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Forward Jet Triggering for an Upgraded CMS

Forward Jet Triggering for an Upgraded CMS. Drew Baden - University of Maryland Jeremy Mans - University of Minnesota Chris Tully - Princeton University. HF. HF Basics. HF covers ~3< h <5 located at ±11.1m from IP Steel absorber and rad hard quartz fibers

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Forward Jet Triggering for an Upgraded CMS

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  1. Forward Jet Triggering for an Upgraded CMS Drew Baden - University of Maryland Jeremy Mans - University of Minnesota Chris Tully - Princeton University CMS SLHC Perugia - Baden

  2. HF HF Basics • HF covers ~3<h<5 located at ±11.1m from IP • Steel absorber and rad hard quartz fibers • Cerenkov light collected via phototubes, uniform HCAL readout • 36f and 12h = 432 towers per side • Df=10° and Dh=0.166 • Each tower has long and short fibers running along z • Short (S) is in the back ~ “ETHAD” • Long (L) is front to back ~ “ETEM+HAD” • Readout after ganging all S and all L • Makes 2x432=864 towers per side CMS SLHC Perugia - Baden

  3. Jets in Level 1 • TPGs • HB/HE: 0.087x0.087 DhxDf 0.5 x 0.35 in HF • CMS Level 1 Jets • Calorimeter organized into “Regions” • 4x4 TPGs per region in HB and HE, formed by RCT • 1 TPG per region in HF, formed by HCAL HTRs and transmitted thru RCT • Regions are sent GCT for jet finding • Jet finding via “sliding window” • Sliding window using 3x3 regions Calorimeter “Region” Barrel/Endcap CMS SLHC Perugia - Baden

  4. CMS Calorimeter Segmentation CMS SLHC Perugia - Baden

  5. Min Bias • Min bias distributions @ 1034 • <n>~20 (assumes ~80mb inelastic) • <dn±/dh> ~ <dn0/dh> ~ 8 @ 14TeV • <ET> ~ few GeV (and falls exponentially) • 20<n> x 8ch x 10dh x 2GeV = 3.2 TeV/interaction (Had) • HF...40% of CMS in Dh coverage • 640 GeV, 72 TPGs/side, ~10 GeV/TPG (@<n>=20) • Current TPG = 0.5 x 0.348 hxf • SLHC upgrade • Increase ET/TPG from minbias scales with increase in <n> • Clearly, the only way to keep up without ramping thresholds up is to look at TPGs on finer scale • New Level 1 triggering will need to… • Sharpen efficiency • Move HLT-like algorithms and resolution as close to L1 as possible Atlas CERN/LHC 96-40 CMS SLHC Perugia - Baden

  6. SLHC Background Reduction • Beat down the background L1A rate • LHC Design luminosity of 1034 has large backgrounds: • Depending on the scheme for high luminosity • <n> ~ current for 25ns SLHC, rates scale with Luminosity • for continuous beam….smaller <n> but large pileup...not sure • 100kHz L1A rate is ingrained, will most likely hold • Size of derandomizing buffers, etc. • Bandwidth to HLT • Number of HLT processors.... • CMS Calorimeter trigger based on TPGs • In HF… • 1 TPG = 6 towers (3h x 2f) • Lack of granularity might make it useless for Level 1 jet triggers with large number of multiple interactions without drastic threshold increases • In HB and HE… • Jet-finding in Level 1, saturation effect due to pileup at high luminosity • t trigger (requires most energy to be in 1 region) difficultie at high pileups • Ditto for isolated e and g triggers CMS SLHC Perugia - Baden

  7. SLHC Signal Enhancement • Add functionality • W Boson Fusion (WBF) dominant experimentally accessible rate • Forward jets + central Higgs decay • Tag jets are in HF+HE so HE will need to be included • Higgs id without a tag is very hard • Gluon fusion backgrounds are too high, esp at 1035 • Current trigger at high luminosity will be difficult • Depends on scheme for increasing luminosity of course… h (tagged “forward” jets) C. Tully & H. Pi JetMetPRS Aug 2004 CMS SLHC Perugia - Baden

