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Stage-1 L1 calorimeter trigger upgrade for Heavy-Ion physics

Stage-1 L1 calorimeter trigger upgrade for Heavy-Ion physics. Alex Barbieri, Christof Roland, Ivan Cali, Bolek Wyslouch, Gunther Roland (MIT) Krisztián Krajczár, Yen-Jie Lee (CERN) Matthew Nguyen (LLR) Wei Li (Rice) CMS Upgrade Project Office 9 th August 2013. The case….

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Stage-1 L1 calorimeter trigger upgrade for Heavy-Ion physics

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  1. Upgrade Project Office Meeting Stage-1 L1 calorimeter trigger upgrade for Heavy-Ion physics Alex Barbieri, Christof Roland, Ivan Cali, Bolek Wyslouch, Gunther Roland(MIT) Krisztián Krajczár, Yen-Jie Lee (CERN) Matthew Nguyen (LLR) Wei Li (Rice) CMS Upgrade Project Office 9th August 2013

  2. Upgrade Project Office Meeting The case… • The readout rate of the CMS detector in HI collisions is limited by the Pixels and the Tracker to about 3kHz • No zero suppression in strips and pixel buffer overruns for large events • 2011: Max. Interaction Rate ~4.5kHz  2.7kHz L1A rate • The current L1 Calo trigger system is (barely) selective enough for HI run in 2011 • For jets and photons about 50% of the hadronic interactions need to be accepted due to the large underlying PbPb event • 2015: expect at least a factor of 4-6 lumi increase • There is strong overlap between the triggersreducing the L1A rate by 2 will require prescaling individual paths by factors of 10-20 • Need a factor of ~20 rejection factor for 2015 • The Stage-1 L1 Calorimeter Trigger upgrade (2015) can achieve the desired rejection factor

  3. Upgrade Project Office Meeting Trigger rate Rate does not respond much to the threshold. Need change in algorithm Rate can becontrolled by the threshold. To be optimized Energy sum seeds for the single track trigger should be replaced by updated jet triggers Note: There is strong overlap between the triggers, reducing the L1A rate by 2 will require prescaling individual paths by factors of 10-20

  4. Upgrade Project Office Meeting Background Subtraction Algorithm Region Energy Distributions PbPb central event HLT/Offline background subtraction: • Process phi rings at const. eta • Calculate average and subtract • Jet finder runs after BG subtraction Current L1 Jet Finder: • Processes eta strips at const. phi • 2 x 11 sectors • 1 sector = 4x4 calo towers • Sliding window jet finder • Current strategy: Jet Finder at L1 and Jet Background subtraction at HLT • The high non-uniformity in η of HI events does not permit a useful BG subtraction within a single 2x11 sector • Access to the full eta phi map at L1 allows for a efficient underlying event subtraction (phi-rings) • Peripheral and central events respond consistently to the thresholds applied to L1 jets

  5. Upgrade Project Office Meeting HI Stage-1 calo upgrade strategy • Make decision in a central place!!! • Trigger “primitives” are available in 18 separate 9U VME crates with custom high-speed backplanes corresponding to φ slices • Insert a processing/communication board: optical Regional Summary Card (oRSC) into existing slot in each RCT crate • Send regional calorimeter trigger products to L2 calorimeter trigger processor (MP7) boards • Program FPGA to do background subtraction in full φ rings using 4x4 tower “regions” to estimate background • Find jets at L1 speeds

  6. Upgrade Project Office Meeting Stage-1 HI algorithm performance Current System Accept rate can be controlled by L1 threshold using Stage-1 and Stage-2 system Stage-1 System Stage-1 System: Reasonable trigger turn-on curvefor both central and peripheral collisions L1 accept rate reduced by a factor of 10-20

  7. Upgrade Project Office Meeting Heavy-Ion Contribution • Manpower: • MIT provides 1 postdoc and 1 student • Rice University provides 1 postdoc and 1 student (starting in September 2013) • The HI group responsibility (in collaboration with WU and IC): • Establishment of the detailed triggering specifications based on the requirements of heavy ion physics • Testing of the boards and firmware at the trigger demonstrator at CERN 904 • Development of FPGA firmware for MP7 boards with specific heavy-ion triggering algorithms • Installation and commissioning of the new trigger in CMS experiment. • Purchase and testing of the 3 prototype oRSC boards • Purchase and testing of the final 22 oRSC boards • Purchase of optical fibers and patch panel • All the existing L1 calorimeter trigger electronics has been designed and produced by the University of Wisconsin and Imperial College (oRSC, CTP6/7, MP7)

