Heavy Photon Search Tracking Software Update · 2011-10-18 · Heavy Photon Search Tracking Software Update Omar Moreno Santa Cruz Institute for Particle Physics University of California,

Heavy Photon SearchTracking Software Update

Omar Moreno

Santa Cruz Institute for Particle PhysicsUniversity of California, Santa Cruz

Santa Cruz, California

[email protected]

October 18, 2011

Omar Moreno (SCIPP) HPS Collaboration Meeting October 18, 2011 1 / 14

Outline

1 Overview of Tracking SimulationTracking Simulation

2 APV25 Readout Chip

3 Simulation of the APV25The APV25 ResponseAPV25 Analog BufferAPV25 Data Streamt0 Extraction

4 Summary

5 To do ...


Overview of Tracking Simulation


Simulation of events is being accomplished using the GEANT4 SLICframework.

A’ signal and trident background events are simulated using MadGraphBeam background is generated by passing “beam electrons” through a.125%X0 W target and HPS detector using GEANT general particle source.

The HPS detector used contains the Silicon Vertex Tracker (SVT), ECal, andvacuum chamber and a uniform B field.The correct event time structure is achieved by combining 2500 beambackground events =⇒ 2 ns bunches

The HPS detector is now in the JLAB coordinates, tracking, however, is stilldone in the coordinate system defined by org.lcsim

The simulation will make use of the org.lcsim framework and currentlyincludes

Charge deposition simulation on SVT Si sensorsAPV25 time response including proper output data streamSingle peak extraction of hit timeClustering, track reconstruction and vertexing ⇐= does not use time evolvedsignal




Overview of Tracking Simulation Tracking Simulation

Tracking Simulation

The HPS tracking algorithm

Raw tracker hits are clustered together ( nearest neighbor algorithm ) intostrip hitsStereo hits are then formed by taking pair of strip hits in adjacent sensors onthe same tracker planeStereo hits from three layers of the SVT are taken and fit to a helical track

Helical fits are extended to the ECal face and checked to see if they lie withinthe ECal acceptanceTrack is matched to an ECal clusterIf the track is found not to satisfy either condition throw it out

Helical fits which pass χ2 and kinematic cuts (seed tracks) are then confirmedby including another layer in the fit and finally extending the fit to the finalavailable layer.

2-track vertexing is done offline ⇒ ( Billior and Qian, NIM A311, 1992)


APV25 Readout Chip

Overview of the APV25

The APV25 readout chip has 128 channels consisting of a pre-amplifiercoupled to a shaping amplifierTotal front end gain of 100 mv/MIP and noise profile of 246 electrons + 36electrons/pFTotal gain of 1 µA/MIPThe shaping time is 50 ns ⇐= adjustableThe shaper signal is sampled every 24 ns intervals into an analog pipeline 192cells deep =⇒ allows for up to ≈ 3.5µs for L1 trigger decision


APV25 Readout Chip

Overview of the APV25

The analog pipeline has a writer and trigger pointer separated in time by thetrigger latency

When a trigger is received, either a single sample, (peak mode), 3 samples(deconvolution mode), or several samples (multi-peak mode) are marked tobe read out =⇒ only “peak” and “multi-peak” mode will be implemented inthe simulation.


Simulation of the APV25 The APV25 Response

The APV25 response

Charge depositions on each sensor strip are readout and shaped using anideal CR-RC pulse on an event by event basis

AQt

Tpe1− t

Tp

A = 100 mv/MIPQ = Input ChargeTp = Shaping Time

time [ns]0 50 100 150 200 250 300 350 400

[mV

]

0

100

200

300

400

500 1 MIP2 MIP

3 MIP

4 MIP5 MIP

500*(x/50)*exp(1-(x/50))

Shaper shape is sampled in 24 ns intervals and the resulting voltage value isstored in a buffer ( Circular Buffer ) ... the voltage value remains in thebuffer until it is read out or overwritten

A global software clock has been implemented which is used by the APV25


Simulation of the APV25 APV25 Analog Buffer

APV25 Analog Buffer

As in the actual chip, the simulation contains both a writer pointer and atrigger pointer

