CMS Tracking Trigger studies for the SLHC

CMS Tracking Trigger studies for the SLHC CMS sLHC Tracking Trigger

1032 cm-2 s-1 1033 1034 1035 CMS from LHC to SLHCMotivation for L1 Tracking Trigger I. Osborne At SLHC CMS faces new challenges, in particular for both Tracking and Triggering CMS sLHC Tracking Trigger

Scope of this Discussion:Outer Tracker • The region of the inner-most Pixel Layers is fundamentally challenging at the SLHC, especially for the Sensor Technology • One may speculate as to the most promising way forward • B-tagging, e/discrimination remain Very Important • Assume 4 or 5 Layers of Fine-Pitch Pixels • To be better defined • Possible L1 Trigger primitives formation under study, but no viable schemes identified yet • Here focus on Outer Tracker as providing also L1 Trigger Primitives • Assume boundary between inner-most Pixel Layers and Outer Tracker is somewhere between 20 ~ 40cm • In any future baseline layout, Outer Tracker and inner-most Pixel Layers will have to make a coherent Tracking System Intelligent Trackers as L1 Trigger Providers for the SLHC

SLHC L1 Tracking Trigger:Reminder of Required Functionality • Electrons/Photons • Rate dominated by high Pt p0 from jets • Is there a high Pt charged track consistent with L1 ECAL Cluster? • Is it Isolated? • Muons • Rate dominated by miss measured muons from jets, below the Pt threshold • Is there a matching high Pt charged track above the Pt threshold? • Is it Isolated? • Taus • Rate dominated by ~ narrow high Pt jets • Is there a narow low multiplicity jet associated to the L1 Calo Cluster? • Is it Isolated? CMS sLHC Tracking Trigger

Required FunctionalityL1 Trigger: Taus • Confirmation of High Pt Narrow Jet Candidates • Tracks with Pt above ~ 10 GeV • Fast, Efficient high Pt Tracking • Good Pt resolution • Isolation • Tracks with Pt above ~ 2 GeV • Fast, Efficient and Clean Tracking down to Pt ~ 2GeV • Longitudinal Primary Vertex association • Required to maintain efficiency at 1035 • Tracks with Pt above ~ 2 GeV • Good Z Vertex resolution CMS sLHC Tracking Trigger

An additional Desirable Feature:rejection of Uncorrelated Combinations • Rejection of Uncorrelated Combinations, from different primary vertices? • At 1035 expect ~ 200 pile-up interactions for each 25ns bunch crossing • Uncorrelated Trigger Primitives from different primary vertices may force higher thresholds Combined Triggers • Longitudinal of Trigger Primitives with Tracks at Vertex would avoid this • May be possible if track Longitudinal Vertex Association, required for Isolation cuts, is available CMS sLHC Tracking Trigger

CMS from LHC to SLHCMotivation for L1 Tracking Trigger Isolated Electron-Photon L1 Trigger with 200 event Pile Up Optimized for 1034 Retuned for ~ 90% Efficiency at 1035 ~ 60kHz at 34GeV (vs ~ 4kHz at 1034) Marcello Mannelli & Anders Ryd SLHC Tracking Trigger

CMS from LHC to SLHCMotivation for L1 Tracking Trigger Isolated TauL1 Trigger with 200 event Pile Up Optimized for 1034 Retuned for ~ 90% Efficiency at 1035 ~ 40KHz at 100GeV (vs ~ 5kHz at 1034) Marcello Mannelli & Anders Ryd SLHC Tracking Trigger

Local Occupancy Reduction • Cannot possibly transfer all Tracker data at 40MHz ! • Crossing Frequency / Event Read-Out ~ 40MHz / 100kHz ~ 1 / 400 • L1 Data reduction by a factor of 10 ~ 100 is required • For L1 Trigger propose to transfer only hits from tracks with Pt > ~ 2 GeV • The aim is to provide useful Isolation information • Tracks with Pt > ~ 2 Gev are less than 1% of the Tracks inside acceptance • This corresponds to the maximum plausibly manageable L1 data rate • In addition, must provide means of rapidly & reliably identifying high Pt (isolated) tracks ( Pt > 10 ~ 25 GeV) CMS sLHC Tracking Trigger

