Status of CMS and the road to first physics results

Jordan Nash

For the CMS Collaboration – ICFA Seminar – SLAC October 2008

Outline

CMS Status Commissioning so far Commissioning plans with first data Physics Topics for the first fb-1

QCD/JETS Electroweak New Physics

The CMS Detector

Minus end just before closure

CMS Closed for September 10th

Last detector to Install

When the detector was closed for the September beam running, all elements of CMS were installed except for the pre-Shower detector in front of the Crystal endcaps

The Preshower detector will soon be completed, and installed during the winter shutdown

“D’s” undergoing final assembly cold testing now

Commissioning with Cosmics

z

(at

surf

ace)

[c

m]

x (at surface) [cm]

Tracker

ECAL

HCAL

Muon System

3 T

Sept 10

0 T

Position of track extrapolated to

surface.Clearly see shaft

More than 300M events

recorded during

summer

Tracks passing through the ECAL

Cosmic running used to test triggers, operation of all detectors

Example: Trigger using Drift Tubes Validate Calorimeter e-gamma Trigger

Verify pre-calibration of ECAL

in detector units

i

n d

ete

cto

r un

its Reconstructed clusters matching muon tracks

(DT triggered events)

Energy deposited in 3x3 ECAL cluster matched to a muon track

Muon reconstruction at 3TReconstructed Muon Momentum using Drift Tubes

Magnet closed for the first time underground late in the summerBefore the Sept 10 Running field raised to 3 T

Tracker operation and alignment Cosmics used to align

tracking detectors Significant improvement

from construction parameters possible already

Multiple algorithms for alignment validated

Look at performance using “split” muons

CRUZET4

before alignment

after alignment

First view of LHC Beam

HCALECAL

LHC Tunnel profile visible

Muon DT

Calorimetric response

Splash on collimators 2 X 109 p hitting the collimator 150 m upstream from the detector

Tremendous amount of energy deposited in the detector DAQ able to cope with enormous

events

Ecal Endcap

Ecal Barrel

Correlation between total

energy in ECAL and HCAL

Conditions with beam captured

HCAL Endca

p

Endcap Muon Trigger Rate for circulation and then capture of

beam

Beam Halo Events

ME+1

ME+2

ME+3

ME+4

Occupancy in Endcap Muon System Discs

Next Steps 300M events at 3.8 T (CRAFT) Goals

Improved alignment of tracking detectors Want sufficient events passing

through pixel detector Experience of continuous operation

of complete detector at full field Will then open CMS to install the

preshower detector

75 M events in first few

days

What do we expect to do with first collisions? Plan over the last year has

been to study what to extract from the first few pb-

1

Re-discover the SM Event rates for SM processes

are large Rate W ~108/fb-1

Rate Z ~107/fb-1

Rate tt ~106/fb-1

Understand detectors e.g. W/Z used for precision

calibrations Understand backgrounds in

searches for new physics, and precision measurements Concentrate on data driven

methods for determining backgrounds

Early studies of event properties

Enormous QCD Cross section New territory in terms of Jet ET

Underlying event measured with very first data Understand environment at 14

TeV Tune MC models Observables Nch, PT

SumTevatron

LHC

Different Tunes/Model

s

Jets/QCD

Potential for discovery of Contact interactions in Dijets, 4 TeV for 10 pb-1

7 TeV for 100 pb-1

10 TeV for 1 fb-1

Measurement of Inclusive Jet Cross Section Understanding of Jet

Energy scales, resolutions PDF Uncertainties

Energy Scale

Uncertainty100 pb-1

Calibrating Jets/Missing ET

Missing ET Vital for many physics channels

calibration is difficult Sensitive to Hot/Dead Channels

Instrumental effects can create large fake signals

Need Real data Need to correct for

Jet Energy , m t, e

Data Driven methods for Jet Energy Scale Corrections e.g. DiJet Balance –relative Z+Jets - absolute

Early Z Measurement 10 pb-1

~4.6K e+e- pairs in the 70<Me,e<110 mass

region

~5.5K μ+μ- pairs in the 70<Mμ,μ<140 mass

region.

