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L1 Track Trigger for ATLAS at HL-LHC Nikos Konstantinidis (University College London) RAL seminar, 18/05/2011.

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Presentation on theme: "L1 Track Trigger for ATLAS at HL-LHC Nikos Konstantinidis (University College London) RAL seminar, 18/05/2011."— Presentation transcript:

1 L1 Track Trigger for ATLAS at HL-LHC Nikos Konstantinidis (University College London) RAL seminar, 18/05/2011

2 Outline High Luminosity LHC (HL-LHC)  Motivation, physics potential, timelines, parameters ATLAS upgrades for HL-LHC  Overview, focus on Level-1 Trigger upgrade The ATLAS L1Track R&D programme  Motivation, challenges, studies, plans Conclusions – Outlook Track Trigger for ATLAS at HL-LHC2 Nikos Konstantinidis

3 The HL-LHC project

4 HL-LHC idea Upgrade the LHC to deliver O(3000fb -1 ) per experiment in the 2020s (x10 the LHC lumi)  O(250fb -1 ) per year, peak luminosity 5e34 Motivation:  Increased discovery potential multi-TeV region, corners of SUSY parameter space…  Detailed studies of discoveries made with 250fb -1 e.g. Higgs couplings, SUSY properties etc  Probe the gauge structure of the SM Vector Boson Fusion at 1TeV, triple gauge couplings… Track Trigger for ATLAS at HL-LHC4 Nikos Konstantinidis

5 Timelines for HL-LHC Current dates for “Long Shutdown 3”:  Dates driven by two factors: Integrated lumi “saturation” Radiation damage of accelerator components Two other long shutdowns in this decade:  LS1 ( ): work to prepare for 14TeV & 1e34 LHC will have delivered ~O(10fb -1 ) at 7TeV  LS2 (2017/18?): upgrades for peak lumi 2e3 LHC will have delivered ~O(50fb -1 ) at 14TeV Track Trigger for ATLAS at HL-LHC5 Nikos Konstantinidis

6 LHC int. luminosity evolution Track Trigger for ATLAS at HL-LHC6 Nikos Konstantinidis If it takes many (>10) years to deliver integrated luminosity that halves statistical errors, then it is not cost-effective. 10fb -1 50fb fb -1

7 LHC: Draft 10-year plan (03/2011) Nikos Konstantinidis Track Trigger for ATLAS at HL-LHC 7

8 How to deliver 250fb -1 /year Upgrade the machine to deliver 10e34 (5e34 with luminosity leveling  Higher current per bunch  Higher field magnets for stronger focusing  Superconducting crab cavities for lumi leveling  Extreme collimation in the collision points  … All these require a lot of R&D Track Trigger for ATLAS at HL-LHC8 Nikos Konstantinidis

9 Lumi leveling with crab cavities Track Trigger for ATLAS at HL-LHC9 Nikos Konstantinidis cc RF crab cavity deflects head and tail in opposite direction so that collision is effectively “head on” for luminosity and tune shift bunch centroids still cross at an angle (easy separation) First proposed in 1988, in operation at KEKB since 2007 → world record luminosity!

10 Lumi profile with leveling Much more manageable for the detectors  ~100 vs. ~200 pp collisions per bunch crossing Also better for LHC  Reduced peak heat deposition in critical cold regions of the machine Track Trigger for ATLAS at HL-LHC10 Nikos Konstantinidis

11 Example HL-LHC parameters Track Trigger for ATLAS at HL-LHC11 Nikos Konstantinidis parametersymbolnom.nom.* HL crabHL sb + lrcHL 50+lrc protons per bunchN b [10 11 ] bunch spacing  t [ns] beam currentI [A] longitudinal profile Gauss rms bunch length  z [cm] beta* at IP1&5  [m] full crossing angle  c [  rad] 285 ( )508 Piwinski parameter  c  z /(2*  x *) tune shift  Q tot potential pk luminosityL [10 34 cm -2 s -1 ] events per #ing effective lifetime  eff [h] run or level timet run,level [h] e-c heat SEY=1.2P [W/m] SR+IC heat KP SR+IC [W/m] IBS  rise time (z, x)  IBS,z/x [h] 59, 10240, 69 38, 668, 3318, 31 annual luminosity L int [fb -1 ]

