the cms all silicon tracker simulation maurizio biasini - university and infn perugia, italy
DESCRIPTION
The CMS all silicon tracker simulation Maurizio Biasini - University and INFN Perugia, Italy On behalf of the CMS Collaboration. Pseudorapidity η. R[mm]. TOB=Tracker Outer Barrel. 5%. TIB=Tracker Inner Barrel. TEC=Tracker End-Caps. TID=Tracker Inner Disks. Pixel. Z [mm]. - PowerPoint PPT PresentationTRANSCRIPT
The CMS all silicon tracker simulationMaurizio Biasini - University and INFN Perugia, Italy
On behalf of the CMS Collaboration
TEC=Tracker End-Caps
TOB=Tracker Outer Barrel
TIB=Tracker Inner Barrel
TID=Tracker Inner DisksPixel
Z [mm]
R[m
m]
Pseudorapidity η
Detailed simulation of active and passive volumes (95% of the total number)
The CMS Tracker is made of a Silicon Pixel vertex detector and a Silicon Microstrip Tracker• (100 x 150) m2 pixels• 320 – 500 m thick microstrip sensors• Surface: 200m2 and 1m2
• 10 million Strips and 66 million pixels
Simulation based on Geant4 and CMS OO framework.Geometry description using Detector Description Language (DDL)
5%
The Compact Muon Solenoid
The Compact Muon Solenoid is a general purpose detector designed to study proton proton and lead lead collisions at the LHC.
Silicon Tracker inside the superconducting solenoid for the reconstruction of charged particles, momentum, position and decay verticies.
The CMS All Silicon Tracker
Silicon Microstrip and Pixels
Tracker Inner Barrel Pixel Barrel
The Tracker Simulation
The detector simulation is fundamental in optimizing reconstruction algorithms and in understanding the detector and the first LHC collinding beam data
Description of Geometry
Material Budget
Simulated Detector Response
Validation of Simulation using Cosmics
Charge release in Silicon288 eV/µm, 3.6 eV/pair25000 e- in t=320 µmδ-ray cutE> 30 keV (pixel) 120 keV (strip)Lorentz AnglePixel: 23° (120 µm drift)Strip: 7° (36-61 µm drift)Charge diffusionσ≈√Ldrift
(Pixel: 7 µm, Strip: 2 µm)
Electronics SimulationElectrical chain gain factorConversion of the released charge into 6/8-bits ADC countsStrip: 250 e- = 1 ADC, Pixel: 135 e- = 1 ADCElectrical NoiseGaussian noise is added(Pixel: σD=350 e-, Strip: σD=1200 e-)Noise increase with radiation damage (even at operation temperature T=-20°C): conservative +50%AC couplingsInter-strip coupling: 3%-1% (11%-7%) of the charge fraction assigned to the neighbours strips for TOB-TIB in peak (deconvolution) mode
The electronics pile-up is simulated processing the signals of the preceding 5 and fhe ollowing 3 bunch crossings when simulating the actual bunch crossing (25 ns)Strips: two readout modes, signal shape in deconvolution reduces the pile-up
Each component has been weighted , from the smallest capacitor (mg) to the whole subdetectors (Tons)Agreement at the 5-10% level found between simulation and measured values
SubdetectorActive Volumes
PassiveVolumes
Pixel Barrel (PXB) 768 10201Pixel Forward (PXF) 672 23670PIXEL 1440 33871Inner Tracker (TIB+TID) 3540 56488Outer Barrel (TOB) 5208 145419Outer End-Caps (TEC) 6400 113158Outer Structures 0 346STRIP 15148 315411TRACKER 16588 349283
Tracker Inner Barrel Pixel Forward
The average density is 0.17 g/cm3: a MIP loses 35 MeV/mBarrel region x/X0=0.4: 40% of the photons converts
Comparison with lab measurement
Subsystem Simulation (kg) Laboratory (kg)
Outer End-Caps (TEC) 691.70 702.22Inner Tracker (TIB+TID) 427.2 452Pixel Barrel 2.455 2.598
Ratio Data/Simulation
1.0151.0581.058
Validation of Simulation using Cosmics
First full Tracker commissioning Cosmic Run At Four Tesla CRAFT 08270 M cosmic events selected – 6.5 M with track in Tracker – 3.2M/110K high quality tracks for Strip/PixelsPossibility to check and validate Tracker Simulation
Charge Distribution for Pixel Barrel (left) and Endcap (right)
MC Simulated and measured cluster charge for the Silicon StripTracker corrected for the track incident angle.
Track Reconstruction Efficiency estimated with three methods (Tracker Barrel)
Tracking resolution estimated after alignmentBased on independent track reconstruction for upper and lower part of cosmic track
RMS of Residuals as a function of transverse momentum for impact parameter (left) and transverse momentum (right)
Efficiency as a function of transverse momentum for the Combinatorial Track Finder