  8. Forward Jets in Level 1 • Jeremy Mans, Chris Tully, monte carlo simulations using ORCA • Try to optimize forward jet trigger to keep the thresholds on central objects from increasing due to pileup at high luminosity • Plot of forward jet trigger rate shows huge effect at low ET • Pileup effects at ~1034 will cause thresholds of ~50-60 GeV to get away from pileup dominating real jets • Signal is reduced to almost nothing • NB: this does not take into account central object trigger…so it’s not as bad as that but it’s still a big loss due to pileup CMS SLHC Perugia - Baden

  9. Jet Shape and Pileup • Diagram for WBF has no “color string” across the detector • QCD forward jets will be much more “active” • This can be seen in the jet shape (2nd moment) • Energy is from pileup is added to jet far from core • Easier to deal with using smaller regions CMS SLHC Perugia - Baden

  10. Another Look at Shapes… • Current scheme • Jet candidates using 3x3 CR sum, DhxDf=1.5 x 1.0 • Slides window by 1 CR, DhxDf=0.5 x 0.35 • New scheme • Construct jet candidates from 4x4 tower sums, DhxDf=0.67 x 0.7 • Slide window by 1 tower, DhxDf=0.17 x 0.17 • Feature bit on if number of cells needed to sum 60% of ET (n60) in 4x4 cluster < cut • Use n60 < 7 to set feature bit • Prelim studies show QCD jets are narrow & well contained • Jets from .5 cone all have 2nd moment < 0.3 in R • Require jet candidate threshold && feature bit = 1 • Can also require perimeter “quiet” for isolation • Not studied yet… CMS SLHC Perugia - Baden

  11. 12.5ns Hardware Design • We propose NOT changing current HTR • 48 QIE channels input • 6 SLB sites • Each SLB transmits 2 TPGs/link over 4 links/cable • For HF, 1TPG = 6 QIE channels • 48/6 = 8 TPG output • HF HTRs will only populate 1 SLB site • We will have 5 free SLB sites to use • Proposal: • Luminosity: dedicate 1 SLB site • Jet trigger: dedicate 3 SLB sites • Means running L and S fibers @ 80MHz, or L+S after summing @ 40MHz • Send data to…TBD…during CMS running parasitically…study study study CMS SLHC Perugia - Baden

  12. HTR Luminosity “consumers” HLX HFJ HFT RCT SLB HF Forward Jet Study Elecctronics • HF Transmitter (HFT) • 3-SLB-site mezzanine card on HTRs • Transmits raw HF towers for clustering investigations • Optical transmitters, 1.6Gbps 8B/10B using 12-way MTP connectors (18 per side) • Already being laid out – expect to have something available for studies at H2 summer 06 • HF Jet Processor (HFJ) • Jeremy Mans/UMN • Receives fiber data and processes into jets… • New GCT Leaf/Wheel cards might be ideal for rapid development for studies 2 HTRs = 4(f) x 12(h) 18 HTRs per + and – side of CMS CMS SLHC Perugia - Baden

  13. Rack Topology • Chris Tully worked this out with Rohlf and Ianos Schmidt, ok’d by Wesley Smith • New “Luminosity” VME crate in the center minimizes distance from the 3 HF crates and doesn’t break topology for Level 1 • Can put any electronics developed for HF forward jet trigger studies here CMS SLHC Perugia - Baden

  14. R&D Program • Scrub design so that we can piggyback on existing system and build cards that can be implemented by LHC startup • Keep entire current VME architecture, but add new capability • Run parasitically, collect data, study, iterate • R&D list for Trigger project • Much simulation needed to settle on algorithm approach • HLT card: • Learn how to use new FPGA’s with embedded processing, DSP, built-in deserializers…. • Continue to verify HTR to HLT @ 80MHz • HLT to HJF transmission • Implement transmitting signals over MTP fiber ribbons @ 1.6Gbps using Rocket IO • Use crystals to drive transmitter as an alternate scheme (asynchronous fifo’s on both ends) • HFJ • Study algorithms for clustering – lots of simulation needed here • Build new types of 9U boards or follow GCT project? CMS SLHC Perugia - Baden

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