What the LHC Will Teach Us About Low Energy Supersymmetry

What the LHC Will Teach Us About Low Energy Supersymmetry Darin Acosta representing ATLAS &

Outline Introduction to SUSY, LHC, and the Detectors Trigger strategies at start-up Inclusive squark/gluino searches SUSY Spectroscopy Di-lepton edges squark and gluino reconstruction Summary SUSY at the LHC, Aspen 23 2

Minimal SuperSymmetry SUSY Symmetry between bosons and fermions Squarks/sleptons: q, l scalar counterparts to the fermions ± Charginos/neutralinos/gluinos:, χ, 12, χ1234,,, g fermion counterparts to SM gauge bosons At least two Higgs doublets (5 scalars): Avoids fine-tuning of SM, can lead to GUTs MSSM Usually consider R P (-1) 3(B-L)+2S conserved LSP is stable 15 new parameters msugra: Require SUSY to be a local symmetry Universal gravitational interactions break SUSY at scale F (1 11 GeV) 2 5 free parameters m : Common scalar mass m 1/2 : Common gaugino mass A : Common scalar trilinear coupling tan β : Ratio of v.e.v. of Higgs doublets Sign(µ) : sign of Higgsino mixing parameter χ χ 1 ± 2 2 χ1 Typically: M M M M g > M q > M χ SUSY at the LHC, Aspen 23 d i d i d i af af af 3 ± hh,, AH,

Large Hadron Collider (LHC) CMS ATLAS R = 4.5 km E = 7 TeV Two proton rings housed in same tunnel as LEP Design luminosity: L = 1 34 cm 2 s 1 = 1 fb -1 /year (Pile up: 2 collisions/crossing) Start-up luminosity: L 1 33 cm 2 s 1 = 1 fb -1 /year Completion: mid 27 SUSY at the LHC, Aspen 23 4

msugra Cross Sections @ LHC Total cross section, q g m 1/2 (GeV) 14 12 1 fb 1 TH 1 fb 8 1 fb 6 1 pb 4 1 pb 2 EX A =, tan β = 35, µ > 5 1 15 2 m (GeV) Squark/gluino production dominates the total cross-section for low energy SUSY Cross sections don t vary much with µ, tanβ SUSY at the LHC, Aspen 23 5

Tile CAL Detectors LAr CAL ATLAS toroids 4T solenoid 2T solenoid TRT and Si tracker muon Cu/Scin HCAL PbWO 4 ECAL Full Si tracker Compact Muon Solenoid (CMS) SUSY at the LHC, Aspen 23 6

SUSY Signatures Complex squark/gluino decay chains Many high-e T jets Heavy-flavor (τ and b, especially at large tanβ) Leptons From sleptons, charginos, W/Z, and b-jets Missing transverse energy (MET) From LSP and neutrinos from taus, sneutrinos Example: m = 1 GeV m 1/2 = 5 GeV tan β = 35 µ > A = CMS event simulation SUSY at the LHC, Aspen 23 7

Trigger Challenge Reduce 4 MHz bx rate (1 GHz pp) O(1 Hz) Inclusive Jet Rate (cone algorithm, R=.5): Full GEANT-based detector simulation on QCD background High lumi CMS DAQ Technical Design Report CERN/LHCC 22-26 Low lumi Expected MET Rate: Recon. MET (hi lumi) Recon. MET (low lumi) Gen. MET (hi lumi) Gen MET (low lumi) Requiring a rate to tape of a few Hz implies an inclusive single jet threshold of 4 6GeV, and an inclusive MET threshold of 1 2 GeV Reconstructed MET rate below 1 GeV mainly from calorimeter energy resolution SUSY at the LHC, Aspen 23 8

SUSY Trigger Exercise (CMS) Consider several points in the m -m 1/2 plane near the Tevatron reach (most difficult for LHC) (1 day of running) Consider points with and without R p conservation For R p choose most difficult case: χ 1 3j Run full GEANT-based detector simulation on SUSY signals and SM backgrounds to evaluate trigger performance Optimize efficiency for a rate to tape O(1 Hz) SUSY at the LHC, Aspen 23 9

