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Measurement of Dark Matter Content at the LHC

Measurement of Dark Matter Content at the LHC. Bhaskar Dutta Collaborators: R. Arnowitt, A. Gurrola, T. Kamon, A. Krislock, D. Toback Texas A&M University. 18 th August’ 08. OUTLINE. DM Relic Density ( W h 2 ) in SUSY mSUGRA Co-annihilation (CA) Region at the LHC

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Measurement of Dark Matter Content at the LHC

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  1. Measurement of Dark Matter Content at the LHC Bhaskar Dutta Collaborators: R. Arnowitt, A. Gurrola, T. Kamon, A. Krislock, D. Toback Texas A&M University 18th August’ 08 Measurement of Dark Matter Content at the LHC

  2. OUTLINE • DM Relic Density (Wh2 ) in SUSY • mSUGRA Co-annihilation (CA) Region at the LHC • Prediction of DM Relic Density (Wh2 ) • Summary Arnowitt, Dutta, Kamon, Kolev, Toback, PLB 639 (2006) 46 Arnowitt, Arusano, Dutta, Kamon, Kolev, Simeon, Toback, Wagner, PLB 649 (2007) 73 Arnowitt, Dutta, Gurrola, Kamon, Krislock, Toback, Phys. Rev. Lett. 100, (2008) 231802 Crockett, Dutta, Flanagan, Gurrola, Kamon, Kolev, VanDyke, ‘08; Measurement of Dark Matter Content at the LHC

  3. Anatomy of sann + …. Co-annihilation (CA) Process Griest, Seckel ’91 + + …. A near degeneracy occurs naturally for light stau in mSUGRA. Precision Cosmology at the LHC 3

  4. Coannihilation, GUT Scale In mSUGRA model the lightest stau seems to be naturally close to the lightest neutralino mass especially for large tanb For example, the lightest selectron mass is related to the lightest neutralino mass in terms of GUT scale parameters: Thus for m0 = 0, becomes degenerate with at m1/2 = 370 GeV, i.e. the coannihilation region begins at Arnowitt, Dutta, Santoso’ 01 m1/2 = (370-400) GeV For larger m1/2 the degeneracy is maintained by increasing m0 and we get a corridor in the m0 - m1/2 plane. The coannihilation channel occurs in most SUGRA models with non-universal soft breaking, 4 Measurementof Dark Matter Content at the LHC

  5. DM Allowed Regions in mSUGRA Below is the case of mSUGRA model. However, the results can be generalized. [Focus point region] the lightest neutralino has a larger Higgsino component [A-annihilation funnel region] This appears for large values of m1/2 [Stau-Neutralino CA region] [Bulk region] almost ruled out Measurementof Dark Matter Content at the LHC

  6. CA Region at tanb = 40 Can we measure DM at colliders? Measurementof Dark Matter Content at the LHC

  7. Smoking Gun of CA Region Low energy taus exist in the CA region However, one needs to measure the model Parameters to predict the Dark matter content in this scenario SUSY Masses Unique kinematics 97% 100% (CDM) 2 quarks+2 t’s +missing energy Measurementof Dark Matter Content at the LHC

  8. pTsoft Slope and Mtt pT and Mtt distributions in true di-t pairs from neutralino decay Number of Counts / 2 GeV Slope of pT distribution of “soft t” contains ΔM information Low energy t’s are an enormous challenge for the detectors ETvis(true) > 20, 20 GeV Number of Counts / 1 GeV ETvis(true) > 40, 20 GeV ETvis(true) > 40, 40 GeV Measurementof Dark Matter Content at the LHC 8

  9. We use ISAJET + PGS4 PLB 639 (2006) 46 Measurementof Dark Matter Content at the LHC

  10. Mtt Distribution Clean peak even for low DM We choose the peak position as an observable. Measurementof Dark Matter Content at the LHC

  11. SUSY Anatomy SUSY Masses 97% 100% (CDM) Meff Mjtt Mtt pT(t) Measuring Relic Density at the LHC 11

  12. 4 j+ETmiss: Meff Distribution • ETj1>100 GeV, ETj2,3,4> 50 GeV [No e’s, m’s with pT > 20 GeV] • Meff > 400 GeV (Meff ETj1+ETj2+ETj3+ETj4+ ETmiss[No b jets; eb ~ 50%]) • ETmiss > max [100, 0.2 Meff] At Reference Point Meffpeak = 1220 GeV (m1/2 = 335 GeV) Meffpeak = 1331 GeV (m1/2 = 365 GeV) Meffpeak = 1274 GeV Measurementof Dark Matter Content at the LHC

