Inclusive SUSY Searches at with Emphasis on Detector Systematics R. Cavanaugh (on behalf of ) University of Florida SUSY06 Detector Background Calibrations Inclusive Search Strategies Detector Systematics Results
Detector SUPERCONDUCTING COIL CALORIMETERS ECAL Scintillating PbWO4 crystals HCAL Plastic scintillator/brass sandwich IRON YOKE TRACKER Silicon Microstrips Pixels Total weight : 12,500 t Overall diameter : 15 m Overall length : 21.6 m Magnetic field : 4 Tesla MUON BARREL Drift Tube Chambers ( DT ) Resistive Plate Chambers ( RPC ) MUON ENDCAPS Cathode Strip Chambers (CSC ) Resistive Plate Chambers (RPC) 14 June, 2006 R. Cavanaugh, Florida, SUSY06 2
SUSY Signature: MET + Jets + 6 hard jets leptons 2 LSPs + 4 ν s Squark gluino production Full Geant4 Detector Simulation 14 June, 2006 R. Cavanaugh, Florida, SUSY06 3
Jet/MET Reconstruction Performance Jets Low luminosity Pileup included E T Resolution Stochastic term 125% / E T Constant term 3% Angular Resolution High E T Jets: better than calo cell size ( φ x η = 0.087 x 0.087) MET QCD Jets Missing Transverse Energy Low luminosity Pileup included <MET> from QCD Stochastic term 123% / ΣE T 1700 GeV ΣE T 700 GeV P T dijets 50 GeV observed MET MET φ Resolution Low MET : approaches Jet size High MET : approaches calo cell size 14 June, 2006 R. Cavanaugh, Florida, SUSY06 4
MET Cleaning from Tevatron MET is very powerful SUSY discriminator Difficult part is to convince yourself that there is a real excess! Tevatron teaches us MET is not easily understood! Non-collisional backgrounds Beam halo Cosmic muons Detector Effects Instrumental Noise junk Run II V. Shary CALOR04 Hot/dead channels (DQM) D. Tsybychev, Fermilab-thesis-2004-58 jets e/γ Run II 14 June, 2006 R. Cavanaugh, Florida, SUSY06 5
Early Study of MET Cleaning in (of course, Real Data will be different!) Apply clean up cuts to remove fake high MET events (inspired by CDF & D0) Response to Beam Halo Simulation of LHC Point 5 Pileup not included 1 central jet ( η <1.7) with 4 tracks 1 vertex F em > 0.1 (Event Electromagnetic Frac.) F ch > 0.175 (Event Charged Fraction) Affect on SUSY Signal tt full sim. Pileup included 14 June, 2006 R. Cavanaugh, Florida, SUSY06 6
QCD Multijet Background Dijets typically back to back MET from jet E mismeasurement Suppress by requiring Well separated Jet & MET objects Typically 3 jets Cut on H T (~ 2 p Hat T ) Muon triggers (include isol.) helps a lot! Prescaled jet triggers extract the low E T shape and normalisation directly from data No cuts µ Trigger µ Trigger + E Jet1 T >900 GeV µ Trigger + E Jet1 T >900 + MET>200 GeV Level 1 14 June, 2006 R. Cavanaugh, Florida, SUSY06 7
Electroweak Multijet Backgrounds: Z µµ Standard Candle Large MET and 3 Jets expected from Z( νν) + 3 jets W( µ(e)ν) + 3 jets W( τν) + 2 jets Z + n-jets x-sect α s N Measure from 2 Jets Data Z( µµ) + 2 jets Z( ee) + 2 jets Z( µµ) + 2 jets (Z peak) Z( µµ) + 2 jets (Z peak normalised) Z( νν) + 2 jets Normalise MC to Data for 3 Jets Assume lepton universality For W + n-jets, use Reduces / Avoids Systematics due to QCD Scale, PDFs (possibly), ISR/FSR, Jet Energy Scale, etc Major Syst. Become Luminosity, Measurement of R, Uncertainty on ρ(n jet ) Still requires tuning MC to Data for kinematic dists. 5% precision (~lumi) expected to be achieved with 1.5 fb-1 14 June, 2006 R. Cavanaugh, Florida, SUSY06 8 See Marc Buehler s talk from D0, yesterday
