From the Standard Model to Discoveries - Physics with the CMS Experiment at the Dawn of the LHC Era Dimitri Bourilkov University of Florida CMS Collaboration SESAPS Meeting, November 11, 2005, Gainesville, FL, USA

D.BourilkovEarly CMS Physics2 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+: fb -1 /year  design luminosity 100 fb -1 /year

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

D.BourilkovEarly CMS Physics4 What’s on the Menu all New Energy Regime – all 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.BourilkovEarly CMS Physics5 Trigger Trigger rates and expected events as function of luminosity Level1 High level triggers (L2 and L3) Filter farm

D.BourilkovEarly CMS Physics6 Event Rates for pp at  s=14 TeV Channels (examples …) Events to tape for 10 fb -1 (per experiment) W   70 x 10 6 Z   11 x 10 6 tt  W b W b   + X 0.8 x 10 6 QCD jets p T >150~ 10 7 Minimum bias~ 10 7 g ~ g ~ m = 1 TeV Expected in the first year: LHC rates 10 3 larger in area of asymptotic TEVATRON reach  Large samples of SM events – understand (calibrate, align etc) detector and LHC physics (check SM at highest Q 2 ) assuming 1% of trigger bandwidth ~ few PB of data per year/experiment  challenge for software and computing beginning …) Computing GRID underway

D.BourilkovEarly CMS Physics7 Very Early (SM) Measurements Luminosity 1 mb -1 1 b -1 1 nb -1 1 pb -1 1 fb -1 Total cross section – not easy QCD: - d N / d P T, d N / d  - higher P T : 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.BourilkovEarly CMS Physics8 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 ~ GeV)

D.BourilkovEarly CMS Physics9 Contact Interactions, Extra Dimensions… general framework for new int.: scale   s (virtual effects) or resonances if   s coupling g (convention g 2 = 4) we constrain g /  operators with canonical dimension N > 4  terms ~ 1/M N-4

D.BourilkovEarly CMS Physics10 Bump Hunting e.g. Z’  μ + μ -, RS-1… Excellent benchmark analysis for CMS Muon Detector Clean (small Drell-Yan background) Very high p T muons (TeV specific problems – showering etc) Mass Reach (S L > 5) Full CMS simulation and reconstruction Un-binned Likelihood Ratio Approach S L = √ 2 ln( L s+b /L b ) Mass Reach (TeV)Luminosity (fb -1 ) > – – No systematic effects

D.BourilkovEarly CMS Physics11 5  discovery curves ~ one year at : up to ~2.5 TeV ~ one year at : up to ~2 TeV ~ one month at : up to ~1.5 TeV cosmologically favoured region Tevatron reach : < 500 GeV Supersymmetry Most important task in early days Most sensitive channel: jets + missing E T (MET – resolution is KEY) squarks / gluinos (clean final states, large rate, favorable signal/bg ratio)

D.BourilkovEarly CMS Physics12 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.BourilkovEarly CMS Physics13 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.BourilkovEarly CMS Physics14 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 the TeV scale, hunting for new physics: LHC will break new ground in exploring the TeV scale, hunting for new physics: Will it be easy? SUSY an early date? Big surprises? Or shall we have to go through years of hard work and lots of data before we can claim a discovery? Cosmic muon recorded in the CMS hadron barrel IP5