1. 1 Searches for Extra Dimensions and Comopsiteness in CMS Guinyun Kim Kyungpook National University, Korea On behalf of CMS collaboration The 16th International Conference on Supersymmetry and the Unification of Fundamental Interactions June 16 – 21, 2008 Seoul, Korea

2. Contents l Introduction è CMS Experiments è Searches for Extra Dimensions Search for New Particles/Physics with High Mass Dijet final states è Search for Contact Interactions with Dijet è Search for New Particles with Dijet Resonances Search for New Particles/Physics with High Mass Dilepton final states è High mass Di-electron final states in CMS è High mass Di-muon final states in CMS l Conclusions

3. SUSY08, G.N. Kim 3 CMS: Compact Muon Solenoid Muons: muon system acceptance: |η|<2.4 muons momentum resolution: σ(1/p T )~10 -2 (p T ~10 GeV) Calorimetry: HCAL|η|<5,δE/E ~ 120% / √E + 5% ECAL |η|<3,δE/E ~ 1.5% / √E + 0.5% + 0.15% / E MUON BARREL Drift Tube Chambers ( DT ) Resistive Plate Chambers ( RPC ) SUPERCONDUCTING COIL IRON YOKE Silicon Microstrips Pixels TRACKER Cathode Strip Chambers (CSC ) Resistive Plate Chambers (RPC) MUON ENDCAPS CALORIMETERS ECAL Scintillating PbWO4 crystals HCAL Plastic scintillator/brass sandwich Total weight : 12,500 t Overall diameter : 15 m Overall length : 21.6 m Magnetic field : 4 Tesla

4. SUSY08, G.N. Kim 4 Searches for Extra Dimensions Large ED (ADD): ● Graviton in bulk ● DY interference, or missing E T TeV -1 ED (DDG): ● Gauge Bosons and Higgs in bulk ● spin-1 KK resonances ● DY interference Warped ED (RS): ● Graviton as narrow spin-2 resonances ll qq  ZZ jet+ME T  +ME T Virtual or Resonance exchange emission Universal ED (UED): ● spin-1 KK resonances Arkani-Hamed, Dimopoulos, Dvali Phys Lett B429 (98) Dienes, Dudas, Gherghetta Nucl Phys B537 (99) Randall, Sundrum Phys Rev Lett 83 (99) Appelquist, Cheng, Dobrescu Phys. Rev. D 64 (01) Searches Concentrated on High mass dijet final states High mass dilepton final states

5. SUSY08, G.N. Kim 5 l Motivation :New Physics Signals 1. Contact Interaction: Indirect observation of an energy scale (  ) of new physics. à Composite Quarks à New Interactions 2. Dijet Resonances: LHC is a parton-parton resonance factory in a previously unexplored region X q, q, g Dijet Resonance s - channel Present limit (95%CL) M q* >775 GeV (D0) M W’ >800, M Z’ >640 GeV (D0) M D >420 GeV (CDF) M  T8 >480 GeV (CDF) M A(C) >980 GeV (CDF) D0: PRD 69 (2004) R111101 CDF: PRD55 (1997) R5263 Search for New Particles/Physics with High Mass Dijet final states 11 11 22 11 11 1+1+ ½+½+ 0+0+ J P qq0.01SingletZ ‘Heavy Z q1q2q1q2 0.01SingletW ‘Heavy W qq,gg0.01SingletGR S Graviton qq,gg0.01Octet  T8 Octet Technirho qq0.05OctetCColoron qq0.05OctetAAxigluon qg0.02Tripletq*Excited Quark ud0.004TripletDE 6 Diquark Chan.  / (2M) ColorXModel Name Contact Interaction

6. SUSY08, G.N. Kim 6 Observation of Dijet in CMS   ETET 0 1 Jet 1 Jet 2 Dijet Mass = 900 GeV proton  =-1 proton Jet 1 Jet 2  =1  Transverse  =0  l Standard jet reconstruction è Cone algorithm à Midpoint & iterative cone indistinguishable at high P T. è Standard jet kinematics  Jet E =  E i, Jet p=  p i   = tan -1 (p y /p x )  E T = Esin , p T =√p x 2 +p y 2 l Dijet is two leading jets. è Invariant mass Jet Reconstruction