Benchmark Test Points Basis of detailed studies in soon to be released Physics TDR Vol. 2 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 Benchmark Optimisation Point 14 June, 2006 R. Cavanaugh, Florida, SUSY06 9
Inclusive Jet + MET Search Selection Criteria MET>200 GeV + Clean-up 3 jets: E T > 180, 110, 30 GeV Indirect lepton veto Cuts on φ between jets and MET H T /M eff =E T1 +E T2 +E T3 +MET>500 GeV Results: LM1 efficiency is 13%, S/B ~ 26 : Number of events (below) for 1 fb -1 ~6 pb -1 for 5σ discovery Lower jet multiplicity requirement reduces sensitivity to higher-order QCD corrections 14 June, 2006 R. Cavanaugh, Florida, SUSY06 10
Inclusive Muon + Jet + MET Search Add muon clean trigger Cuts (optimize @ LM1) 1 isolated muon p T > 30 GeV MET > 130 GeV 3 jets: E T > 440, 440, and 50 GeV η < 1.9, 1.5, and 3 Cuts on φ between jets and MET Backgrounds (10 fb -1 ) Trigger Efficiency SM Backgrounds No Cuts msugra LM-1 p T of leading muon (GeV) Single-µ OR Di-µ HLT + Pre-selection LM1 Signal (10 fb -1 ) 311 events SUSY LM1 14 June, 2006 R. Cavanaugh, Florida, SUSY06 11
Inclusive SS Dimuon + Jet + MET Even cleaner signature Low background due to same sign requirement Concentrate here on Identifying the SUSY diagrams giving prompt muons Strong muon isolation & tight quality cuts Selection Critera Muon trigger Muon isolation Muon track parameters High PT jets Large Missing Transverse Energy Background (10 fb-1) 1.5 (ttbar) events LM1 Signal (10 fb-1) 341 events 65% efficient at identifying SUSY diagrams, 90% pure 14 June, 2006 R. Cavanaugh, Florida, SUSY06 12 p + p + g% q% X q% q % χ ± 1 q ν% 0 χ% 1 ν µ µ ± µ ± % χ ± 1 ν% q ν µ 0 χ% 1
Jet Energy Calibration/Systematics Direct photon production: qg qγ (90%) qqbar gγ (10%) p T (Jet) = p T (γ) use peak position to eliminate effect of tail from ISR Estimated Jet Energy Scale Uncertainty: Between 3% and 10% for P T [20, 50] GeV γ jet t t measured shift C meas ttbar WWbb jjlνbb Rescale jet with relative energy shift C Fit resulting W mass spectrum & constrain to world avg. m W ( C data) = M W PDG Compare with Monte Carlo For ~6 fb-1: C meas = -14.96 ± 0.26 % ( C true = -14.53 %) Requires well understood b-tag (tracker) Limited by pileup syst. uncertainty: 3% C(%) JES Systematic Uncertainty for P T > 50 GeV 14 June, 2006 R. Cavanaugh, Florida, SUSY06 13
MET Shape Systematics Study effect of non-gaussian tails in jet E T resolution contributing to fake MET Approx. 15% of all jets are mismeasured Exaggerate non-gaussian Tails Weight each jet (up to 3) in event t t Jet in Non-Gaussian tail: 1.15 Jet in Gaussian peak : 1.00 Combine into one event weight Three different scenarios 3 jets under measured 2 jets under measured 1 jet under measured Overall Systematic Effect : 7% 14 June, 2006 R. Cavanaugh, Florida, SUSY06 14
Expected Reach for 1 fb -1 14 June, 2006 R. Cavanaugh, Florida, SUSY06 15
Expected Reach for 10 fb -1 14 June, 2006 R. Cavanaugh, Florida, SUSY06 16
