G. Pugliese Phase II Upgrade of the CMS Muon System

G. M. I. Pugliese (Cern, INFN and Politecnico of Bari)

on behalf of the CMS Muon group

Second Iran and Turkey Joint Conference on LHC Physics, Tehran, 23-26 October 2017

G. Pugliese

Current CMS Muon SystemEndcap region:Cathode Strips Chambers & RPC4 planar stations (disks) interleaved withthe steel return yoke plates

The CMS Muon system was designed to providemuon identification, excellent triggering, timingand momentum measurements at LHC nominalluminosity of 1034 cm-2 s-1

Muon acceptance: |η| < 2.4

Barrel region:Drift Tube & Resistive Plate Chamber4 coaxial stations interleaved with the steel return yokeplates, grouped into 5 wheels around the beam line

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Three gas detector technologies

RPCs

Sensitive layers area: 18.000 m2Number of channels: 172000Number of hits: 32 Spatial resolution ≈ 100 µmTime resolution 2 ns

Sensitive layers area: 7.000 m2Number of channels: 477000Number of hits: 24Spatial resolution≈50 ÷140 µmTime resolution ≈ 3 ns

Sensitive layers area: 3.200 m2Number of channels: 123000Number of hits: 6 (4 )Spatial resolution ≈ 1 cmTime resolution ≈ 1.5 ns

DTs

CSCs

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Muon performance at LHC (run2)

CSC station spatial resolution

CSC Trigger Primitive efficiency

Barrel Trigger Primitive efficiencyExcellent muon performance duringup to a luminosity of 1.6 10 34 cm-2s-1

DT Time resolution for muon reconstructed

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Expected HL-LHC & CMS conditions

LHC HL-LHCultimate HL-LHC

Collider instantaneous luminosity (cm–2s–1)

1034 5×1034 7.5×1034

pileup collisions 30 150 200integrated luminosity (fb–1) 500 3000 4000

CMS L1 trigger (kHz) 100 500 750L1 trigger latency (μs) 3.6 12.5

The challenging conditions require the muon system

upgrade

We are here 5

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Muon Upgrade Concept

1. Upgrades of the existing muon detectors • Confirm muon system performance at HL-LHC conditions• Upgrade electronics to ensure longevity, cope with trigger and

readout requirements

2. Enhance the system in the forwardregion 1.6 < |η| < 2.4• Gas Electron Multiplier (GEM)

in the 1st and 2nd station• Improved RPC in the 3rd and 4th

station3. Extension of muon coverage to the

very forward region |η| < 2.8• GEM in ME0

iRPCGEM 6

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Muon system longevity

DT and RPC

CSC & RPC

Accelerated longevity tests: detectors and electronics are being exposed to irradiation at the Gamma Irradiation Facility at CERN

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Detector Longevity (1)

Gas Gain decrease for MB1/±2(“hottest” chamber)

Tests of full-size DT chamber and a small-sizeprototype at GIF++ are ongoing. Expected integratedcharge at HL-LHC: 20 mC/cm

first results (2.5 mC/cm) show a gas gaindecrease as a function of the integratedluminosity

single-layer efficiency is expected to drop to43% for an integrated charge equivalent to3000fb-1 in the most exposed station(corresponding to 15% of DT system)

Effect on muon reconstruction efficiency (dueto the DT system redundancy): ~90% efficiency

Mitigation measures are being implemented:no gas recirculation, adjusting HV, lower-threshold discriminators for new electronics,shielding for outer chambers

– perfect system– if nothing is done – with HV adjustments

CMS Preliminary

CMS Preliminary

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Detector Longevity (2)Test of full-size ME1/1 and ME2/1 chambers atGIF++. Expected charge at HL-LHC: 110 mC/cmand 80 mC/cm

Performance remains stable after 3×(HL-LHC)integrated charge

Ongoing irradiation test with 2 % of CF4 (frompresent 10%)

HL-LHC

Tests of full-size RE2/2 and RE4/2 chambers fromdifferent production periods are ongoing at GIF++.Expected charge at HL-LHC: 280 mC/cm2

So far (260 mC/cm2), no signs of aging

need ~1 year more to reach 3×(HL-LHC)

CMS Preliminary

CMS Preliminary

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Electronics Upgrade

DT and RPC

CSC & RPC

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DT Electronics upgrade motivationOn-detector electronics: readout and trigger electronics is located in board“minicrate’’, attached to each DT chamber.

