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Introduction to Supersymmetry in Particle Physics

Explore the fascinating world of supersymmetry and its experimental searches at the LHC, with insights on production mechanisms, decay modes, and analysis tools. Witness recent results and interpretations of Higgs signals, and delve into SUSY search methodologies.

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Introduction to Supersymmetry in Particle Physics

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  1. S. Muanza, CPPM Marseille, CNRS-IN2P3 Introduction to Supersymmetry "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  2. PART II Experimental Searches "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  3. LHC Personal Bias: I’ll present results from the ATLAS experiment "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  4. LHC - Experiments - • 3 Experiments can carry SUSY searches: • Direct: ATLAS & CMS • Indirect: LHCb "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  5. LHC - Nominal Features - 25 ns Event rate: N = L x (pp)  109 interactions/s Mostly soft ( low pT ) events Interesting hard (high-pT ) events are rare "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  6. LHC - 2012 Integrated Luminosity - eDAQ = 95.3% Counting rate from L detectors "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  7. Data Taking Conditions Evolution of the instantaneous luminosity Evolution of the nber of p bunches <Nber> of collisions per bunch crossing A Multiple pp Collision "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  8. "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  9. Analyses: Higgs Searches - Trigger: On-Line Selection - "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  10. Production Mechanisms LO Feynman Diagrams Cross Sections Unique opportunity to measure the top Yukawa coupling! "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  11. Decay Modes LO Feynman Diagrams Branching Ratios "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  12. Search Topologies - 2 Examples - 2 photons 4 charged leptons Signal Background Irreducible: Reducible: Z+bb, tt+jets "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  13. Analyses - Offline Selection - • Events read from tape • Improved signal vs background separation "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  14. ATLAS Candidates (1) Photon candidates are unconverted. Event number: 56662314 Run: 203779 at sqrt(s) = 8 TeV g1: pT = 62.2 GeV and h = 0.39 g2: pT = 55.5 GeV and h = 1.18 M(gg) = 126.9 GeV "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  15. ATLAS Candidates (2) EventNumber: 71902630 RunNumber: 204769 M(4m)=125.1 GeV M12=86.3 GeV, M34=31.6 GeV m1: pT=36.1 GeV, h=1.29, f=1.33 m2: pT=47.5 GeV, h=0.69, f=-1.65 m3: pT=26.4 GeV, h=0.47, f=-2.51 m4: pT=71.7 GeV, h=1.85, f=1.65 "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  16. CMS Candidates "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  17. Recent CMS Results - HCP2012, 12-16 Nov 2012 - Confirmation of the dicovery Parity Signal strength by channel "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  18. SUSY Interpretation of a Higgs Signal (1) • Modified Couplings: • Decoupling Limit: • Additional contribution to loops: • could make differences in h0 BRs and explain the currently observed tensions between • the decay channels => h0 is light and has SM-like couplings Realized in practice when: "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  19. SUSY Interpretation of a Higgs Signal (1) • Large Mixing in Stop Sector: Max. Mixing: "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  20. SUSY Searches - Production Mechanisms (1) - • How are these Sparticles produced? • Gluino pairs: • Squark pairs: • Gluino+Squark pairs: • Chargino pairs: • Chargino+Neutralino pairs: "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  21. SUSY Searches - Production Mechanisms (2) - • What are the cross sections? • Obtained with Prospino (include NLO-QCD corrections) • They determine which Sparticles are accessible and the hierarchy in their search "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  22. SUSY Searches - Decay Modes - • How do these Sparticles decay? • Squarks: • Gluinos: • Search topologies are chosen wrt to some decay chains • In RPC searches the phase space is limited by a DM "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  23. SUSY Searches - Decay Modes - • What are the serach topologies? "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  24. Analysis Tools - Kinematic Variables - • Pseudo-rapidity: • Angular distance in space: • Missing Transverse Energy: • Total Transverse Energy: • It’s a scalar sum • : • Lower bound helps reduce from jets mis-measurements "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  25. Analysis Tools - Anti-kT Jets - • Definition: It’s a recombination algorithm • Properties: • it is IR-safe • it can easily be implemented in theoretical or experimental analyses • it can be defined at any order of the perturbation theory • Description: • Recombines successively closest