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Relic Density at the LHC

Relic Density at the LHC. B. Dutta. In Collaboration With:. R. Arnowitt, A. Gurrola, T. Kamon, A. Krislock, D.Toback. Phys.Lett.B639:46,2006 , hep-ph/0608193 (Phys. Lett.B), To appear. SUSY in Early Stage at the LHC. The signal to look for: 4 jet + missing E T. Example Analysis.

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Relic Density at the LHC

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  1. Relic Density at the LHC B. Dutta In Collaboration With: R. Arnowitt, A. Gurrola, T. Kamon, A. Krislock, D.Toback Phys.Lett.B639:46,2006, hep-ph/0608193 (Phys. Lett.B), To appear

  2. SUSY in Early Stage at the LHC The signal to look for: 4 jet + missing ET

  3. Example Analysis Kinematical Cuts and Event Selection • ETj1>100 GeV, ETj2,3,4> 50 GeV • Meff > 400 GeV (Meff  ETj1+ETj2+ETj3+ETj4+ ETmiss) • ETmiss > Max [100, 0.2 Meff] Phys. Rev. D 55 (1997) 5520

  4. Relic Density and Meff SUSY scale is measured with an accuracy of 10-20% • This measurement does not tell us whether the model can generate the right amount of dark matter. • The dark matter content is measured to be 23% with an accuracy of less than 5% at WMAP • Question: To what accuracy can we calculate the relic density based on the measurements at the LHC?

  5. Strategy • We establish the dark matter allowed regions from the detailed features of the signals. • We accurately measure the masses. • We calculate the relic density and compare with WMAP.

  6. Dark Matter Allowed Regions We choose mSUGRA model. However, the results can be generalized. • Neutralino-stau coannihilation region • A-annihilation funnel region – This appears for large values of m1/2 • Focus point region – the lightest neutralino has a larger higgsino component

  7. Relic Density Calculation +… In the stau neutralino coannihilation region Griest, Seckel ’91

  8. 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 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,

  9. Coannihilation Region tanb = 40, m > 0, A0 = 0 Can we measure DM at colliders?

  10. SUSY at LHC Signals Hard t p p p p Soft t Soft t Hard t Hard t In Coannihilation Region of SUSY Parameter Space: Soft t Final state: 3/4 ts+jets +missing energy

  11. Observables Use Hadronically Decaying t and construct 3 observables • Sort τ’s by ET (ET1 > ET2 > …) and use • OS-LS method to extract t pairs from the decays 2. Use Counting Method (NOS-LS) & Ditau Invariant Mass (Mtt) to measure mass difference 3. Measure the PT of the low energy t

  12. SUSY Parameters Since we are using 3 variables, we can measure DM, Mgluino and the universality relation of the gaugino masses i.e. Mgluino measured from the Meff method may not be accurate for this parameter space since the tau jets may pass as jets in the Meff observable. The accuracy of measuring these parameters are important for calculating relic density.

  13. Mttvisin ISAJET ETvis(true) > 20, 20 GeV ETvis(true) > 40, 20 GeV Number of Counts / 1 GeV ETvis(true) > 40, 40 GeV ETt > 20 GeV is essential! Version 7.69 (m1/2 = 347.88, m0 = 201.06)  Mgluino = 831 • Chose di-t pairs from neutralino decays with • (a) |h| < 2.5 • (b) t = hadronically-decaying tau

  14. ETmiss+ 1j+3tAnalysis Path Extracting t Pairs from Decays EVENTS WITH CORRECT FINAL STATE : 1t + 3j + ETmiss APPLY CUTS TO REDUCE SM BACKGROUND (W+jets, …) ETmiss > 100 GeV, ETj1 > 100 GeV, ETmiss + ETj1 > 400 GeV ORDER TAUS BY PT & APPLY CUTS ON TAUS: WE EXPECT A SOFT t AND A HARD t PTt > 40, 40, 20 GeV, LOOK AT t PAIRS AND CATEGORIZE THEM AS OPPOSITE SIGN (OS) OR LIKE SIGN (LS) OS: FILLLOW OSPT HISTOGRAM WITH PT OF SOFTER t FILLHIGH OSPT HISTOGRAM WITH PT OF HARDER t LS: FILLLOW LSPT HISTOGRAM WITH PT OF SOFTER t FILLHIGH LSPT HISTOGRAM WITH PT OF HARDER t LOW OS-LS LOW OS LOW LS HIGH OS HIGH LS HIGH OS-LS

  15. 3 t+1 Jet ETmiss + 1j+3tAnalysis • Much smaller SM background, but a lower acceptance • [1] ISAJET + PGS sample of ETmiss, 1 jet and at least 3 taus with pTvis > 40, 40, 20 GeV and et= 50%,fake (fjt) = 1%. Final cuts : • ETjet1 > 100 GeV, ETmiss > 100 GeV, ETjet1 + ETmiss > 400 GeV • [2] Select OS low di-tau mass pairs, subtract off LS pairs Small dependence on the uncertainty of fjt Note: fjt = 0%  1.6counts/fb-1

