ATLAS SUSY Working Group B.C.Allanach, A.Barr, L.M.Drage, J.Heatherington, C.G.Lester, D.Morgan, M.A.Parker, B.R.Webber. University of Cambridge UK ATLAS PHYSICS MEETING 15/12/99
Contents • Overview of SUSY Studies at Cambridge • Developments in R-Parity Violating Decay Studies – R-Parity Violating Decays – Variation of the λ ” coupling 212 – Identification of χ 0 parents ~ 1 – Variation of Tan β due to limit on M Higgs Debbie Morgan ATLAS UK Physics Meeting 15/12/99
Motivation • R=(-1) 3B+L+2S • If R is conserved: SUSY particles are created in pairs, LSP is stable weakly interacting missing energy signature • No theoretical reason to conserve R-parity • 3 cases of R-parity violation: − ν 0 → l + l Lepton number violating, λ coupling χ ˜ 1 0 → qq l , χ qq ν Lepton number violating, λ ’ coupling ˜ 1 0 → qqq χ Baryon number violating, λ ” coupling ˜ 1 Debbie Morgan ATLAS UK Physics Meeting 15/12/99
RPV Analysis • mSUGRA: Point 5 ~ • λ ” non-zero, which allows the decay cds or cds χ 0 212 1 q • Final State: 8 jets ~ q L 2 leptons ~ χ 0 NO missing energy 2 ~ χ 0 l ± 3 jets from each decay ~ ± 1 l q ± ~ l q R ~ χ 0 ~ χ 0 1 1 c d s c d s Debbie Morgan ATLAS UK Physics Meeting 15/12/99
SUSY Reconstruction: χ 0 ~ 1 • λ ” = 0.005 Events / 6 GeV Constant 520.2 Mean 120.1 212 Sigma 18.59 500 • Point 5 mSUGRA, where χ 0 400 mass = 122GeV 1 300 • HERWIG 6.002 200 • Mass reconstruction in 12 jet events after 100 background subtraction 0 0 50 100 150 200 250 300 m jjj (GeV) Debbie Morgan ATLAS UK Physics Meeting 15/12/99
SUSY Reconstruction: χ 0 , l ~ ~ 2 Debbie Morgan ATLAS UK Physics Meeting 15/12/99
χ 1 ~ ~ χ 2 0 0 mass, using cuts from mass Debbie Morgan ATLAS UK Physics Meeting 15/12/99
Variation of λ ” 212 • At λ ” = 0.005 212 RPV couplings Branching fraction 1 are small 0.8 • What happens at higher λ ” ? 0.6 d R →χ 0 212 1 d - c - d R → s 0.4 • Can the analysis still be used to 0.2 χ 1 ~ 0 reconstruct the ? 0 -3 -2 -1 • Looked at λ ”= 0.5 10 10 10 1 // Yukawa coupling λ 212 212 0.000005 Debbie Morgan ATLAS UK Physics Meeting 15/12/99
Results for changing λ ” 212 ~ χ mass using 0 ~ No.peak ~ ~ λ ” χ mass χ mass 0 0 1 l mass ~ χ mass cuts 212 events 0 1 2 2 0.5 115.4 440 157 235.0 112.8 0.05 118.3 465 157 235.5 110.1 0.005 120.1 520 157 235.0 114.9 0.0005 119.2 550 158 234.3 113.2 0.00005 116.4 600 157 235.1 106.8 0.000005 116.8 520 156 235.7 113.6 • Taken from a sample of 700k events ≡ 32 fb -1 Debbie Morgan ATLAS UK Physics Meeting 15/12/99
Identification of the parents χ 1 ~ 0 Debbie Morgan ATLAS UK Physics Meeting 15/12/99
χ 1 ~ 0 parents • λ ” coupling only ‘talks’ to the right-handed 212 quarks χ 1 ~ • As λ ” increases, the decay without a 0 212 q dominates: ~ q R q χ 1 ~ 0 • See this is the number of reconstructed from q R -q R : 1 at 0.5, 8 at 0.000005 Debbie Morgan ATLAS UK Physics Meeting 15/12/99
Variation of Tan β • All results use mSUGRA Point 5, with M Higgs = 93 GeV • Current LEP2 limit: M Higgs ≅ 109 GeV (?!) • By varying 1 of the parameters within mSUGRA Point 5 we can increase M Higgs – Tan β = 4 −−> M Higgs = 107 GeV – Tan β = 10 −−> M Higgs = 113.2 GeV Debbie Morgan ATLAS UK Physics Meeting 15/12/99
mSUGRA: Tan β = 10 Events / 6 GeV 600 Constant 535.9 Mean 116.4 Sigma 17.58 500 400 300 200 100 0 0 50 100 150 200 250 300 m jjj (GeV) Debbie Morgan ATLAS UK Physics Meeting 15/12/99
Conclusions χ 1 ~ • Can reconstruct the in RPV decays using λ ” 0 212 couplings from 0.5 to 0.000005 • Identification of the parents allows us to see the effect of changing λ ” 212 • Have varied Tan β in order to give a non- χ 1 ~ 0 excluded Higgs mass, and the is still reconstructable Debbie Morgan ATLAS UK Physics Meeting 15/12/99
Future Work • Upgrade to HERWIG 6.1 (just released) χ 0 • Make a lifetime cut on the to limit 1 reconstruction to those that have decayed in the beam pipe ~ • Reconstruct the q produced in the initial q ~ decay, so that the q mass can be reconstructed Debbie Morgan ATLAS UK Physics Meeting 15/12/99
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