2. G Watts/UW Seattle2 SM Hidden Sector Phenomenology as complex as you wish Decay back to SM particles Scalar

3. G Watts/UW Seattle3 Hidden Sector Decay back to SM particles

4. G Watts/UW Seattle4 Hidden Sector Decay back to SM particles Phenomenology Particles do not interact with SM matter Proper Lifetime of HS particles Decay depends on particles in HS Quarks (usually heavy) Leptons

5. G Watts/UW Seattle5 Is really an excuse to generate long lived particles Many other models contain structures that give long lived particles RPV SUSY Split SUSY GMSB Etc. In many cases some of the most likely models now contain long lived particles The SM already has quite the variety! Easy to generate Squeezed phase space Small coupling Conserved quantum number Strong motivation to make search as model independent as possible.

6. G Watts/UW Seattle6 Decay probability is a falling exponential All parts of detector are sensitive for varying proper lifetimes Muon Spectrometer Cal ID

7. G Watts/UW Seattle7 Simulate at a unique proper lifetime Calculate efficiencies as a function of decay length Phys.Lett.B651:374-379,2007 (M. Strassler, K. Zurek) g g

8. G Watts/UW Seattle8

9. 9 Detector is designed for prompt Detector is not designed for non-prompt

10. G Watts/UW Seattle10 calorimeter muon spectrometer Different techniques are required for each section of the detector

11. G Watts/UW Seattle11 Position of Decay Decay Products Each detector requires a new strategy Jets – Many charged particle tracks Leptons – usually a lepton-jet Stefano’s talk!

12. G Watts/UW Seattle12 1 1 Traditional Trigger: Associated Production 2 2 Custom Trigger: Direct Production Lower cross section Well understood signature High cross section Trigger development and constraints are hard! (see WH with lepton jets)

13. G Watts/UW Seattle13 Physics Level 1 Level 2/HLT Offline Analysis Discovery specially designed triggers level 1 is typically hardware – restricted!! mostly designed at upper levels Level 2/High level triggers room for innovation full event in HLT some hardware restrictions in Level 2 (ATLAS).

14. G Watts/UW Seattle14 b-tagging triggers long lived neutral particle triggers neutral particle decays mid-detector appearance trigger Introduced in the 2011 run

15. G Watts/UW Seattle15 trackless jet trigger decays late in inner detector decays beyond the EM calorimeter muon spectrometer cluster trigger three muon clusters all close by no jets, no tracks very good efficiency decays beyond the calorimeter

16. G Watts/UW Seattle16

17. G Watts/UW Seattle17 Displaced Decay

18. G Watts/UW Seattle18 Require 3 clusters of muon segments (RoI’s) No jets pointing to the clusters No tracks pointing to the clusters

19. G Watts/UW Seattle19 It can do more than particle ID! Efficiency x- checked with punch-thru jets The ATLAS muon spectrometer is designed to reconstruct muon tracks stand alone Muon reconstruction algorithm Traditional Vertexing Algorithm Custom Muon Segment Builder Allows for very large segment impact parameters!!

20. G Watts/UW Seattle20

21. G Watts/UW Seattle21

22. G Watts/UW Seattle22 1 Trigger 1 Vertex 2 Trigger 1 Vertex P(2 nd Vertex|No Trigger) P(2 nd Vertex|Trigger) 1 Trigger 2011 Data (1) Expected Backgrounds: arXiv:1203.1303v1

23. G Watts/UW Seattle23 equal systematic error contributions from theory and efficiency verification for our signals.

24. G Watts/UW Seattle24 OpportunityChallenge Pile-up will foul isolation requirements Larger datasets will improve sensitivity Turn on of other LLP production Higher boost means shorter lifetime sensitivity Higher boost more narrow objects (detector resolution) Trigger single object thresholds increase

25. G Watts/UW Seattle25 Major work underway to improve custom triggers MS Vertex Finder will run in Reconstruction Will be available with all topologies Hopefully incorporated with other search strategies

26. G Watts/UW Seattle26 eQuarks e Displaced Prompt HV provides a rather generic benchmark model to look for displaced decays. New techniques were developed to search in the ATLAS Muon Spectrometer Trigger Object ID (MS Vertex) SUSY searches with displaced vertices have been performed the inner detectors Other detectors coming Lots of combinations to go. Run 2 preparations well underway