Alex Barbieri, Christof Roland, Ivan Cali, Bolek Wyslouch, Gunther Roland (MIT) Krisztián Krajczár, Yen-Jie Lee (CERN) Matthew Nguyen (LLR) Wei Li (Rice)

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

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

August 9, 2013 Upgrade Project Office Meeting 1


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 triggers reducing 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


Trigger rate

L1 Algo L1 Accept Fraction

HLT Accept Fraction

4.5 kHz (2011)

40 kHz (2015)

100kHzAfter LS2

SingleJet36 35% 0.5%(Jet65) 1600Hz 14 kHz 36kHz

SingleJet52 28% 0.08%(Jet80) 1300Hz 12 kHz 29kHz

SingleJet68 24% 1100Hz 10kHz 24kHz

SingleJet92 20% 900Hz 8.0kHz 20kHz

SingleJet128 14% 600Hz 5.3kHz 13kHz

SingleEG5 22% 0.3%(Photon20) 1000Hz 8.9kHz 22kHz

SingleEG8 8% 350Hz 3.1kHz 7.8kHz

SingleEG12 1% 0.02%(Photon40) 50Hz 0.4kHz 1.1kHz

SingleEG15 0.6% 26Hz 0.2kHz 0.6kHz

DoubleMuOpenHQ 1% 40 Hz 0.4kHz 0.9kHz

SingleMu3 1% 50 Hz 0.4kHz 1.1kHz

ETT100 37% 0.4%(Track14) 1700Hz 15kHz 38kHz

ETT140 34% 1550Hz 15kHz 34kHz

ETT220 31% 1400Hz 12kHz 31kHz

ETT800 18% 840Hz 7.5kHz 19kHz

ETT2000 14% 630Hz 5.6kHz 14kHz

Total L1A 60% 5% 2700Hz 24kHz 60kHz

Rate can be controlled by the threshold.To be optimized

Rate does not respond much to the threshold. Need change in algorithm

Energy sum seeds for the single track trigger should be replaced by updated jet triggersNote: There is strong overlap between the triggers, reducing the L1A rate by 2 will

require prescaling individual paths by factors of 10-20


Background Subtraction Algorithm

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

Region Energy Distributions PbPb central event

• 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

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



Stage-1 HI algorithm performance

Accept rate can be controlled by L1 threshold using Stage-1 and Stage-2 system

Stage-1 System:

Reasonable trigger turn-on curvefor both central and peripheral collisions

L1 accept rate reduced by a factor of 10-20

Stage-1 System

Current System

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)

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.



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


Backup slides


Track trigger: trigger turn-on curves

It is feasible to seed high pT track with L1 jet trigger

Provides a factor of 5-10 reduction of the L1 accept rate

“Peripheral event”

60-100%

“Central event”

0-20%

For ApprovalFor Approval


The high non-uniformity in η does not permit a useful BG subtraction within a single 2x11 sector

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

Current L1: Sector wise subtraction

Before After


Trigger Turn On: 2015 L1 system

Jet + Central UE

Jet + Peripheral UE

• 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


Trigger Turn On: Current L1 system

Jet + Central UE

Jet + Peripheral UE

• Lack of UE subtraction does not allow for a consistent threshold for central and peripheral events

• Poor control over L1 accept rates

High Threshold

Low Threshold


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


b-jet physics performance

• 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

PAS


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


High pT reach of tracks and jets

High pT track High pT Jet (Anti kT R =0.3)

Ent

ries

Track Jet pT (GeV/c)

PAS HIG-12-054Approved

Stage-1 Calo Upgrade system


Documents

Alex Barbieri, Christof Roland, Ivan Cali, Bolek Wyslouch, Gunther Roland (MIT) Krisztián Krajczár, Yen-Jie Lee (CERN) Matthew Nguyen (LLR) Wei Li (Rice)