12 ATLAS Upgrades for HL-LHC

13 ATLAS Upgrades this decade At LS1 ( )  New Pixel barrel layer very close to the beam (+new beam pipe) The existing innermost Pixel layer becomes inefficient above 1e34 At LS2 (2017/18?)  New Muon inner endcap Wheels Too high rate in existing chambers above 1e34 New wheels will give sharper L1 muon thresholds in forward region  Trigger upgrades L1 topological processor Hardware track finder after L1 (FTK) Track Trigger for ATLAS at HL-LHC13 Nikos Konstantinidis

14 ATLAS upgrades for Upgrades are necessary to retain performance at 5e34 or to withstand irradiation up to ~3000fb-1  New, all-silicon tracker (pixels + strips)  New calorimeter readout to provide higher granularity information for the L1 Calo trigger  Major redesign of the L1 Trigger hardware and other upgrades to Trigger-DAQ system  Changes in the very forward calorimeters Present Calorimeters, Muon Chambers and Magnets don’t change Track Trigger for ATLAS at HL-LHC14 Nikos Konstantinidis

15 Current TDAQ architecture L1 uses only Calo/Muon 40MHz  L1  75kHz  Unlikely to change hugely, given material constraints L2 accesses only ~10% of event data (in RoIs) Rate to disk ~200Hz  Unlikely to change hugely, given increased event size Track Trigger for ATLAS at HL-LHC15 Nikos Konstantinidis

16 L1 Trigger upgrade for 5e34 Physics at HL-LHC will still require triggering on signatures at the electroweak scale (W/Z/H)  Raising the p T thresholds effectively cancels the benefits of upgrading the LHC luminosity! L1 Trigger has to achieve 5x higher rejection in much more complex events  E.g. electron/muon isolation may be less effective Reading out the tracker at ~500kHz not an option  Costly, wasteful and introduces a lot of material Track Trigger for ATLAS at HL-LHC16 Nikos Konstantinidis

17 Options for ATLAS Upgrade L1Calo  Use finer granularity information from Calorimeters Upgrade L1Muon  Sharpen pT thresholds, reject more fake triggers Use tracking info at L1  Known to be a key element for rejection at L2 A combination of all of the above Track Trigger for ATLAS at HL-LHC17 Nikos Konstantinidis

18 L1Calo upgrades for 5e34 Finer granularity info for L1Calo is the main physics driver for Calo readout upgrade  Currently 0.1x0.1 trigger towers Studies ongoing to understand what info is most important for L1Calo  In depth or lateral shower profile  Which HLT Calo techniques can be ported to L1 Strips of  =0.003 in 1 st LAr sampling are essential for rejecting  0 s ATLAS Trigger upgrade plans and activities18 Nikos Konstantinidis

19 L1Muon rates at 5e34 Track Trigger for ATLAS at HL-LHC19 Nikos Konstantinidis Rates for muons from b/c/W can be extracted by convoluting p T resolution with physics x-section p T resolution drives the physics rates: >50kHz for MU20, >25kHz for MU40 The above estimates do not include cavern background nor charged  /K decays in flight, hence they give a lower bound

20 L1Muon upgrades for 5e34 New Small Wheels (to be installed at LS2) will provide in forward region  significant reduction of fake triggers  sharper pT thresholds Barrel L1Muon is harder to improve, but less sensitive to fakes Ongoing studies  Possible L1Mu barrel improvements  to characterize fully the L1Muon performance in MC and project from data to higher luminosities Track Trigger for ATLAS at HL-LHC20 Nikos Konstantinidis All L1 Triggers L1 Triggers with offline muon Endcaps

21 The ATLAS L1Track R&D

22 Why tracking at L1 Tracking is key for rate reduction at L2, so it would enhance the purity of the L1-accepted events  For electrons, muons, taus (high-pT tracks)  For double/multi-object triggers (ensure that they come from the same pp collision) Will provide additional flexibility, redundancy & robustness to the L1 trigger in the harsh and uncertain conditions of HL-LHC  Otherwise we’ll have to rely exclusively on pT thresholds for controlling the L1 rates Track Trigger for ATLAS at HL-LHC22 Nikos Konstantinidis

