SUSY the LHC Jet MET Searches Adam Avakian

SUSY @ the LHC Jet & MET Searches Adam Avakian PY 898 - Special Topics in LHC Physics 3/23/2009 1

Overview • SUSY summary • Production and Decay Modes • Dijet search @ CMS 2

The Standard Model • L = Lgauge + Lmatter + LYukawa + Lhiggs • 19 parameters total (masses, couplings, etc. ) • Describes nearly all accelerator data • Still leaves plenty of mysteries 3

Parameters of the Standard Model Symbol me mμ mτ mu md ms mc mb mt θ 12 θ 23 θ 13 δ g 1 g 2 g 3 θQCD μ λ Description Electron mass Muon mass Tauon mass Up quark mass Down quark mass Strange quark mass Charm quark mass Bottom quark mass Top quark mass CKM 12 -mixing angle CKM 23 -mixing angle CKM 13 -mixing angle CKM CP-violating Phase U(1) gauge coupling SU(2) gauge coupling SU(3) gauge coupling QCD Vacuum Angle Higgs quadratic coupling Higgs self-coupling strength Value 511 ke. V 106 Me. V 1. 78 Ge. V 1. 9 Me. V 4. 4 Me. V 87 Me. V 1. 32 Ge. V 4. 24 Ge. V 172. 7 Ge. V 0. 229 0. 042 0. 004 0. 995 0. 357 0. 652 1. 221 ~0 Unknown 4

What’s wrong with the Standard Model? • It fails to explain: – Neutrino masses and mixing angles – Baryogenesis – Dark Matter – Dark Energy 5

SUSY (SUper. SYmmetry) • “Standard way beyond the Standard Model” Altarelli & Feruglio • Spacetime symmetry (“square root” of a translation) • Stable theory from Mweak (103 Ge. V) to MGUT (1016 Ge. V) • New “superpartner” particles • MSSM (Minimal Supersymmetric SM) is the simplest SUSY extension to SM 6

MSSM (Minimal Supersymmetric SM) • Construct Lagrangian that changes only by total derivative under SUSY (action is invariant) • Add all “soft SUSY breaking” terms – Same physics at UV, symm. broken in IR • Minimal extension has 124 parameters instead of 19 now! 7

More SUSY models • m. SUGRA (minimal SUper. GRAvity) – 5 basic parameters (m 0, m 1/2, A 0, tan , sign( )) determine phenomenology at LHC scale • GMSB (Gauge-Mediated Symmetry Breaking) • AMSB (Anomaly-Mediated Symmetry Breaking) • etc. 8

Mass Spectra under m. SUGRA Note that all scalar masses converge and all spin 1/2 masses converge 9

Superpartners • Each SM particle has a superpartner • New conserved charge/quantum number • Naming conventions for “sparticles”: – Fermions: prepend with “s”, e. g. squark – Bosons: add “-ino” suffix, e. g. gluino – • Spin = Spin § 1/2 10

List of sparticles 11

Where are the sparticles? • Produced at higher energy scales than previous colliders have achieved • Lightest Supersymmetric Particle (LSP) is stable and must be weakly interacting – m. SUGRA: bino/wino/higgsino/gravitino? – GMBS: gravitino – AMSB: wino • It would be a strong candidate for Dark Matter WIMP 12

LSP (Lightest Supersymmetric Particle) • If LSP is weakly interacting, how can we produce and observe such particles? - Indirectly! • Higher energy sparticles need not be weakly interacting • They can be produced in sparticle/anti-sparticle pairs and decay to LSP • LSP is observed indirectly as an MET signature 13

SUSY Events • We always expect MET from LSPs • The other particles produced in the sparticle decays may hadrons, leptons, etc. • Events generally classified based on the number of leptons produced 14

SUSY Candidate Event M. Spiropulu [Eur. Phys. J. C (2009) 59: 445– 462] 15

Gluino Pair Production 16

Squark Pair Production 17

Squark-Gluino Associated Production 18

Sparticle Production Cross-Sections and dominate SUSY signatures at LHC if 1 Te. V 19

Sparticle Production Tevatron LHC 20

Gluino Decay Modes 21

Squark Decay Modes � 22

Gluino Decays 23

Particle Cascade Decays Ultimately, we expect something more like this Run MC simulations (ISAJET, PYTHIA) for multiple points in parameter space and try to match the LHC data 24

Sample LHC SUSY Event Source: Baer 25

Meff = MET + E(jet 1) + E(jet 2) + … + E(jetn) Rough Estimate of squark/gluino masses from Meff ATLAS TDR (F. Paige) 26

Missing MET & HT distributions M. Spiropulu [Eur. Phys. J. C (2009) 59: 445– 462] 27

Dijet Event Search @ CMS • Works best in parameter space squarks have large branching decay to LSP • 28

Dijet Event Process • – 2 jets + MET – Search for events with exactly two jets above certain threshold – Require minimum MET 29

Dijet Background • QCD dijet events (MET due to mismeasurement, cracks, etc. ) • Z + Jet (Z ) 30

Dijet Event Preselection Cuts 31

Dijet Event - cut < 2 /3 cuts out almost the entire QCD background CMS Collaboration [CMS PAS SUS-08 -005] 32

New variables for cuts: , T 33

Dijet Event Search CMS Collaboration [CMS PAS SUS-08 -005] 34

The additional cuts • Meff > 500 Ge. V • < 2 /3 • or T > 0. 55 35

Dijet Event Search CMS Collaboration [CMS PAS SUS-08 -005] 36

Prospects for the LHC • Center-of-mass energy = 14 Te. V • Should be able to produce sparticles at a rate high enough to determine signal over background • We may see sparticles for the first time! 37

LHC Reach vs. earlier experiments Baer, Belyaev, Krupovnickas, Tata: JHEP 0402, 007 (2004) 38

Reach of LHC at 100 -1 fb Baer, Balasz, Belyaev, Krupovnickas, Tata: JHEP 0306, 054 (2003) 39

Reach of CMS for various Integrated Luminosities We’re maybe just a couple of years from seeing evidence of SUSY! 40

Conclusion • If SUSY exists and squarks and gluinos have a mass under 3 Te. V, then we should be able to see evidence within of few years of taking data at the LHC • If they have a mass of about 1 Te. V, then we should see them much sooner, possibly in the dijet signature 41