Super LHC - SLHC

1. Super LHC - SLHC LHC Detector Upgrade Dan Green Fermilab

2. Outline • Physics Basics • Z’ vs • Rapidity Range • Minbias • Pileup and Jets • Occupancy and Radiation Dose • Tracker Upgrade • Calorimetry • Muons • Trigger and DAQ CERN-TH/2002-078 “Physics Potential and Experimental Challenges of the LHC Luminosity Upgrade” 10x will be challenging!

3. Mass “Reach” and L • The number of Z’ detected in leptonic decays is: • For , if N = 100 is discovery level then M ~ 5.3 TeV is ~ the mass “reach” in 1 year (M=4 -> 5.3 TeV). • The leptons will be sharply limited to low |y| or large angles (“barrel”).

4. Mass Reach vs L VLHC LHC Tevatron In general mass reach is increased by ~ 1.5 TeV for Z’, heavy SUSY squarks or gluinos or extra dimension mass scales. A ~ 20% measurement of the HHH coupling is possible for Higgs masses < 200 GeV. However, to realize these improvements we need to maintain the capabilities of the LHC detectors.

5. Kinematics 5 TeV 1 TeV barrel y barrel Heavy States decay at wide angles. For example Z’ of 1 and 5 TeV decaying into light pairs. Therefore, for these states we will concentrate on wide angle detectors.

6. Inclusive Interactions • The inclusive p-p interaction has an inelastic, non-diffractive cross section ~ 50 mb. • It produces ~ equal numbers of which are distributed ~ uniform in rapidity, y, with a “density” ~ 9 pions per unit of y. • The pions have a distribution in transverse momentum with a mean, ~ 0.6 GeV.

7. LHC SLHC s 14 TeV 14 TeV L 1034 1035 100 1000 Bunch spacing dt 25 ns 12.5 ns N( interactions/x-ing) ~ 12 ~ 62 dNch/d per x-ing ~ 75 ~ 375 Tracker occupancy 1 5 Pile-up noise 1 ~2.2 Dose central region 1 10 Detector Environment Bunch spacing reduced 2x. Interactions/crossing increased 5 x. Pileup noise increased by 2.2x if crossings are time resolvable.

8. Pileup and Luminosity • For ~ 50 mb, and = 6 charged pions/unit of y with a luminosity and a crossing time of 12.5 nsec : • In a cone of radius = 0.5 there are ~ 70 pions, or ~ 42 GeV of transverse momentum per crossing. This makes low Et jet triggering and reconstruction difficult.

9. Z’(120) at L/5 and L ET(GeV) Jet cone and 90 degrees to cone in  dR Log(z), z = k/ET

10. Z’(120) Mass Resolution Note that the calorimeter cells are still fairly sparsely populated (granularity ) at 1034 . With the cuts shown, the dM/M with Gaussian fits is the same at L/5 and at L. Use the fact that QCD implies that there is a core of the jet at small dR and large z. Extend to 10x L using tracker and energy flow inside the jet? If x-ing is time resolvable, pileup is “only” 5x. Tracker can be used (energy flow) to remove charged energy deposits from vertices within the x-ing which are not of interest. M(GeV)

11. Tracker and Energy Flow • For 120 GeV Z’ match tracks in  and  to “hadronic” clusters within the jet. Improves dijet mass resolution. Units are HCAL tower sizes. Also use track match to remove charged pion deposits from pileup vertices ? d d ET(GeV)

12. WW Fusion and “Tag Jets” Pileup, R=0.5, |y|=3 These jets have ~ pileup R = 0.5 and <y> ~ 3. Lose 5x in fake rejection. We must use the energy flow inside a jet cone to further reduce the fake jets due to pileup (~ uniform in R). WW fusion

13. Tracking Detectors • Clearly, the tracker is crucial for much of the LHC physics [e.g. e, , jets (pileup, E flow), b tags]. • The existing trackers will not be capable of utilizing the increased luminosity as they will be near the end of their useful life. • It is necessary to completely rebuild the LHC tracking detectors.

14. Tracker - Occupancy • The occupancy, O, for a detector of area dA and sensitive time time dt at (r,z) is • e.g. Si strip 10 cm x 100 m in a 12.5 nsec crossing at r = 20 cm is 1.5 % • For higher luminosity, decrease dA, or decrease dt (limit is x-ing time) or increase r – smaller, faster or further away.

15. Tracker Occupancy • Preserve the performance using : • Push Si strips out to ~ 60 cm. – development • Push pixels out to 20 cm. – development • For r < 20 cm. Need new technologies – basic research • Shrink dA 5x at fixed r to preserve b tagging? If 12.5 nsec bunch x-ing, need 5x pixel size reduction. • Possibilities • 3-d detectors – electrodes in bulk columns • Diamond (RD42) - radhard • Cryogenic (RD39) – fast, radhard • Monolithic – reduced source capacity.

