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SUSY Physics @ LHC

SUSY Physics @ LHC. Darin Acosta University of Florida On behalf of the ATLAS and CMS Collaborations. Outline. Concentrate on inclusive search strategies for SUSY New proto-analyses from CMS Physics TDR Canonical SUSY searches : Jets + Missing transverse energy

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SUSY Physics @ LHC

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  1. SUSY Physics @ LHC Darin Acosta University of Florida On behalf of the ATLAS and CMS Collaborations

  2. Outline • Concentrate on inclusive search strategies for SUSY • New proto-analyses from CMS Physics TDR • Canonical SUSY searches : • Jets + Missing transverse energy • Lepton + jets + Missing transverse energy • Dileptons (OS, SS) + Jets + Missing transverse energy • Di-taus + jets + Missing transverse energy • Heavy Reconstructed Object based SUSY searches • Z0 + Missing transverse energy • top + Missing transverse energy • sParticle spectroscopy and spin analysis: • MSSM Higgs covered in previous talk acosta @ phys.ufl.edu

  3. Supersymmetry • A symmetry between fermions and bosons • Avoids fine-tuning of SM, can lead to GUTs, prerequisite of String Theories, possible dark matter candidate (LSP) • Generally assume LSP is stable (Rp conservation) • SUSY breaking mechanism is unknown  many params. • mSUGRA: • Supergravity inspired model, 5 free parameters: • m0, m1/2, A0, tan , Sign(µ) acosta @ phys.ufl.edu

  4. A0=0, tan(β)=10, sign(µ)=+1 Cross Sections and Signatures • Complex decays chains • MET (LSP) • High PT jets ( q, g ) • Leptons ( , l, W, Z ) • Heavy flavor (high tan) ~ ~ ~ ~ acosta @ phys.ufl.edu

  5. The Large Hadron Collider • Proton-proton collider, s = 14 TeV • Low luminosity phase: L = 21033 cm-2s-1 • 5 inelastic pile-up collisions • High luminosity phase: L = 1034 cm-2s-1 (100 fb-1/yr) • 25 inelastic pile-up collisions • Start-up slated for 2007, second half R = 4.5 kmE = 7 TeV CMS Atlas CERN acosta @ phys.ufl.edu

  6. The Compact Muon Solenoid (CMS) Expt. One of two large general purpose experiments at the LHC 4T magnet Muon chambers Silicon Tracker:charged particle tracking and b/ id PbWO4 Crystals:  / e detection Hadronic calorimeter:Jets, missing ET () acosta @ phys.ufl.edu

  7. CMS at Surface Assembly Hall 2/06 acosta @ phys.ufl.edu

  8. A Toroidal LHC ApparatuS (ATLAS) Complementary detector technologies to CMS Calorimeters (LAr):  / e, Jets, missing ET () measurements Silicon and TRT Tracker 0.6T Toroids Muon chambers 2T solenoid acosta @ phys.ufl.edu

  9. ATLAS Underground 5/06 acosta @ phys.ufl.edu

  10. New Analysis Developments from CMS http://cmsdoc.cern.ch/cms/cpt/tdr/ • CERN/LHCC 2006-001 CERN/LHCC 2006-021 • Published Coming June 2006

  11. CMS Physics TDR • CMS has recently published Volume 1 of its Physics Technical Design Report, with Volume 2 to come next month (but new results included here) • ATLAS Physics TDR: CERN/LHCC 1999-14/15 • Volume 1: • Compendium of detector performance, calibration & alignment strategies, and reconstruction algorithms for physics objects (e, , µ, , b, jet, MET) • Volume 2: • Detailed study of several benchmark analyses, including SUSY, to demonstrate key performances of the detector and including all the methodology of a real data analysis • Background estimation, systematic uncertainties, etc. • Comprehensive collection of analyses that span most final state topologies to determine overall reach (e.g. mSUGRA) • Analyses based on GEANT4 detector simulations (or derived parameterizations) for backgrounds and signals and real reconstruction algorithms studied in Vol.1 acosta @ phys.ufl.edu

  12. Inclusive Search Strategies for Final States with MET

  13. Strategy • Use Missing Transverse Energy (MET) as the key signature for SUSY in analyses presented here • Rp conservation, neutral LSP • SUSY benchmark points studied in detail using GEANT-based detector simulation and full reconstruction algorithms • Consider all backgrounds as well as lepton fakes • QCD multi-jets, W/Z+jets, t-tbar, diboson • Optimize significance to determine cuts at a particular benchmark point(s) • Determine 5 reach in mSUGRA space using fast simulation acosta @ phys.ufl.edu

  14. MET Reconstruction • Sum over calorimeter towers • Can correct for jets, muons • MET Resolution • Measure from data • Use min-bias and prescaled jet triggers to measure resolution • CMS stochastic term ~0.6–0.7 • Jet calibration crucial to improve resolution Variety of techniques possible • -Jet balancing, di-jet balancing, • W mass constraint in hadronic W decays in top pair events • CMS: Achieve 3% JES uncertainty for ET>50 GeV with 1–10 fb-1 QCD Minbias acosta @ phys.ufl.edu

  15. CMS Benchmark Test Points • Basis of detailed studies • Low mass points for early LHC running but outside Tevatron reach • High mass points for ultimate LHC reach • Indirect constraints from WMAP for strict mSUGRA exclude most except LM1, 2, 6, 9 acosta @ phys.ufl.edu