Example Trigger Strategy (CMS) Low luminosity case, L = 2 1 33 cm -2 s -1 Possible triggers at Level-2 (looser requirements at Level-1): 1 jet E T >18 GeV & MET>12 GeV 4 jets E T >11 GeV (values at 95% gen. effic.) Overall efficiencies to pass both trigger levels for the SUSY points are: ε=.63,.63,.37,.43,.38,.23 4 5 6 4R 5R 6R 2 nd jet With R P 1 st jet Background rate of 12Hz dominated by QCD More exclusive triggers involving angular correlations among objects can be added to further improve efficiency Trigger becomes more efficient at high luminosity since one expects to explore higher masses SUSY at the LHC, Aspen 23 1

Lepton and Photon Triggers Anticipated thresholds by ATLAS and CMS for an initial luminosity of L = 2 1 33 cm -2 s -1 1e: P T > 25 GeV 2e: P T > 15 GeV 1µ: P T >2 GeV 2µ: P T >1 GeV 1τ: P T >85 GeV 2τ: P T >6 GeV 1γ: P T > 6 8 GeV 2γ: P T > 2 4 GeV ) 2 1 Differential Rate ( Hz/GeV/c 1 1-1 1-2 33 L = 2x1 Minimum Bias * Z/ γ µ + X t t µ + X CMS 1-3 1-4 2 4 6 8 1 12 14 16 18 2 2 ( GeV /c ) Di-muon invariant mass at Level-3 µµ M inv Sufficient handle on muon trigger rate: SUSY at the LHC, Aspen 23 11

Fast Simulation Full simulation of signals and backgrounds like that shown for trigger exercise is too CPU intensive for complete SUSY reach determination Require O(1 8 ) events, but full GEANT simulation takes tens of minutes per event Use physics generators + parameterized detector performance ATLFAST: Tracks (µ): P T /P T =.4P T 1% (P T in TeV) EM resolution: σ/e 1%/ E.3% (E in GeV) Jet resolution: σ/e 6%/ E 2% (E in GeV) CMSJET: Tracks (µ): P T /P T =.15P T.5% (P T in TeV) EM resolution: σ/e 5%/ E.5% (E in GeV) Jet resolution: σ/e 1%/ E 5% (E in GeV) SUSY at the LHC, Aspen 23 12

Inclusive q, g Search Counting excess events over SM background Discovery mode SUSY search at LHC Explicit sparticle reconstruction not done 6 Analyses: E miss T : Ol: 1l: 2lOS: 2lSS: 3l: CMS Study: Common cuts: jets+met, no lepton requirements no leptons 1 lepton 2 leptons, opposite sign 2 leptons, same sign 3 leptons MET>2 GeV, 2 jets, Lepton identification E T jet > 4 GeV, η <3 Electron: P T >2 GeV, isolated, η <2.4 Muon: P T >1 GeV, isolated or not, η <2.4 Vary cuts in 6 categories (1 4 combinations) #Jets, MET, Jet E T, φ(l,met), Circ., µ Iso. Optimize S/ (S+B) in a counting experiment Probe 5 (m, m 1/2 ) points 1 6 signal events, 1 8 QCD, tt, W/Z+jets Plot 5σ sensitivity contours SUSY at the LHC, Aspen 23 13

CMS q, g Reach m 1/2 (GeV) 14 12 g (3) l + 1l + 2l OS miss E T L dt = 1 fb -1 A =, tan β = 35, µ > miss E T (3 fb -1 ) h(123) ISAJET 7.32 + CMSJET 4.5 g (25) 1 1l l 8 TH q (2) 2l OS 2l SS 3l g (2) q (25) 6 g (15) q (15) h 2 =.4 h 2 = 1 4 g (1) h 2 =.15 q (1) 2 q (5) h(11) g (5) EX 5 1 15 2 m ( GeV) Jets+MET search gives greatest sensitivity Opposite-sign leptons useful for sparticle recon. Nucl. Phys. B547 (1999) 6 SUSY at the LHC, Aspen 23 14

