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PixelThresholdClusterizer overview

Located in RecoLocalTracker/SiPixelClusterizer/plugins/ in CMSSW, these files (PixelThresholdClusterizer.h and .cc) provide the declaration of the PixelThresholdClusterizer class.

It inherits from PixelClusterizerBase (declared in the same directory, in PixelClusterizerBase.h).

The class' main purpose is to create Clusters, given PixelDigis.

Other functionality has been integrated in it, such as:

  • Duplicate Digi removal

UML diagram

classDiagram

class PixelClusterizerBase

class PixelThresholdClusterizer{
    +SiPixelArrayBuffer theBuffer
    +vector~PixelPos~ theSeeds
    +vector~bool~ theFakePixels
    +vector~SiPixelCluster~ theClusters
}

PixelClusterizerBase <|-- PixelThresholdClusterizer

class SiPixelArrayBuffer{
    +int nrows
    +int ncols
    +set_adc()
    +add_adc()
    +setSize()
}

direction LR
PixelThresholdClusterizer -- "1" SiPixelArrayBuffer : theBuffer

Class attributes

theBuffer

A 2D matrix of SiPixelArrayBuffer type. Its purpose is to represent the Pixel Detector and store ADC values for each Pixel.

thePixelOccurence

A simple vector of type uint8_t to store the number of occurences that each Digi is encountered. Used to detect duplicates due to noise.

thePixelThreshold

A constant ADC threshold above which a pixel is regarded as active.

theSeedThreshold

A constant ADC threshold above which an active pixel is also considered as a Seed, i.e. a starting point for the Clusterization algorithm.