Probing the Sevolution of the Universe at the LHC

1. Probing the Sevolution of the Universe at the LHC Amitava Datta Department of Physics Jadavpur University Kolkata

2. INTRODUCTION AND BASIC FACTS

3. DARK MATTER : Most popular Candidate Wilkinson Microwave Anisotropy Probe (WMAP) Data

4. EVOLUTION OF THE UNIVERSE AND DARK MATTER Early Universe: particles and sparticles in thermal equilibrium. Universe Cools and Expands : Too little thermal energy to produce heavy Sparticles. They annihilate and decay into particles and the LSP LSP and particles in equilibrium

5. The Expansion Continues: LSP density decreases, annihilation rate becomes small compared to the expansion rate of the universe, EQUILIBRIUM IS LOST AND THE LSP EXPERIENCES FREEZE OUT The LSP density today is determined by this small rate and further dilution due to expansion of the universe. Compute using MICROMEGAS, DARKSUSY…………

6. Important parameters: LSP mass and annihilation x-sec (depends on other SUSY parameters) Co-annihilation: Slightly heavier sparticles may exist longer in equilibrium with the LSP with comparable numbers and annihilate each other. This co-annihilation x-sec (depends on other SUSY parameters) is also important for the LSP relic density.

7. LSP Annihilation and Co-annihilation The Generic Scenarios

8. LSP Annihilation Diagram Bino-like LSP and light sfermion (R-type) gives reasonably high x-sec and not too large density ( The Bulk Region )

9. Resonant annihilation into Higgses

10. LSP Co-annihilation Examples

11. Annihilation into Gauge Bosons • The LSP has significant • Higgsino components ( e.g., The Focus Point/Hyperbolic Branch region in mSUGRA)(J. Feng et al hep-ph/9909334; K.Chan et al hep-ph/ 9710473 ). • Wino component ( e.g., The AMSB model) • See, e.g., Utpal Chattopadhyaya et al hep-ph/0610077

12. Plan of TheTalk • Realization of various scenarios in mSUGRA • Tests at LHC • Beyond mSUGRA • Conclusions Ref1: Tevatron-for-LHC Report, S. Abdullin et al, hep-ph/0608322

13. Realization of various scenarios in mSUGRA

14. mSUGRA low tan H. Baer et al in Ref 1 Focus Point Region ???

15. Allowed Regions in mSUGRA A. Belyaev : Hunting for SUSY……(2005)

16. LHC REACH Tip of the Higgs funnel? FP region?

17. Tests at LHC Distinctive features of the signal for each region of the parameter space (circumstantial evidences) Quantitative or semi-quantitative tests (determination of masses and mass differences –certainly ILC will do a better job if the sparticles are accessible)

18. LHC SIGNALS OF FOCUS POINT SUPERSYMMETRY Very heavy squark , sleptons ; relatively light gauginos • Gluino pair-production • Parton level simulation (U. Chattopadhyay et al hep-ph/000822 ) :large number of b-jets in the signal. • Electroweak gaugino production and decay H. Baer et al hep-ph/0507282

19. Further works on gluino pair-production • Simulation at the generator level ( P. G. Mercadante et al hep-ph/0506142) b-tagging improves the discovery reach. • Inclusion of hitherto neglected but potentially dangerous backgrounds (S.P. Das, A. D., M. Maity and M. Guchait – in preparation)

20. Handling the New Backgrounds • tttt, ttbb, bbbb, ttqq, bbqq,…………… • Events generated with CompHEP, ALPGEN, MADGRAPH • Events interfaced with Pythia for simulation

21. Signal Features Cut Background removed

23. New backgrounds under control

24. The stau coannihilation Recent work:R.Arnowitt et al hep-ph /0603128 • Distinctive feature: large number of low energy -pairs in the signal . • Detection efficiency of low PT taus ? ( assume detection efficiency >50% for PT visible > 20 GEV) • Measurement of M ( approximately 15 GeV or smaller) ( 3 –10 • fb-1 of data)

25. Invariant mass distribution (VISIBLE)

26. Shift of the peak with M

27. The (“disfavoured”)Bulk Region Disfavoured in mSUGRA for A0 = 0

28. LEP constraints A0=0(LEP-SUSY WG)

29. Weaker constraints for large A0

30. The BULK revisited • Light sleptons • Light stop: discovery at Tevatron ? • Potential constraints (for large A0 )

31. Allowed Region Large A0 L. S. Stark et al hepph/0502197

32. Allowed Region Large A0with CCB Constraint

33. A Point in the WMAP Allowed Bulk Region m0 m1/2 A0 sign( ) tan  80 200 -500 + 10 Key features BR(chi_1+ stau_1 + neutrino) = 90% (ISAJET) BR(chi_2 0  stau_1 + neutrino) = 86% Lots of  s in the final state; very few isolated e or .

