XTF track format
Each XTRP track
is received in the XTrp Fanout (XTF) board
as a single word packet. For each track the XTF board sends
out a two word packet, the first word is for use by the
Associative Memory, the second is for use by the Track Fitter.
The AM requires the layer field to be added, so some XTRP
information is dropped, while to the TF we send the full XTRP data,
after substituteing the 7-bit Pt bin number with a 7-bit curvature
information.
The data for the AM goes trough a lookup table within the
XTF board so that the SuperStrip (SS) corresponding to the XFT
track can be assigned using the full Pt-phi information.
XTF outputs in the first word a 12-bit XTF-hit
which is then mapped into SS by the AMS/HB, it is padded with zeroes
as needed. Since the
AMS drops the four least significant bits, the XTF-hit starts at bit 4.
Packet structure
| 24 |
23 | 22 |
21 | 20 |
19 | 18 |
17 | 16 |
15 | 14 |
13 | 12 |
11 | 10 |
9 | 8 |
7 | 6 |
5 | 4 |
3 | 2 |
1 | 0 |
| HD | DS | 0 | 0 |
Layer=5 |
0 | 0 |
XTF-hit(12) |
0 | 0 |
0 | 0 |
| HD | DS | 0 | 1 |
XTRP data(21) |
More explicitely:
| 24 |
23 | 22 |
21 | 20 |
19 | 18 |
17 | 16 |
15 | 14 |
13 | 12 |
11 | 10 |
9 | 8 |
7 | 6 |
5 | 4 |
3 | 2 |
1 | 0 |
| HD | DS | 0 | 0 |
1 | 0 | 1 |
0 | 0 |
XTF-hit(12) |
0 | 0 |
0 | 0 |
| HD | DS | 0 | 1 |
eta | iso |
sign |
curvature(6) |
phi angle(12) |
Notes:
- in the first word the 5 in bits 18-20 is the layer number, fixed
as 5 for XFT tracks as needed for proper working of AMchips.
- This allow e.g. to
ouptut here global phi at SVX radius as XTF-hit and then to
convert it into local phi in each wedge.
- in the second word the sign bit is 0 for positive tracks, 1 for negative
- the 6 bits of curvature indicate one of 64 possible evenly
spaced curvature bins. Bin 0 is 0 curvature. Curvature bin i (i>0)
corresponds to Pt = 96GeV/i, so bin 1 is 96 GeV, bin 63 is 1.52 GeV.
- The XTRP data are defined elsewhere.
Please, make sure that you trust that source (not this page) in case
of discrepancy.
BACK to the
SVT data words format page