Jets+MET Reach vs. Luminosity m 1/2 (GeV) 14 12 g (3) miss E T (1 fb -1 ) L dt = 1, 1, 1, 3 fb -1 A =, tan β= 35, µ > miss E T (3 fb -1 ) h(123) CMS g (25) 1 TH q (2) g (2) q (25) 1 year @ L=1 34 8 E T miss (1 fb -1 ) 6 g (15) 1 year @ L=1 33 4 h 2 =.4 h 2 = 1 q (15) miss E T (1 fb -1 ) g (1) 1 month @L=1 33 1 week @L=1 33 2 (but one year for sparticle reconstruction) q (5) h(11) EX h 2 =.15 g (5) q (1) 5 1 15 2 m ( GeV) Tevatron reach <.5 TeV Squarks/gluinos probed to 1.5 TeV with 1 fb -1 Up to 2.5 TeV at design luminosity (1 fb -1 ) SUSY at the LHC, Aspen 23 15

Other Parameter Choices ATLAS TDR 15 CERN/LHCC 99-15 8 1l l tan β = 1, µ < L=1 fb 1 1 year @ L=1 33 6 4 2 2l,j OS 3l,j SS 3l 8 6 l 1l tan β = 1, µ > SS OS 3l 4 2 2l,j 3l,j 5 1 15 2 m (GeV) Similar cuts and optimization as for CMS study Sensitivity for lower tanβ also derived, but lower mass Higgs inconsistent with present limits SUSY at the LHC, Aspen 23 16

R-Parity Violation Non-conservation of R P (-1) 3(B-L)+2S leads to 3 new terms in SUSY superpotential: W = λ L L E + λ QL D + λ U L D ijk i j k c ijk i j k c ijk i c j c k c Choose most challenging of baryon number violation (last case): χ 1 3j ATLAS Study of Point 5 m =1 GeV, m 1/2 =3 GeV, tanβ=2, µ>, A =3 MET is reduced, but still substantial Number of jets increases Leptons from neutralino decays Should still be able to explore much of the parameter space as with msugra Events/1 GeV/3 fb -1 1 3 1 2 Probability.16.14.12.1.8.6.4 1 2 4 6 8 1 E miss (GeV) T.2 2 4 6 8 1 12 14 16 18 2 N jet Figure 2-85 E miss T distribution for SUGRA Point 5 Figure 2-86 Total jet multiplicity ( p jet T > 15GeV ) in the case of R-parity conservation (shaded histogram) and R-parity violation (empty histogram). distribution for R-parity conservation (shaded) and R- parity violation at SUGRA Point 5. The jets are reconstructed using a topological algorithm based on joining neighbouring cells. SUSY at the LHC, Aspen 23 17

Exclusive Di-Lepton Reconstruction Measure invariant mass distribution of OS same flavor leptons as evidence for χ χ l + l or χ l l χ 2 1 2 + 1 l + l χ 2 can be produced via Drell-Yan χ 1 ± χ2, q, g but more prevalent in cascade decays of Endpoint in mass spectrum exhibits sharp edge: Events/4 GeV/3 fb 1 M(l + l ) (GeV) SUSY e + e + µ + µ SM background This point selected by: χ χ l l 2 1 ATLAS Point 4 : m =8GeV m 1/2 =2GeV tanβ=1 µ> A = L=3 fb 1 + Some Z from other gauginos SM background is small Two OS leptons (e,µ), P T >(2,1) GeV, η <2.5 MET>2 GeV, 4 jets: P T1 >1 GeV, P T 234 >5 GeV d i d i 3-body decay endpoint: mll max = m χ m 2 χ1 2-body: mll max 2 m m l m l m / = χ χ m l ch e d 2 i 2 ie 2 ch 2 d 1 i i ch SUSY at the LHC, Aspen 23 18