7. SUSY08, G.N. Kim 77 Jet Response and Corrections Jets in Barrel have uniform response in  and are sensitive to new physics  Jet response changes smoothly and slowly up to | jet  | = 1.3 Measure relative response vs. jet  in data with dijet balance è Data will tell us what is the region of response we can trust. l Measured jet p T in the calorimeter is less than true jet p T (particles in cone) l Measured jets are corrected so p T is the same as true jet p T è Scales Jet (E,p x,p y,p z ) by à ~1.5 at p T = 70 GeV à ~1.1 at p T = 3 TeV à for jets in barrel region |  |<1.3 |  |<1 Jet Response vs  relative to Barrel CMS Preliminary Jet Response vs p T in Barrel Jets we use (GeV)

8. SUSY08, G.N. Kim 8 l Many signals are also large  Either large PDFs or  or both. Dijet Rates and Cross Sections l Rate = Cross Section x Luminosity è Luminosity (L) is rate of protons / area supplied by the LHC. è Design L=10 34 cm -2 s -1 ~ 10 fb -1 /month l Cross section from two factors è Parton distributions functions (PDFs) à Probability of finding partons in proton with fractional momentum x à Valence quarks u and d have large PDFs at high x (high dijet mass).  Parton scattering cross section  ^ | jet  | < 1 l QCD dijet cross section is large.   from color force is large ^ ^ Jet 1 Jet 2 Proton PDF(x a ) PDF(x b )

9. SUSY08, G.N. Kim 9 Search for Contact Interactions with Dijet New physics at large scale   Composite Quarks  New Interactions Modeled by contact interaction  Intermediate state collapses to a point for dijet mass <<   For example, the standard contact interaction among left-handed quarks introduced by Eichten, Lane and Peskin (PRL50,811) Excluded for  + < 2.7 TeV (D0:PRL82, 2457) l Observable Signatures è Effects at high p T and dijet mass. à Rate: Higher rate than QCD à Angle: Angular distributions can be very different from QCD. Quark Contact Interaction  M ~  Composite QuarksNew Interactions M ~  Dijet Mass <<  q q q q q q q q L = ± [2  /   ] (q   q) (q   q) cos  * QCD Background Signal 01 dN  / dcos  *

10. SUSY08, G.N. Kim 10 Inclusive Jet P T and Contact Interactions l Contact interactions create large rate at high P T and immediate discovery possible è Error dominated by jet energy scale (~10%) in early running (10 pb -1 )   E~ 10% not as big an effect as   = 3 TeV for P T >1 TeV. è PDF “errors” and statistical errors (10 pb -1 ) are smaller than E scale error With 10 pb -1 we can see new physics beyond Tevatron exclusion of   < 2.7 TeV. Rate of QCD and Contact Interactions Sensitivity with 10 pb -1 P A S PAS: CMS PAS SBM_07_001

11. SUSY08, G.N. Kim 11 Dijet Ratio: Simple Angular Measure Jet 1 Jet 2 Numerator Sensitive to New Physics |cos    ~ 0 Denominator Dominated by QCD |cos  *| ~ 0.6, usually Jet 1 Jet 2 (rare) or z z Dijet Ratio = N(|  |<0.7) / N(0.7<|  |<1.3)  Number of events in which each leading jet has |  |<0.7, divided by the number in which each leading jet has 0.7<|  |<1.3 l Simplest measurement of angular distribution è Most sensitive part for new physics è It was first introduced by D0 (PRL82, 2457). l Dijet angular distributions are sensitive to new physics. cos  * QCD Background Signal 01 dN  / dcos  *  = -1.3 -0.7 0.7 1.3