  13. 3 j+1b+ETmiss :Meff(b) Distribution • ETj1>100 GeV, ETj2,3,4> 50 GeV [No e’s, m’s with pT > 20 GeV] • Meff(b)> 400 GeV (Meff(b)ETj1=b+ETj2+ETj3+ETj4+ ETmiss[j1 = b jet]) • ETmiss > max [100, 0.2 Meff] At Reference Point Meff(b)peak = 933 GeV (m1/2 = 335 GeV) Meff(b)peak = 1122 GeV (m1/2 = 365 GeV) Meff(b)peak = 1026 GeV Meff(b) can be used to determine A0 and tanb even without measuring stop and sbottom masses Phys. Rev. Lett. 100, (2008) 231802 13 Measurementof Dark Matter Content at the LHC

  14. Observables • Sort t’s by ET (ET1 > ET2 > …) • Use OS-LS method to extract t pairs from the decays SM+SUSY Background gets reduced • Ditau invariant mass: Mtt • Jet-t-t invariant mass: Mjtt • Jet-t invariant mass: Mjt • PT of the low energy t • Meff : 4 jets +missing energy • Meff(b) : 4 jets +missing energy All these variables depend on masses => model parameters Since we are using 7 variables, we can measure the model parameters and the grand unified scale symmetry (a major ingredient of this model) 14 Measurementof Dark Matter Content at the LHC

  15. Determining SUSY Masses (10 fb-1) ~ ~ Meff(b) = f7(g, qL, t, b) 7 Eqs (as functions of SUSY parameters) 1s ellipse 10 fb-1 ~ ~ Invert the equations to determine the masses Phys. Rev. Lett. 100, (2008) 231802 Measurementof Dark Matter Content at the LHC

  16. DM Relic Density in mSUGRA ~ c 0 1 ~ c 0 2 [1] Established the CA region by detecting low energy t’s (pTvis > 20 GeV) [2] Determined SUSY masses using: Mtt, Slope, Mjtt, Mjt, Meff e.g., Peak(Mtt) = f (Mgluino, Mstau, M , M ) [3] Measure the dark matter relic density by determining m0, m1/2, tanb, and A0 Measurementof Dark Matter Content at the LHC

  17. Determining mSUGRA Parameters Measurementof Dark Matter Content at the LHC

  18. Mass Measurements mSUGRA Mttpeak, Meff(b)peak …. Sensitive to A0 , tanb, m0andm1/2 Mjttpeak, Meffpeak …. Sensitive to m0, m1/2 Measurementof Dark Matter Content at the LHC

  19. Determining mSUGRA Parameters • Solved by inverting the following functions: 10 fb-1 Phys. Rev. Lett. 100, (2008) 231802 Measurementof Dark Matter Content at the LHC

  20. Focus Point (FP) Br(g → χ20 tt) = 10.2% Br(g → χ20 uu) = 0.8% Br(g → χ30 tt) = 11.1% Br(g → χ30 uu) = 0.009% - ~ ~ - - ~ - ~ • m0 is large, m1/2 can be small, e.g., m0= 3550 GeV, m1/2=314 GeV, tanb=10, A0=0 M(gluino) = 889 GeV, ΔM(χ30- χ10) = 81 GeV, ΔM(χ20- χ10) = 59 GeV, ΔM(χ30- χ20) = 22 GeV 20 Measurementof Dark Matter Content at the LHC

  21. Dilepton Mass at FP Events/GeV M(ll) (GeV) Baer, Barger, Salughnessy, Summy, Wang , PRD, 75, 095010 (2007), Crockett, Dutta, Flanagan, Gurrola, Kamon, Kolev, VanDyke, 08; 21 Measurementof Dark Matter Content at the LHC

  22. Determination of masses: FP Higher jet, b-jet, lepton multiplicity requirement increase the signal over background rate Relic density calculation depends on m, tanb and m1/2 All other masses are heavy m1/2, m and tanb can be solved from M(gluino), ΔM (χ30- χ10) and ΔM (χ20- χ10) M(gluino), ΔM (χ30- χ10) and ΔM (χ20- χ10) can be measured with an accuracy of ~ 10% 22 Measurementof Dark Matter Content at the LHC

  23. Summary ~ c 0 1 ~ c 0 2 [1] Established the CA region by detecting low energy t’s (pTvis > 20 GeV) [2] Determined SUSY masses using: Mtt, Slope, Mjtt, Mjt, Meff e.g., Peak(Mtt) = f (Mgluino, Mstau, M , M ) Gaugino universality test at ~15% (10 fb-1) [3] Measured the dark matter relic density by determining m0, m1/2, tanb, and A0 using Mjtt, Meff,Mtt, and Meff(b) Measurementof Dark Matter Content at the LHC

  24. Summary… [4] For large m0, when staus are not present, the mSUGRA parameters can still be extracted, but with less accuracy [5] This analysis can be applied to any SUSY model [6] It will be interesting to determine nonuniversal model Parameters, e.g., m (Higgs sector nonuniversality) work in progress… Measurementof Dark Matter Content at the LHC

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