CMS statusA walk through the performance of CMS at

LHC

Will try to avoid overlap with later presentations on physics performance

Acknowledgements: the material presented here is the result of work of > thousand people who have

built, commissioned CMS over the years and to those who have

analyzed the data which has been pouring in the last months: to them goes

the merit of the results shown, mine are only the mistakes/omissions

T. Camporesi , CERN

CMS

How are we doing93% lumi livetime during stable

beam:Most losses due to study beam

related issues with readout: fixed since end of August

Running with L1 trigger rate between 45 and 70 KHz (sustained peaks at 90 KHz) and logging rate between

350 and 600 Hz

L=1027Hz/cm2L=1028Hz/cm2L=1029Hz/cm2

L=1030Hz/cm2

L=3 1030Hz/cm2

L= 1031Hz/cm2

L= 5 1031Hz/cm2

PixelStrip

EB+EEEBEEES

HCALHBHEHFHODT

RPCCSC

CASTOR

93 94 95 96 97 98 99 100 101% Usable Channels

Today

Trackers and tracking

Tracker material TDR MC now

and it seems correct

Conversions Conversions

Conversions Nuclear Interactions

Magnet•In order to

achieve P resolution goals the magnetic field has to be understood to the permill level

Analitical fit reproduces measurement to 0.01%

Low P

J/ΨTDR: almost mission accomplished for

low P

Single track pt resolution extracted from J/Ψ width

Y(1,2,3S)

Intermediate PNo bias with a

precision of 0.15%

Z→mmW→mn

High P (cosmics)

~8% for pt=500 GeV

Split cosmic track at point of closest approach to ‘IP’

Tag-leg

Probe-legEstimate momentum

scale bias by assuming no infinite P tracks

-0.044±0.022 TeV-1

Vertex and IP resolution

Alignment: cosmics and early data I.P.

Vertex resolution

Pixel

Silicon Tracker

XZ

€

D0 →K −π +π −π +

D0 →K −π +

Tracking efficiency

and it is not affected by pileup

Probes passing the matching

Probes failing

the matching

J/Psi Tag and probe

Muons

Muon trigger barrell

transition endcap

J/Ψ ms

Tag&probe

Performance“Soft muon”: a tracker track matched to at least one CSC or DT stub, to collect muons down to pT about 500 MeV in the endcaps (e.g. for J/Ψ)

“Tight muon”: a good quality track from a combined fit of the hits in the tracker and muon system, requiring signal in at least two muon stations to improve purity.

J/Ψ msTag&probe

J/Ψ msTag&probe

μ charge id•Cosmics ( track split and two

halves compared)

Mis-ID ~1%

Electrons,g and ECAL

ECAL triggerL1 5 GeV thresholdBarrell (50%) 5.6

GeVEndcap (50%)6.7

GeV

L1 8 GeV thresholdBarrell (50%) 8.9

GeVEndcap (50%) 10.8

GeV

HLT 15 GeV g efficiency vs Supercluster energy

reconstructed

ECAL TDR

and test beam exposure ( 25% of detector)confirmed the potential of the PbWO crystals

small constant term needed to detect narrow

gg resonances

but key point is crystal intercalibration :only 25% have been exposed to e beam

ECAL calibration:π0

Online π0 streams

comparison with e-beam

calibrated crystals

p0 combined with splashes and f symm Reaches 0.5 to 1.2 % depending on h in barrel

p0 250 nb-1

p0,splashes, f-symm 250 nb-1

ECAL energy scale

in the barrel the scale is now set by the π0 calibrationEB ~ 1% ….. EE

~ 3%

HCAL & Jets

HLT efficiencies: calo

Jets: just data

i.e. use μ-triggeredevents and

check turn-on curves on recojets without

any energy corr. Barrel

Endcap

Trigger : L1 E> 6GeV

Trigger : L1 E> 6GeV

Just data l

JES corrected

HLT Trigger : E> 15GeV

HLT Trigger : E> 15GeV

isolated part response

Particle flow jets

Down to pt=20 GeV and 5% Jet Energy

Scale

Jet Triggered Charged particle Spectra

Using Jet trigger it is possible to extend the momentum range of charged particle spectra

Cross sections scaled empirically by (√s)5.1

Missing Et

Events with isolated g

CALO TC-MET PF-MET

€

u|| = r u T ⋅r q T

u||

qT

= CMET (Q flavor,JES)

