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Candidate Kinematical Variables

The following kinematical variables are available for candidates at both the micro- and reco- level. This means that any analysis module that was written using these variables (for vertexing, for example) for a micro-level analysis can be used again, transparently, for a reco-level analysis; and vice-versa.

Pointer Needed to Reference Micro Variables

 BtaCandidate* aBtaCandidate;

Candidate Info

Quantity Type Description
aBtaCandidate->charge() Int charge (-1, 0, +1) of the candidate as determined by the direction of its curvature in the BaBar solenoid.
aBtaCandidate->energy() Float energy (GeV) of the candidate in the lab frame:
for neutrals, it is the (uncalibrated) energy deposited in the calorimeter
for charged tracks, it is the relativistic energy, assuming the pion mass hypothesis if none has been assigned yet.
aBtaCandidate->p4()
aBtaCandidate->p4(HepPoint)
HepLorentzVector 4-momentum of the candidate in the lab frame:
for neutrals, as determined from the energy and mass
for charged tracks, as determined by the curvature of the track (track based on hits in both the drift chamber AND the SVT)
aBtaCandidate->p4Err()
aBtaCandidate->p4Err(HepPoint)
BbrError covariance. Note, for neutrals, you must use the method which takes a HepPoint as its argument.
aBtaCandidate->p4WCov() BbrLorentzVectorErr 4-momentum with errors
aBtaCandidate->decayVtx() BtaAbsVertex Information on the decay vertex of this candidate.
aBtaCandidate->recoTrk()->fitResult()->helix(0).covariance() HepSymMatrix error matrix of the helix fit parameters
aBtaCandidate->doca(HepPoint) double doca of the track to a given point in 3D
aBtaCandidate->docaXY(HepPoint) double doca of the track to a given point in 2D
aBtaCandidate->docaErr(HepPoint) double error on doca of the track to a given point in 3D
aBtaCandidate->docaXYErr(HepPoint) double error on doca of the track to a given point in 2D
aBtaCandidate->docaErr(BbrPointErr) double same as with HepPoint, but allowing error on the point with respect to which the DOCA is made
aBtaCandidate->docaXYErr(BbrPointErr) double same as with HepPoint, but allowing error on the point with respect to which the DOCA is made
aBtaCandidate->recoObject()->position(HepPoint) HepPoint the POCA (to the HepPoint) of the BtaCandidate (add BtaAbsRecoObject::XY as second argument if the POCA must be in 2D)
aBtaCandidate->recoObject()->positionErr(HepPoint) BbrPointErr error on the POCA (to the HepPoint) of the BtaCandidate (add BtaAbsRecoObject::XY as second argument if the POCA must be in 2D)
aBtaCandidate->recoObject()->momentum(HepPoint) Hep3Vector value of the BtaCandidate momentum after it has been swum to the POCA of the HepPoint. (add BtaAbsRecoObject::XY as second argument if the POCA must be in 2D) In many cases, this is the same as aBtaCandidate->momentum(HepPoint)
aBtaCandidate->recoObject()->momentumErr(HepPoint) BbrVectorErr value of the BtaCandidate momentum error matrix after it has been swum to the POCA of the HepPoint. (add BtaAbsRecoObject::XY as second argument if the POCA must be in 2D)

To obtain the components of 4 momenta of BtaCandidates, use the methods:

aBtaCandidate->p4().x();
aBtaCandidate->p4().y();
aBtaCandidate->p4().z();
aBtaCandidate->p4().rho();  //magnitude of 3-momentum
aBtaCandidate->p4().e();   // energy component of 4-vector

A Beta Candidate also contains objects of the TrkRecoTrk and AbsRecoCalo classes, which provides Reco-level interfacing.


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Author: Chris Roat

Last modification: 8 May 2003
Last significant update: 8 May 2003