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D.BourilkovEarly CMS Physics3 Length : ~20 m Radius : ~7 m Weight : ~ tons ECAL crystals Barrel HCAL CMS Endcap Muon Chambers Silicon tracker Coil + inner vacuum tank
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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
D.Bourilkov Early CMS Physics 3
Length : ~20 m Radius : ~7 m Weight : ~ 13000 tons
ECAL crystals
Barrel HCAL
CMS
Endcap Muon Chambers
Silicon tracker
Coil + inner vacuum tank
D.Bourilkov Early CMS Physics 4
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 …
D.Bourilkov Early CMS Physics 5
Trigger
Trigger rates and expected events as function of luminosity
Level1High level
triggers (L2 and L3)
Filter farm
D.Bourilkov Early CMS Physics 6
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
D.Bourilkov Early CMS Physics 7
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/, …
D.Bourilkov Early CMS Physics 8
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)
D.Bourilkov Early CMS Physics 9
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
D.Bourilkov Early CMS Physics 10
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
D.Bourilkov Early CMS Physics 11
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)
D.Bourilkov Early CMS Physics 12
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
D.Bourilkov Early CMS Physics 13
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
D.Bourilkov Early CMS Physics 14
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