L1 Track Trigger for ATLAS at HL-LHC Nikos Konstantinidis (University College London) RAL seminar,...
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Transcript of L1 Track Trigger for ATLAS at HL-LHC Nikos Konstantinidis (University College London) RAL seminar,...
L1 Track Trigger for ATLAS at HL-LHC
Nikos Konstantinidis
(University College London)
RAL seminar, 18/05/2011
Outline
High Luminosity LHC (HL-LHC)Motivation, physics potential, timelines, parameters
ATLAS upgrades for HL-LHCOverview, focus on Level-1 Trigger upgrade
The ATLAS L1Track R&D programmeMotivation, challenges, studies, plans
Conclusions – Outlook
Track Trigger for ATLAS at HL-LHC 2Nikos Konstantinidis
The HL-LHC project
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 etcProbe the gauge structure of the SM
Vector Boson Fusion at 1TeV, triple gauge couplings…
Track Trigger for ATLAS at HL-LHC 4Nikos Konstantinidis
Timelines for HL-LHC
Current dates for “Long Shutdown 3”: 2021-22Dates driven by two factors:
Integrated lumi “saturation”Radiation damage of accelerator components
Two other long shutdowns in this decade:LS1 (2013-14): work to prepare for 14TeV & 1e34
LHC will have delivered ~O(10fb-1) at 7TeVLS2 (2017/18?): upgrades for peak lumi 2e3
LHC will have delivered ~O(50fb-1) at 14TeV
Track Trigger for ATLAS at HL-LHC 5Nikos Konstantinidis
LHC int. luminosity evolution
Track Trigger for ATLAS at HL-LHC 6Nikos Konstantinidis
If it takes many (>10) years to deliver integrated luminosity that halves statistical errors, then it is not cost-effective.
10fb-1
50fb-1 250fb-1
Track Trigger for ATLAS at HL-LHC 7
LHC: Draft 10-year plan (03/2011)
Nikos Konstantinidis
How to deliver 250fb-1/year
Upgrade the machine to deliver 10e34 (5e34 with luminosity levelingHigher current per bunchHigher field magnets for stronger focusing Superconducting crab cavities for lumi levelingExtreme collimation in the collision points…
All these require a lot
of R&D
Track Trigger for ATLAS at HL-LHC 8Nikos Konstantinidis
Lumi leveling with crab cavities
Track Trigger for ATLAS at HL-LHC 9Nikos Konstantinidis
qc
• 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!
Lumi profile with leveling
Much more manageable for the detectors~100 vs. ~200 pp collisions per bunch crossing
Also better for LHCReduced peak heat deposition in critical cold
regions of the machine
Track Trigger for ATLAS at HL-LHC 10Nikos Konstantinidis
0.E+00
2.E+34
4.E+34
6.E+34
8.E+34
1.E+35
0 2 4 6 8 10 12
Lum
inos
ity
(cm
-2s-1
)
time (hours)
Nominal
1035 - no levelling
Levelling at 5 10
35
34
0.E+00
2.E+34
4.E+34
6.E+34
8.E+34
1.E+35
0 5 10 15 20 25
Lum
inos
ity
(cm
-2 s
-1)
time (hours)
1035 - no level Level at 5 1035 34
Average no level
Average level
Example HL-LHC parameters
Track Trigger for ATLAS at HL-LHC 11Nikos Konstantinidis
parameter symbol nom. nom.* HL crab HL sb + lrc HL 50+lrc
protons per bunch Nb [1011] 1.15 1.7 1.78 2.16 3.77
bunch spacing Dt [ns] 25 50 25 25 50
beam current I [A] 0.58 0.43 0.91 1.09 0.95
longitudinal profile Gauss Gauss Gauss Gauss Gauss
rms bunch length sz [cm] 7.55 7.55 7.55 5.0 7.55
beta* at IP1&5 *b [m] 0.55 0.55 0.15 0.15 0.15
full crossing angle qc [mrad] 285 285 (508-622) 508 508
Piwinski parameter =f qcsz/(2*sx*) 0.65 0.65 0.0 1.42 2.14
tune shift DQtot 0.009 0.0136 0.011 0.008 0.010
potential pk luminosity L [1034 cm-2s-1] 1 1.1 10.6 9.0 10.1
events per #ing 19 40 95 95 189
effective lifetime teff [h] 44.9 30 13.9 16.8 14.7
run or level time trun,level [h] 15.2 12.2 4.35 4.29 4.34
e-c heat SEY=1.2 P [W/m] 0.2 0.1 0.4 0.6 0.3
SR+IC heat 4.6-20 K PSR+IC [W/m] 0.32 0.30 0.62 1.30 1.08
IBS e rise time (z, x) tIBS,z/x [h] 59, 102 40, 69 38, 66 8, 33 18, 31
annual luminosity Lint[fb-1] 57 58 300 300 300
ATLAS Upgrades for HL-LHC
ATLAS Upgrades this decade At LS1 (2013-2014)
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 upgradesL1 topological processorHardware track finder after L1 (FTK)