23 Track Trigger for ATLAS at HL-LHC23 Nikos Konstantinidis

24 Possible L1Track designs Self-seeded L1Track: use closely-spaced (few mm) Si layers electrically connected and instrumented with coincidence logic that is satisfied only by high-p T tracks (the CMS idea)  Coincidences have to be sent off-detector at 40MHz and combined in a further step The L0/L1 idea (or RoI-based L1Track)  L1Calo/L1Muon reduce the rate from 40MHz to ~500kHz and identify Regions of Interest (Level-0)  Tracker data from these RoIs are readout and processed by L1Track; L1Track info is added to the L1Calo/L1Muon info to form global L1 decision Track Trigger for ATLAS at HL-LHC24 Nikos Konstantinidis Cannot readout the whole tracker at 40MHz

25 The RoI-based L1Track L0 is a synchronous pipelined trigger with latency ~3.2us (pretty much like current ATLAS L1 trigger) Subsystems (e.g. Muons, Calorimeters) can either readout at the full L0 rate (~500kHz), ignoring L1, or have additional buffers (e.g. tracker) in their front-ends where L0-Accapted events are kept until the L1 decision arrives L0 RoI information is converted into Regional Readout Requests that target specific modules in the tracker From L0 to L1, the system is asynchronous; makes overall design more flexible Depending on the size of the additional buffers, the L1 decision can take up to O(100us) Track Trigger for ATLAS at HL-LHC25 Nikos Konstantinidis

26 Track Trigger for ATLAS at HL-LHC26 Nikos Konstantinidis Example: strips readout chip design

27 Advantages of RoI-based L1Track No impact on the tracker layout  Can be optimized for offline tracking performance Full tracking information available (in principle) For larger L1 latency, L1 rate can be significantly below 100kHz  Implications for the tracker’s material budget Track Trigger for ATLAS at HL-LHC27 Nikos Konstantinidis

28 ATLAS vs. CMS L1 upgrades Conclusions depend on initial conditions  At least ~2 years ago, CMS had the constrain for L1 6.4us/100kHz (no change of ECAL electronics) ATLAS has more options for improving L1Calo and L1Muon  High granularity of LAr calorimeter is an advantage  Muon Small Wheels Of course, with more options it is harder to converge Track Trigger for ATLAS at HL-LHC28 Nikos Konstantinidis

29 Inner detector = 3.2 μs Level-1 Track ID Tracks Level-1 MDT Tracks Central Topology Processor L0A Pre-Trigger Processor Muon detectors Level-0 Muon μ Calorimeters (Digitisation) e/γ ETET Jet Level-0 Calo R3 Trigger & Timing distribution L0A, L1A L1A 25 ns per pipeline step = < μs A possible architecture: L0/L1 40MHz ~500kHz? <100kHz? Nikos Konstantinidis29Track Trigger for ATLAS at HL-LHC

30 RoI-based L1Track parameters Key parameters for the design of L1Track are  L0 rate  L1 rate could be <100kHz if enough rejection is achieved  Number/size of RoIs hence the fraction of the tracker to readout at L0 rate  Number of tracker layers to readout not necessarily all Ongoing simulation studies to determine these parameters Track Trigger for ATLAS at HL-LHC30 Nikos Konstantinidis

31 Regional Readout studies Track Trigger studies31 Nikos Konstantinidis Module number in Z Frequency (in %) inside an RoI PIXEL STRIPS RoI:  =0.2,  =0.2 at Calo  z=40cm at beamline

32 RoI-based L1Track – issues All ATLAS sub-detector should either be able to readout at the L0 rate (~500kHz) or change their readout electronics  Not an issue for tracker (new), Calorimeters (new electronics) and other small sub-detectors  BUT: potential problem with Muon system: max readout rate 100kHz (max latency 3.2us) and replacing all electronics is a very long operation – unlikely to fit in a 2-year shutdown Alternatives are under investigation Unlikely that any L1Track scheme can fit within 3.2us/100kHz Track Trigger for ATLAS at HL-LHC32 Nikos Konstantinidis

33 Conclusions – Outlook The HL-LHC will dominate the high energy discovery frontier in the 2020s Major upgrades of the detectors will be required to cope with the high-lumi environment (up to 200 pp collisions / bunch crossing) ATLAS is evaluating a number of alternatives for the upgrades of L1Calo and L1Muon, as well as the use of tracking information at L1 An RoI-based L1Track appears to be an attractive solution for ATLAS, but more studies are needed to converge to the optimal L1 architecture Track Trigger for ATLAS at HL-LHC33 Nikos Konstantinidis


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