Evolution of Di-Lepton Edges Events / 4 GeV 1 4 1 3 1 2 1 m = 9 GeV, m 1/2 = 22 GeV µ>, A = tanβ = 2 m χ2 o = 164 GeV, m er = 129 GeV ee,µµ m τ1 = 128 GeV 1 3 χ e 2 R e / µ R µ χ ee,µµ e 2 R e / µ R µ 1 2 χ 2 τ 1 τ 5 fb -1 5 fb -1 eµ 1 m = 1 GeV, m 1/2 = 19 GeV µ>, A = tanβ = 1 m χ2 o = 14 GeV, m er = 132 GeV eµ m τ1 = 124 GeV SM 1 1 2 3 M(I + I - ) (GeV) SM 1 1 M(I + I - 2 3 ) (GeV) 1 3 m = 9 GeV, m 1/2 = 22 GeV 1 3 µ>, A = tanβ = 2 1 2 eµ 1 2 m = 1 GeV, m 1/2 = 19 GeV µ>, A = tanβ = 25 m χ2 = 167 GeV, m er = 132 GeV m χ2 = 141 GeV, m er = 132 GeV ee,µµ m τ1 = 13 GeV m τ1 = 91 GeV eµ 5 fb -1 5 fb -1 ee,µµ 1 1 1 SM 1 SM D_D_217c 1 2 3 1 2 3 M(I + I - ) (GeV) M(I + I - ) (GeV) SUSY may reveal itself early through peculiarities in the the di-lepton spectra Structures tend to be less evident with increasing tanβ, where dominates SUSY at the LHC, Aspen 23 19 χ χ τ + τ 2 1

Di-Tau Edge Reconstruction ATLAS Physics TDR study (Full GEANT simulation) to select hadronic tau decays Select narrow isolated jets: R jet =.2, R iso =.4 Require.8 GeV < M jet < 3.6 GeV Biased against 1-prong decays, but improves M ττ resolution (less neutrino momentum) Di-tau efficiency is 41% M vis =.66 M ττ Additional event selection cuts 4 jets: E T 1 > 1 GeV, E T 2-4 > 5 GeV, MET>1 GeV, no e,µ leptons with p T >2 GeV ATLAS Point 6 : m =2GeV m 1/2 =2GeV tanβ=45 µ< A = d BR χ 2 ττ = 99. 9% i Events/2.4 GeV/1 fb -1 1 5 L=3 fb 1 Real τ from SUSY Fake τ from SUSY SM background 25 5 75 1 M ττ (GeV) Mvis = 4 GeV Expected edge = 6 GeV SUSY at the LHC, Aspen 23 2

Exclusive Sparticle Reconstruction Completely reconstruct a SUSY decay chain: p p ATLAS Study g Point 3 of Physics TDR m =2 GeV, m 1/2 =1 GeV, tanβ=2, µ<, A = CMS Study [Chiorboli] b b Investigate Points B & G of Proposed Post-LEP Benchmarks for SUSY (hep-ph/1624) B: m =1 GeV, m 1/2 =25 GeV, tanβ=1, µ>, A = σ TOT (SUSY) = 58 pb G: m =12 GeV, m 1/2 =375 GeV, tanβ=2, µ>, A = σ TOT (SUSY) = 6. pb l b m χ 2 ± q (,, qg qq gg dominate) l χ l 1 ± ISASUGRA PYTHIA CMSJET SUSY at the LHC, Aspen 23 21

Di-Lepton Edge Reconstruction p p g qq b b l b m χ 2 ± l χ l 1 ± BR=16% Start with reconstructing χ 2 (tanβ not too large) Two OS isolated leptons, P T >15 GeV, η <2.4 MET>15 GeV, E(ll)>1 GeV Events / 3 GeV 9 8 7 6 5 4 3 Point B SUSY tt - Z + jet L=1 fb 1 CMS Events / 2 GeV 5 4 3 2 Subtract opposite flavors Edge= 79±2 GeV 2 1 1 25 5 75 1 125 15 175 2 Select 15 GeV window around di-lepton endpoint χ1 at rest in χ2 rest frame v χ χ 2 1 v p F m d i d ii 1 l + l = + p H G + mdl lik J d i Can estimate m dχ1 i from di - lepton endpoint and m χ 2m χ Point B: 174 GeV, d i M(e + e - )+M(µ + µ - ) (GeV) d i 2 1 but analysis not too sensitive to details 2 4 6 8 1 12 14 16 18 2 M(e + e - )+M(µ + µ - )-M(e + µ - )-M(µ + e - ) (GeV) SUSY at the LHC, Aspen 23 22

