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What is “Discovering SUSY” ?

What is “Discovering SUSY” ?. E.g. – what makes Supersymmetry different to Universal Extra Dimensional models with Kaluza-Klein particles. One part of the answer:. SPIN. Not all things that quack are ducks!. QUACK !. UED. SUSY. QUACK !. We will see two important themes:.

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What is “Discovering SUSY” ?

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  1. What is “Discovering SUSY” ? • E.g. – what makes Supersymmetry different to Universal Extra Dimensional models with Kaluza-Klein particles. • One part of the answer: SPIN

  2. Not all things that quack are ducks! QUACK ! UED SUSY QUACK !

  3. We will see two important themes: • Mass measurements will precede(*) spin determinations • “Spin measurement”(**) should not be confused with “sensitivity to spin” (*) or will at best be simultaneous with (**) Here “spin measurement” means “determining unambiguously the correct nature (scalar, fermion, vector) of one or more particles in a decay chain or model

  4. (more info at)A REVIEW OF SPIN DETERMINATION AT THE LHCLian-Tao Wang and Itay Yavin arXiv:0802:2726

  5. Spin determination topics • Consistency checks • Spins in “QLL chain” • A.Barrhep-ph/0405052 • Smillie et al hep-ph/0605286 • Florida etc arXiv:0808.2472 • Biglietti et al ATL-PHYS-PUB-2007-004 • Slepton Spin (production) • A.Barrhep-ph/0511115 • MAOS method • Cho, Kong, Kim, Park arXiv:0810.4853 • Gluino chain spin • Alvez, Eboli, Plehnhep-ph/0605067 • Spins in chains with charginos • Wang and Yavinhep-ph/0605296 • Smillie hep-ph/0609296 • Spins in chains radiating photons • Ehrenfeld et al arXiv:0904.1293

  6. Spin Consistency Check

  7. Spin Consistency Check • Consistent with: • Phase-space • Scalar slepton (SFSF) • Fermion KK lepton (FVFV) Straight line Relative Frequency Di-Lepton Invariant Mass (GeV)

  8. “NEAR” “FAR” How can we tell from ? QL Spin Determination (A.Barr) 2 problems: How can we distinguish the ‘near’ lepton from the ‘far’ lepton?

  9. L+L- and L+L- and ANTI-QUARKS QUARKS Back to backin 20 frame Back to backin 20 frame _ QL+ QL- Phase space (spin-0) Phase space (spin-0) Probability density Probability density _ _ QL- QL+ sin ½θ* sin ½θ* Quark+NearLeptoninvariant mass distributions for: • hep-ph/0405052

  10. In experiment, can only distinguishRED(QL+,_ L+) from BLUE(QL-,_L-) Can only distinguish lepton chargeRED(QL+,QL+) from BLUE(QL-,QL-) Experimental problem • Cannot reliably distinguish QUARKs from ANTI-QUARKs

  11. QL+ SUM SUM jL+ jL- _ QL+ _ QL- QL- Expect QUARK and ANTI-QUARK contributions to cancel:

  12. QL+ SUM SUM jL+ _ QL+ _ QL- jL- QL- But LHC is Proton-Proton machine • hep-ph/0405052 • More Quarks than Anti-Quarks! So get: Asymmetry!

  13. “NEAR” “FAR” “Far” Lepton washout?

  14. parton-level Spin-½ jL+ spin-0 Asymmetry “A” detector-level MjL/ GeV  sin ½θ* jL- So define mjL+, mjL- asymmetry where

  15. Different method altogether

  16. Direct slepton spin detection: qq→Zγ* →slepton slepton slepton slepton • hep-ph/0511115

  17. Look at slepton production angle in c.o.m. hep-ph/0511115 ATL-PHYS-PUB-2005-023

  18. Have some access to desired angle Distribution of is correlated with decay angle hep-ph/0511115 ATL-PHYS-PUB-2005-023

  19. Direct slepton spin (A.Barr) • hep-ph/0511115 2 years high luminosity? Signal only

  20. Different again

  21. Spin Determination (T.Plehn et.al.) • What if we want to investigate chain from gluino? • Crucial to test gluino nature • Cannot rely on quarkcharge asymmetry “NEAR” “FAR” “NEAR” “FAR” hep-ph/0605067

  22. _ B Instead, rely on b-tag B

  23. _ B Instead, rely on b-tag B

  24. MBL+ and MBL- distributions SUSY UED hep-ph/0605067 Room for an asymmetry!

  25. So define asymmetry Signal, no cuts hep-ph/0605067

  26. After realistic cuts, SPS1A, 200 fb-1 Asymmetry stillobservable Acceptance cuts: Cuts to reject Standard Model hep-ph/0605067

  27. Back to long chains

  28. F F F S F S F Spin sensitivity elsewhere in the llq chain(Smillie et.al.)Later more general follow-up (Matchev, Kong, et al) arXiv:0808.2472 hep-ph/0605286 Cannot distinguish:

  29. But masses matter SPS1a mass spectrum: (GeV) UED-type mass spectrum: (GeV) (R-1 ~ 800 GeV)

  30. Maybe masses are not too important for mll distribution hep-ph/0605286 SPS1a masses UED type masses

  31. … but this fun …. hep-ph/0605286

  32. …. is spoiled.  MJL+ MJL+ UED type SPS1a hep-ph/0605286 MJL- MJL-

  33. Example asymmetries: (a big mix of spin and mass spectrum)  A A SPS1a UED type MJL MJL hep-ph/0605286

  34. Yet another game one can play

  35. qbar gluino gluino q MT2-assisted (MAOS) spin determination Use splitting for which leads to MT2 solution to assign 4-momenta to invisible particles: Finds the spin of these gluinos Then do conventional Dalitz plot for each side. Then do conventional Dalitz plot for each side. Cho, Choi,Kim,Park, 0810.4853

  36. MT2-assisted (MAOS) spin determination assign 4-momenta SUSY UED SUSY UED Cho, Choi,Kim,Park, 0810.4853

  37. Reminder: cross sections reveal spins Higher spins mean higher cross sections (for given masses) Datta, Kane, Toharia hep-ph/0510204

  38. End Notes • QLL chain • Some spin “sensitivity” – but no strong UED/SUSY separation • Reduced discriminatory power when considering general couplings (Matchev/Kong). • Di-slepton production • Better chance of separating UED/SUSY • Still model dependent • Both require large cross sections • Masses inextricably intertwined.

  39. Backup slides

  40. Both prefer high invariant mass Helicity dependence Process 1 (SUSY) Process 1 (UED, transverse Z*: P /P = 2x) T L

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