The Z produces a very clean signal. Use Tag

and Probe to calculate efficiencies from Data

2 Isolated High PT (20 GeV) tracks (muons)2 Isolated High ET (20 GeV) electrons, loose electron ID

Early W Measurement Single Isolated High PT Lepton

Muon (>25 GeV), Electron (>30 GeV) QCD Background estimation from Data

Invert Isolation Cuts Missing ET Shape from Data

Use γ*/Ζll events Measure missing ET excluding the 2nd

lepton Event rates (at 10 TeV are about 70% the

rate at 14 Tev)

28K Weν events and ~ 6K QCD events

64K Wμν events and ~16K QCD events

W Mass –precision measurements 1 fb-1 gives MW to about 40 MeV/c2

Limit energy linearity(e), MET scale(m) 10 fb-1 measure MW to about 20 MeV/c2

(statistical uncertainty 15 Mev/c2) Ultimate precision about 15 MeV/c2

Limited by MET Scale, resolution Theoretical uncertainties PDFs, PT(W)

WZ/ZZ

Understanding vital for searches These are major irreducible backgrounds for searches Ultimately measure TGCs

300 pb-1

Events per fb-1

•Find Same Flavour Opposite Sign leptons for Z candidate• PT Leptons > 15 GeV•Add 3rd lepton with PT > 20 GeV• Form MT with Missing ET -Require MT > 50 GeV

Looking for Supersymmetry Signatures

Leptons Jets Missing Energy

Requires excellent understanding of the detector

Builds on our measurements of SM processes

SUSY parameter space Where to look? Detailed studies at a

set of potential SUSY mass scenarios Full MC analysis Understand analysis

strategies, systematic uncertainties

Extrapolate to cover the full plane using Fast simulation

Low Mass points for early discovery potential

High Mass points for looking near potential limits

Early SUSY searches Jets + Missing ET signature

>= 3 Jets (180, 110, 30 GeV) , HT > 500 GeV, Missing ET > 200 GeV

Must control backgrounds, and understand missing transverse energy – QCD events with mis-measurements have very different

topologies Irreducible background from Z to neutrino decays Use Z + Jets (Z to leptons) to estimate bkgd Also Use g + jets

Remove photon

LM1 1 fb-1

HM Points/DiJets

Jets+Missing ET at HM points HT > 1500 GeV, Missing ET > 600 GeV

Also looking at new variables Look at Dijet events using discriminator

suggested by Randall/Tucker-Smith Two High PT Jets (HT > 500 GeV) a > 0.55 Sensitive to squark pair production

HM1 1 fb-1

Missing ET + Jets + leptons

Two Same Sign Muons PT > 10 GeV >= 3 Jets (175/130/55) GeV Missing ET > 200 GeV

Backgrounds in these channels are very low SM Backgrounds produce

opposite sign leptons

At least 1 isolated Muon PT > 30 GeV

>= 3 Jets (440/440/50) GeV

Missing ET > 120 GeV Signal/Background High

SUSY Searches Summary 10 fb-1

Discovering SUSY parameters

No Mass peak, but kinematic edges possible to observe

Same Flavour Opposite Sign leptons PT > 10 GeV

>= 3 Jets (120/80/30) GeV Missing ET > 200 GeV Estimate backgrounds from

Opposite flavour events Fit for endpoint

Sensitivity (statistical) ~1 GeV/c2 for 1 fb-1

Signal

Bkgd

Cascade Higgs Decays

Other Possible BSM extensions have similar signatures (i.e. leptons, jets, large missing ET,) Technicolor ED Little Higgs

May be possible to see Hadronic h decays with large missing ET signatures

h02

bmissTE01

b

Heavy Stable Charged Particles

32

Models with Charged Stable Particles GMSB - staus Kaluza-Klein taus Long lived stop

ct of order meters Measure Time of Flight in the

Muon DT system Measure DE/Dx in the

Tracker Momentum from Tracking

Conclusions

CMS Detector will be complete and commissioned at the start of next year’s run Substantial data collected at full field with all

detectors Experience of 24/7 operation

Rapid understanding of first data will be vital to be ready for early discoveries Physics preparation concentrating on preparing

data-driven analysis to: Recover SM Understand detector performance Look for evidence of new physics

Many new physics signals detectable with a few fb-1

Expected Day 0

Ultimate goals

ECAL uniformity

~4% < 1%

Lepton energy 0.5-2% 0.1%

HCAL uniformity

2-3% < 1%

Jet energy <10% 1%

Expected Day 0

Goals for Physics

Tracker alignment

20-200 mm in Rf

O(10 mm)