Protoypes not containing at least two tracks that are incompatible with any other prototype are removed one by one in order to avoid fake vertices caused by track outliers. This is annealing phase is continued down to a configurable temperature Tmin. In subsequent iterations, separated prototypes can again split as required. To separate and track assignment weights start to differ. As the temperature decreases and the assignment becomes less soft, the two protoypes start If all tracks are compatible with a single vertex, the two protoypes collaps to the same position. For each iteration the protoype is split into two identical prototypes separated by tiny distance in z. The clustering starts with a single protoype at high T. The gradual decrease of the temperature is called annealing. At infinite temperature all assignement weights are equal, while at T=0 the weights are either 0 or 1. The softness of the assignment is controlled by a "temperature" paramter. the weights can be any number between 0 and 1 based on the compatibilty of vertex and track. A global chi^2 in which each track is assigned to vertex prototypes is minimized.
The DA clustering is based on the same principles as the AdaptiveVertexFitter or the MultiVertexFitter. The format of the config files now permits selecting the different clustering algorithms.Ī config file running the deterministic annealing clustering has been added under the name OfflinePrimaryVertices_cfi.py andĪn example for running it can be found in demoProducePrimaryVertex_cfg.py. The track selection now uses layers with hits instead of hits.Īn alternative clustering algorithm is now available. two or more mutually incompatible tracks). A configurable cut on the minimal number of degrees of freedom has been introduced to permit the rejection of vertices effectively consisting of only one track (i.e. The config file format has changed slightly for CMSSW_3_6_0. This can be done when the generalTracks are present in the input file. The vertex reconstruction may have to be redone when the reconstruction parameters used at the time of the original processing were not Redoing primary vertex reconstruction on the fly Opening a this file in root, the data of the primary vertices (such as the coordinates, chi-squared, degrees of freedom) can be viewed directly.Ī simple analysis of the primary vertices is described in the Workbook. This produces the file pv_reco.root, which contains the data collections retained, tracks and vertices. The tracks used on input are also copied, for analysis and debugging. The module sequence is defined in the following CMSSW config file ].
#Mytracks gaps how to#
The example below shows how to reconstruct primary vertices from a file containing tracks, and store these vertices in a file called pv_reco.root. This requires some changes in the configuration files that are described below. ( config in git )īetween CMSSW 4.2.X and CMSSW 4.4.x the producer was reorganized such that the clustering is only done once for both, the unconstrained and the constrained collection.
#Mytracks gaps Offline#
The vertices are stored in the event as reco::Vertex collections.
#Mytracks gaps full#
The reconstruction of Primary vertices using the full tracks is part of the default reconstruction sequence, using the tracks from the generaltracks collection and the offlineBeamSpot BeamSpot. In this case, the vertex contains no tracks (as non have been used), the chi^2 and the ndof are 0, and the flag isFake() is set to true. įrom CMSSW 1.8.0 onwards, if no reconstructed vertex is found in an event, a vertex based on the beam-spot is put into the event. A description of the gap and DA clustering can be found in CMS IN-2011/014. Starting with CMSSW 4.2.0.pre7 the clustering algorithm is the deterministic annealing (DA) clustering, which is briefly described below.
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