Motivation for Upgrade:

Can not cope with L1 specification HL-LHC: limited to L1 rate of 300 kHz

Radiation tolerance: designed for TIDscorresponding to 500 fb-1

Difficult maintenance: attached to eachDT chamber, inside the steel yoke

Not robust against single-hit inefficiencyTrigger primitives are generated locally.Aging of DTs could lead to significantlocal trigger inefficiency

The electronics will be replacedduring Long Shutdown3

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PresenterPresentation Noteswhich perform digitization, trigger primitive generation, slow control, readout pipeline

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DT Electronics upgrade designNew on-detector electronics: Same analog front-end New Minicrate2

Only time digitization (using rad-hard, flash-basedFPGAs) and slow control

CERN GBT links Improves time resolution from 12.5 ns to ≈ 1 ns One type of board (from 6 types) Lower power consumption (60 % of current Minicrate)

Back-end electronics: Located in service cavern New ATCA boards with powerful FPGAs will generate the trigger primitives and

transmit DT data Sampling time resolution from 12.5 ns to 1 ns Dead-time after hit from 400 ns to 80 ns Include RPC/HO information

New trigger primitive algorithms will be able to use information from allchambers able to mitigate single-hit inefficiency and determine bending moreprecisely. 12

PresenterPresentation NotesTrigger primitives generation in new back-end Full streaming of chamber hits in order to move trigger primitive logic to back end-electronics

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CSC Electronics Upgrade motivation

On-chamber and off-chamber electronics will be replaced in order to handle theCMS trigger requirements at HL-HC

It will be replaced duringLong Shutdown 2 & 3Designs based on ME1/1boards installed in LS1

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RPC Link System Upgrade: motivation

Off-detector electronics: consists of Link andControl Boards ("Link System") and is locatedin crates on the balconies around CMS

FEBFEB

FEB

Resistive Plate ChambersUp to 6 layers of detectors.480 chambers in Barrel, 648 in Endcap

FEBFEB

FEB

Control & diagnosticLink BoardLink BoardLink Board

Synchronization Unit & LMUX

Optic Links 90 m @ 1.6 GHz

492 fibers

Cu-cables

1376 Link Boardsin 108 Crates,

Steered by 216 Control Boards

Control Board

Motivation for Upgrade: Operation issues:

the CBs are connected into token ringconfiguration. If one CB fails then theentire ring does not work, leading to aloss of 6 % of the system

Maintenance: it is a custom electronics. Notenough LB/CB spares available (rely on oldASICs)

Low speed data transmission links (1.6Gbps)

Electronics will be replaced during Long Shutdown3 14

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RPC New Link System Design

New LB and CB will be produced by the IPM groupin Tehran.

Back compatible with the present Link Boxes.Signal cables from the chambers will be notremoved.

Based on Xilinx 7 FPGAs (replace ASICs)

RPC signal sampling frequency will be 640 MHzclock from the present 40 MHz clock

Time resolution will be improved: from 25ns to 1.6 ns. Impact on muon trigger andoffline reconstruction.

More robust: Ethernet switch board replaces tokenring

Higher bandwidth (10 Gbps output) See B. Boghrati’s talk on Link System Upgrade overview 15

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System enhancement in the forward region

iRPCGEM

VERY CHALLENGING REGION, both for trigger and offline reconstruction

high rates due to n/γ-induced background, punchthrough and muons

small bending of muons by magnetic field

small number of hits per muon in forward direction (present system); smaller than in the barrel

UPGRADE: augment the system by adding new detectors in the forward direction:

GEM: ME0, GE1/1 and GE2/1 iRPC: RE3/1 and RE4/1

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Overview of the GEM upgrades

Based on triple-GEM technology:High spatial resolution O(100 µm)Rate capability to MHz/cm2High gas gain 104Gas mixture: Ar (70%) & CO2 (30%) 17

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Improved RPC in RE3/1 and RE4/1

RE3/1 RE4/1

The 3th and 4th stations will be equipped with a new generation of RPC withimproved performance (iRPC): each chamber spans 20° in φ for a total of 72chambers (18 ch/disk)

Performance iRPC:• Handle up to 2 kHz/cm2 (3 x HL-LHC)• Spatial resolution:in φ ~ 5 mm in η ~ 2 cm (from ~17 cm) by reading both sides of strips (2D readout) 18

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Improved RPC design

Design of iRPC: Reduced gas gap from 2 mm to 1.4 mm Reduced electrode resistivity: about 1010 Ωcm New generation of Front-End Board electronics

to reduce the charge threshold from 150 fC to50 fC

@ 1.9 kHz/cm2

New readout schema reading both end of strip New FEB will include a TDC (50 -100 ps

resolution) to define the muon position alongthe strip with a spatial resolution of 2 cm

HL-LHC conditions has been satisfied

CMS Preliminary

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L1 muon trigger performance

L1 muon trigger efficiency benefits from theaddition of GEM and iRPC in the high ηregion.