Conclusion has recently completed several inclusive SUSY analyses for potential discovery Full detector simulation, reconstruction All backgrounds included Estimate low P T QCD from pre-scaled jet triggers Estimate EW from Z µµ Standard Candle Systematic uncertainties Jet Energy Scale, MET Shape, Misalignment, etc Results to be published in Physics Technical Design Report Vol. 2 With 1fb -1, can discover (or exclude) all of the low mass benchmark points Including expected systematic effects Low mass SUSY visible almost immediately Provided systematic effects are under control Current focus is now on commissioning and startup scenarios 14 June, 2006 R. Cavanaugh, Florida, SUSY06 17
Backup Slides
14 June, 2006 R. Cavanaugh, Florida, SUSY06 19
The Calorimeters Hadronic Outer Hcal barrel and EndCap EM barrel and EndCap Very Forward Calorimeter EM calorimeter η < 3 : PbW0 4 crystals 1 longitudinal section/preshower 1.1 λ η ϕ = 0.0174 0.0174 Central Hadronic η < 1.7 : Brass/scintillator 2 + 1 Hadronic Outer long. sections 5.9 + 3.9 λ ( η =0) η ϕ = 0.087 0.087 Forward calorimeter 2.9 < η < 5: Fe/quartz fibers η ϕ = ~0.175 0.17 Endcap Hadronic 1.3< η < 3 : Brass/scintillator +WLS 2/3 longitudinal sections 10λ η ϕ = ~0.15 0.17 14 June, 2006 R. Cavanaugh, Florida, SUSY06 20
Muon System MB4 MB3 MB2 1.6 MB1 ME1 ME2 ME3 ME4/1 restored 14 June, 2006 R. Cavanaugh, Florida, SUSY06 21
Early Jet Energy Calibration Require at least one of the two leading jets to have η <1. Call it the barrel jet, the other jet is called the probe jet. If both jets have η <1 then they are both barrel and probe jets. Require Barrel Jet P T = Probe Jet P T Can be used at Startup! dijet Data shown here could be taken in 1 hour @ low lumi running Single day s data taking could calibrate with decent precision. A statistical error of better than 0.5% for every 0.1 unit of eta in the Barrel. A statistical error of better than 2% for every 0.1 units of eta in the Endcap and HF 14 June, 2006 R. Cavanaugh, Florida, SUSY06 22
Use Track and Muon System (Z µµ) to Calibrate Calorimeter (MET) Variation on a Z µµ Candle theme Derive MET corrections from Z µµ Sample Apply to SUSY Sample (to test) Some fine tuning required But basically works SUSY LM1 14 June, 2006 R. Cavanaugh, Florida, SUSY06 23
Inclusive Search Strategies Use Missing Transverse Energy (MET) as the key signature for SUSY in analyses presented here R-parity 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) Anticipate systematic effects and estimate uncertainties Determine 5σ reach in msugra space using fast simulation 14 June, 2006 R. Cavanaugh, Florida, SUSY06 24
Inclusive OS Dilepton + Jet + MET Cuts (optimize @ LM1): 2 OS SF isolated leptons (e,µ) p T > 10 GeV MET > 200 GeV 2 jets: E T1 >100 GeV E T2 >60 GeV η < 3 Background (1 fb -1 ) 200 events, mostly t-tbar Systematic uncertainty 20% LM1 Signal (1 fb -1 ) 850 events Subtract different favor leptons m ll max = 80.4 ± 0.5 (stat) ± 1.0 (misalign) GeV 14 June, 2006 R. Cavanaugh, Florida, SUSY06 25
Effects of Misalignment Misalign Tracker and Muon System separately Evaluate the impact on the dilepton end point Two scenarios: First Data, 6 months, 100 pb -1 to 1 fb -1 di-muon efficiency decreased by ~30% di-electron efficiency decreased by ~10% Long Term, >6 months, >1fb -1 di-muon efficiency decreased by ~13% di-electron efficiency decreased by ~2% 14 June, 2006 R. Cavanaugh, Florida, SUSY06 26