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Multi-Jet Resonances at the Tevatron and the LHC

Multi-Jet Resonances at the Tevatron and the LHC. Can Kılıç Johns Hopkins University w ork done with Takemichi Okui, Steffen Schumann, Minho Son and Raman Sundrum arXiv: 0802.2568. Outline. Why look at multijets? A minimal model: Description: qualitative Phenomenology: quantitative

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Multi-Jet Resonances at the Tevatron and the LHC

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  1. Multi-Jet Resonances at the Tevatron and the LHC Can Kılıç Johns Hopkins University work done with Takemichi Okui, Steffen Schumann, Minho Son and Raman Sundrum arXiv: 0802.2568

  2. Outline • Why look at multijets? • A minimal model: • Description: qualitative • Phenomenology: quantitative • Constraints • Looking for a colorful needle in a haystack • At the Tevatron • At the LHC • Outlook and Conclusions

  3. INTRODUCTIONTHE AGE OF COLOR • The 90’s and 00’s: The Tevatron Age • Run I: ECM=1.8 TeV • Run II: ECM=1.96 TeV • The 10’s (and 20’s?): The LHC Age: ECM=14 TeV • Our greatest strength is the production of new colored states. • Our greatest weakness is the production of old colored states. • Discovery strategy for most BSM models lie in distinctive signatures: • leptons • heavy flavors • missing energy

  4. Solutions to the hierarchy problem: New states carry EW quantum numbers Highly constrained by precision data Must be heavy, small cross section (usually 22). Background reasonable Many search strategies devised Incidentals: (“Who ordered this?”) New states can be EW singlets Then color is our best (only) bet Need large signal to beat large background (21 ideal) Search strategies based on kinematic signatures INTRODUCTIONWHAT DREAMS MAY COME (TRUE)

  5. INTRODUCTIONA BRIEF HISTORY OF COLORONS KK Gluons TeV Gravity V8 non-minimal TC Topcolor

  6. INTRODUCTIONA MORE GENERAL MOTIVATION • This should be familiar from • Also known as mixing • Resonant production, large cross section

  7. INTRODUCTIONDIFFICULTIES • Coming from the coloron can decay back to dijets. • O(1) BF into dijets has been excluded in the sub-TeV regime. • O(1) coupling to excluded by top production measurements. • is allowed.

  8. INTRODUCTIONMAIN STATEMENTS • The coloron is a generic object that can arise in many BSM scenarios, motivated or incidental. • A light coloron is consistent with existing bounds if it carries no EW charge and is flavor blind. • It can be detected in the multijet channel at the Tevatron (with present data) and the (early) LHC. • The multijet channel has so far been ignored in new physics searches . At the LHC we should leave no stone unturned.

  9. A MINIMAL MODELQUALITATIVE DESCRIPITION Ingredients: • New colored fermions (EW singlets) • Confining gauge interactions (“Hypercolor”) Consequences: • QCD gauges unbroken flavor symmetry • For GHC=SU(3) with massless hyperquarks, we can use QCD as an analog computer. • Renormalizable, possible separation of scales from EWB or flavor physics

  10. A DICTIONARY

  11. DICTIONARY, cont`d

  12. MOVING ON UP - I

  13. MOVING ON UP - II

  14. MOVING ON UP - III

  15. So what’s new? • Additional renormalizable interaction allowed by SU(3)color (vanishes in the HC/QCD analogy) KK-gluons have x=1 as a consequence of Lorentz invariance (related to unitarity at high energies). Two-site model also has x=1. • There are also various nonrenormalizable interactions, the most important one for resonant production is

  16. Coloron Decay Channels

  17. Constraints on • Dijet resonance searches • production • Multi-jet studies Run I (105 pb-1) Severe cuts • Global searches

  18. Constraints on • is loop suppressed • : for • Tevatron Run I: for • Pair production • How light?

  19. Other Sources of Constraints • LEP direct searches • Precision Electroweak • FCNC • Compositeness • Other states: Lightest Hyper-Baryon Stable if is exact Same quantum numbers as a gluino Straightforward to break alternatively one can introduce a SM singlet to carry off the HB-number.

  20. Search Strategy - Tevatron • Signal Background: QCD 4j • Effect of PDF’s • Margin of error • Two benchmarks: • Emulate triggers leading jet pT120GeV

  21. Case I : Lighter Coloron • Event generation: parton level: MadEvent shower/hadronization: Pythia detector simulation: PGS cone jets: ΔR=0.7 • Use different pT hierarchy in signal vs. background Cut: Four jets with pT40GeV • Signal: 1fb-1, 3.6 pb after cuts Background: 2fb-1, 66 pb after cuts • Pairing: signal: 2.7 pb after cuts background: 21 pb after cuts • Significance estimate

  22. The Result (significance 32σ)

  23. Case II : Heavier Coloron • Light coloron discoverable despite low trigger efficiency, larger background • Now we can impose harder cuts (4 jets with pT90GeV) • Signal: 1fb-1, 0.36 pbBackground: 2fb-1, 0.99pb • Pairing: signal: 0.27 pb background: 0.38 pb • Significance: 17σ

  24. LHC Search • Effect of PDF’s,  pair production cross section depends on . • Two benchmarks: • Search in two channels • Background issues, need for Sherpa, Comix (why we are not insane)

  25. LHC Search – 4j Channel (750 GeV coloron) • Cuts: pT4j>150 GeV signal: 372pb3.3pb background: 1.5nb Δm<50GeV signal: 2.2pb background: 34pb • 2j peak stands out 1fb-1 gives 37σ Eff. lum. for lower plot is 67 pb-1

  26. LHC Search – 4j Channel (1.5 TeV coloron) • Cuts: pT4j>250 GeV signal: 12.8pb0.27pb background: 38pb Δm<100GeV signal: 0.22pb background: 1.5pb • 10fb-1 gives 43σ • Eff. lum. for lower plot is 2fb-1.

  27. LHC Search – 8j Channel (750 GeV coloron) • Sequential pT cuts {40/60/90/125/160/200/250/320} GeV • Signal: 21pb4.2pb Background: 3.2pb • Pairing, combinatorics signal: 0.4pb • Eff. lum. for mass plot is 1.2fb-1.

  28. LHC Search – 8j Channel (1.5 TeV coloron) • Sequential pT cuts {75/115/180/240/300/380/470/600} GeV • Signal: 75fb15fb Background: 10fb • After pairing signal: 2.0fb • Eff. lum. for mass plot is 200fb-1.

  29. OUTLOOK AND CONCLUSIONS • There is currently no search for new physics in the multijet channel. We present a wide class of theories which would give pure jet signatures with large cross section. • QCD analog model experimentally allowed for masses as light as few hundred GeV. • Search strategy in multijet channel at the Tevatron (with present data) and the (early) LHC looks promising for a range of parameters. Ongoing study in CDF QCD group (Craig Group, Ian Flanagan, Nathan Goldschmidt) • Work in progress: • Inputless search strategy • Angular correlations • Variations of the model: • additional states: CHAMPs, R-hadrons, DM candidate • extension to electroweak sector very interesting (ongoing work)

  30. BACKUP SLIDES

  31. Search Plot Without ColoringLighter Coloron

  32. Search Plot Without ColoringHeavier Coloron

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