Upgrade of the ATLAS Muon Spectrometer for Operation at the … · 2016-02-25 · The ATLAS 1stlevel muon trigger in LHC run I 0 Big wheel m 0 5 10 15 5 10 y [m] z [m] Measure of

Upgrade of the ATLAS Muon Spectrometer forOperation at the HL-LHC

Oliver Kortner

on behalf of the ATLAS muon collaboration

Max-Planck-Institut fur Physik, Munich

February 18, Vienna Conference on Instrumentation 2016

The roadmap to High-Luminosity LHC

Plan to increase the LHC luminosity by an order of magnitude.

Increase of the particle fluxes/rates by an order of magnitude from the

LHC to the HL-LHC requires a major detector upgrade.

Muon spectrometer upgrade in two steps during long shut downs 2 and 3.

22

2

Physics motivation for the HL-LHC

Study of the electroweak symmetry breaking

Precision measurements of Higgs boson couplings and spin-CP quantum

numbers as a probe for physics beyond the Standard Model.

Search for deviations from the Standard Model and for rare and invisible

Higgs decays.

3-4 times higher sensitivity in direct searches for additional Higgs

bosons than the LHC.

Search for sypersymmetric particles

Much larger are area of SUSY parameter space accessible at the

HL-LHC than the LHC.

If SUSY is found at the LHC, the HL-LHC is needed to study its exact

nature.

Model independent search for heavy resonances (di-jet, di-photon ``, tt)

4 times higher sensitivity to heavy resonances at the HL-LC than the

LHC.

Search for dark matter

2 times higher sensitivity in direct dark matter searches at the HL-LHC

than the LHC.

33

3

The ATLAS muon spectrometer at the LHC

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Barrel magnet coil

CSC

trigger chambers

TGC RPC trigger chambers

Precision MDT muon chambersµ

µ

z [m]2010 1550

5

0

10

y [m]

magnet

End−cap

CSC

Fast trigger chambers: RPC, TGC

(<10 ns time resolution, moderate spatial resolution ∼mm-cm ).

High-resolution tracking detectors: CSC, MDT (40 µm spatial resolution ).

Optical alignment system with 50 µm resolution.

Pseudorapidity coverage: |η| <2.7.

44

4

The ATLAS 1st level muon trigger in LHC run I

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Big

wheel

µ

10 1550

5

0

10

y [m]

z [m]

Measure of momentum

µ

Measure of momentum

p

wheel

Small

ATLAS uses as 3-level trigger system.

The level-1 high pT muon trigger built out of a coincindence of three

RPCs in the barrel or three TGCs in the big end-cap wheel.

Muon momentum estimate from the size of the deviation of hits from an

infinite momentum track from the interaction point.

55

5

Sources of 1st level muon triggers in LHC run I

Low p muonsT

L1 10 GeV muon trigger

matched to reconstructed muon

Tmatched to p >10 GeV muon

Fakes

BarrelEnd−cap C End−cap A

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Big

wheel

Fake high−p

muon triggerT

µ

10 1550

5

0

10

y [m]

z [m]

Measure of momentum

µ

p

wheel

Small

Muon trigger rate dominated by fake triggers in the end-caps caused by

charged particle not emerging from the interaction point.

Real muon triggers contaminated with sub-pT-threshold muon due to the

reduced momentum resolution caused by the moderate spatial resolution

of the trigger chambers.

66

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The ATLAS muon spectrometer at the HL-LHC

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small wheel

Newtagger

High−η

TGCs with

higher

resolution

sMDT

chambers

Barrel magnet coil



µ

z [m]2010 1550

5

0

10

y [m]

trigger chambers

sTGCs MicroMegas

RPCs

Thin−gapmagnet

End−cap

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New small wheel with high-resolution trigger chambers to reject fake

muon triggers and improve momentum resolution at trigger level.

New TGCs with higher resolution to cope with background at |η| ∼ 2.7.

New thin-gap RPCs to close acceptance gaps of the barrel muon trigger.

New sMDT chambers to free space for new RPCs.

High-η tagger to identify muons up to |η| = 4.0.

+ New on- and off-chamber electronics for new trigger architechture.

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New small end-cap wheels

Extrapolated hit rates

Distance from beam line [cm]100 150 200 250 300 350 400 450

]2C

ount

ing

rate

[kH

z/cm

0

1

2

3

4

5

6

7

8

CSC

MDT

Ratecapability limits

ATLAS

-2cm-1 s34L=7x10

The ATLAS muon spectrometer is operated

in a large background of neutrons and γ rays.

At the HL-LHC the background rates in the

present small wheels would exceed the rate

capabilities of the CSC and MDT chambers.

