reads the old, incorrect layout of the TkID tag. If I've missed something, or confused you hopelessly, feel free to ask me questions. Rob Shanks [log in to unmask]