  16. 3 t+1 Jet (contd) • Next: combine NOS-LS and Mtt values to measure DM and Mgluinosimultaneously Mass rises with Mgluino Counts drop with Mgluino dDM/DM ~15% and dMgluino/Mgluino ~6%

  17. ETmiss + 2j +2tAnalysis Path EVENTS WITH CORRECT FINAL STATE : 2t + 2j + ETmiss APPLY CUTS TO REDUCE SM BACKGROUND (W+jets, …) ETmiss > 180 GeV, ETj1 > 100 GeV, ETj2 > 100 GeV, ETmiss + ETj1 + ETj2 > 600 GeV ORDER TAUS BY PT & APPLY CUTS ON TAUS: WE EXPECT A SOFT t AND A HARD t PTall > 20 GeV, PTt1 > 40 GeV LOOK AT t PAIRS AND CATEGORIZE THEM AS OPPOSITE SIGN (OS) OR LIKE SIGN (LS) OS: FILLLOW OSPT HISTOGRAM WITH PT OF SOFTER t FILLHIGH OSPT HISTOGRAM WITH PT OF HARDER t LS: FILLLOW LSPT HISTOGRAM WITH PT OF SOFTER t FILLHIGH LSPT HISTOGRAM WITH PT OF HARDER t LOW OS-LS LOW OS LOW LS HIGH OS HIGH LS HIGH OS-LS

  18. top SUSY Mgluino = 830 GeV (DM=10.6 GeV) ETmiss + 2j + 2t Analysis [1] ISAJET + ATLFAST sample of ETmiss, 2 jets, and at least 2 taus with pTvis > 40, 20 GeV and et= 50%,fake (fjt) = 1%. Optimized cuts : ETjet1 > 100 GeV; ETjet2 > 100 GeV; ETmiss > 180 GeV; ETjet1 + ETjet2 + ETmiss > 600 GeV [2] Number of SUSY and SM events (10 fb-1): Top : 115 events W+jets : 44 events SUSY : 590 events

  19. 2tAnalysis :Discovery Luminosity 10-20 fb-1 Negligiblefjt dependence +5% -5% [Assumption] The gluino mass is measured with dM/Mgluino = 5% in a separate analysis. A small DM can be detected in first few years of LHC.

  20. PTsoft in ISAJET PT STUDY Phys.Lett. B639 (2006) 46, hep-ph/0603128 Slope of PT distribution contains ΔM Information. Slope of the soft t PT distribution has a DM dependence

  21. ETmiss + 2j +2t Analysis:PTsoft [1] ETmiss , at least 2 jets, at least 2 t’s with PTvis > 20, 40 GeV [2] et = 50% , fake rate 1% [3] Cuts: ETjet1 > 100 GeV, ETjet2 > 100 GeV, ETmiss > 180 GeV ETjet1 + ETjet2 + ETmiss > 600 GeV OS OS-LS LS

  22. PT Study Can we still see the dependence of the PT slope on DM using OS-LS Method?

  23. Slope of PT PT does not depend on the mass or the mass Measuring DM from the PT Slope • Luminosity = 40 fb-1

  24. Slope of PT  DM • How accurately can DM be measured for our reference point? • Considering only the statistical uncertainty: We can measure DM to ~ 6% accuracy at 40 fb-1 & ~ 12% accuracy at 10 fb-1 for mass of 831 GeV.

  25. Model Parameters • Can parameterize the our observables as functions of DM, , & • NOS-LS , to first order, does not depend on mass. A large increase or decrease in mass is needed to obtain a point that lies outside the error bars • Cross-Section is dominated by the gluino mass

  26. Model Parameters

  27. Testing Gaugino Universality CONTOURS OF CONSTANT VALUES ( L = 40 fb-1 ) • Intersection of the central contours • provides the measurement of DM, • , & • Auxilary lines determine the 1s • region • 1st order test on Universality

  28. Determination of m0 and m1/2 DM and Mgluinom0 and m1/2 (for fixed A0 and tanb) We determine dm0/m0 ~ 1.2% and dm1/2/m1/2 ~2 % (for A0=0, tanb=40)

  29. Determination of DM and Mgluino (for fixed A0 and tanb) dWh2/Wh2 ~ 7% (for A0=0, tanb=40)

  30. Conclusion Meff will establish the existence of SUSY Different observables are needed to establish the dark matter allowed regions in SUSY model at the LHC • Analysis with visible ETt > 20 GeV establishes stau-neutralino coannihilation region 2t analysis: Discovery with 10 fb-1 • d DM/DM ~ 5% , d mg/mg ~ 2% using Mpeak, NOS-LS and pT Universality of gaugino masses can be checked The analyses can be done for the other models that don’t suppress c20 production. dWh2/Wh2 ~ 7% for A0=0, tanb=40

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