b Reconstruction p p g qq b b l b m χ 2 ± l χ l 1 ± BR 5% Add most energetic b-jet to reconstruct b E b-jet >25 GeV, η <2.4 b-jet: 2 tracks with IP significance > 3σ Require MET>15 GeV E(ll)>1 GeV Result of fit: M(b) = 5±7 GeV σ M = 42 GeV Events / 28 GeV 35 3 25 2 Point B SUSY L=1 fb 1 CMS tt - ID Entries Mean RMS 13 291 54.6 152.8 25.38 / 2 P1.374E-13 P2 -.1512E+16 P3.255E+13 P4.2699E+11 P5 -.6571E-2 P6 25.57 P7 5.1 P8 42.22 Generated masses: M(b L ) = 496 GeV M(b R ) = 524 GeV 15 1 5 σ BR dominates 2 4 6 8 1 M( 2 b) (GeV) Mass (GeV) SUSY at the LHC, Aspen 23 23

g Reconstruction p p g qq b b l b m χ 2 ± l Add another b-jet closest in φ to reconstruct g & 4 GeV < Mb < 6 GeV 35 ch Result of fit: M(g) = 594±7 GeV σ M = 42 GeV χ l 1 ± Events / 28 GeV 3 25 2 15 BR 1% SUSY tt - CMS L=1 fb 1 Point B ID Entries Mean RMS 23 153 626.7 91.15 12.39 / 1 P1.143E-12 P2.1678E+15 P3 -.578E+14 P4.117E+12 P5 -.9486E-2 P6 19.45 P7 593.5 P8 42.37 Events / 15 GeV 35 3 25 2 15 1 5 Generated mass: M(g) = 595 GeV af c h d i mg mb is independent of m χ 1 : Point B CMS Entries 124 8.681 / 7 P1 -.23E-9 P2 -.255E+9 P3.1989E+8 P4 -.1692E+8 P5 -.2288E-1 P6 27.32 P7 92.41 P8 16.91 SUSY Expect 87 GeV tt - -1 1 5 Events/4 GeV/1 fb 2 3 4 5 6 7 8 9 1 M( 2 b b) (GeV) 2 15 1 5 Mass (GeV) ATLAS Point 3 Expect 2 GeV 5 1 15 2 25 3 M( 2 b b) - M( 2 b) (GeV) Mass (GeV) SUSY at the LHC, Aspen 23 24 2 4 6 8 1 M(χ 2 bb)-m(χ 2 b) GeV

q Reconstruction q BR 5% Same di-lepton edge selection as before Two jets with p T >2 GeV, η <2.4 MET > 1 GeV Veto all b-jets Track with second largest IP significance < 2σ Helps reject sbottom and stop decays Less luminosity required (1 fb -1 ) Result of fit: M(q) = 536±1 GeV σ M = 6 GeV Generated masses: M(q L ) = 543 GeV M(q R ) = 537 GeV CMS L=1 fb 1 Point B Mass (GeV) SUSY at the LHC, Aspen 23 25

Events / 6 GeV Point G Reconstruction Cross section 1 smaller Smaller branching ratios 14 12 1 8 6 4 E b-jet >35 GeV, MET>35 GeV sbottom ID Entries Mean RMS 11 89 739.9 26.3 1.13 / 9 P1.3413E-12 P2.3982E+14 P3 -.941E+12 P4.2531E+1 P5 -.5623E-2 P6 9.488 P7 719.7 P8 81.6 Require 3 fb -1 >1 year @ 1 34 Result of fit: M(b) = 72 ±26 GeV σ M = 81 GeV Generated masses: M(b L ) = 72 GeV M(b R ) = 748 GeV 2 4 6 8 1 12 14 M( 2 b) (GeV) gluino Result of fit: M(g) = 85±4 GeV σ M = 13 GeV Events / 6 GeV 25 2 15 ID Entries Mean RMS 21 112 898.4 141.6 9.9 / 4 P1.6774E-13 P2.3944E+16 P3 -.796E+14 P4.12E+12 P5 -.6384E-2 P6 13.8 P7 852.7 P8 13.6 1 Generated mass: M(g) = 86 GeV 5 4 6 8 1 12 14 M( 2 b b) (GeV) SUSY at the LHC, Aspen 23 26

