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Searches for Heavy Resonances at the LHC

Searches for Heavy Resonances at the LHC. Tetiana Berger- Hryn’ova (LAPP, CNRS-IN2P3) For the ATLAS and CMS collaborations Moriond QCD 2014. Higgs Discovery & Searches. Following the discovery of a scalar boson Standard Model (SM) is complete (but for an axion ) and self-consistent

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Searches for Heavy Resonances at the LHC

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  1. Searches for Heavy Resonances at the LHC Tetiana Berger-Hryn’ova (LAPP, CNRS-IN2P3) For the ATLAS and CMS collaborations Moriond QCD 2014

  2. Higgs Discovery & Searches • Following the discovery of a scalar boson Standard Model (SM) is complete (but for an axion) and self-consistent • A lot of questions still need answers: • Why is Higgs light? • What is dark matter? • How to accommodate gravity? • Why are there three generations? • … • Is there a theory which answers all our questions? • We are looking for something • we do not know what • neither where to look • nor if there is any chance of finding it… Does it remind you of something? T. Berger-Hryn'ova Moriond QCD 2014

  3. It sounds like a quest • How do we search • Approach 1 • Pick a Theory • Pick a model • Look at various • production/decaymodes • of new states! • (model-independently) • Approach 2 • Pick a final state & look • (model-independently) • Get lucky! Go there- I don’t know where, Bring that – I don’t know what T. Berger-Hryn'ova Moriond QCD 2014

  4. Look for Signatures! Interesting Models: • Extended Gauge Groups • Compositeness • Wraped Extra Dimentions • Technicolor etc … Interesting Signatures: • Dibosons • /W/Z+jet(s) • Di/Tri-jet • Dileptons (ll, ) etc… • Focus on selection of results • Apologies if your favourite is left out • All limits are quoted at either 95% • Confidence Level or Credibility Level (CL) Look for bumps on smooth SM backgrounds! T. Berger-Hryn'ova Moriond QCD 2014

  5. Today’s menu • Searches in +jet final state • Dilepton searches • Diboson searches • Tri-jet resonant searches • XHHbbbb T. Berger-Hryn'ova Moriond QCD 2014

  6. Searches in +jet final state Background fit function: Selection CMS(ATLAS): pTj/>175(125) GeV +  iso; ||<1.44(1.37), |j|<3.0(2.8) |,j|<2.0(1.6) No significant excess seen. Exclude m(q*)<3.5 TeV@ 95% CL T. Berger-Hryn'ova Moriond QCD 2014 ATLAS: PLB 728, 562 (2013)

  7. +jet limits • Limit behaviour quite similar for various models: • (QBH/q*)~83-72/85-80% • What happens at high mass? Quantum Black Hole (QBH) q* T. Berger-Hryn'ova Moriond QCD 2014

  8. Effect on limits from Signal Shapes Usual signal Breit-Wigner shape  Parton-luminosity tail Parton distribution functions • Increased fraction of the off-shell production • for the signal events (“parton-luminosity tail”) • as the kinematic production limit is • approached • size increases with the resonance width. • Noticeable impact of this tail on cross-section • limit values when >5-10% of events in the tail This affects most of the limits (q*, Z’ etc)! T. Berger-Hryn'ova Moriond QCD 2014

  9. Effect on limits from Signal Shapes QBH Production is a threshold! MD=fundamental scale of quantum gravity MTH=threshold for black hole production  MD=MTH Mass • For thresholds or resonances with suppressed low-mass contributions (Z*) “parton-luminosity tail” effect is not present • It is also not present it the resonance shape is input “by hand”, e.g. assuming a Gaussian or Breit-Wigner of certain width, instead of using shape from simulation T. Berger-Hryn'ova Moriond QCD 2014

  10. +jet limits:width effects Width assumptions matter at low masses: smaller width = better limits Also parton luminosity tail is larger for wider resonances, which leads to worse limits T. Berger-Hryn'ova Moriond QCD 2014

  11. Dilepton Resonant Searches Data consistent with SM predictions CMS signal shape assumption: Breit-Wigner with Z’width (/M=0.5%) convoluted with Gaussian of signal resolution ATLAS signal shape assumption: Monte-Carlo based Z’SSM shape (with width /M~3%) T. Berger-Hryn'ova Moriond QCD 2014

  12. Dilepton Resonant Search Results Limits @ 95% CL are: M(Z’SSM) > 2.96TeV (CMS) & 2.8TeV(ATLAS) M(Z’)>2.60TeV (CMS) & 2.38TeV(ATLAS) Those assumptions affect the final results, making limits not comparable directly: effects of parton luminosity tail visible T. Berger-Hryn'ova Moriond QCD 2014

  13. VV & Vq (V=W/Z) Resonant Search k/MPl=0.1 Jets Cambridge-Aachen R=0.8, W/Z-tag jet, isolated leptons, kinematic cuts No excess over SM backgrounds is seen xBR(XWW)>70 (3)fb @ 0.8(2.5)TeV; m(G*ZZ)>710 GeV for k/MPl=0.5 Different channels to enhance sensitivity k/MPl=0.1 T. Berger-Hryn'ova Moriond QCD 2014 See also ATLAS-CONF-2012-150 (ZZlljj) & ATLAS-CONF-2013-015 (WWlll)

  14. Search for XHH(bb)(bb) 2 back-to-back boosted doubly btagged di-jet systems 4 b-jets (MV1, eff 70%) anti-kt 0.4 pT>40GeV, R(2b)<1.5, pTjj>200GeV Hadronicttbar veto <1.6 Background: multijet (90%); ttbar (<10%); Z+jets No evidence of signal is found Exclude @95% CL fork/MPl=1.0 590<M(G*RS)<710GeV T. Berger-Hryn'ova Moriond QCD 2014

  15. XX(3j)(3j)Resonant Search No excess over SM backgrounds is seen. Limits on m(gluino) of 650GeV at 95% CL is set for light flavour jets 835GeV at 95% CL for 2 light and 1 b-jets T. Berger-Hryn'ovaMoriond QCD 2014 See also ATLAS-CONF-2013-091, dijet: CMS PAS EXO 059, ATLAS-CONF-2012-148

  16. Perspectives/Conclusions We should not give up! • Resonant searches are very powerful • Many final states have been explored • But no new physics seen in 8TeV data yet… LHC Run 2 will provide us with more luminosity to explore lower couplings & LHC energy increase to higher masses. T. Berger-Hryn'ova Moriond QCD 2014

  17. Perspectives/Conclusions We should not give up! • Resonant searches are very powerful • Many final states have been explored • But no new physics seen in 8TeV data yet… LHC Run 2 will provide us with more luminosity to explore lower couplings & LHC energy increase to higher masses. Stay tuned to new exciting results in 2015! T. Berger-Hryn'ova Moriond QCD 2014

  18. Documentation • https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsEXO • https://twiki.cern.ch/twiki/bin/view/AtlasPublic/ExoticsPublicResults T. Berger-Hryn'ova Moriond QCD 2014

  19. Backup slides T. Berger-Hryn'ova Moriond QCD 2014

  20. T. Berger-Hryn'ova Moriond QCD 2014

  21. T. Berger-Hryn'ova Moriond QCD 2014

  22. Dijet Search T. Berger-Hryn'ova Moriond QCD 2014 CMS PAS EXO 059, ATLAS-CONF-2012-148

  23. Z’ hadronicsearch No excess over SM backgrounds seen. Excluded M(Z’SSM)<1.89TeV @ 95%CL Z’hadhad (~42% of the BF)

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