⇒ New small wheels with chambers with

increased high-rate capability:

Small strip TGCs (sTGCs) for triggering,MicroMegas for triggering and precisiontracking.

Installation 2019-2020 during LS2.

sTGC schematic Micromegas schematic (see F. Kuger’s talk)

Strips used for improvedmomentum measurement at trigger level

1.8 mm

3.2 mm

Pads used in trigger coincidence

88

8

Mode of safe RPC operation at the HL-LHC

RPC rate estimates [Hz/cm2] for HL-LHC

Rate above limit of safe operation

η=1η=0η=−1

φ

Average

Longevity of the RPCs depends

on the charge accumulated during

ten years of HL-LHC operations.

According to irradiation tests in

the GIF limit for safe operation of

present RPCs: 100 Hz/cm2.

Limit exceeded by up to a

factor of 2 at |η| &0.7!

Plan to reduce operating voltage to keep the gap currents/accumulated

charge within the safety margin.

⇒ Reduced gas gain/pulse heights lead to inefficiencies as the preamplifiers

cannot be replaced by more sensitive ones.

99

9

Barrel muon trigger coverage

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Big

wheel10 1550

5

0

10

y [m]

z [m]p

η=0 η=0.4 η=0.75 η=1.0

wheel

Smallη

−1 −0.5 0 0.5 1

Eff

icie

ncy

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Efficiency drop due to non−instrumented detector regions

L1_MU10 (2 stations)

L1_MU11 (3 stations)

|

ATLASPreliminaryData 2011η |<1.05muon

The high pT muon trigger acceptance is limited to ≈ 72% due to

non-instrumented regions of the muon spectrometer.

η =0: Non-instrumented region of the spectrometer to provide space for

services of the inner detector and the calorimeters.

η =0.4, 0.75, 1.0: Non-instrumented region due to toroid and rib

structures.

101010

Reinforcement of the barrel muon trigger

Installation of additional RPCs with increased high-ratecapability in the inner barrel layer to recuperate thereduced muon trigger efficieny.

Replacement of MDT chambers with sMDT chambers insmall barrel sectors to free space for RPCs.

Pilot project: BIS-7/8.

1st

leve

l e

ffic

ien

cy w

rt o

fflin

e [

%]

100

80

60

40

20

00−0.5 0.5−1 1

η

Installation of trigger chambers in BI

closes acceptance gaps and recuperates

RPC inefficiencies!

111111

Barrel upgrade pilot project

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TGCs with

higher

resolution

sMDT

chambers

Barrel magnet coil



10 1550

5

0

10

y [m]

sTGCs MicroMegas

RPCs

Thin−gap

z [m]

µ

magnet

End−cap

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Pilot project

Installation of 16 new muon stations inside the barrel toroid coils at the

boundary between barrel and end caps during LS2 (2019-2020).

To improve the selectivity of the muon trigger in the barrel end-captransition region;To increase of high-rate capability.

Technology: Integrated sMDT-RPC chambers.

sMDT chambers for precision tracking.New thin-gap resistive plate chambers (RPC) for triggering.

121212

Thin-gap RPCs

Electrode

ElectrodeElectrode

ElectrodeElectrode

Electrode

1 mm gas gap

1 mm gas gap

1 mm gas gap

52.4

Very challenging space constraints:

∼5 cm space for a triplet of 1 mm gas

gaps.

New amplifier

in SiGe

technology

in silicon technologyImproved amplifier

ATLAS preamplifier

A new highly sensitive low-noise

preamplifier in SiGe technology allows

the efficient operation at 4 times

smaller gas gain than with the current

ATLAS preamplifier.

⇒ >4 times greater high-rate

capability, which is substantially

more than required.

131313

sMDT chambers

BIS−7

BIS−8

RPC triplet

sMDT chamber

Characteristics of sMDT chambers

Monitored drift-tube chambers with 15 mm

diameter tubes instead of 30 mm diameter

tubes as currently in ATLAS.

⇒ 10 times greater high-rate capability than

present ATLAS chambers.

Unprecedented wire positioning accuracy of 5 µm

(4 times higher accuracy than in present MDT chambers)

Distance of wire from nominal position [mm]0.04− 0.02− 0 0.02 0.04

0

20

40

60

80

100

120

140

160

180

= (4.8±0.2) µmσ

(RMS: 5.5 µm)

Further details: H. Kroha’s presentation.

141414

ATLAS trigger scheme for HL-LHC

New trigger scheme:

Only two trigger levels: level 0 (L0) and high-level trigger (HLT).L0 rate: 1 MHz. L0 latency: 6-10 µs.

⇒ In this scheme all muon chambers have to send their data off to USA15

continuously for further processing.

