This page overviews the variables of tracks and dimuons that are reconstructed by kTracker. The variables are stored in SRecEvent. The exact definition of the variables should be found in the source code.

Variable	Meaning
charge	+1 for μ+ and -1 for μ-.
num_hits	The number of drift-chamber hits associated with this track.
chisq	χ2 of track fitting with drift-chamber hits.
chisq_target
chisq_dump
chsiq_upstream

Variable	Meaning
pos	The initial position of dimuon
mom	The initial momentum of dimuon
mom_pos	The initial momentum of μ+
mom_neg	The initial momentum of μ-

Tracklet is an intermediate object made during the track reconstruction in kTracker.

Type	Station ID	List index	Note
D0 tracklet	1	0
D1 tracklet	2	0
D2 tracklet	3	1
D3p tracklet	4	2
D3m tracklet	5	2
D2+3 tracklet	6	3	a.k.a. back-partial track
Global track	7	4

Some events pass the reconstruction stage successfully, while others fail. The RecStatus variable stores an integer indicating the outcome: success or failure. If an event fails, the integer reflects the specific stage at which the failure occurred.

Definition can be found here.

RecStatus	Meaning
0	Event reconstructed successfully
-1	Event reconstruction failed due to hit multiplicity
-2	Event reconstruction failed rough muon ID ??
-3	Event reconstruction failed due to no matching st:2 tracklets??
-4	Event reconstruction failed due to no matching st:3 tracklets??
-5	Event reconstruction failed due to no matching backpartial tracklets??
-6	Event reconstruction failed due to no global tracklets??
-7	Event reconstruction failed due to no enough tracks (two) to form dimuon??
-10	Event reconstruction failed due to no matching tracks to form a dimuon??
-20	Event reconstruction failed due to ??

The algorithm (i.e. code) can be found here. It is usually applied after the in-time cut. After the in-time cut, we suppose that all remaining hodoscope hits are in time (i.e. coming from the triggered RF bucket) but chamber hits are a mixture of in time and out of time. The c-to-h matching is to remove the remaining out-of-time chamber hits.

In the c-to-h matching, we check if each chamber hit matches with any hodoscope hit in X-Y plane at the station of the chamber hit. If so, the chamber and hodoscope hits should be created by an in-time muon, and thus the chamber hit is kept. If not, the chamber hit is removed.

• Overall reconstruction flow: DocDB 1283
  • Updates: DocDB 1683
• Sec. 4.2 of Kei's PhD thesis
• kTracker Q&A @ E906 UIUC TWiki