34. All squark gluino events generated by PYTHIA (parton level); tau abd b decays switched off. #of events with at least one tau : 81% # of events with one tau pair + 2b jets +missing energy =29% ( Signal?) Bonus: light stop (218) .

35. The Potential Constraints The scalar potential in MSSM is a complicated object – function of many scalars including charged and coloured fields. Require: no minimum for a non-zero charged or coloured fielddeeper than the EWSB minimum

36. Example Minimization  Constraints on mSUGRA parameters A.D and A. Samanta hep-ph/0406129 Upper bounds on sparticle masses

37. What if we leave in a false vacuum with a life time larger than the age of the universe?

38. Conclusions (mSUGRA) • Several interesting regions of WMAP allowed parameter space are within the striking range of the LHC. • By and large third generation sfermions lead to characteristic signatures in all regions • Detection efficiencies- important experimental issue.

39. In sptite of extensive analyses there are still open questions • Focus point region: backgrounds from tttt, ttbb,ttgg,…….. seems to be manageable; gluino mass reach? • Increase the reach in the tau co-annihilation region (high tan ), Higgs funnel and focus point region. • The bulk region for large A_0 has not been fully analyzed ; may lead to qualitatively new signatures.

40. Beyond mSUGRA • Co-annihilation with light stop • Electroweak baryogenesis - light stop once more! • Discovery at Tevatron ? • Nonuniversal scalar masses – the VLSPs revisited

41. Coannihilation with lighter stop Recent work C. Balazs et al in reference 1 Stop LSP mass difference < 30 GeV Beyond mSUGRA scenario Discovery at Tevatron? Confirmation at LHC? 2 b-jets+ 2 LS dilepton+ missing transverse energy from gluino pairs Production followed by gluino decays into top and stop ( Kraml and Rakhlev in ref 1)

42. Stop Co-annihilation

43. Baryogenesis and Light stop Recent analysis C. Balazs et al ref 1. (MSSM) EWBG needs a boson with mass ~ EW scale and strongly coupled to the Higgs boson – stop is a viable candidate. Require Discovery at Tevatron ? CP Phase (EDM constraint?)

44. Stop co-annihilation (with CP Phase)

45. Stop Search ProspectTevatron Stop search at Tevatron R. Demina et al hep-ph/ 9910 275 (c-tagging?, 4-body decay?) Both CDM(stop co-annihilation and EW baryogeneis via light stop?

46. The 4-body decay of the stop C. Boehm et al hep-Ph/9907428 : May be the dominant mode. A strong Higgs mass bound reduces the allowed parameter space: S. P. Das hep-ph/0512011

47. The VLSP Scenario • Right slepton heavier than left sleptons ( forbidden in mSUGRA; allowed in models with non-universal scalar mass) • Large numder of e and  in the final state • Invisible decay of sneutrino and the second lightest neutralino Many interesting signatures (Qualitatively different from the ones in mSUGRA) at LEP and Tevatron were proposed: S.Chakrabarty, AD, Asesh Datta, M. Drees, M. Guchait, B. Mukhopadhyaya and M. K. Parida. LHC??

48. WMAP Allowed VLSP Scenario chi_1+ Snuelec :102.0 (NLSP) 173.6 MICROOMEGAS Thanks to Utpal Chattopadhyaya, Debottam Das and Sujoy Poddar!

49. Decay BRs (SDECAY) Sneutrino (NLSP)decay invisibly BR(~chi_20 -> ~nu_eL nu_eb) 10% Six such invisible channels BR(~chi_20 -> ~e_L- e+) 5% BR(~chi_20 -> ~tau_1- tau+) 10% Lots of e and in the final state (not allowed even in the resurrected bulk of mSUGRA

50. Can one rule out a model because of too little or too much dark matter? Too little: May be there are non-sparticle or even non-particle dark matter Too much: A little RPV (induced by physics at the high scale) will make the LSP cosmologically unstable but stable at colliders.