Test of an ATLAS drift tube based Level-1muon trigger

Oliver Kortner, Hubert Kroha, Sebastian Nowak, Robert Richter,Sebastian Ott, Philipp Schwegler

nowak@mpp.mpg.de

Max-Planck-Institut für Physik, Munich

DPG-Tagung

March 25, 2014

The ATLAS Muon Spectrometer

designed for LHCnominal luminosity:

L = 1034 cm−2s−1

HL-LHC luminosity(planned, 2022):L = 7 ∗ 1034 cm−2s−1

Precision tracking chambers1150 Monitored Drift Tube Chambers (MDT)32 Cathode Strip Chambers (CSC)

Level-1 trigger chambers606 Resistive Plate Chambers (RPC)3588 Thin Gap Chambers (TGC)

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The ATLAS MDT chambers

3 or 4drift tube

layers

�

0.05 mm

W−Re wire

r

30 mm

Al tube wall

RO

HV

length: 1−6 m

width: 1 −2 m

Gas mixture: Ar/CO2 (93/7)

3 bar absolute pressure

Max. drift time: ≈ 700 ns

Single tube resolution: 80 µm

Wire positioning accuracy: ≈ 20 µm

Chamber tracking resolution: ≈ 40 µm

SupportFrame

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Performance of the existing L1 muon trigger

Total muon production cross section

pT = 20 GeV

Faketriggers

cross section forpT > 10 GeV: ∼400 nb

cross section forpT > 20 GeV: ∼47 nb

The interesting physics ismainly at pT above ∼ 20 GeV(see W,Z cross section)

The slope of the inclusive pT

spectrum is rising very steeplywith decreasing pT

−→ threshold definition of the L1trigger must be sharp to avoidhigh trigger rates from low pT

muons

ATLAS Level-1 muon trigger efficiency

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Level-1 muon trigger (HL-LHC)

50 kHz trigger rate for trigger chambersAdditional rate reduction to 20-30 kHz by use of 1 mrad precision ofthe track slope measurement by the MDT chambers at level 1

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New trigger implementation based on MDT

RPC 3 The RPC logicidentifies high-pT

candidates

The existingreadout structurewill be preserved

MDTcoord.

TowerMaster

Hit

posi

tion

inRPC3Search path

for MDT hits

MiddleCSM

InnerCSM

OuterCSM

RPC 2

RPC 1

Trigger tower (schematic)

SectorLogic

The existing L1trigger path ispreserved

CTP

Reference point for the search path

Additionalfast read-out

example barrel

Additional fast MDT read-out necessary (existing read-out takes too long)Fast read-out is triggered by RPC/TGC→ Bunch crossing ID and muon incidence angle are knownTrigger latency increases (2.5 µs to 20 µs)

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Demonstrator setup for fast MDT read-out

For first studies with real data a demonstrator setup has been designed

Properties:

Fast read-out is implemented as second TDC (40 MHz clock)→ resolution: 25√

12= 7.22 ns→ 229 µm

Fast read-out and normal read-out are used in parallel

Fast read-out data has to be analyzed offline

Fast read-out deadtime: 2500 ns

MDT chamber Standard read-outFast read-out

USB PC

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Test of new hardware and fast tracking algorithmCERN Gamma Irradiation Facility (GIF) - 2013/2014

Goal: Measurement of efficiency and resolution

Source

Cs137

500 GBq

Filters

Scintillator

Lead

Lead

Scintillator

μ (cosmic)

MDT chamber

Reference chamber

50 cm

MDT chamber used for test6 tube layers, 50 cm length

No muon beam in the GIF→ use cosmic muons

Fast read-out and normal read-out are triggered by scintillators

Angle seed according to reference chamber: 4.7 mrad

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Drift time spectra of new fast read-outData taken at CERN in 2014, no background radiation

HPTDCEntries 104564Mean 225.9RMS 191.6

Drifttime [ns]0 100 200 300 400 500 600 700 800

En

trie

s

0

50

100

150

200

250

300

350

400

HPTDCEntries 104564Mean 225.9RMS 191.6Standard read-out

Fast read-out

Spikes in fast read-out data are caused by 25 ns TDC time resolution

Data is modified with correct trigger time (spikes are smeared out)9 / 14

Resolution and efficiency of new fast read-outData taken at CERN in 2014, no background radiation

Drift radius [mm]0 2 4 6 8 10 12 14 16

Effi

cien

cy

0.8

0.82

0.84

0.86

0.88

0.9

0.92

0.94

0.96

0.98

1

Standard read-out

Fast read-out

Drift radius [mm]0 2 4 6 8 10 12 14

Res

olut

ion

[mm

]

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Standard read-out7.22 ns time resolutionFast read-out

Muontrack

ReferencehitsAnalysis layerAnalysishit

DResolution:

Use 5 out of 6 layers for track fitting

Calculate distance between track and hit

Correct this value with track resolution

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Fast track finding algorithm

Histogram based track pattern recognition

α

bin width

without background with background

Muons incidence angle α is used as seed

Project hits in plane perpendicular to theapproximate track and fill into histogram

Parameter:2 mm bin width of the hit histogramAt least 4 hits to set trigger

The tracks angle is finally reconstructed using linear regression

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First fast track fitting resultsShielded chamber is used as reference (seed angle resolution of 4.7 mrad)

[mrad]ref-mrecm-0.015 -0.01 -0.005 0 0.005 0.01 0.015

0

100

200

300

400

500Entries 6531

Mean -0.0001454

RMS 0.002441

85.9%

14.1%

(90.8%)

No background occupancyPattern recognition efficiency: 93.4%

[mrad]ref-mrecm-0.015 -0.01 -0.005 0 0.005 0.01 0.015

0

50

100

150

200

250

300Entries 4636

Mean -0.0002082

RMS 0.002883

80.3%

19.7%

(89.3%)

10% background occupancyPattern recognition efficiency: 74.3%

Two categories:

Good: |mrec −mref | < 3 mrad (simulated value in brackets)

Poor: |mrec −mref | ≥ 3 mrad12 / 14

Summary and Outlook

Improvement of the ATLAS muon trigger by use of MDT basedLevel-1 trigger

Demonstrator setup with additional fast MDT read-out has beendesigned

Fast read-out shows expected resolution and efficiency

Future developments

Upgrade from prototype to a production version (80 MHz clock,avoiding dead time by use of FIFO)

Implementation of fast tracking algorithm in hardware (FPGA)

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Hardware implementation

MDT_FPGA_R2

Test Setup Board

Actel FPGA

Actel FPGA

Serial configuration of ASDs

L0 Trigger Decoding

L0 Counters

L0 Counter Serial Encoding

Serial TDC data decoding

ENC (L1, ECR, EBR, GR)

Data transfer to MC

L0 Trigger Encoding

L0 Serial Decoding

ASD

ASD

ASD

HPTDC

Hit[23:0]

Serial Interface

MC USB

Windows-PC

Software

Test Setup Adaption

Analysis Extension

3 phys. trigger inputs

USB

40-pin flat cable

MDT chamber

Scintillator module

MDT L0-Trigger Prototype Scheme

Unit / Board

Chip / Circuit

Ready

To be done

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