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Hadronic SUSY @ CMS

Hadronic SUSY @ CMS. Saeid Paktinat School of Particles and accelerators, IPM On behalf of the CMS Collaboration DIS 2012: XX International Workshop on Deep-Inelastic Scattering and Related Subjects, 26-30 Mar 2012 , University of Bonn (Germany ). Disclaimer.

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Hadronic SUSY @ CMS

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  1. Hadronic SUSY @ CMS SaeidPaktinat School of Particles and accelerators, IPM On behalf of the CMS Collaboration DIS 2012: XX International Workshop on Deep-Inelastic Scattering and Related Subjects, 26-30 Mar 2012, University of Bonn (Germany)

  2. Disclaimer • It is a short review of the CMS reach plan for search for SUSY, for a complete review https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsSUS • Here SUSY is just a paradigm of any new physics in which stable neutral particles (e.g. Dark Matter candidates) are produced in the cascade of pair-produced heavy particles SaeidPaktinat DIS2012, Bonn

  3. Why SUperSYmmetry(1) SM describes a lot of experimental results very precisely, butFermionic loop corrections to higgs mass diverge quadratically:L is a cut-off scale (upper limit for SM validity  Mpl = 2.4*1018GeV). Huge disparity between EW scale and Mpl is not natural(Hierarchy Problem) Saeid Paktinat DIS2012, Bonn

  4. Why SUperSYmmetry(2) If another scalar couples to higgs new correction is Proper couplings  This correction can cancel the quadratic divergencies.SUSY introduces new particles that cancel quadratic div and fill the scale between EW and Mpl(solves the hierarchy problem). Saeid Paktinat DIS2012, Bonn

  5. Important Features • Every SM particle has a SUSY partner (sparticle) which are exactly same, but differ in spin by ½ . • R=(-1)2S+3B+L • Consider R-parity conservation → pair-production of sparticles • Lightest SUSY particle (LSP) stable → dark matter candidate • Hadron collider: squark/gluino production is dominant (if not too heavy). SaeidPaktinat DIS2012, Bonn

  6. SUSY Fingerprint • Long decay chain  a lot of jets and leptons. • Seems easy to find, but how to isolate the signal (~1pb) from the SM backgrounds(~nb). • Jets + MET is a classical signature. • Jet multiplicity, , Saeid Paktinat DIS2012, Bonn

  7. Jets + MET CMS PAS SUS-11-004 • At least 3 jets, • No well identified/isolated electron or muon. • Multijet QCD has a huge cross section with a big chance to be mismeasured as an unbalanced event. • Special method is used to predict the QCD contribution. Saeid Paktinat DIS2012, Bonn

  8. SM Background Prediction • QCD: Jets are Rebalanced and Smeared. All distributions can be rebuilt using the smeared jets. • W/Z , ttbar: A muon control sample is used. • Znn: g+jets when g is ignored. Saeid Paktinat DIS2012, Bonn

  9. QCD Safe Distributions CMS PAS SUS-11-003 • separates events with low MET or mismeasurementfrom genuine events. • QCD is completely suppressed. • > 2jets: Minimizing the HT difference between the mega-jets. • RaT= N(aT > 0.55)/N(aT < 0.55) is flat vs HT for the SM bkg. Saeid Paktinat DIS2012, Bonn

  10. CMS PAS SUS-11-005 QCD Safe Distributions(2) • MT2: stransverse mass, an extension of MT in case of 2 decay chain with “missing particles”: • QCD does not enter the search region, • Data driven methods confirm this. (both QCD multijet and total jet lost are considered.) • > 2 jets: Minimizing the Lund distance. SaeidPaktinat DIS2012, Bonn

  11. CMS PAS SUS-12-005 QCD Safe Distributions(3) • Razor: Approximates the scale and distribution. • Bkg predicted by 2D templates (MR, R2). • > 2Jets: Minimizing the sum of M2 of megajets. V+jets SUSY-LM6 Saeid Paktinat DIS2012, Bonn

  12. Interpretation in CMSSM Model • No excess is seen over the predicted bkg, • Hybrid frequentist CLs estimator is used to find the limits. • Signal efficiency is estimated using NLO & NLLO prospino cross sections. • CTEQ6 and MSTW describe the PDF/scale uncertainty. Razor 4.4 fb-1 Saeid Paktinat DIS2012, Bonn

  13. Interpretation in Simplified Models Very simple models to ease the communication with theoreticians. Half a TeV colored sparticles are excluded. Saeid Paktinat DIS2012, Bonn

  14. Conclusion • CMS has a reach plan to search for SUSY in fully hadronic final states. • New variables are introduced to move the QCD out of the search region. • New results with the full 2011 data (~ 5 fb-1) will appear shortly. • Be tuned for SUSY results in 8 TeV by summer. Saeid Paktinat DIS2012, Bonn

  15. Back up Saeid Paktinat DIS2012, Bonn

  16. p-values for Razor analysis Saeid Paktinat DIS2012, Bonn

  17. High MT2 exclusion Saeid Paktinat DIS2012, Bonn

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