from the standard model to discoveries - physics with the cms experiment at the dawn of the lhc era...

From the Standard Model to Discoveries - Physics with

the CMS Experiment at the Dawn of the LHC Era

Dimitri BourilkovUniversity of FloridaCMS Collaboration

SESAPS Meeting, November 11, 2005, Gainesville, FL, USA

D.Bourilkov Early CMS Physics 2

LHC Start-up

• 2007 : machine cool-down / machine commissioning

• July 1, 2007: CMS closed and ready for beam• August 2007: first (single) beams• October/November 2007: two beams in the

machine first pp collisions at 14 (?) TeV• Short pilot run with initial detector:

0.01 – 0.1 fb-1 ?• First physics run in 2008: 1 – few fb-1

• Physics runs in 2009+: 10-20 fb-1/year design luminosity 100 fb-1/year


Length : ~20 m Radius : ~7 m Weight : ~ 13000 tons

ECAL crystals

Barrel HCAL

CMS

Endcap Muon Chambers

Silicon tracker

Coil + inner vacuum tank


What’s on the Menu

• New Energy Regime – allall events are important!

• Large variation of rates; expect to measure them one-by-one with increasing luminosity

• Compare measurements to theory predictions, tune theory tools (e.g. MC generators)

• Measure minimum-bias, underlying events

• LHC will be a W factory, a Z factory, a top factory, a Higgs factory, a b factory, heavy ions laboratory …


Trigger

Trigger rates and expected events as function of luminosity

Level1High level

triggers (L2 and L3)

Filter farm


Event Rates for pp at s=14 TeV

Channels (examples …) Events to tape for 10 fb-1

(per experiment)W 70 x 106

Z 11 x 106

tt W b W b + X 0.8 x 106

QCD jets pT>150 ~ 107

Minimum bias ~ 107

g~g~ m = 1 TeV 103 - 104

Expected in the first year: LHC rates 103 larger in area of asymptotic TEVATRON reach Large samples of SM events – understand (calibrate, align etc) detector and LHC physics (check SM at highest Q2)

assuming 1%of trigger bandwidth

~ few PB of data per year/experiment challenge for software and computing(esp. @ beginning …)

Computing GRID underway


Very Early (SM) Measurements

Luminosity

1 mb-1

1 b-1

1 nb-1

1 pb-1

1 fb-1

Total cross section – not easyQCD: - d N / d PT , d N / d

- Jets @ higher PT: 100 GeV ; B production

500 GeV (S)ElectroWeak: W (calibration, alignment, PDF, later W mass)

Drell-Yan, Z (calibr., align., PDF, later EW mixing angle)

Top pairs (later top mass)

Boson pairs: WW, ZZ, W, Z Quarkonia: J/, …


Early Discoveries? Fix Scale for New Physics

“Easy”: new resonance decaying into e+e- or μ+μ- or , e.g. Z’ μ+μ- of mass 1-2 TeV; compositeness, extra dimensions, little Higgs, surprises …

“Not-so-easy”: SUSY proving a direct link between SUSY, dark matter and cosmology – probably higher importance than Higgs !

“Far-from-easy”: light Higgs (m ~ 115-140 GeV)


Contact Interactions, Extra Dimensions…

general framework for new int.:

• scale s (virtual effects)or resonances if s

• coupling g (convention g2

= 4)• we constrain g / • operators with canonical

dimension N > 4 terms ~ 1/MN-4


Bump Hunting e.g. Z’ μ+μ-,

RS-1…

Excellent benchmark analysis for CMS Muon DetectorClean (small Drell-Yan background)Very high pT muons (TeV specific

problems – showering etc)Mass Reach (SL > 5)

Full CMS simulation and reconstructionUn-binned Likelihood Ratio Approach

SL = √ 2 ln( Ls+b/Lb)

Mass Reach (TeV) Luminosity (fb-1)

> 1 0.1

2.6 – 3.4 10

3.4 – 4.3 100No systematic effects


5 discovery curves

~ one year at 1034: up to ~2.5 TeV

~ one year at 1033 : up to ~2 TeV

~ one month at 1033 : up to ~1.5 TeV

cosmologically favoured regionTevatron reach : < 500 GeV

Supersymmetry

Most important task in early days

Most sensitive channel: jets + missing ET (MET – resolution is KEY)

squarks / gluinos(clean final states, large rate, favorable signal/bg ratio)


The Higgs Boson

PYTHIA generation (LO) What is the origin of Electro-

weak Symmetry Breaking? If Higgs field at least one new

scalar particle should exist: The Higgs

LHC will cover the full range up to 1 TeV; final word about the SM Higgs by 2009 or so


Standard Model Higgs

Advancing detailed studies (large scale full detector simulations, lots of CPU)

CMS Full simulation

M < 140 GeV: low rates, high bg, difficult


The LHC is Coming!The LHC is Coming!• LHC and CMS are on track for first

collisions in 2007 and physics runs in 2008

• The challenge: commissioning of machine / detectors of unprecedented scale, complexity and performance

• LHC should be decisive in revealing the Electro-weak Symmetry Breaking mechanism in the SM (Higgs/no Higgs)

• LHC will break new ground in exploring LHC will break new ground in exploring the TeV scale, hunting for new physics:the TeV scale, hunting for new physics:Will it be easy? SUSY an early date?Will it be easy? SUSY an early date?Big surprises?Big surprises?Or shall we have to go through years of Or shall we have to go through years of hard work and lots of data before we can hard work and lots of data before we can claim a discovery?claim a discovery?

Cosmic muon recordedin the CMS hadronbarrel calorimeter @ IP5

from the standard model to discoveries - physics with the cms experiment at the dawn of the lhc era...

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