SUSY @ the LHC

SUSY @ the LHC

SUSY @ the LHC Jet & MET Searches Adam Avakian PY898 - Special Topics in LHC Physics 3/23/2009 QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. 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 Description Value

Symbol me m m mu md ms mc mb mt

12 23 13 g1 g2 g3 QCD

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 511 keV 106 MeV

1.78 GeV 1.9 MeV 4.4 MeV 87 MeV 1.32 GeV 4.24 GeV 172.7 GeV 0.229 0.042 0.004 0.995

0.357 0.652 1.221 ~0 Unknown Unknown 4 Whats wrong with the Standard Model? It fails to explain:

Neutrino masses and mixing angles Baryogenesis Dark Matter Dark Energy 5

SUSY (SUperSYmmetry) Standard way beyond the Standard Model - Altarelli & Feruglio Spacetime symmetry (square root of a translation) Stable theory from Mweak (103 GeV) to MGUT (1016 GeV) 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 mSUGRA (minimal SUperGRAvity) 5 basic parameters (m0, m1/2, A0, tan, sign()) determine phenomenology at LHC scale

GMSB (Gauge-Mediated Symmetry Breaking) AMSB (Anomaly-Mediated Symmetry Breaking) etc. 8 Mass Spectra under mSUGRA 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 mSUGRA: 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/antisparticle 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 QuickTime and a TIFF (Uncompressed) decompressor

are needed to see this picture. M. Spiropulu [Eur. Phys. J. C (2009) 59: 445462] 15 Gluino Pair Production 16 Squark Pair Production

17 Squark-Gluino Associated Production 18 Sparticle Production CrossSections

and dominate SUSY signatures at LHC if 1 TeV 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(jet1) + E(jet2) + + E(jet ) n Rough Estimate of

squark/gluino masses from Meff ATLAS TDR (F. Paige) 26 Missing MET & HT distributions

QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. M. Spiropulu [Eur. Phys. J. C (2009) 59: 445462] 27 Dijet Event Search @ CMS Works best in parameter space squarks have large branching

decay to LSP QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. 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 QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. 31

Dijet Event - cut < 2/3 cuts out almost the entire QCD backgroun d QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture.

CMS Collaboration [CMS PAS SUS-08005] 32 New variables for cuts: , T 33 Dijet Event Search

QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. CMS Collaboration [CMS PAS SUS-08005] 34 The additional cuts Meff > 500 GeV < 2/3

or T > 0.55 35 Dijet Event Search QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. CMS Collaboration [CMS PAS SUS-08005]

36 Prospects for the LHC Center-of-mass energy = 14 TeV 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 Were 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 TeV, 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 TeV, then we should see them much sooner, possibly in the dijet signature 41

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