“Hidden Valleys” and their Novel Signals at Colliders

1. “Hidden Valleys”and theirNovel Signals at Colliders Matthew Strassler University of Washington - hep-ph/0604261,0605193 w/ K Zurek - hep-ph/0607160 - in preparation

2. Hidden Valleys – Preview

5. Theoretical Motivation • Many beyond-the-standard-model theories contain new sectors. • Common in top-down constructions (especially in string theory) • Increasingly common in bottom-up constructions (twin Higgs, folded supersymmetry…) • Could be home of dark matter • Could be related to SUSY breaking, flavor, etc. • New sectors may decouple from our own at low energy • SUSY breaking scale? • TeV scale? • Learning about these sectors, which may contain many particles, could open up an entirely new view of nature.. • Missing these sectors experimentally would be to miss a huge opportunity • Therefore we should ensure that we understand their phenomenological manifestations.

6. Hidden Valleys – Preview • “Hidden Valley” sectors • Coupling not-too-weakly to our sector • Containing not-too-heavy particles may be observable at Tev/LHC • Possible subtle phenomena include • High-multiplicity final states (possibly all-hadronic) • Highly variable final states • Many low-momentum partons • Unusual parton clustering • Breakdown of jet/parton matching • Sharp alteration of Higgs decays; • new discovery modes • Sharp alteration of SUSY events • Usual search strategies may fail, need replacements • Possibly low cross-sections; high efficiency searches needed • Predictions may require understanding non-perturbative dynamics in new sector – theoretical challenge

7. Hidden Valley Models (w/ K. Zurek) April 06 • Basic minimal structure Communicator Hidden Valley Gv with v-matter Standard Model SU(3)xSU(2)xU(1)

8. A Conceptual Diagram Energy Inaccessibility

9. Hidden Valley Models (w/ K. Zurek) • Basic minimal structure Communicator Hidden Valley Gv with v-matter Standard Model SU(3)xSU(2)xU(1)

10. Communicators New Z’ from U(1)’ Hidden Valley Gv with v-matter Standard Model SU(3)xSU(2)xU(1)

11. Communicators Higgs Boson Or Bosons Hidden Valley Gv with v-matter Standard Model SU(3)xSU(2)xU(1)

12. Communicators Lightest Standard Model Superpartner Hidden Valley Gv with v-matter Standard Model SU(3)xSU(2)xU(1)

13. Communicators Heavy Sterile Neutrinos Hidden Valley Gv with v-matter Standard Model SU(3)xSU(2)xU(1)

14. Communicators Loops of Particles Charged Under SM and HV Hidden Valley Gv with v-matter Standard Model SU(3)xSU(2)xU(1)

15. Communicators • Note that the communicator for production need not be the communicator for the decays… New Z’ from U(1)’ Hidden Valley Gv with v-matter Standard Model SU(3)xSU(2)xU(1) Higgs Bosons

16. The Hidden Valley (“v”-)Sector Communicator Hidden Valley QCD-like Theory Standard Model SU(3)xSU(2)xU(1)

17. The Hidden Valley (“v”-)Sector Communicator Hidden Valley QCD-like Theory With N Colors With n1 Light Quarks And n2 Heavy Quarks Standard Model SU(3)xSU(2)xU(1)

18. The Hidden Valley (“v”-)Sector Communicator Hidden Valley Gluons only Standard Model SU(3)xSU(2)xU(1)

19. The Hidden Valley (“v”-)Sector Communicator Hidden Valley Gluons Plus Adjoint Matter Standard Model SU(3)xSU(2)xU(1)

20. The Hidden Valley (“v”-)Sector Communicator Hidden Valley KS Throat/RS Model Standard Model SU(3)xSU(2)xU(1)

21. The Hidden Valley (“v”-)Sector Communicator Hidden Valley Multiple Gauge Groups Standard Model SU(3)xSU(2)xU(1)

22. Many Models, Few Constraints • Number of possibilities is huge! • Constraints are limited • LEP : production rare or absent • Precision tests: new sector is SM-neutral, very small effects • Cosmology: few constraints if • Efficient mixing of species • One species with lifetime < 1 second to decay to SM • In general, complexities too extreme for purely analytic calculation • Event Generation Software Needed! • Reasonable strategy: • Identify large class of models with similar experimental signatures • Select a typical subset of this class • Compute properties • Write event generation software • Explore experimental challenges within this subset • Infer lessons valid for entire class, and beyond

