high -level trigger studies - phys.ufl.eduacosta/oo/acosta_hlt_doe600.pdf · Ł learning curve: p...

June 29, 2000 DOE/NSF USCMS Computing and Software Report. HLT Studies D. Acosta 1

High-Level Trigger Studies

Darin AcostaUniversity of Florida

DOE/NSF Report on US CMSSoftware and Computing

DOE GermantownJune 29, 2000


CMS DAQ ArchitectureCMS DAQ ArchitectureCMS has a multi-tiered trigger system:

è L1 reduces rate from 40 MHz to 75 kHzp Custom hardware processes calorimeter and muon data to

select electrons, photons, jets, muons, ET above threshold

è L2, L3,… (HLT) reduces rate from 75 kHz to 100 Hzp Commercial CPU farm runs online programs to select

physics channels

HLT


DAQ / HLT ChallengeDAQ / HLT Challenge

è HLT selection algorithms must keep only 1 eventout of 1000

p Limited by ability to filter a L1 data sample which is already rich in physics

è DAQ bandwidth is finitep Total event size is 1 MB, event rate is 75 kHzp Bandwidth limited by switch and link technology

First HLT milestone:

Demonstrate that L2 can achieve 10X rate reductionusing only 25% of the event data

è Partial event reconstruction using only calorimeterand muon data


CMS Physics GroupsCMS Physics GroupsPhysics Reconstruction and Selection (PRS)groups were established by CMS in 1999:

è Electron/Photon C. Seezè Muon U. Gaspariniè Jet/Missing ET S. Enoè b/tau A. Caner

p Overall coordination by P. Sphicas

Charge is to evaluate the physics capability of CMS from L1 to offline

US-CMS has substantial involvement in the Electron/Photon, Jet/MET and Muon groups

è Focus of the Calorimeter, Endcap Muon, andTriDAS construction project communities


Context of StudiesContext of StudiesThe L1 Trigger TDR is targeted for November, 2000

è Final design efficiencies and rates beingdetermined

The DAQ TDR is targeted for November, 2001è Need to understand the rejection capability of the

HLT triggers and the amount of data each steprequires to validate possible hardware solutions

A Physics TDR is targeted for 2003è It was delayed to allow for the transition to

object-oriented software

In all cases, we need to validate the algorithms for the CMS physics plan, taking into account all possible backgrounds


HLT HistoryHLT HistoryFirst HLT milestone was set for November 1999,6 months after the creation of the PRS groups

Despite rapid progress, milestone was not met:è Growing pains:

p First wide scale use of ORCA as a toolè Learning curve:

p Many inexperienced users and developers tackling C++è Not enough time:

p More validation needed of reconstruction softwarep Endcap Muon software not completedp HLT algorithms developed only at the last minute

è Insufficient manpower and resources

HLT milestone postponed until July 21, 2000


Recent DevelopmentsRecent DevelopmentsTransition from ORCA3 to ORCA4

è Full migration to Objectivity in place of Zebra filesè Additional functionality

p Inclusion of endcap muon code (L1 and reconstruction)p Correct handling of out-of-time b.x. in calorimeter

è Further validation testsProduction of large simulated event samples

è Why? σσinel = 55 mb and L = 1034 (⇒⇒ 17.3 collisions/b.x.)

è GEANT3 production at CERN, Italy, and U.S.(Caltech, UFlorida, UCDavis)

è OO hit formatting and digitization done at CERNp 2 weeks for each on a large Linux PC farm

è Users access a User Federationp All file/database details hidden from userp Standard ntuples produced for physics groups


ORCA Production 2000ORCA Production 2000Signal

Zebra fileswith HITS

ORCADigitization

(merge signal and MB)

ObjectivityDatabase

HEPEVTntuples

CMSIM

HLT AlgorithmsNew

ReconstructedObjects

MC Prod.

ORCA

Prod.

HLT

Grp Databases

ORCAooHit

FormatterObjectivityDatabase

MB

ObjectivityDatabase

Catalog import

Catalog import

ObjectivityDatabaseObjectivityDatabaseytivitcejbOytivitcejbOesabataDesabataD

Mirrored D

b’s(U

S, Russia, Italy..)


Data SetsData Setse/γγ and Jet/MET groups:

è 0.9 Mevt (0.8 TB) è Supplement 1999 Monte Carlo production

p 0.6 Mevt QCD dijet (various ET ranges)p H→→ bb, H→→ ττ ττ , SUSY, min. bias pile-up, single particle

Muon group:è 1.3 Mevt (1.3 TB) è Production redone in 2000 to update Pythia,

endcap geometry, and event weightingp 0.9 Mevt minimum bias events for rate and pile-upp H→→ ZZ →→ 4µµ , H→→ WW →→ 2µµ , W→→ µνµν , Z →→ µµµµ , single µµ

CMS operations:è Expect 1000 TB/year

HLT milestone is a 0.1% Mock Data Challenge!


Muon Physics PlanMuon Physics PlanValidate L1 trigger decision and use as a seed for muon reconstruction

Improve PT resolutionè Refit with vertex constraint

using reconstructed hitsè Extrapolate to outer tracker

and refit

Apply isolation requirementè Extrapolate to calorimeter

and sum energy in cone

U.S. physicists working on L1 and Reconstruction for EMU

Mu

on

Rat

eEffective PT Threshold


Results: Single Results: Single µµµµ L1 EfficiencyL1 Efficiency

First look with ORCA4

Recoverable


Barrel/Endcap Overlap RegionBarrel/Endcap Overlap Region

Cathode Strip Chambers

Drift Tubes

Must include ME2-ME3 tracks for redundancy, despite poor PTresolution

We are learning from the simulation…


e / e / γγγγ and Jet / MET Physics Planand Jet / MET Physics PlanElectrons:

è Bremsstrahlung recovery (>½X0 of silicon tracker)è ππ0 rejectionè Isolationè Track match and E/p cuts (L3)

Jets:è Finer tower granularityè Improved jet axisè Energy calibration (non-linearity, pile-up)

p All this improves the ET resolution MET:

è Improve the ET resolution Taus:

è Improve shape cuts


Jet Jet Resol’nResol’n before & after Correctionbefore & after Correction

Average for |ηη| < 3

Cone R=0.5 No Pileup Cone R=0.5 Pileup


ConclusionsConclusionsClosing in on HLT milestone for L2 performance

è Expect results in mid – Julyè However, this is just a first pass at the code that will eventually run

online. Will have to optimize, etc.

The task is challenging and work intensive!è Production is finally complete, analysis is underway

The HLT groups are driving (US)CMS software & computing

Significant work performed by U.S. physicists in Endcap Muon, Jet/MET, and e/γγ groups

è Could use even more manpower, since the “users” are often the code developers as well

User facilities and software/computing support are essential for U.S. physicists to maintain the prominent role taken so far

high -level trigger studies - phys.ufl.eduacosta/oo/acosta_hlt_doe600.pdf · Ł learning curve: p...

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