p20-p21 Muon certification criteria with new track quality definitions

Last modified: 12-Dec-09 by Dave Hedin


Reconstructed muon candidates are classified using two parameters: muon type and muon quality. The definitions in p20/p21 are identical to those in p17, expect for the removal of the "tight" definition. The definitions in p17 are the same as in p14.
In addition for p20-21 we defined three types of track quality for the track matched to the muons. In December 2009 we modified these tracking definitions.


Exclusive type

The type of muon is given by the parameter nseg. A positive value of nseg indicates that the muon reconstructed in the muon system (``local muon'') was matched to a track in the central tracking system. A negative value of nseg tells that the local muon could not be matched to a central track. The absolute value |nseg|= 1, 2, or 3 respectively indicates that the local muon is made up of A-layer only hits, B or C-layer only hits (outside the toroid), or both A- and B- or C-layers hits.

Overview of the different muon types:

nseg Muon Type Central track matching algorithm MTC matching criterion
3 Central track +
local muon track
(A and BC layer) 		Muon to central if local
muon track fit converged.
Central to muon otherwise 		Delta eta, Delta phi between MTC and
central track extrapolated
to calorimeter
2 Central track + BC only central to muon as above
1 Central track + A only central to muon as above
0 Central track + muon hit
or central track + MTC		 central to muon
central to calorimeter		 as above
-1 A segment only no match Delta eta, Delta phi between MTC
and A-layer segment
-2 BC segment only no match Delta eta, Delta phi between MTC and
and BC-layer segment
-3 local muon track
(A + BC)		 no match Delta eta, Delta phi between MTC and
local muon track at
A-layer if fit converged
or else A-segment position


p20 Certification Criteria

The second parameter used to classify muons is the quality. The muon quality can be ``Loose'', ``Medium'' or ``Tight''. The Tight definition has remained unchanged since p10. As of p14, the Medium and Loose efficiencies were optimized by loosening the requirements on the local muon in regions with reduced acceptance and by instead requiring in these regions a confirmation from the central tracking system:

The definitions read:

|nseg|=3 medium/loose muons
 |nseg|=3 muons are muons with a A and a BC segments matched or not with a central track.
A |nseg=3| muon is medium if it has:

  • at least two A layer wire hits
  • a A layer scintillator hit
  • at least two BC layer wire hits
  • at least one BC scintillator hit (except for central muons with less than four BC wire hits).

    • A |nseg=3| loose muon is defined as a medium muon but allowing one of the above tests to fail, with the A wire and scintillator requirement treated as one test and requiring always at least one scintillator.

    nseg=2 loose/medium muons
         nseg=2 muons are muons with a BC segment matched with a central track.
    A nseg=2 muon is loose if it has:
  • at least one BC scintillator hit
  • at least two BC layer wire hits.

    • A nseg=2 muon is defined as medium if it fullfills the above requirements and if it is located in the bottom part of the detector (octant 5 and 6 with |detector eta|<1.6).

    nseg=1 loose/medium muons
         nseg=1 muons are muons with a A segment matched with a central track.
    A nseg=1 muon is loose if it has:
  • a A scintillator hit
  • at least two A layer wire hits.

    • A nseg=1 muon is defined as medium if it fullfills the above requirements and if it is located in the bottom part of the detector (octant 5 and 6 with |detector eta|<1.6).
    Low momentum nseg=1 muons are also defined as medium. A nseg=1 muon is qualified as low momentum muon if its probability to reach the BC layer is less than a parameter set by RCP. The probability maps as a function of momentum and |eta| are also set by RCP. Here are the probability plots (red curves) computed with Geant informations for generated muons with 3<p<4 GeV, 4<p<5 GeV and 5<p<6 GeV.

    In December 2009 we introduce new track quality definitions. Both versions are currently in caf_util with version=1 being the old and version=2 being the new definitions.
    new p20 tracking quality version=2
         loose_track

    medium_track newmedium_track tight_tracks
  • it is a newmedium_track
  • There is at least one SMT hit attached to the track

    old p20 tracking quality version=1
         loose_track medium_track tight_tracks
  • it is a medium_track
  • There is at least one SMT hit attached to the track