  8. Upgrade Project Office Meeting Status and schedule • Contributing to the setup of the test system/demonstrator in CERN 904. The system includes 2 RCT crates and 1 MCC crate • XDAQ application to allow easy control and pattern test of trigger electronics (JCC, JSC, oRSC) • Gained hand on experience with the RCT system and with oRSC and MP7 • Specific HI algorithm implementation schedule: • September 2013: Defined requirements for HI running • October 2013: Algorithms performance studies offline completed (it will include also the test of the existing stage-1 pp algorithm) • February 2014: Algorithm implemented in MP7 • June 2014: Basic performance tests completed • Fall 2014: System ready for data-taking • MIT and Rice groups will collaborate with the Wisconsin and Imperial College groups for the installation and commissioning of the system in the CERN/P5 CMS experimental hall.

  9. Upgrade Project Office Meeting Summary • The upgraded Stage-1 system • Significantly improve the online jet trigger • Sufficient for data taking with heavy-ion collisions in 2015 • Achieve similar performance for calo-jets as the HL-LHC system • Active collaboration with Wisconsin and Imperial college group already started • XDAQ application for 904 tests developed • Hand on experience with the electronics acquired (RCT, oRSC, MP7) • Definition of HI algorithm for the 2015 data-taking is ongoing • Schedule/milestones for algorithm implementation is defined • A first L1 jet UE background subtraction algorithm for HI already tested offline

  10. Upgrade Project Office Meeting Backup slides

  11. Upgrade Project Office Meeting Track trigger: trigger turn-on curves “Central event” 0-20% “Peripheral event” 60-100% For Approval For Approval It is feasible to seed high pT track with L1 jet trigger Provides a factor of 5-10 reduction of the L1 accept rate

  12. Upgrade Project Office Meeting Current L1: Sector wise subtraction Before After • The high non-uniformity in η does not permit a useful BG subtraction within a single 2x11 sector

  13. Upgrade Project Office Meeting Current L1: Sector wise subtraction Before After • Test on 3 data samples • Min. Bias, Jets and central events • Can’t apply a threshold that keeps full efficiency for jets while rejecting a sufficient fraction of min bias events

  14. Upgrade Project Office Meeting Trigger Turn On: 2015 L1 system • Access to the full eta phi map allows for a efficient underlying event subtraction (phi-rings) • Peripheral and central events respond consistently to the thresholds applied to L1 Jets Jet + Central UE Jet + Peripheral UE

  15. Upgrade Project Office Meeting Trigger Turn On: Current L1 system High Threshold • Lack of UE subtraction does not allow for a consistent threshold for central and peripheral events • Poor control over L1 accept rates Jet + Central UE Jet + Peripheral UE Low Threshold

  16. Upgrade Project Office Meeting Physics performance plots • b jet quenching performance • Assuming the same amount of quenching as light jet • 3-jet event performance • R32 (3-jet / 2-jet ratio), access to gluon jet • High pT track RAA and v2 performance • Increased the pT reach from 100 to 160 GeV/c

  17. Upgrade Project Office Meeting b-jet physics performance PAS • Goal: di-b-jet asymmetry as done for inclusive jets in HIN-10-004 and HIN-11-013 • Proposed observable: • Dijet asymmetry (AJ) & RB (fraction of balanced di-b-jet) • Expect similar systematics as light jets + (b tagging uncertainty & light jet contamination) • Use 2011 kinematic cuts: pT,1 > 100 GeV/c and pT,2 > 30 GeV/c

  18. Upgrade Project Office Meeting Physics performance of 3-jet events • Access to gluon jets: three jet events • R32 may be modified due to jet quenching • Similar study as QCD-10-012 • All jet pT threshold > 100 GeV/c • No existing experimental measurements in heavy ion collision • Simulated with PYTHIA at 5.5 TeV PAS

  19. Upgrade Project Office Meeting High pT reach of tracks and jets High pT Jet (Anti kT R =0.3) High pT track Entries PAS HIG-12-054 Approved Jet pT (GeV/c) Track

  20. Upgrade Project Office Meeting Stage-1 Calo Upgrade system

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