Missing recoil energy = Missing Et

correction factor (depends on Quark

flavor and JES)

qT distribution of g-jet candidates

b-Tagging

Data-MC comparison for b-tagging observables

DATA/MC ratio is

close to 1 for all

observables

Trigger requirements

Event rate

Selected eventsto archive

HLT input

Level-1 input

ON

-lineO

FF-line

Online requirementCollision rate 40 MHzEvent size 1 MbyteLevel 1 Trigger Input 40 MHzHLT trigger input 100 KHz

Mass storage rate 300 HzSystem Deadtime ~%In early phases: keep L1 rate

<70KHz (only 50% of Filter farm installed) and use

HLT trigger menus adapted to Luminosities to reduce logging

rate to <500 Hz

trigger• Name of the game: keep trigger as loose as

possible: new L1 and HLT menus ~every doubling of lumi ( LHC lumi doubling time has been ~10 days since start of collisions!)

Level 1 rates: predicted first

from MC and after first fills

extrapolated to higher Lumi.

Keep unprescaled single physics

object threshold compatible with total rate < 70

KHz+ lower threshold

multiplicity and isolation triggers

High Level Trigger• With initial luminosities L1 trigger 0-bias or prescaled min-bias

+ low threshold ‘objects’ (e.g. eγ > 5 GeV, Jets > 10 GeV, loose μ) to keep rate <70 KHz

• Adaptive HLT menus in steps of peak lumi: predicted from MC first and then extrapolated from earlier data taking

Conclusions• The goals set out by the CMS founding fathers

are close to be met: a feat we did not dreamed to be possible this early in the game

• CMS is more ready to produce physics than we ever expected

• What will be presented at this workshop are the measure of the quality of the detector and just an appetizer for the future

• Last but not least we salute the amazing performance of LHC

for (much) more details see : http://cdsweb.cern.ch/collection/CMS%20Physics%20Analysis%20Summaries?ln=en

Backup slides

A figure sums it allBest TOP production candidate

Top candidate Mass in the 160-220 GeV range

secondary vertex6σ ellipse

Tracker De/Dx

Trigger & DAQ

Event selection ~ µsec latency

TriggerData

Timing with beamUsed early fills to do detailed timing scans for calorimeters, CSC, pixel, tracker

Optimize delays for data pipelines and trigger primitive generation Good timing essential

for background rejection:e.g ECAL

Trigger synchronizationSynchronization initially defined from cosmics, beam splashes refined

with timing scansMonitored using Zero Bias and/or min bias:

Zero bias = trigger on coincidence of beam crossings(L1 trigger =0-bias while # on crossings/orbit was up to 8, ie. L1 rates

< 100 KHz

Low P resolution•Use Ks, Φ, J/Ψ to monitor/calibrate

vs (η,Pt)

Ks

Φ

Φ

J/Ψ

Use dE/dXto sel. K

In situ ECAL calib• Use γ from π0 decay and Φ symmetry

(assume that integrating over large # of min bias events the energy deposited in crystals at a given pseudorapidity is the same then use test beam pre-calibrated crystals to cross-calibrate various Φ rings) and beam-splashes

• For endcaps use beam-splash events form 2008-2009

• Compare with cosmics calibration and electron test beam pre-calibrated crystals to estimate precision

• Ultimate calibration will be W en events

Φ symmetry (EB)• 7 TeV data— 7 TeV MC

900

GeV

7 TeV

Syst < 0.5%

Missing Et

And pileup seems to be under control

Jet Energy scale• Jets are defined using 3 algos: calo only, Calo+ tracks, Particle flow +

anti Kt clustering with R = 0.5

• At start use MC to estimate corrections vs (η,pt)

• Then use data based methods: dijets pt balance and γ-jet events ( not used YET in physics analyses)

Corrects noise and

pileup

Effect of distribution

(vs η) of material and

detector structure

Corrects pt dependance due to non compensating

nature of CMS calorimeters

Calo-jets Calo+Trk (JPT) ParticleFlow-jets

PFJ rely less on’combined-calo’

65% Trk, 25% ECAL,

10% HCAL+ECAL

JES: dijet pt balance

18 <pt<31 GeV

70<pt<120 GeV

Calo-jets

JPT-jets

P-flow-jets

Calo-jets

JPT-jets

P-flow-jets

after relative response correction

(shown is error band of 2%⋅η

adopted inphysics analyses

The observed trend of higher response in data wrt MC for η>2 is consistent with what

is observed in single particle studies

JES: γ + jet• difficulty to define ‘single jet’: use Missing Et

Projection Fraction ( MPF) method (used by CDF)