Local Occupancy Reduction Tracks with Pt > 1 GeV < 10% of Tracks in acceptance Tracks with Pt > 2.5 GeV < 10% of the remaining Tracks Intelligent Trackers as L1 Trigger Providers for the SLHC

Local Occupancy Reductionwith Local Track Vectors J. Jones (~2005) CMS Tracker SLHC Upgrade Workshops • Pairs of Sensor Planes, for local Pt measurement • High Pt tracks point towards the origin, low Pt tracks point away from the origin • Use a Pair of Sensor Planes, at ~ mm distance • Pairs of Hits provide Vector, that measure angle of track with respect to the origin • Note: angle proportional to hit pair radius • Keep only Vectors corresponding to high Pt Tracks α Intelligent Trackers as L1 Trigger Providers for the SLHC

Possible Tracker LayoutsIncorporating Stacked Module Layers • Several potential layouts for an SLHC Outer Tracker are under study • Want to provide both Tracking Trigger & Optimal Tracking in future Tracker • Options under study range from minimal Tracking Trigger with conventional (much improved) Tracker, to fully integrating Tracking Trigger and Tracker functionality • No final decision on layout of tracker until final requirements determined, and feasibility and performance potential of different options understood Minimal Hybrid Layout Long Barrel Straw-Man Intelligent Trackers as L1 Trigger Providers for the SLHC

Possible Tracker LayoutsIncorporating Stacked Module Layers • Several potential layouts for an SLHC Outer Tracker are under study • Want to provide Tracking Trigger & optimal Tracking in future tracker • Options under study range from minimal Tracking Trigger with conventional (much improved) Tracker, to fully integrating Tracking Trigger and Tracker functionality • Here focus on the Long Barrel Straw Man as it allows evaluating the full range of possible Tracking Trigger architectures which build on the Stacked Module approach Minimal Hybrid Layout Long Barrel Straw-Man Intelligent Trackers as L1 Trigger Providers for the SLHC

A Hierarchical Scheme withDouble Stack Layers • Stubs from the Stacked Modules • Combine clusters across Stacked Module to form Track Vectors, or Stubs • Reduce rate by rejecting stubs with Pt below ~ 2GeV • Low threshold driven by Isolation cut requirement • Tracklets from the Double Stack Layers • Combine Stubs across Double Stack Layer Stubs to form Tracklets, in a “local” and computationally efficient way • Tracklets are 4 Vectors with useful Pt, f and q resolution • Use Tracklets as seeds for L1 Tracks which combine stubs from other Double Stack Layers • Allow for hit loss, to provide robust system • A Long Barrel Straw Man Layout • Which uses Double Stack Layers for both L1 Tracking Trigger and Full Track Reconstruction CMS sLHC Tracking Trigger

Long Barrel Straw Man Layout:3 Double Stack Layers + 2 Short Fwd Barrels CMS sLHC Tracking Trigger

Tracking Trigger Simulations:Goals and Program of Work • Consider three levels of L1 Tracking Trigger Primitives • Hits above threshold -> Valid L1 Clusters • Valid L1 Clusters -> Accepted L1 Stubs • Accepted L1 Stubs -> Accepted L1 Tracklets • Build L1 Tracking Trigger Objects for High Pt Leptons & Isolation • Using combinations of Tracklets and/or L1 Tracks • Combine with Calo and/or Muon to build Combined L1 Trigger Objects • Using first High Pt Lepton Tracking Trigger Primitives • Then seeing effect of adding Tracking Trigger Isolation criteria • Validate and study Efficiency vs Rate at each step • Standard Plots CMS sLHC Tracking Trigger