Combine information from GEM-CSC instations 1 and 2 will give much moreaccurate measurement of pT and, hence,the L1 muon trigger rate drops (gain is aslarge as a factor of 10)

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Muon reconstruction

The high pileup conditions expectedat HL-LHC will reduce the muonreconstruction efficiency

Adding iRPC, GE2/1, and ME0 stations:

substantially increases efficiency ofmuon reconstruction in the range 1.6< η < 2.4

makes possible to reconstruct muonsin the extended range 2.4 < η < 2.8

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New Physics opportunities

Factor of 4-5 improvement

The upgrade of the RPC Link System will allow us to explore the RPC intrinsic timeresolution ≈ 1.5 ns (from the present 25 ns readout window).

A new RPC trigger (RPC-HSCP) will be devoted to identify very slow “Heavy StableCharged Particle (HSCP)”

The RPC HSCP trigger capabilities will beextended up to β ∼ 0.2.

L1 Trigger efficiency as a function of an HSCP velocity β for the ’regular’ muon trigger (in blue) and a dedicated HSCP trigger (red points)

It will be based on TOF technic to identifythe slow particle and to measure the β

The efficiency of the present muon triggerdrops for particle with β < 0.6

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PresenterPresentation Notesby measuring their time of flight to each RPC station

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ConclusionsThe design of the CMS Muon upgrade project iswell advanced. The “Phase-2 Muon UpgradeTDR” is ready.

It includes:1. Assess longevity of detectors to withstand

at HL-LHC conditions

2. Electronics replacement to cope withtrigger and readout requirements and toenhance muon system capabilities

3. Muon system enhancement in the most forward region. Two newdetectors (iRPCs and GEMs) will be installed to improve trigger andmuon reconstruction and open to new physics

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Thanks

H → ZZ → μμμμ

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Backup slides

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New Physics opportunities (2)

ME0 extends the muon system coverage from 2.4 to 2.8many physics analyses will also benefit from the extended muon acceptance search for lepton-flavor violating decays τ3μ: signal acceptance doubles search for BSM physics with two same-sign leptons and MET: suppression of the

main WZ background with one lost muon in forward direction improves by factor of two

Higgs studies in HZZ4μ decays: signal acceptance improves by 17%

With ME0, signal acceptance is doubled

D/Bτ, τ3μ Background WZμ±μ±

With ME0, WZ bkg reduced by nearly factor of two

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New physics opportunities (2)GEM+CSC tandems in stations 1 and 2

much improved muon trigger rates (by factor of ~10): impact on many analyses– allow one to trigger on displaced muons (no IP constraint) in the forward direction – boost cross section sensitivity to production of long-lived exotic particles decaying

into muons O(1) m away from interaction point by a factor of 3

Trigger Cross section limit vs lifetime

factor of 50 improvementfactor of 3 improvement

Lifetime (cτ) of a particle with m=200 GeV

Expe

cted

XS

limit

in a

bsen

ce o

f sig

nal

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CSC Electronics Upgrade

On chamber Electronics:Cathode Front End Board (CFEB) will be updatewith Digital CFEB. DCFEBv2 very similar to DCFEB (installed in

2013-14 in ME1/1 ring) Relies on two custom ASICsAnode local charged Track (ALCTs) designs based on ALCT mezzanine boards installed

in ME1/1 and ME4/2 during LS1 Based on spartan-6 FPGALow Voltage Distributor Boards will be update toprovide power to new DCFEBs and ALCTs

Off chamber Electronics:Trigger Motherboard (TMB): replaced with Optical TMB in order to receiveDCFEB trigger data; increased algorithmic powerData Mother Boards (DMB): replaced with Optical DMBs based on new generation Artix-7 FPGAs new optical fibers at 6.4 Gb/s 28

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Technologies developed for GE1/1Modules for GE2/1 and ME0 have very similar designs to GE1/1 modules

Description of design and R&D in CERN-LHCC-2015-012

Almost a decade optimizing performance and reliability About 30 large GE1/1 prototypes have undergone systematic

testing 10 test chambers for slice test installed in CMS in 2017

GE1/1 TDR approved in 2015 29

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Muon Reconstruction

Local reconstructionPerformed within single chamber

Tracker track reconstruction

Standalone Muon reconstruction

Performed using DT/CSC segments & RPC hits

Global muon reconstruction (out side –in): a standalone muon is propagated to match a trackertrack. If matching is positive a global fitting is performed.Tracker Muon (inside – outside): a tracker track is propagated to muon system and qualified asmuon if matching with standalone or one segment.

