1 / 41

Unraveling SUSY: Spin in Particle Chains

Delve into the intricate world of Supersymmetry (SUSY) and Universal Extra Dimensions (UED) with a focus on spin determinations in particle decay chains. Discover the challenges and methods involved in deciphering the nature of particles based on spin, distinguishing quarks from leptons, and detecting slepton spins. Explore the complexities of spin consistency checks, quark-antiquark interactions, and asymmetry measurements in collider experiments. Uncover the significance of mass measurements and cross-section interactions in distinguishing between UED and SUSY models. This comprehensive review navigates the nuances of spin determination in the search for new physics beyond the Standard Model.

rochellet
Download Presentation

Unraveling SUSY: Spin in Particle Chains

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related