12. SUSY08, G.N. Kim 12 Dijet Ratio from QCD l We have optimized the dijet ratio for a contact interaction search in barrel  Old dijet ratio used by D0 and PTDR was N(|  |<0.5) / N(0.5<|  |<1.0)  New dijet ratio is N(|  |<0.7) / N(0.7<|  |<1.3) l Dijet ratio from QCD agrees for GenJets and Corrected CaloJets è Flat at 0.6 for old ratio, and flat at 0.5 for new ratio up to around 6 TeV. Old Dijet RatioNew Dijet Ratio P A S PTDR

13. SUSY08, G.N. Kim 13 l Optimization dramatically increases sensitivity to contact interactions. è Raising the signal and decreasing the QCD error bars.  Value of   we can discover is increased by 2 TeV for 100 pb -1  From   ≈ 5 TeV with old dijet ratio (PTDR) to   ≈ 7 TeV with new dijet ratio. Old Dijet Ratio (PTDR) 3 5 10  + (TeV) QCD New Dijet Ratio 3 5 10  + (TeV) QCD P A S CMS Sensitivity to Contact Interactions from Dijet Ratio

14. SUSY08, G.N. Kim 14 Mass Rate M New particles, X, produced in parton-parton annihilation will decay to 2 partons (dijets). Signature: dijet resonances → mass bumps. Tevatron has searched but not found any dijet resonances so far. Best limits on dijet resonances by CDF RUN II (CDF note 9246). X q, q, g time space Search for New Particles with Dijet Resonance ModelExcluded (GeV)ModelExcluded (GeV) A or C260 - 1250D290 - 630  T8 260 - 1110W'280 - 840 q*260 - 870Z'320 - 740 1-1- 1-1- 2-2- 1-1- 1-1- 1+1+ ½+½+ 0+0+ J P qq0.01SingletZ'Heavy Z q1q2q1q2 0.01SingletW'Heavy W qq, gg0.01SingletGR S Graviton qq, gg0.01Octet  T8 Octet Technirho qq0.05OctetCColoron qq0.05OctetAAxigluon qg0.02Tripletq*Excited Quark ud0.004TripletDE 6 Diquark ChannelG / (2M)ColorXModel Name

15. SUSY08, G.N. Kim 15 Dijet Mass Resolution From the study of Dijet mass resolution: l Gaussian core of resolution for |  |<1 and |  |<1.3 is similar. l Resolution for corrected calorimeter jets (CaloJets) is follows: è 9 % at 0.7 TeV è 5.7% at 2 TeV è 4.5 % at 5 TeV 2 TeV Z’ |η| < 1.3 Corrected CaloJets GenJets Natural Width Dijet Mass Resolution 5.7% P A S

16. SUSY08, G.N. Kim 16 Rate of Dijet Resonances l Measure rate as a function of corrected dijet mass and look for resonances. è Use a smooth parameterized fit or QCD prediction to model background QCD Backgound PAS: CMS PAS SBM_07_001 P A S PTDR Dijet Mass (TeV) p 0, p 1, p 2 : arbitrary parameters

17. SUSY08, G.N. Kim 17 Searches using Rate of Dijet Resonance Fractional difference between new particles and QCD dijets PTDR l Strongly produced resonances can be seen è Convincing signal for a 2 TeV excited quark (q*) in 100 pb -1 à Tevatron excluded up to 0.775 TeV (D0) and 0.87 TeV (CDF). Resonances with 100 pb -1 P A S Resonances with 1 fb -1

18. SUSY08, G.N. Kim 18 Systematic Uncertainties l Jet Energy Scale è CMS estimates +/- 5 % is achievable by 1 fb -1 è Changes dijet cross section between 30% and 70% l Parton Distributions è CTEQ 6.1 uncertainty l Resolution è Bounded by difference between particle level jets and calorimeter level jets. l Systematic uncertainties on the cross section as a function of dijet mass are large. è But they are correlated vs. mass. The distribution changes smoothly. PTDR Energy scale PDF Resolution