⇒ New on-chamber (MDT ASD and TDC chips, multiplexers ) and off-chamber

electronics (trigger logic, Felix ) needed!

Multiplexer

Multiplexer

Multiplexer

TDCs

Felixto ethernet switch/ROD

read out data after L0 trigger

Central trigger processor

On−detector electronics

RPCs

TGCs

MDTs

ASDs

ASDs

ASDs

Off−detector electronics

GBT fibres Trigger logic

L0 muon trigger L0 trigger

151515

The ATLAS 1st level muon trigger at the HL-LHC

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small wheel

New

Regions of interest

Barrel magnet coil



µ

z [m]2010 1550

5

0

10

y [m]

trigger chambers

RPCs

Thin−gapmagnet

End−cap

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��Precision track segment

Processing step Time after pp collision

1. Continuous stream of muon hit data to off-detector trigger logic.

2. Pre-muon-trigger based on coincidences of trigger-chamber hits in theinner, middle, and outer layers.

3. Use of precision NSW and MDT hits for the refinement of muon pTmeasurement in regions of interest defined by the trigger chambers.

4. Final muon trigger based on refined momentum measurement.

1 µs

2 µs

3 µs

6 µs

161616

Reason for integrating MDT data in the 1st trigger level

Inclusive muon cross section Muon first-level trigger efficiency

c →µ

b →µ

t →µ

W →µ

Z/γ* →µ

π/K →µ

Shower muons Punch−through

|ηµ| < 2.7

10−6

10

10

−5

−5

10

10

−4

−4

10

10

−3

−3

10

10

−2

−2

10

10

1−1

−1

1 10

10 100

dσ/d

p T

T

(µbarn

/GeV

)

pT (GeV/c)µ

0 10 30 40 50µ

dn /d

p (

kH

z/G

eV

) at L=

10 /(

cm

²s)

34

ATLAS Muon TDR

20

Fake

triggerslevel 1

[GeV]T

p

8 10 12 14 16 18 20 22 24 26

Eff

icie

ncy

0

0.2

0.4

0.6

0.8

1

without MDTs

with MDTs

1st level 20 GeV muon trigger

The interesting electroweak physics is mainly at pT > 20 GeV.

The inclusive muon cross section is very steeply rising with decreasing pT.

Present 1st level 20 GeV muon trigger accepts a lot of muons with10 GeV< pT <20 GeV due limited spatial resolution of trigger chambers.

⇒ Sharpening of trigger turn-on curve by the use of precision muondrift-tube (MDT) chambers to limit the trigger rate.

171717

MDT trigger: fast track reconstruction algorithm

Tube in ROI

Drift radius

Hit positions (two−fold ambiguity)

Histogram with

projected hit

positions

Muon Restrict pattern recognition to the ROI.

Incident angle is known from trigger chambers(with 3 mrad resolution).

Project hits into the plane perpendicular to thetrigger chamber track and fill the into ahistogram.

Correct hit pattern leads to the highest peak inthe histogram (ideally with 6 hits).

Final track: straight line fitted to the correct hitpattern.

In practice there are less than 6 hits due to

the dead area introduced by the tube

walls,

masking of muon hits by δ and Compton

electrons.

181818

First results of timing study

Demonstrator hardware

Plan to use a microprocessor for

fast floating point operations.

Demonstrator hardware: Xilinx

Evaluation Kit ZC806 (SoC

Zynq-7045 with 1 GHz ARM

Cortex-A9).

Algorithm programmed in ARM

assembler.

Test under realistic background conditions

Test with experimental data

recorded in CERN’s gamma

irradiation facility.

Processing time < 3.5 µs even at

20% occupancy!

191919

Single-muon trigger rates at the HL-LHC

Single-muon trigger rates

(estimated from run-I data)

threshold [GeV]T

p5 10 15 20 25 30 35 40 45

Muo

n 1s

t lev

el tr

igge

r rat

e [k

Hz]

1

10

210

310

-1s-2cm3410⋅=14 TeV, L=7sRun-I muon trigger•Muon trigger with NSW•Muon trigger with NSW+MDTs•

Unacceptably high rate of run-I

20 GeV muon trigger: ∼150 kHz.

Removal of fake triggers by

including the NSW in the trigger

coincidence.

⇒ Rate reduced to ∼ 70 kHz.

Sharpening of the turn-on curve

with MDT data reduces trigger

rate to ∼ 18 kHz.

⇒ ∼ 130 kHz free for other triggers!

202020

Summary

LHC and HL-LHC will dominate accelerator particle physics for the next

two decades.

Upgrade of the ATLAS detector to fully exploit the HL-LHC’s physics

potential.

