The SLHC and the Challenges of the CMS Upgrade

William FergusonFirst year seminar

March 2nd 2010

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Introduction• Increased luminosity at the SLHC will

expose detectors to much greater particle fluences

• Project is working on the necessary upgrade to CMS for the SLHC

• Work is needed on tracker and trigger systems in particular

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Outline• CMS detector• Super Large Hadron Collider• Tracker - Present tracker

- Tracker upgrade

• Trigger - Present trigger

- Trigger upgrade

• Research plan

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CMS

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• Compact Muon Solenoid• General purpose detector• Interaction point 5, north side of LHC ring

• Aims are to – Study physics at TeV scale– Search for Higgs– New physics beyond SM

• Measures particle energies and trajectories

CMS

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• Composed of concentric cylindrical layers with endcaps either end

SLHC

• SLHC – Super Large Hadron Collider• An order of magnitude increase in beam

luminosity to ~1035 cm-2s-1

• Principle aim - MORE STATISTICS - should improve accuracy of SM parameters

- extend discovery in high mass regions- improve sensitivity to rare processes

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SLHCBut – there is a downside...• Increasing luminosity also increases– Detector occupancy– Trigger rates– Radiation damage

• To benefit, detector performance must remain

• Two notable areas for development are- TRACKER- TRIGGER

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Tracker• Silicon detector system – measures trajectories• Composed of inner pixel layer, and outer

microstrip layer• Endcaps complete the system and provide

coverage up to |η| < 2.5 • Analogue signals are transferred to off-detector

front end drivers (FEDs)• ADC is done off-detector to reduce electronics

and cooling requirements8

Tracker UpgradeLarge luminosity increase introduces problems

• Radiation damage – High fluences of energetic particles damage the

silicon lattice

• Over occupancy– Higher granularity required → more electronics,

more material, more unwanted interactions

• Power and cooling systems

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Trigger• LHC bunch crossing rate is 40 MHz gives 109

interactions per second• Only 102 can be recorded

→ Trigger needs rejection factor of ~107

• Triggering is done in 2 levels…– Level 1 Trigger (L1T)–Higher Level Trigger (HLT)

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Trigger• L1T– Reduces data rate from 109 → 105 Hz– Uses calorimeter and muon system data only– Trigger logic is contained off-detector in ASICs,

FPGAs, PLDs

• HLT– Reduces data rate from 105 → 102 Hz– Uses data from all sub detectors

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Trigger Upgrade• Large luminosity of SLHC

- Increases background- Reduces efficiency

• L1T must maintain 105 Hz rate• Stricter pT and ET cuts are not acceptable

- Put low mass discoveries out of reach- Reduces efficiency

• Proposal is to use TRACKER data in the L1T12

Trigger UpgradeIssues• On detector data reduction required• More power required → more material• Impossible to read out full tracker data quickly

enough - Identify just high pT tracks

- Stacked tracking

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Research plan• Project is study of electronics, detectors

and systems for the CMS upgrade

- Studies of DAQ systems for new Si strip detector - inc beam tests and data analysis

- Testing, analysis and development of new readout ASIC

- Module development for trigger and outer tracker - inc simulations and data analysis

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