Can msugra Escape LHC? M.Battaglia et al., Eur.Phys.J. C22 (21) 535 (hep-ph/1624) proposed several SUSY benchmark points in the post-lep era Two of them would lead to sparticles beyond the reach of the LHC except for a light Higgs squark/gluino masses > 2.5 TeV But most other points covered well Sparticles reconstructed in 1 fb -1 X Sparticles reconstructed in 3 fb -1 Di-lepton edge not observable X If SUSY exists, prospects at LHC look favorable SUSY at the LHC, Aspen 23 27

LHC Summary Discovery of SUSY, if it exists, is almost assured at the LHC Inclusive msugra squark/gluino discovery reach to 1.5 TeV with 1 fb 1, 2.5 TeV with 1 fb 1 Difficult part will be untangling decay chains and measuring mass relations Possibility to reconstruct squark/gluino/neutralino decays in msugra for several prototype analyses Mass resolution <1% under some assumptions Generally require tanβ<35 Generally require much more data (years) Trigger strategies identified for efficient coverage Many more exhaustive SUSY studies at the LHC experiments are available: ATLAS TDR 15 CERN/LHCC 99-15 CMS Note 1998/6 Looking forward to studying SUSY spectroscopy before the end of the decade! SUSY at the LHC, Aspen 23 28

Minimal GMSB Gauge Mediated Symmetry Breaking Uses SM gauge interactions instead of gravity to break SUSY Solves FCNC problem SUSY breaking scale much less than msugra scale F << 1 11 GeV Particles get mass from SM gauge interactions at a messenger scale M m O(1 TeV) << M Pl n = number of SU(5) messenger fields Λ = F / M m 1 TeV G is LSP ( m<< 1 GeV) NLSP: χ1 Gγ ( n= 1, low tan β) l Gl ( n> 1, high tan β) NLSP lifetime: cτ 13. m F HG 1 GeV M NLSP I KJ F H G 5 4 F 1 TeV cτ >> detector size slepton ( τ ) is a long-lived heavy lepton (like µ) neutralino leads to MET, like MSSM cτ detector size Measure NLSP lifetime Estimate F cτ << detector size radiative decay with γ I K J SUSY at the LHC, Aspen 23 29

particles / 2 GeV GMSB Heavy Lepton (τ) Search Use drift-tube muon systems of ATLAS and CMS to measure time-of-flight for heavy leptons (σ 1ns) 2 CMS: 7 6 5 4 3 2 1 Measure 1/β and p reconstruct mass Require 2 muons with P T >45 GeV, M>97 GeV η <1 for CMS drift-tube system Can measure stau mass from 9 7 GeV: n=3, tanβ=45, Λ=5-3 TeV, 114GeV; L=1/fb; eff=5% M/Λ=2 CMS CR 1999/19 1/β 1.8 1.6 1.4 1.2.8.6 33GeV; L=1/fb; eff=15% 1 2 4 6 8 1 12 14 momentum (GeV) 636GeV; L=1/fb; eff=26% ATLAS 1 2 3 4 5 6 7 8 9 1 reconstructed mass (GeV) SUSY at the LHC, Aspen 23 3

GMSB N 1 Lifetime Measurement Look for N 1 decays inside detectors: 1) Electromagnetic showers not pointing to vertex Use fine angular resolution from LAr EM calorimeter (ATLAS) and PbWO 4 crystals (CMS) ATLAS vertex resolution for H γγ ATLAS: if no non-pointing γ s in 3 fb -1 cτ > 1km (Λ=9 TeV, M = 5 TeV, n=1) Events/.2cm 3 2 1 σ =1.33 cm -1-5 5 1 z cal ō z true (cm) σ + (cτ)/cτ 2) Showers in muon system Identify showers with high hit multiplicity CMS: Overall sensitivity to measure cτ: 1 L=143/fb; eff kin =1% m(n 1 )=291GeV 1 1-1 µ µ ECAL counting CAL counting µ ECAL/ CAL ECAL impact CAL slope COMBINED 1-2 1-1 1 1 1 2 1 3 cτ (m) SUSY at the LHC, Aspen 23 31