The shaper signal is sampled and stored beginning with the position of thewriter pointer until the position of the trigger pointer is reached or the signalgoes below zero

This is done on an event by event basis so pileup effects can be simulated

When a trigger signal is received, samples are read out and cleared beginningat the position of the trigger pointer ... Currently, six samples are readout,two before the peak and four after



APV25 Analog Buffer







APV25 Analog Buffer







APV25 Analog Buffer







APV25 Analog Buffer

24 ns Buckets0 20 40 60 80 100 120 140 160 180 200

mV

0

100

200

300

400

500

600



APV25 Analog Buffer

24 ns Buckets0 20 40 60 80 100 120 140 160 180 200

mV

0

100

200

300

400

500

600



APV25 Analog Buffer

24 ns Buckets0 20 40 60 80 100 120 140 160 180 200

mV

0

100

200

300

400

500

600



APV25 Analog Buffer

24 ns Buckets0 20 40 60 80 100 120 140 160 180 200

mV

0

100

200

300

400

500

600


Simulation of the APV25 APV25 Data Stream

APV25 Data Stream

The APV25 output consist of a 12 bit header, 128 bits of channel data and asingle trailing bit.When a trigger is received, the simulation stores 6 consecutive outputs fromeach “APV25” in the simulation for further processing.


Simulation of the APV25 t0 Extraction

Single peak extraction of t0

Currently, only single peak extraction of t0 is present in the simulation.

The six samples per channel obtained from the APV25 are fit using

f(t) = At− tpeak + Tp

Tpe1−

t−tpeak+Tp

Tp

The fit is done several times using different values of tpeak until the bestresidual χ2 is achieved

ns20 40 60 80 100 120 140 160

mV

60

70

80

90

100

110







Tpe1−

t−tpeak+Tp

Tp


ns20 40 60 80 100 120 140 160

mV

60

70

80

90

100

110







Tpe1−

t−tpeak+Tp

Tp


ns20 40 60 80 100 120 140 160

mV

60

70

80

90

100

110







Tpe1−

t−tpeak+Tp

Tp


ns20 40 60 80 100 120 140 160

mV

60

70

80

90

100

110







Tpe1−

t−tpeak+Tp

Tp


ns20 40 60 80 100 120 140 160

mV

60

70

80

90

100

110







Tpe1−

t−tpeak+Tp

Tp


ns20 40 60 80 100 120 140 160

mV

60

70

80

90

100

110







Tpe1−

t−tpeak+Tp

Tp


ns20 40 60 80 100 120 140 160

mV

60

70

80

90

100

110


Summary

Summary

ECal

SVT

Clustering

ClusteringTrack RecoVertexing ...

Ecal Raw Hits

Charge DepositionSimulation

Sim Tracker Hits

HPSAPV25:Shaper signal

Sampling … Timeevo.

Basic ReadoutChip

Trigger:Flash Trigger

or 1-bit

If all trigger cuts are passedsend a trigger signal

Apply trigger latencySingle trigger within 16 ns window

?ADC

Output: LCIO

Extraction of t0Single peakMulti peak

LCIO...?

Global Clock


To do ...

What still needs to be done

APV25

ADC conversion of APV25 output streamAdd noise and shaper signal jitter?What is considered a hit?Implement multi-peak algorithm to extract t0Adapt tracking to use the time evolved signal

Hit and cluster reconstruction

Incorporate timing information in clustering and stereo hit making

TrackingThe main priority here is to improve the speed of the tracking algorithm

Remove the outer hits of the inner region since they cannot make tracksMake the tracking algorithm concurrentOptimize seeding strategy

Study tracking in a non-uniform magnetic field

What is the structure of the LCIO file that will be stored offline? ECalclusters, Raw Tracker Hits? Stereo Hits ...


Documents

Heavy Photon Search Tracking Software Update · 2011-10-18 · Heavy Photon Search Tracking Software Update Omar Moreno Santa Cruz Institute for Particle Physics University of California,