Evgeny Kryshen (PNPI)

Mikhail Ryzhinskiy (SPbSPU)

Vladimir Nikulin (PNPI)

Detailed geometry of MUCH detector Detailed geometry of MUCH detector in cbmrootin cbmroot

Outline

Motivation Realistic module design Implementation in cbmroot New segmentation algorithm Occupancy study Visual display for MUCH

Supported from INTAS project 05-103-7484

Currently used geometryCurrently used geometry

Evgeny Kryshen CBM collaboration meeting, 27 February 2008

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• Stations are simulated as simple shapes – 3mm disks filled with argon gas

• Distances between layers and absorbers are not realistic (too small)

• No support structures, no module design

• Segmentation algorithm is not flexible

• Parameter files are huge, full of irrelevant numbers, hardly readable, not flexible

• Geometry and segmentation parameters are described in different files

Module design in ALICEModule design in ALICE

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Schematic layout of GEM moduleSchematic layout of GEM module

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Support structure

PadsPads

FastenersFasteners

SpacerSpacer

PCBPCB Readout electronicsReadout electronics

ArgonArgon

GEM foilsGEM foils

Implementation of module designImplementation of module design

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Front side Back side

Layers:

Modules are arranged in rows on both sides of each layer

There is an overlap of active volumes to avoid dead zones in y direction

Overlap

Support structures and modulesSupport structures and modules

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Support structures:

Each support structure is composed of two parts to assure easy installation around the pipe

Estimated thickness ~ 1.5 cm

Material: carbon plastics (ρ = 0.1 ρC)

Implemented as composite shapes in cbmroot

Y spacersY spacers

Active volumeActive volume

X spacersX spacers Module:

Module size is mostly restricted by the GEM foil production technology (up to 60 x 60 cm with the new machine at CERN)

Active volume: 30 x 30 cm x 0.3 cm, argon

Spacers: 5 cm in y, 0.5 cm in x; material: noryl, implemented as composite shapes

Active volume implemented as TGeoBox for simple modules and as composite shapes for modules with a hole

Detailed geometry: general viewDetailed geometry: general view

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• Two layers at each station

• Three layers at the last trigger station

• Modules are automatically located on the surface of support structures

• Cables, gas tubes, PCBs and front-end electronics are neglected at the moment

Geometry input file: much_detailed.geoGeometry input file: much_detailed.geo

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# General informationMuchCave Zin position [cm] : 105Acceptance tangent min : 0.1Acceptance tangent max : 0.5Number of absorbers : 6Number of stations : 6

# Absorber specificationAbsorber Zin position [cm] : 0 38 76 114 162 215Absorber thickness [cm] : 20 20 20 30 35 100Absorber material : I I I I I I

# Station specificationStation Zcenter [cm] : 29 67 105 151 206 327.5Number of layers : 2 2 2 2 2 3Detector type : 1 1 1 1 1 1Distance between layers [cm]: 7 7 7 7 7 7Support thickness [cm] : 1.5 1.5 1.5 1.5 1.5 1.5Sigma X minimum [cm] : 0.04 0.04 0.04 0.04 0.04 0.04Sigma Y minimum [cm] : 0.04 0.04 0.04 0.04 0.04 0.04Sigma X maximum [cm] : 0.32 0.32 0.32 0.32 0.32 0.32Sigma Y maximum [cm] : 0.32 0.32 0.32 0.32 0.32 0.32Maximum occupancy : 0.05 0.05 0.05 0.05 0.05 0.05

# GEM module specification (type 1)Active volume lx [cm] : 30Active volume ly [cm] : 30Active volume lz [cm] : 0.3Spacer lx [cm] : 0.5Spacer ly [cm] : 5Overlap along y axis [cm] : 2

Class hierarchyClass hierarchy

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CbmMuchGeoSchemeCbmMuchGeoScheme

CbmMuchStationCbmMuchStation

CbmMuchLayerCbmMuchLayer

CbmMuchModuleCbmMuchModule

CbmMuchLayerSideCbmMuchLayerSide

CbmMuchSectorCbmMuchSector

CbmMuchPadCbmMuchPad

Segmentation: algorithmSegmentation: algorithm

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Hit density vs R

Each sector have to satisfy two conditions:

Estimated pad resolution in X and Y must belong to the allowed range, which is specified for each station in the parameter file

Estimated occupancy must be smaller than maximum allowed one

x

y

Segmentation: resultsSegmentation: results

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1 station1 station 3 station3 station 4 station4 station

Sector sizes at the first station are mostly determined by occupancy restrictions

Starting from the 3rd station sector sizes are determined by the required resolution

The smallest pad size in the default setup is ~2.3 mm (resolution ~ 680 μm).

OccupanciesOccupancies

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Occupancy plots are produced by normalizing fired pad radial distributions by all channels radial distributions

Maximum occupancy at the first MUCH station ~ 5%

Occupancy at each station reduces at the outer regions of the station

Occupancies reduce down to 0.01% at the last station

Somewhat higher occupancies are expected for GEM

Track statistics / central eventTrack statistics / central event1 2 3 4 5 6

Total 691 186 65 15.9 5.16 1.853Primary 105 26 8 2.4 1.54 1.251Secondary 586 161 57 13.5 3.62 0.601Protons 114 44 15 2.9 0.51 0.030Pions 179 52 15 2.6 0.39 0.029Electrons 372 76 26 5.9 1.53 0.291Muons 10 7 5 3.6 2.52 1.498Kaons 15 7 3 0.9 0.22 0.005

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Track statistics after the first absorber is dominated by secondary electrons (electromagnetic shower)

Visual Event Display: Layer viewVisual Event Display: Layer viewLayer view functionality:

• Switch between stations and layers

• Info on stations

• Zoom

• Show info on hits, points and sectors

• Switch off sectors, modules, layer sides, hits and points

• Select particles with required PDG code and mothers

• Browse events

• Clickable sectors producing zoomed module views

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Visual Event Display: Module ViewVisual Event Display: Module View

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Zoomed module viewZoomed module view

Fired pads are marked with blue gradient colors reflecting the accumulated chargeFound hits are marked with black markers

Visual Event Display: Cluster ViewVisual Event Display: Cluster View

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Cluster view can be opened by clicking on a cluster in a module frame.It is aimed to help in optimization of hit finding algorithms.

Future plansFuture plans

See the talk by Misha Ryzhinskiy

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