1 / 32

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

alijah
Télécharger la présentation

Multi-Jet Resonances at the Tevatron and the LHC

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related