  16. Inclusive MET + Jets • Most sensitive signature • For low mass Supersymmetry, no problem to have a large excess of events over the SM at the LHC • Difficult part is to convince yourself that there is a real excess! • MET dataset cleanup • Use e.g. Tevatron-inspired event shape cuts for non-collision backgrounds (no LHC data yet!) • Event EM fraction >0.1 • Event charged fraction >0.175 • 1 vertex • Set up control regions that enhance background over signal to calibrate from data W/Z+jets, top pairs, QCD dijets • Understanding of systematic uncertainties • Sensitivity to Jet Energy Scale uncertainty and resolution D. Tsybychev, Fermilab-thesis-2004-58 EEMF ECHGF acosta @ phys.ufl.edu

  17. MET calibration using Z-candle • Measure Z+jets with Zµµ in data to normalize the Z (invisible) contribution and calibrate MET spectrum CMS • With ~1fb-1 we will have enough Z+jets in the PT(Z)>200 region of interest to normalize within 5% the Z invisible process as well as W+jets through the W/Z ratio and lepton universality acosta @ phys.ufl.edu

  18. Inclusive MET + Jets CMS • Cuts • MET>200 + Clean-up • 3 jets: • ET> 180, 110, and 30 GeV • ||< 1.7, 3, 3 • Cuts on  between jets and MET • HT=ET1+ET2+ET3+MET >500 GeV • Indirect lepton veto • Results • LM1 efficiency is 13% • S/B ~ 26 • Systematic uncertainty: • ~6 pb-1 for 5 discovery • Low jet multiplicity requirement reduces sensitivity to higher-order QCD corrections acosta @ phys.ufl.edu

  19. Inclusive MET+Jets+Muons A0=0, tan(β)=10, sign(µ)=+1 • Add lepton, clean trigger • Cuts (optimize @ LM1): • 1 isolated muon • pT > 30 GeV • MET > 130 GeV • 3 jets: • ET> 440, 440, and 50 GeV • ||< 1.9, 1.5, and 3 • Cuts on  between jets and MET • Background (10 fb-1) • 2.5 events, Systematic uncertainty 20% 60 fb-1 30 fb-1 30 fb-1 and 60 fb-1 : Re-optimised cuts for higher lumi 10 fb-1 m1/2 Optimised cuts for 10 fb-1 luminosity m0 acosta @ phys.ufl.edu

  20. Same-Sign Muon Signature • Signal: Background: • Motivation and Strategy: • Clean objects for trigger and reconstruction (muons) • Reduced detector uncertainties vs pure Jets/MET • Low background (same-sign signature) • Isolate the SUSY diagrams with strong isolation and quality cuts on the reconstructed muons • Theoretical studies include: • H. Baer et al. PR D41, #3 (1990); R. Barnett et al. PL B315 (1993), 349; K. Matchev and D. Pierce hep-ph/9904282 (1999) acosta @ phys.ufl.edu

  21. LEP Tevatron Same-Sign Muon: Reach A0=0, tan(β)=10, sign(µ)=+1 • Cuts (optimize @ LM1): • 2 SS isolated muons • pT > 10 GeV • MET > 200 GeV • 3 jets: • ET1>175 GeV • ET2>130 GeV • ET3>55 GeV • Background (10 fb-1) • 1.5 events • Systematic uncertainty 23% CMS Optimized cuts for 10 fb-1 luminosity m1/2 m0 acosta @ phys.ufl.edu

  22. MET + Opposite Sign Leptons CMS • Cuts (optimize @ LM1): • 2 OS SF isolated leptons • pT > 10 GeV • MET > 200 GeV • 2 jets: • ET1>100 GeV • ET2>60 GeV • || < 3 • Background (1 fb-1) • 200 events, mostly t-tbar • Systematic uncertainty 20% • LM1 Signal (1 fb-1) • 850 events acosta @ phys.ufl.edu

  23. Opposite Sign Leptons: Mass Edge • Measure invariant mass distribution of same-flavor opposite-sign (SFOS) leptons as evidence for • or • Striking signature: endpoint in mass spectrum exhibits sharp edge dependent on sparticle masses • LM1 with 1 fb-1 : • with uncertainty on alignment and energy scale Subtract different favor leptons acosta @ phys.ufl.edu

  24. Inclusive MET + Z0 • Catch • Mostly from q, g decays • Z0 gives extra handle against non-resonant dilepton bkg • Cuts (optimize @ LM4): • MET > 230 GeV • 2 OS SF leptons • pT(e) > 17 GeV, or • pT(µ) > 7 GeV • 81 < Mll < 96.5 GeV •  < 2.65 rad • Background (10 fb-1) • SM: 200  40 (t-tbar + diboson) • Systematic uncertainty 20% • LM4 Signal (10 fb-1) • 1550  30 ~ ~ CMS e+e– acosta @ phys.ufl.edu

  25. Inclusive MET + Top • Catch stop decays to top • Search (optimize @ LM1): • MET>150 GeV • Hadronic top selection and 2C fit • 1 b-jet + 2 non-b jets • Use the W and top mass constraints to fit top and require good 2 • LM1: ~200 pb-1 for 5 observation! acosta @ phys.ufl.edu

  26. sParticle Spectroscopy, circa “2010” End of decade: excess observed in a channel like one these shown! What are the masses? Is it SUSY? The fun begins…

  27. MET + di-Tau • Catch • Measure di-tau endpoint and infer sparticle masses • But no sharp reconstructed endpoint due to  • Fit to signal + background can be translated to endpoint measurement • Measure a number of invariant mass distributions, e.g. • 2-tau, tau1+jet, tau2+jet, tau1+tau2+jet • Extract the masses of the sparticles by solving for the kinematics of the decay chain; example measurement at 40 fb-1 at LM2: CMS acosta @ phys.ufl.edu

  28. ATLAS sParticle acosta @ phys.ufl.edu

  29. ATLAS Spin acosta @ phys.ufl.edu

  30. Conclusions acosta @ phys.ufl.edu

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