16. Monolithic Pixel - DEPFET Combine the detector and the readout for pixels?

17. Tracker – Ionizing Dose • The ionizing dose due to charged particles is: • The dose depends only on luminosity, r, and exposure time . • For example, at r = 20 cm, the dose is ~3 Mrad/yr – ignoring “loopers”, interactions, ….  “naïve” expectation.

18. Tracker ID vs. Radius 1 2 3 naive Define 3 regions. With 10x increase in L, need a ~ 3x change in radius to preserve an existing technology.

19. Tracking R&D -I • Region 1: r < 20cm • Occupancy -> Need pixels of a size factor ~ 5 smaller than used today (125x125 m2 -> ~ 50 x ~ 50 m2) -> benefit b-tagging • R&D: Pixels Sensor Technologies • new sensor materials – defect engineered Si, CVD diamond, SiC, passivated amorphous Si etc. • 3-D detectors and new biasing schemes • Cryogenic Si tracker development • monolithic pixel detectors • Region 2: 20<r<60 cm Need cell sizes 10 times larger than current pixels but at 10 times lower cost/channel than current Si microstrips -> benefit p-resolution and pattern recognition Si Macro-pixels of an area < 1mm2 : pads or shorter  strips ? Could be upgrades of innermost Si  strip layers of current detectors R&D: to demonstrate low-cost macro-pixels concept, thin Si detectors.

20. Tracking R&D - II • Region 3: r > 60 cm • Si-strips –decrease size of strips i.e. increase no. of channels by > 50% • Use standard ‘radiation resistant’  strip technology • R&D: Feasibility of processing detectors on 8” or 12’ Si wafers. Monitor commercial production progress. • Engineering • R&D: new materials, light weight, stable structures, cooling, alignment, implications for cryogenic operation, installation and maintenance aspects • Activation: 250 mSv/h – implications for access and maintenance • Cost: Reduce cost/channel by a factor of 10 • Timescale : Need ~ 8-10 years from launch of R&D ~ 4 years to build, after ~ 4 years of R&D and prototyping ?

21. 10mm P. Sharp Industry 1mm Research 0.1mm 1985 2000 Electronics – Moore’s Law • Micro-electronics: line-widths decrease by a factor 2 every 5 years. DSM (0.25 m) is radiation hard.Today 0.13 m is commercially available. In the lab 0.04 m, e.g. extreme UV lithography, is in existence. Expect trend will continue for a decade. • R&D • Characterize emerging technologies •  more radiation tolerance required – dose and Single Event Effects •  advanced high bandwidth data link technologies • system issues addressed from the start

22. ECAL – Shower Dose • The dose in ECAL is ~ due to photon showers and is: • In the barrel, SD is ~ . In the endcap, SD ~ • At r = 1.2 m, for Pb with Ec = 7.4 MeV, the dose at y=0 is 3.3 Mrad/yr, at |y|=1.5 it is 7.8 Mrad/yr.

23. HCAL and ECAL Dose ecal hcal naive The dose ratio is ~ . Barrel doses are not a problem. For the endcaps a technology change may be needed for 2 < |y| < 3 for the CMS HCAL. Switch to quartz fiber as in HF?

24. ECAL • For both ATLAS and CMS the barrel will probably tolerate the increased dose. There are issues of ~ 2.2x increased pileup noise and poorer isolation for electrons. Shorter shaping times to resolve x-ing? • ATLAS LA has space charge and current draw issues. CMS has APD leakage current noise issues in the barrel. The CMS endcap needs development.

25. HCAL - CMS • Both ATLAS and CMS will function in the barrel region. • In the 3<|y|<5 region, a reduction to y < 4.2 keeps the dose constant. The loss of efficiency is not terrible (peak “tag”rate at |y|=3). Or replace quartz fibers with high pressure gas? Better tower granularity might be needed due to pileup and “fake” jets. • At |y| ~ 3 the CMS scintillator needs development – improved scintillator or go to quartz fibers ( volume degraded is quite small).

26. HCAL - Coverage Reduced forward coverage to compensate for 10x L is not too damaging to “tag jet” efficiency

27. Scintillator - Dose/Damage |y|=2, 1 yr. This technology will not survive gracefully at |y| ~ 3. Use the technology that works at LHC up to |y|~ 5, quartz fibers?

28. Muons and Shielding There is factor ~ 5 in headroom at design L. With added shielding, dose rates can be kept constant if angular coverage goes from |y|<2.4 to |y|<2. r r z

29. Trigger and DAQ • Assuming LHC initial program is successful, raise the trigger thresholds. • Rebuild trigger system to run at 80 MHz. Utilize those detectors which are fast enough to give a BCID within 12.5 nsec (e.g. Calorimetry, Tracking). • Examine algorithms to alleviate degraded e isolation, for example. • Design for the increased event size (pileup) with reduced L1 rate and/or data compression. • For DAQ track the evolution of communication technologies, e.g. 10 Gb/sec Ethernet.

