The 3DBox projection allows the user to investigate a small 3D region around a newly formed secondary vertex. Every time a new secondary vertex is formed from a list (see 3.3.4 Lists Window), the direction of flight of the incoming particle is calculated as the vector joining the primary vertex to the reconstructed vertex. A 3D box of default size 2 mm x 2 mm x 4 cm is formed around this axis. The box has three vertically oriented planes and transparent front and top faces. The left hand plane contains the primary vertex, which is represented by the red point. The axis of the direction of flight of the decaying particle lies horizontally on the screen. The middle and right hand plane are at decay distances of 2 cm and 4 cm, respectively. Tracks fully contained withing the box are represented as straight lines and their intersections with the three planes are shown as ellipses representing the correlated impact parameter errors of the track. The dashed sections of tracks correspond to regions where they pass behind behind a plane.
The user may interact with the region shown in the box via the 3DBox interaction. When the 3D box interaction is selected the size of the box may be adjusted in a manner analogous to the zooming performed in the ZMR (see 4.1 Zoom/Move/Rotate (ZMR)) interaction.
There are two operations which may be performed:
Changing the volume contained by the box
The volume contained by the box is changed by dragging any point of the picture towards or away from the central point represented by a small red circle superimposed on the picture. Dragging towards the central point will increase the volume of the box. Dragging away from the central point will decrease the volume of the box. The length of the box may be changed independently of the width by holding down the H key of the keyboard. The width of the box may be changed independently of the length by holding down the V key of the keyboard.
Rotation
In order to obtain a rotation of the tracks around the horizontal axis corresponding to the direction of flight of the decaying particle you drag any point on the picture while keeping the R key of your keyboard pressed.
The 3D Box Pop-up Menu
The 3DBox Pop-up Menu can be accessed by right-clicking into the desired canvas pad while keeping the R key of your keyboard pressed. It contains the following set of utility operations:
Default box Volume - reset the volume of the box to correspond to the default values.
Modifier Key Summary
Table 5.3. Modifier key summary
Modifier Key | Action |
---|---|
left-press only | Change the volume of the box |
Z + left-press | Change the volume of the box |
H + left-press | Change the length of the box |
V + left-press | Change the width of the box |
R + left-press | Rotate the tracks around the direction of flight of the decaying particle |