pairs area fluctuates and depends on pT area fluctuates, depends less on pT constant area (circular jets) • Implementation: http://www.fastjet.fr "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  26. Analysis Tools - Kinematic Variables - • Effective Mass: • sensitive to • Stransverse mass: • lower bound on mass of particle decaying semi-invisibly • Contransverse mass: • useful for identical parent particles decay semi-invisibly HT invisible visible where (usual transverse mass) "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  27. SUSY  Multijets+mET (1) L=1.04 fb-1 • Dataset: • 2011 p+p collisions • Trigger: • LVL1: multijets • HLT: 5j55 or 6j45 • Performance: e=99% • Data Quality: • Remove bad L blocks • Remove evts w/ bad jets • Reject evts w/ cosmics or noise • Object ID: • Jets: • anti-kT, DR=0.4 • pT > 20 GeV • |h|<2.5 • e: medium, pT > 20 GeV, |h|<2.47 • e isolation: HT(tracks) (DR=0.2)<10% pT(e) • m: matched, pT > 20 GeV, |h|<2.4 • m isolation: HT(tracks) (DR=0.2)<1.8GeV • Veto isolated e or m "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  28. SUSY  Jets+mET (3) • Main Background Processes: • Z+jets: especially Z(nn)+jets • W+jets: especially W(tn)+jets or W(e/mn)+jets w/ missed e/m • QCD multijet • Background Estimation: • Evaluate each process in a « Control Region » (5 CRs x 5 SRs) • Extrapolate the CR to SR using transfer factors: • Estimate Signal Sensitivity: • Profile log-likelihood fit (with correlated systematic uncertainties and CRs cross-contamination) "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  29. SUSY  Jets+mET (3) "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  30. SUSY  Jets+mET (3) "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  31. SUSY  Jets+mET (3) "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  32. SUSY  Jets+mET (3) "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  33. SUSY  Jets+mET (3) "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  34. SUSY  Jets+mET (3) Event w/ highest meff found 5 jets with pt > 40 GeV: pt = 528, 418, 233, 171, 42 GeV met = 460 GeV meff =1810 GeV (4 leading jets) "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  35. SUSY  Jets+mET (3) "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  36. SUSY  Jets+mET (3) "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  37. SUSY Searches - ATLAS Summary - "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  38. II. ILC "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  39. Main Features structures the beam bunches • Advantages: • Very clean and flexible environment: • tuneable E: • polarized beams: • low rate: 15-30 kHz • sensitivity to virtual effects • Drawbacks: • large gg background (0.1 evt / bunch X) • 10% evts w/ • monitor accolinearity of Bhabha’s • to estimate accelarating niobium cavities (Phase I: ~500 fb-1) (Upgrade  Phase II) "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  40. Detector Concepts (1) B=4 T Large Detector Concept B=5 T Silicon Dectector "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  41. Detector Concepts (2) B=3.5 T Global Detector Concept • « Triggerless Mode » Collider: • Low rate enables: • No hardware trigger • Just a software-based • trigger for loose filtering • Typical Requirements: • Inner Tracking: • Vertex Detector: • Outer Tracking: • Calorimetry: • EM: • Jets: "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  42. SUSY Benchmark • SPS1a: • Old SUSY benchmark in the bulk region • Outside the recent allowed region from WMAP "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  43. SUSY Measurements "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  44. Thresholds & Edges Measurements L=200 fb-1 Beam Polarization "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  45. Threshold Scans L=100 fb-1 Sharp production thresholds => E scan gives good sensitivity M(FS) "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  46. mSUGRA Fit SFitter "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  47. III. Indirect Accelerator Constraints • Hereafter I describe some virtual effects • measured at accelerators that indirectly • constrain SUSY: • am =1/2(g-2)m • bsg (not covered today) • Bsm+m-,… "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  48. Bsm+m- (1) • In SM Bs+- is suppressed (need FCNC) SM predicts • SUSY can enhance BR by 1 order of magnitude Ref: M. Blanke et al., JHEP 0610 (2006) 003 A key early measurement for LHC "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  49. Bsm+m- (2) L=3.7 fb-1 L=6.1 fb-1 CDF Result: No excess seen Aug 2009 D0 Result: No excess seen Jun 2010 "Introduction to Supersymmetry", L. Vacavant & S. Muanza

  50. Bsm+m- (3) • ATLAS & CMS: • |hm|<2.5, L=1032-33 cm-2s-1 • Single & di-muon triggers • LHCb: • 1.9<|hm|<2.5, L=2x1032 cm-2s-1 • Low pT trigger (sensitivity to sbb 2.3 larger than ATLAS & CMS) • Evt Selection: • based upon several variables, including Mmm • mass resolutions: 90 MeV (ATLAS), 53 MeV (CMS), 22 MeV (LHCb) CMS: 1fb-1 (incl. syst.) "Introduction to Supersymmetry", L. Vacavant & S. Muanza

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