23. This talk • Carry out above program for simplest subset of simplest class • General setup • Simulation and results • Harder case: no long-lived particles • Easier case: long-lived (neutral) particles • Different communicators with simple v-sector • Effects on Higgs • [more generally, discovering Higgs via highly-displaced vertices] • Effect on SUSY • [more generally, on any model with new global sym] • Others… • Other physics in the v-sector • Heavy v-quarks • One light v-quark • Pure YM plus heavy v-quarks • SUSY YM • And beyond…

24. Simplest Class of Models • Easy subset of models • to understand • to find experimentally • to simulate • to allow exploration of a wide range of phenomena • This subset is part of a wide class of QCD-like theories New Z’ from U(1)’ Hidden Valley v-QCD with 2 (or 3) light v-quarks Standard Model SU(3)xSU(2)xU(1)

25. Two-flavor (v)QCD • A model with N colors and two light v-quarks serves as a starting point. • The theory is asymptotically free and becomes strong at a scale Lv • All v-hadrons decay immediately to v-pions and v-nucleons. • All v-hadrons are electric and color neutral, since v-quarks are electric and color-neutral • If v-baryon number is conserved, v-baryons are stable (and invisible)

26. Two-flavor (v)QCD • All v-hadrons decay immediately to v-pions and the lightest v-baryons • Two of the three v-pions cannot decay via a Z’ • But the third one can! pv+ ~Q1Q2~stable pv- ~Q2Q1~stable pv0 ~Q1Q1-Q2Q2 (Z’)* f f pv0 b Z’ b Pseudoscalars: their decays require a helicity flip; branching fractions proportional to fermion masses mf2

27. Long lifetimes The v-hadrons decay to standard model particles through a heavy Z’ boson. Therefore – no surprise -- these particles may have long lifetimes Notice the very strong dependence on what are essentially free parameters LEP constraints are moderate; cosomological constraints weak Thus displaced bottom-quark pairs and tau pairs are common in such models, but not required.

28. q q  Q Q : v-quark production v-quarks Q q Z’ q Q

29. LHC Production Rates for v-Quarks For a particular model. Others may differ by ~ factor of 10 ~ 100 events/year

30. q q  Q Q : v-quark production v-quarks Q q Z’ q Q

31. q q  Q Q v-gluons Q q Z’ q Q

32. q q  Q Q q Q Z’ q Q

33. q q  Q Q v-pions pv+ ,pv- ;pvo For now, take masses in range 20-350 GeV so that dominant pvo decay is to b’s q Q Z’ q Q pv+ ,pv- ;pvo

34. q q  Q Q v-pions q Q Z’ q Q

35. q q  Q Q v-pions The pv+ ,pv- are invisible and stable q Q Z’ q Q

36. q q  Q Q v-pions q Q Z’ q Q

37. q q  Q Q v-pions But the pvos decay in the detector to bb pairs, or rarely taus q Q Z’ q Q

38. How to simulate? Analogy… Pythia is designed to reproduce data from 70’s/80’s

39. q q  Q Q

40. q q  Q Q ISR

41. q q  Q Q FSR ISR

42. q q  Q Q Jet Formation FSR ISR

43. q q  Q Q Jet Formation FSR Underlying Event ISR

46. Event Display • This is my own event display -- not ideal or bug-free • Face on along beampipe – • Color indicates angle (pseudorapidity) • Blue – heading forward • Red – heading backward • Green/Yellow -- central • Notes: • No magnetic field; tracks are straight • No tracks below 3 GeV are shown • All photons/neutrals shown starting at calorimeter CMS

48. Top quark pair event

49. Long lifetimes The v-hadrons decay to standard model particles through a heavy Z’ boson. Therefore – no surprise -- these particles may have long lifetimes Notice the very strong dependence on what are essentially free parameters LEP constraints are moderate; cosomological constraints weak Thus displaced bottom-quark pairs and tau pairs are common in such models, but not required.

50. Harder Case – All decays prompt • Events with • Multiple jets • Some b-tags • Possibly taus • Some missing energy from invisible v-hadrons • Events fluctuate wildly (despite all being Z’ decays) • Events cannot be reconstructed • Kinematic information is scrambled well-beyond repair • Backgrounds? Not computable • What clues may assist with identifying this signal?