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TPG digitization

Abingdon 30/10 -03 Rikard Sandström Geneva University. TPG digitization. A particle going through the detector generates a hit at each gas slice ( i.e. sensitive detector).

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TPG digitization

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  1. Abingdon 30/10 -03 Rikard Sandström Geneva University TPG digitization

  2. A particle going through the detector generates a hit at each gas slice ( i.e. sensitive detector). • All hits are written to file (Sim.out) together with information about slice number of the hit, 3D-coordinates of the hit etc. Simulation=> hits

  3. Digits A digit consists of identifiers for • Up/down stream detector • Sampling period • Strip layer • Strip number • Time of signal (since event was initiated) • Amplitude in Volts • and others, not written to output file

  4. Digitization #1starting from hits… For every hit: • A certain number of empty digits are created, corresponding to area covered by 3 sigma transversal of drifting. • The number of electrons in the hit is computed. • A Poisson distributed number of clusters in the hit is randomly chosen. • The electrons per cluster parameter is used for setting the total number of electrons in the hit. The digits resulting from the hit know this value.

  5. Digitization #2… to digits … Processing the digits involves • Longitudinal & transversal diffusion (drift) • Diffusion from GEMs • Amplification fluctuation • The charge on each strip is given by a sum of products (due to multiple Gaussian distributions from GEMs etc) of probabilities like P(x1<X<x2)=1/2((1+erf((x2-X)/sqrt(2)sigma))-(1+erf((x1-X)/sqrt(2)sigma))) in effect giving 2nd rank BesselK functions. Hence, the digit is assigned an amplified number of electrons that hit its strip.

  6. voltage t Digitization #3… signals are sampled and written to file • The electrons on the strip gives a signal shape of voltage vs time. Several digits after the first arriving electron from the hit are created, and their amplitude is computed. • Noise is added. • By sampling every 500ns from the first electrons of the event reach the hexaboard, several digits originating from different hits are sampled into a one signal each for a specific sample. • Digits that beat threshold are not rejected and written to output file (Digits.out). samplings

  7. Resultsup&down stream, 1 muon, 1 graph = 1 layer Stripnumber Sampling number

  8. Future plans • Feed output to reconstruction, w/wo background • Using special input files that give a very accurate description of number of electrons per cluster (Garfield). • Compare probability distributions for electron on strip with experiments. • Increase speed

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