30. 300 GeV Pion – H2 test Beam E HTR - Bunch crossing number (LHC) The shape of the pulse in time is ~ as expected – due largely to scint flours. Bunch crossing ID can be extended to 12.5 nsec ( 80 MHz) as established in test beam.

31. Summary • The LHC Physics reach will be substantially increased by higher luminosity. • To realize that improvement, the LHC detectors must preserve performance. • The trackers must be rebuilt – with new technology at r < 20 cm. • The calorimeters, muon systems, triggers and DAQ will need development. • The upgrades are likely to take ~ (6-10) years. Accelerator is ready ~ (2012, 2014). The time to start is now, and the people to do the job are those who did it for the present detectors - integration. However, new people are needed.

32. SLHC Detector - Summary • Tracking and b-tagging • Isolated high pT (> 20 GeV) tracks - it should be possible to maintain similar efficiency and momentum resolution • without a tracker upgrade, for fixed b-tagging efficiency, rejection against light quarks will deteriorate by factor ~8 (pT ~ 50 GeV) • Electron identification and measurement • For electron efficiency of 80% jet rejection decreases by ~ 50% • Muon identification and measurement • If enough shielding is provided expect reconstruction efficiency and momentum resolution not to deteriorate much • Forward jet-tagging and central veto • Essential handle to increase S/N for WW and ZZ fusion processes • Performance can be significantly degraded – though algorithms could be optimized • Trigger • High thresholds for inclusive triggers; use of exclusive triggers selecting specific final states.

33. Calorimeters: CMS ECAL • Crystals • Barrel: OK • Endcap : 3krad/hr at y=2.6 • Further studies at high dose rates, long term irradiation • Photosensors • Barrel: APDs – higher leakage current a higher noise ~100 MeV/ch • Endcaps: VPTs – R&D: on new devices may be needed • Electronics • Barrel: OK • Endcap: R&D: More rad-hard electronics at |y|~3? • Activation: in endcaps reach several mSv/h – access will be difficult

34. Calorimeters: ATLAS LAr • Space Charge Effects • GeV/cm2/s • Comfortable margin in Barrel. Inner parts of em endcap and FCAL may be affected • HV Voltage Drop • Comfortable margin in Barrel. Small ‘wheel’ of em endcap sees a large current • Precision meas. not possible • Electronics: Probably OK? • R&D: Use of another cryogenic liquid, with less charge deposited per GeV, or a cold dense gas to address issues of space-charge and HV voltage drop Critical density

35. Muon System • Current ATLAS/CMS muon systems designed with safety factor of 3-5 w.r.t. background estimations (establish real safety margin once LHC operates) • Strong geometric dependence of radiation rates , • Possible strategy: • extra shielding at high |y| reduces background everywhere • restrict high |y| limit of muon acceptance • Radio-activation at high |y| of shielding, supports and nearby detectors - may limit maintenance access • Balance super robust detectors vs shielding and reduced high- |y| acceptance • R&D: Study limit of current detectors - use of CSCs in barrel, at high- |y| - higher rates – use straw chambers? MSGCs/GEMs?

36. Level-1 Trigger • Trigger Menus • Triggers for very high pT discovery physics: no rate problems – higher pT thresholds • Triggers to complete LHC physic program: final states are known – use exclusive menus • Control/calibration triggers with low thresholds (e.g. W, Z and top events): prescale • Impact of Reduced Bunch Crossing Period • Advantageous to rebuild L1 trigger to work with data sampled at 80 MHz • Could keep some L1 trigger electronics clocked at 25 ns • Require modifications to L1 trigger and detector electronics • R&D Issues • Data movement is probably the biggest issue for processing at 80 MHz sampling • Processing at higher frequencies and with higher input/output data rates to the processing elements. Technological advances (e. g. FPGA ) will help • Synchronization (TTC) becomes an issue for short x-ing period

37. DAQ • Continuous and extraordinary evolution of computing and communication technologies – monitor the evolution of: • Readout Network • Follow LHC machine luminosity – exploit parallel evolution of technologies • main building block of DAQ is the switch – interconnecting data sources (event digitizers) and processing nodes (event filters) • rapid progress in interconnection technologies started recently – LHC needs cannot yet be satisfied using a completely off-the-shelf system • Technology Tracking • Complexity Handling • Online computing systems will have ~ 10000 CPUs, issues of hardware and software management, reliability,remote access, security, databases • Technology Tracking (e.g. those found in ISPs) • R&D: How to handle bandwidth (rate  size) Bandwidth is an issue both for readout and for event building