CMS Sensitivity to Dijet Resonances Robert M. Harris (Fermilab)

1. CMS Sensitivity to Dijet Resonances Robert M. Harris (Fermilab) Kazim Gumus and Nural Akchurin (Texas Tech) Selda Esen (Brown) DPF Meeting November 1, 2006 1

2. Introduction • This study performed at the LHC Physics Center at Fermilab (LPC) • A center of CMS software and analysis expertise in the U.S. • Where students and postdocs learn CMS analysis from Tevatron experts. • Publicly available as CMS Note 2006 / 070 • http://cms.cern.ch/iCMS/jsp/openfile.jsp?type=NOTE&year=2006&files=NOTE2006_070.pdf • Ph.D thesis of Kazim Gumus at Texas Tech University. • Uses a jet trigger proposed in CMS Note 2006 / 069 • http://cms.cern.ch/iCMS/jsp/openfile.jsp?type=NOTE&year=2006&files=NOTE2006_069.pdf • Part of the Ph.D thesis of Selda Esen now at Brown. • She talked earlier today on “CMS sensitivity to contact interactions using dijets”. • Analysis • Estimate 5s discovery and 95% CL exclusion sensitivity for dijet resonances. • √s=14 TeV and ∫Luminosity of 100 pb-1 (2008?), 1 fb-1 (2009?), 10 fb-1 (2011?). • Uses a full simulation of signal and background in the CMS detector. Robert Harris, Fermilab

3. q, q, g q, q, g X q, q, g q, q, g Motivation • Dijet Resonances • S-channel parton-parton resonances. • Observe two high pT jets: Dijets. • Dijet mass forms narrow resonance peak. • Theoretical Motivation • Dijet resonances are in many models that address important questions: • Why Flavor ? g Technicolor or Topcolor g Octet Technirho or Coloron • Why Generations ? g Compositeness g Excited Quarks • Why So Many Forces ? g Grand Unified Theory g W’ & Z’ • Can we include Gravity ? g Superstrings g E6 Diquarks • Why is Gravity Weak ? g Extra Dimensions g Randall-Sundrum Gravitions • Experimental Motivation • LHC is a parton-parton resonance factory in a previously unexplored region. • We search for generic narrow dijet resonances, not specific models. • Nature may surprise us with unexpected new particles. It wouldn’t be the first time … Robert Harris, Fermilab

4. Dijet Analysis • Jets are reconstructed using a cone algorithm • Energy inside a circle of radius R centered on jet axis is summed: ENDCAP BARREL ENDCAP - p f Jet 1 • Dijet is two highest pT jets. • Require each jet to have | h | < 1 • Reduces t-channel QCD background. • Dijet mass • Jet E and p are corrected for • Calorimeter non-linear response • Pile-up of extra soft proton-proton collisions on top of our dijet event • Correction varies from 33% at pT= 75 GeV to 7% at pT =2.8 TeV. 0 Jet 2 p h | h | < 1 Robert Harris, Fermilab

5. Narrow Resonance Shape in CMS • Model narrow resonance line shape at CMS with Z’ Simulation. • All resonances with a width less than our resolution look like this in CMS. • Corrected dijet mass peaks around generated value • Gaussian core with resolution • Long tail to low mass comes mainly from QCD radiation. • Data here is in bins equal to the measured mass resolution above. Robert Harris, Fermilab

6. Signal and Background • QCD cross section falls smoothly as a function of dijet mass. • Resonances produce mass bumps we can see if xsec is big enough. Robert Harris, Fermilab

7. Signal / QCD • Many resonances give obvious signals above the QCD error bars • Resonances produced via color force • Excited Quark (shown) • Axigluon • Coloron • Color Octet rT • Resonances produced from valence quarks of each proton • E6 Diquark (shown) • Others may be at the edge of our sensitivity. Robert Harris, Fermilab

8. Statistical Sensitivity to Dijet Resonances • Sensitivity estimates • Statistical likelihoods done for both discovery and exclusion • 5s Discovery • We see a resonance with 5s significance • Likelihood found from a sample that has a large signal. • 95% CL Exclusion • We don’t see anything but QCD at 95% CL. • Likelihood found from a sample with QCD only. • Plots show resonances at 5s and 95% CL • Compared to statistical error bars from QCD. 5 TeV 2 TeV 0.7 TeV 0.7 TeV 2 TeV Robert Harris, Fermilab

9. Systematic Uncertainties • Uncertainty on QCD Background • Dominated by jet energy uncertainty (±5%) which produces rate uncertainty. • Background will be measured. • Trigger prescale edge effect • Jet energy uncertainty has large effect at mass values just above where trigger prescale changes. • Resolution Effect on Resonance Shape • Bounded by difference between particle level jets and calorimeter level jets. • Radiation effect on Resonance Shape • Long tail to low mass which comes mainly from final state radiation. • Luminosity • We include all these systematic uncertainties in our sensitivity estimates. Robert Harris, Fermilab

10. Sensitivity to Resonance Cross Section • Cross Section for Discovery or Exclusion • Shown here for 1 fb-1 • Also for 100 pb-1, 10 fb-1 • Compared to cross section for 8 models • CMS expects to have sufficient sensitivity to • Discover with 5s significance any model above solid black curve • Exclude with 95% CL any model above the dashed black curve. • Can discover resonances produced via color force, or from valence quarks. Robert Harris, Fermilab

11. CMS can discover the strongly produced models up to many TeV. Discoveries with only 100 pb-1 ! 95% CL Sensitivity to Dijet Resonances 5s Sensitivity to Dijet Resonances CMS 100 pb-1 CMS 1 fb-1 CMS 10 fb-1 Published Exclusion (Dijets) CMS 100 pb-1 CMS 1 fb-1 CMS 10 fb-1 E6 Diquark Excited Quark Axigluon or Coloron Color Octet Technirho E6 Diquark Excited Quark Axigluon or Coloron Color Octet Technirho W ’ R S Graviton Z ’ 0 1 2 3 4 5 Mass (TeV) 0 1 2 3 4 5 6 Mass (TeV) Sensitivity To Resonance Models Robert Harris, Fermilab

12. Conclusions • CMS will perform a generic search for narrow dijet resonances • We’ve presented sensitivity estimates for 100 pb-1, 1 fb-1 and 10 fb-1 • CMS capability to discover (5s) or exclude (95% CL) resonances. • We can discover some models up to many TeV. • Axigluon, Coloron, Excited Quark, Color Octet Technirho or E6 Diquark • Produced via the color force or from the valence quarks of each proton. • Sensitivity to any new narrow resonance can be determined. • Compare the model’s cross section for |h|<1 to results in our CMS Note. • Theorists can compare their latest ideas with CMS sensitivity estimates. • We look forward to the discovery of new physics at the LHC. Robert Harris, Fermilab