19. SUSY08, G.N. Kim 19 Sensitivity to Resonance Cross Sections of New Particles l Cross Section for Discovery or Exclusion è Shown here for 1 fb -1 l Compared to cross section for 8 models l CMS expects to have sufficient sensitivity to  Discover with 5  significance any model above solid black curve è Exclude with 95% CL any model above the dashed black curve. P T D R

20. SUSY08, G.N. Kim 20 Discovery Sensitivity for Models l Resonances produced by the valence quarks of each proton è Large cross section from higher probability of quarks in the initial state at high x.  E6 diquarks (ud  D  ud) can be discovered up to 3.7 TeV for 1 fb -1 l Resonances produced by color force è Large cross sections from strong force è With just 1 fb -1 CMS can discover à Excited Quarks up to 3.4 TeV à Axigluons or Colorons up to 3.3 TeV à Color Octet Technirhos up to 2.2 TeV. l Discoveries possible with only 100 pb -1 è Large discovery potential with 10 fb -1 Mass (TeV) E6 Diquark Excited Quark Axigluon or Coloron Color Octet Technirho CMS 100 pb -1 CMS 1 fb -1 CMS 10 fb -1 5  Sensitivity to Dijet Resonances 0 1 2 3 4 5 P T D R

21. SUSY08, G.N. Kim 21 Exclusion Sensitivity to Models E6 Diquark Excited Quark Axigluon or Coloron Color Octet Technirho W ’ R S Graviton Z ’ Tevatron Exclusion (Dijets) CMS 100 pb -1 CMS 1 fb -1 CMS 10 fb -1 Mass (TeV) 95% CL Sensitivity to Dijet Resonances 0 1 2 3 4 5 6 l Resonances produced via color interaction or valence quarks. è Wide exclusion possibility connecting up with many exclusions at Tevatron l Resonances produced weakly are harder. è But CMS has some sensitivity to each model with sufficient luminosity. è Z’ is particularly hard. à Weak coupling and requires an anti-quark in the proton at high x. P T D R

22. SUSY08, G.N. Kim 22  /Z/Z'/KKZ/G q(g) q e,e, e+, +e+, + (g) Heavy resonances with mass above 1 TeV/c 2 decaying into a lepton pair Beyond Standard Model 1. Z’ boson predicted by Grand Unified Theories (GUT): Z SSM within the Sequential Standard Model (SSM) Z  Z  and Z  : E 6 and SO(10) GUT group Z LR :left-right symmetry model Z ALR : alternative left-right symmetry model 2. Kaluza-Klein (KK) excitations of Z, KKZ: TeV -1 model 3. KK excitations of a graviton, G: Randall-Sundrum model Standard Model 1.Drell-Yan Process LHC 1 fb -1 Total Cross-section for Drell-Yan process Search for New Particles with High Mass Dilepton final states

23. SUSY08, G.N. Kim 23 1.5 TeV Drell-Yan events based on RS Model Drell-Yan line-shape vs m ll at LHC for M G =1.5 TeV Cross-section for Drell-Yan production at LHC of the first two KK excitations c=0.5 c=0.1 c=0.05 c=0.01 M G (GeV) H. Davoudiasl et al., PRD63-075004 M G (GeV) Experimental and Theoretical constraints on the RS model when the SM lies on the TeV-brane LHC 10 fb -1 LHC 100 fb -1 The sensitivity reach at LHC by the Drell-Yan events : 10 fb -1 : 100 fb -1 : H. Davoudiasl et al., PRL 84 (2000) 2080

24. SUSY08, G.N. Kim 24 High mass Di-electron final states in CMS 1.Selection of Di-electron events E HCAL /E ECAL < 10 % Isolation cut : 0.1<  R<0.5 ( ) A track is requested to be associated for each electron candidate 2.Correction Saturation correction Energy correction z-vertex distribution Final State Radiation Recovery Ratio M ee /M true before and after corrections P T D R