Track Trigger Primitive Simulations • Simulated threshold curves for Stubs, with 2GeV pt acceptance cut, for various sensor separations within a Stack, in different Barrel Layers • The Pt thresholds are sharper at larger radii, as expected CMS sLHC Tracking Trigger

Track Trigger Primitive Simulations • Simulated threshold curves for Stubs, with a 1mm Sensor separation within a Stack, for various Pt acceptance cuts, in different Barrel Layers • The Pt thresholds are sharper at larger radii, as expected CMS sLHC Tracking Trigger

Agenda Tracking Trigger Working GroupCMS Upgrade Week, April 2010 • Benchmark code for Clusters & Stubs • Rates and FAST versus FULL Sim Comparisons • L1 Tracking Triggers, and performance of Benchmark code • Muon Triggers • Electron Triggers • Tau Triggers • L1 Pixel Jet Triggers • Proposed Architecture for Tracklet and L1 Track formation • Discussion • Implementation of Tracklet and L1 Track Algorithm CMS sLHC Tracking Trigger

Track Trigger Primitive Simulations:Benchmark Code for Clusters & Stubs CMS sLHC Tracking Trigger

Track Trigger Primitive Simulations:Benchmark Code for Clusters & Stubs • Comparison of • Full Simulation • Full Sim no ou-of-time PU • Fast Simulation • Detailed Simulations in place • There still remain • Substantial Discrepancies • Peculiar Features • => Uncertainties in Rates… • Work with Fast Simulation • Present thinking based on conservative assumptions Hits Clusters Stubs CMS sLHC Tracking Trigger

Muon BarrelTracking Trigger Studies CMS sLHC Tracking Trigger

Muon End-CapTracking Trigger Studies CMS sLHC Tracking Trigger

ElectronTrack Trigger Studies CMS sLHC Tracking Trigger

Why Tracklets? • Consider 3 layers and no tracklets (track hits but no Pt) • To find tracks need to test all combinations of tracks from all layers (minimum Pt covers entire sector) • Must be completed in 25 ns. • Tracklets allow projection of the track hit from one layer to another • reduces the range to check in the destination layer • All hits can be compared simultaneously in an FPGA • Practical limit is ~10 hits/layer • Subdivide layer to stay within this limit Tracklets allow reduced scan range 3 track 3 layer example CMS sLHC Tracking Trigger

Why Tracklets? • For example, project Tracklets from inner 2 layers to outer layer segment (independently) • Projection from an Inner Layer requires complete Tracklet • 2/2 Stubs, 4/4 Clusters • Outer layer uses stubs • Reduces effect of hardware failures • Segments must overlap due to imprecise projection M. Johnson, U. Heintz et al See presentation by U. Heintz CMS sLHC Tracking Trigger

Why Tracklets? • Repeat for the other Layers (independently) • With this scheme Tracklets in a given layer can be put into coincidence with Tracklets or Stubs in the other Layers • Recover possible missing stubs in up to two Layers • Minimize sensitivity to hardware failures and inefficiency • Must remove duplicates M. Johnson, U. Heintz et al See presentation by U. Heintz CMS sLHC Tracking Trigger

Conclusions and Prospects • Benchmark code for Clusters and Stubs exists • Studies ongoing to understand rates etc • Combinations of Stubs from different layers demonstrate encouraging performance potential across a wide range of studies • Now moving to implement benchmark code for Tracklets and L1 Tracks • Inspired by proposed back-end architecture proposed by M. Johnson et al • This will make available the full suite of possible Tracking Trigger primitives across the e, m and t channels • Other studies may follow • Work is also continuing on the feasibility of inner pixel based jet triggers CMS sLHC Tracking Trigger

Back-Up slides CMS sLHC Tracking Trigger

CMS Tracking Trigger studies for the SLHC