Track Trigger for ATLAS at HL-LHC 13Nikos Konstantinidis
ATLAS upgrades for 2021-22 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-LHC 14Nikos Konstantinidis
Current TDAQ architecture
L1 uses only Calo/Muon
40MHz L175kHz 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 sizeTrack Trigger for ATLAS at HL-LHC 15Nikos Konstantinidis
L1 Trigger upgrade for 5e34 Physics at HL-LHC will still require triggering on
signatures at the electroweak scale (W/Z/H) Raising the pT 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 materialTrack Trigger for ATLAS at HL-LHC 16Nikos Konstantinidis
Options for ATLAS
Upgrade L1CaloUse finer granularity information from Calorimeters
Upgrade L1Muon Sharpen pT thresholds, reject more fake triggers
Use tracking info at L1Known to be a key element for rejection at L2
A combination of all of the above
Track Trigger for ATLAS at HL-LHC 17Nikos Konstantinidis
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 Dh=0.003 in 1st LAr sampling are essential for rejecting p0s
ATLAS Trigger upgrade plans and activities 18Nikos Konstantinidis
L1Muon rates at 5e34
Track Trigger for ATLAS at HL-LHC 19Nikos Konstantinidis
Rates for muons from b/c/W can be extracted by convoluting pT resolution with physics x-section
pT resolution drives the physics rates: >50kHz for MU20, >25kHz for MU40 The above estimates do not include cavern background nor charged p/K
decays in flight, hence they give a lower bound
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-LHC 20Nikos Konstantinidis
All L1 Triggers
L1 Triggers with offline muon
Endcaps
Endcaps
The ATLAS L1Track R&D
Why tracking at L1
Tracking is key for rate reduction at L2, so it would enhance the purity of the L1-accepted eventsFor 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-LHCOtherwise we’ll have to rely exclusively on pT
thresholds for controlling the L1 ratesTrack Trigger for ATLAS at HL-LHC 22Nikos Konstantinidis
Track Trigger for ATLAS at HL-LHC 23Nikos Konstantinidis
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-pT 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-LHC 24Nikos Konstantinidis
Cannot readout the whole tracker at 40MHz
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-LHC 25Nikos Konstantinidis
Track Trigger for ATLAS at HL-LHC 26Nikos Konstantinidis
Example: strips readout chip design
Advantages of RoI-based L1Track
No impact on the tracker layoutCan 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-LHC 27Nikos Konstantinidis
ATLAS vs. CMS L1 upgrades
Conclusions depend on initial conditionsAt 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 L1MuonHigh granularity of LAr calorimeter is an advantageMuon Small Wheels
Of course, with more options it is harder to converge
Track Trigger for ATLAS at HL-LHC 28Nikos Konstantinidis
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 ETJet
Level-0 Calo
R3
Trigger & Timing distribution
L0A, L1A
L1A
25 ns perpipeline step
= < 256 - 3.2 μs
A possible architecture: L0/L1
40M
Hz
~50
0kH
z?<
100k
Hz?
Nikos Konstantinidis 29Track Trigger for ATLAS at HL-LHC
RoI-based L1Track parameters
Key parameters for the design of L1Track areL0 rateL1 rate
could be <100kHz if enough rejection is achievedNumber/size of RoIs
hence the fraction of the tracker to readout at L0 rateNumber of tracker layers to readout
not necessarily all
Ongoing simulation studies to determine these parameters
Track Trigger for ATLAS at HL-LHC 30Nikos Konstantinidis
Regional Readout studies
Track Trigger studies 31Nikos Konstantinidis
Mod
ule
num
ber
in Z
Frequency (in %) inside an RoI
PIXEL
STRIPS
RoI: Df=0.2, Dh=0.2 at Calo Dz=40cm at beamline
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-LHC 32Nikos Konstantinidis
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-LHC 33Nikos Konstantinidis