25. SUSY08, G.N. Kim 25 Invariant Mass Distribution for (a) KK Z boson, (b) SSM Z’ boson and (c) Graviton production for an integrated luminosity of 30 fb -1 M=4.0 TeV/c 2 M=3.0 TeV/c 2 M=1.5 TeV/c 2, c=0.01 Drell-Yan background Table P T D R High mass Di-electron final states in CMS

26. SUSY08, G.N. Kim 26 Discovery potential of CMS P T D R 5  discovery limit on the resonance mass (TeV/c 2 )

27. SUSY08, G.N. Kim 27 High mass Di-muon final states in CMS Selection of Di-muon events: l Level-1 trigger:  Two muons with P T > 3 GeV or one inclusive muon with P> 14 GeV. l HLT: single-muon OR di-muon (non-isolation)  Two muons of opposite sign reconstructed by the Global Muon Reco algorithm  Acceptance |  | < 2.4  P T > 20 GeV/c for each muon  Isolation:  P T < 3 GeV/c in a cone of  R < 0.3 Trigger EfficiencyInvariant mass resolution CMS Note 2006/123

28. SUSY08, G.N. Kim 28 Discovery potential in Z'→  +  - channel Summary of the signal significance expected for different Z’ models Integral Luminosity needed to reach 5  significance (S L =5) P T D R

29. SUSY08, G.N. Kim 29 Trigger: Single muon & dimuon (L1+HLT) p T >7 GeV(μμ), 19 GeV(single μ) Efficiency > %98 Event selection: M(μμ) inv > M cut Different M cut for different M S : M cut = 1TeV for M S = 3TeV M cut = 1.5TeV for M S =4 and 5TeV M cut = 2.0TeV for M S =7 and 10TeV I.Belotelov, I.Golotvin, A.Lanyov, E.Rogalev, M.Savina, S.Shmatov, D.Bourikov, CMS-NOTE 2006/076 Leading Order DY cross section (in fb) for ADD graviton with n=3 and 6 and M S =3,4,5,7 TeV/c 2 Landsberg code + STAGEN + PHYTIA + ORCA + OSCAR Backgrounds: For M(μμ) inv >1TeV ZZ/WZ/WW: σ = 2.59x10 -4 fb -1 tt: σ = 2.88x10 -4 fb -1 Discovery potential in G ADD →  +  - channel From bottom to top:SM, n=6,5,4,3.

30. SUSY08, G.N. Kim 30 Discovery potential in G ADD →  +  - channel Significance values for S cL for the ideal detector 5  limit on M S

31. SUSY08, G.N. Kim 31 Discovery potential in RS graviton G KK →  +  - channel I.Belotelov, I.Golotvin, V. Palichik, A.Lanyov, E.Rogalev, M.Savina, S.Shmatov, CMS-NOTE 2006/104

32. SUSY08, G.N. Kim 32 Discovery potential in RS graviton G KK →  +  - channel C=0.01 C=0.02 C=0.05 C=0.1 P T D R EW correction, Hard-scale and PDF uncertainties Systematic uncertainties due to P T D R

33. SUSY08, G.N. Kim 33 Conclusions l Discussed CMS search plans for new particles with Dijet and Dilepton. l New Particles/Physics with Dijet : è Rate of high p T jet could give a convincing contact interaction signal:  Can discover  + = 3 TeV in 10 pb -1 even if jet energy errors are 10%. è Dijet ratio will probe contact interactions in dijet angular distributions :  Can discover  + = 4, 7, 10 TeV in 10, 100, 1000 pb -1 with small systematics. è Ratio of high dijet mass can be used to discover new particles up to several TeV: à Axigluon, Coloron, Excited Quark, Color Octet Technirho, Graviton, or E 6 Diquark l New Particles/Physics with Dilepton: è Gives a convincing signal for various new particles (hevay gauge bosons, Extra dimensions) with luminosity more than 10 fb -1. l CMS is preparing to discover new particles/physics at the TeV scale using Dijet and Dilepton.