The upgrade of the muon spectrometer driven by the need for a highlyefficient and selective single muon trigger:

New small wheel to reject fake muon trigger.New RPCs in the inner barrel to maximize acceptance.Inclusion of MDT data in the 1st level muon trigger to maximizeselectivity.

212121

References

The ATLAS Muon Collaboration, ATLAS Muon Spectrometer TechnicalDesign Report, CERN/LHCC 97-22.The ATLAS Collaboration, The ATLAS Experiment at the CERN LargeHadron Collider, JINST 3 (2008).The ATLAS Muon Collaboration, ATLAS New Small Wheel Technical DesignReport, CERN-LHCC-2013-006.The ATLAS Collaboration, ATLAS Phase-II Upgrade Scoping Document,CERN-LHCC-2015-020.

222222

Supplementary material

232323

Higgs physics at the HL-LHC

Precision measurements of Higgs boson couplings and spin-CP quantum numbersas a probe for physics beyond the Standard Model.

[GeV]im

−110 1 10210

iy

−310

−210

−110

1Z

W

t

b

τ

µ

ATLAS Simulation Preliminary

= 14 TeVs

νlνl→WW*→4l, h→ZZ*→, hγγ→h

γZ→, hµµ→bb, h→, hττ→h

]µκ, τκ, bκ, tκ, Wκ, Zκ[

=0i,uBR

−1dt = 300 fbL∫−1dt = 3000 fbL∫

[GeV]im

−110 1 10 210

Ra

tio

to

SM

0.80.9

11.11.2

LHC

HL−LHC

Measurement of deviations of Higgs couplings fromSM values with per-cent precision at the HL-LHC.

Search for deviations from SM and for rare andinvisible Higgs decays.

Evidence for Higgs boson self-coupling possible atthe HL-LHC.

3-4 times higher sensitivity in directsearches for additional Higgs bosonsat the HL-LHC than the LHC.

[GeV]Hm

200 300 400 500 600 700 800 900 1000

4l)

[fb]

→Z

Z→

BR

(H×σ

210

110

1

10

210

4l)→BR(H×SM

σ

Expected CLs

σ1

σ2

1 Ldt = 300 fb∫Expected

Preliminary, SimulationATLAS

=14 TeVs, 1

L dt = 3000 fb∫gluonfusion

LHC

HL−LHC

242424

Supersymmetric and other new particles at the HL-LHCSearch for supersymmetric particles

HL−LHC

LHC

Run I

Much larger area of the SUSY parameterspace accessible at the HL-LHC than atthe LHC.

Sensitivity to 1.5 times larger neutralino andchargino masses in WZ-mediated SUSY atthe HL-LHC than the LHC.

If SUSY is found at the LHC, the HL-LHCneeded to study its exact nature.

Model independent search for heavy resonances (di-jet, di-photon ``, tt)

LHC

HL−LHC

Mass [TeV]

Run I

Search performed in several final states, e.g.di-jet, di-photon, di-lepton, tt.

Di-jet resonances predicted by severaltheories, e.g. excited quarks, quantum blackholes.

4 times higher sensitivity to di-jet resonancesat the HL-LHC than at the LHC.

252525

Dark matter at the HL-LHC

Search for dark matter in Higgs boson decays

Signature of Higgs boson decays into darkmatter: H → invisible.

Direct search in vector boson fusion and W/Zassociated Higgs boson production.

95% confidence upper limits on BR(H → inv.)Run I LHC HL-LHC0.49 0.22 0.13

Indirect search via precision measurement ofHiggs boson couplings.

[GeV]χm1 10

2103

10

]2

[cm

Nχ

σ

5710

5510

5310

5110

4910

4710

4510

4310

4110

3910

DAMA/LIBRA (99.7% CL)CRESST (95% CL)CDMS (95% CL)CoGeNT (90% CL)XENON10 (90% CL)XENON100 (90% CL)SuperCDMS (90% CL)LUX (95% CL)

Scalar WIMPMajorana WIMP

Vector WIMP

ATLAS

Preliminary

Simulation

Higgs portal model:

ATLAS (95% CL) in

1dt = 3000 fbL∫ = 14 TeV, s

,νlνl→WW*→4l, h→ZZ*→, hγγ→h

µµ→bb, h→, hττ→, hγZ→h

Search for dark matter production in association

with Standard Model particles

Similar increase in sensitivity from LHC to HL-LHC as above.

q

q

χ

χ

, W/Zγjet,

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Documents

Upgrade of the ATLAS Muon Spectrometer for Operation at the … · 2016-02-25 · The ATLAS 1stlevel muon trigger in LHC run I 0 Big wheel m 0 5 10 15 5 10 y [m] z [m] Measure of