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RPC

Barrel Station

Forward Station

Barrel and Endcap chambers have different geometries and have been built indifferent sites with different construction techniques.

Gaps: in Italy for the Barrel and Korea for Endcap Chambers: Bulgaria and Italy for Barrel and China, Pakistan and Cern for

endcap.

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Test facilities: GIF++ (CERN) 137Cs source photons: 662 keV intensity: 13.5 TBq filters allow one to moderate the intensity large bunker allows for testing full-size chambers study performance in presence of the HL-LHC like background rates conduct accelerated detector aging tests

9 October 2017 – LHCC Review kick-off meeting,

CERN 32

GIF++ radiation intensity map

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Test facilities: CHARM (CERN)

9 October 2017 – LHCC Review kick-off meeting,

CERN 33

CERN High-energy AcceleRator Mixed field (CHARM) facility: mixture of neutrons, photons, electrons/positrons, and charged hadrons overall environment is very similar to what one sees at LHC / HL-LHC achieved by colliding 24 GeV protons with copper target used extensively for testing electronics (and some detectors as well) NB: neutron spectrum spreads from 100 MeV down to thermal minimum

Neutrons at LHC CHARM

neutrons

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Eco-friendlier gas New regulation: in 2014, the European Commission adopted a new regulation limiting the

total amount of important fluorinated greenhouse gases (F-gases) that can be sold in the EU from 2015 onward and phasing them down in steps to one-fifth of 2014 sales in 2030

CSC and RPC F-gas footprint 1700 m3/hr of CO2 equivalent (yearly, ≈12K cars)

CSCs use 10% CF4: 274 m3/hr of CO2 equivalent RPCs use 95.2% C2H2F4 and 0.3% SF6: 1440 m3/hr of CO2 equivalent

F-gases used by CSCs and RPCs prevent aging and ensure reliable operation

Solutions new eco-friendlier gas options RPCs explore operation with CF3I, C3H2F4 (GWP

≈ 0, 4) F-gas consumption reduction CSCs explore operation with 2% CF4 Other measures being explored: improved recuperation (currently, CSCs only and ~40% efficient) add an “abatement” system to burn off F-gases on the exhaust into harmless

compounds 34

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RPCROC front end boardFront-end board baseline based on PETIROC:- Fast pre-amp and disc. 350 nm SiGe- TSCM 130 nm CMOS under study PETIROC Specifications- Minimum Qth = 50 fC -> 10 fC- Time jitter: 20 ps @ 300 fC -> 100 ps- Bandwidth: 10 GHz -> 2 GHz- Time over Threshold facility- 32 -> 64 channels per chip

Expected dose in the electronic position: 1 kRadTechnology used in PETIROC has been tested up tovalue above 2 kRadTests have been planned reach about 10 kRadon the present PETIROC

GND

coax coaxFEadapt. board adapt. board

strip

PCB layout: • single sided PCB with strips• Readout from both strip’s sides• Strip-FEB connection with coax. cable• Adaptor board for impedance matching

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Phase II Upgrade of the CMS Muon SystemCurrent CMS Muon SystemThree gas detector technologiesMuon performance at LHC (run2)Expected HL-LHC & CMS conditionsMuon Upgrade ConceptMuon system longevityDetector Longevity (1)Detector Longevity (2)Electronics Upgrade DT Electronics upgrade motivationDT Electronics upgrade designCSC Electronics Upgrade motivationRPC Link System Upgrade: motivationRPC New Link System DesignSystem enhancement in the forward region Overview of the GEM upgradesImproved RPC in RE3/1 and RE4/1Improved RPC designL1 muon trigger performanceMuon reconstructionNew Physics opportunities ConclusionsThanksBackup slidesNew Physics opportunities (2)New physics opportunities (2)CSC Electronics UpgradeTechnologies developed for GE1/1Muon ReconstructionRPCTest facilities: GIF++ (CERN)Test facilities: CHARM (CERN)Eco-friendlier gasSlide Number 35