34. Backup Slides

35. SUSY08, G.N. Kim 35 The CMS Detector Hadronic Electro- magnetic Calorimeters Protons

36. SUSY08, G.N. Kim 36 CMS Barrel & Endcap Calorimeters (r-z view, top half)          HCAL BARREL ECAL BARREL SOLENOID HCAL END CAP ECAL END CAP HCAL END CAP ECAL END CAP Z                     HCAL OUTER 3 m HCAL > 10  I ECAL > 26 0

37. Trigger and Luminosity l Collision rate at LHC is expected to be 40 MHz è 40 million events every second ! è CMS cannot read out and save that many. l Trigger chooses which events to save l Two levels of trigger are used to reduce rate in steps è Level 1 (L1) reduces rate by a factor of 400. è High Level Trigger (HLT) reduces rate by a factor of 700. l Trigger tables are intended for specific luminosities è We’ve specificied a jet trigger table for three luminosities è L = 10 32 cm -2 s -1. Integrated luminosity ~ 100 pb -1. à LHC schedule projects this after ~1 months running. è L = 10 33 cm -2 s -1. Integrated luminosity ~ 1 fb -1. à LHC schedule projects these after ~ 1 year of running. è L = 10 34 cm -2 s -1. Integrated luminosity ~ 10 fb -1. à One months running at design luminosity. 4 x 10 7 Hz 1 x 10 5 Hz 1.5 x 10 2 Hz Event Selection CMS Detector L1 Trigger HLT Trigger Saved for Analysis

38. Path L1HLTANA E T (GeV) Pre- scale Rate (Hz) E T (GeV) Rate (Hz) Dijet Mass (GeV) Low252000146602.8 Med6040971202.4330 High1401442502.8670 Super4501146002.81800 L = 10 32 100 pb -1 Ultra2701194002.61130 L = 10 33 1 fb -1 Add New Threshold (Ultra). Increase Prescales by 10. Mass values are efficient for each trigger, measured with prior trigger L = 10 34 10 fb -1 Add New Threshold (Super). Increase Prescales by 10. Jet Trigger Table and Dijet Mass Analysis l CMS jet trigger saves all high E T jets & pre-scales the lower E T jets. è Prescale means to save 1 event out of every N events. As luminosity increases new trigger paths are added Each with new unprescaled threshold.

39. |  |<1.3 |  |<1 Jet response vs  relative to |  |<1.3 CMS Preliminary Jet  Region l Barrel jets have uniform response & sensitive to new physics  Jet response changes smoothly and slowly up to | jet  | = 1.3  CaloTowers with |  |<1.3 are in barrel with uniform construction.  CaloTowers with 1.3<|  |<1.5 are in barrel / endcap transition region  Some of our analyses use | jet  |<1.3, others still use | jet  |<1  All are migrating to | jet  |<1.3 which is optimal for dijet resonances Measure relative response vs. jet  in data with dijet balance è Data will tell us what is the region of response we can trust. Barrel Jet (|  |<1.3) Probe Jet (any  ) Dijet Balance  = 1.3 HB HE Hcal towers and  cuts Transition Region  = 1

40. SUSY08, G.N. Kim 40 Optimization of  cut QCD cross section rises dramatically with |  | cut due to t-channel pole.  Z’ signal only gradually increases with |  | cut  optimal value at low |  |. Optimal cut is at |  | < 1.3 for a 2 TeV dijet resonance. è Optimization uses Pythia Z’ angular distribution for the resonance.  cut and cross section  cut and sensitivity P A S

41. Dijet Event Cleanup l Dijet events do not usually contain large missing E T  A cut at MET /  E T 99% efficient for P T > 100 GeV è Won’t change the QCD background to new physics. l Most unphysical background contain large missing E T è Catastrophic detector noise, cosmic ray air showers, beam-halo backgrounds  A simple cut at MET /  E T < 0.3 should remove most of these at high jet P T. è This cut is our first defense, simpler and safer than cutting on jet characteristics. 99% Efficiency Cut & Chosen Cut MET /  E T for QCD Dijets and Cut