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Overview of decaying long-lived particle (DLLP) analysis

Overview of decaying long-lived particle (DLLP) analysis. Goal: search for heavy particles with t ~ 3 ps – 1 ns, eg., from SUSY with R-parity violation Split-SUSY Hidden valley For first attempt, require muon in vertex to reduce background Require trigger EF_mu40_MSONLY

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Overview of decaying long-lived particle (DLLP) analysis

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  1. Overview of decaying long-lived particle (DLLP) analysis • Goal: search for heavy particles with t ~ 3 ps – 1 ns, eg., from • SUSY with R-parity violation • Split-SUSY • Hidden valley • For first attempt, require muon in vertex to reduce background • Require trigger EF_mu40_MSONLY • No plan to prescale in 2011 data • (For second round of the analysis, will develop a dedicated HLT trigger) Avner, Nimrod (TAU) N. Barlow (Cambridge), CW. Loh (British Columbia), V. Jain (Indiana)

  2. Vertex reconstruction & selection • Vertex any number of tracks that satisfy • pT > 1 GeV • d0 > 2 mm. Sharply suppresses prompt tracks • c2/ndof < 5 • At least 2 SCT hits • No shared hits • Track’s c2 contribution to vertex < 6 • Vertices separated by less than 3s or 1 mm are merged • Further vertex cuts: • |rDV – rPV| > 4 mm • Decay length signif > 6 • Vertex not in material (determined from high-density of low-mass vertices) • Vertex has at least 5 tracks • Vertex mass > 15 GeV 41 GeV background vertex at beampipe

  3. Signal efficiency, data yield • Signal MC is SUSY with RPV, mq = 700 GeV, two varieties: • mc0 = 108 GeV, e = 3.2% • RPV coupling l’ = 150.e-06, ct = 101 mm <gb> = 3 • mc0 = 494 GeV, e = 8.5% • RPV coupling l’ = 3.e-06, ct = 78 mm <gb> = 1 • Least efficient single cut is muon in the vertex, e ~ 27%.

  4. Sensitivity • Tuning the analysis on a ~6 pb-1 training sample • Sensitivity estimate: Since no background in 2 pb-1, can extract limit vs. <gbct>,given signal efficiency vs. <gbct>

  5. Good data-MC agreement in material, etc. • Vertex position in r & z for looser cuts (mostly material interactions)

  6. Validating MC efficiency for high-d0 track reconstruction • Use KS as source of high-d0 tracks: • KS pT dist in data and MC are in reasonable agreement: Data MinBias MC • Agreement in d0 distributions of KS daughter tracks validates d0 dependence of MC tracking efficiency :

  7. Validation efficiency of high-d0 muon tracking and MS-ID match: • For each d0 bin, plot fraction of trk-mu matches • (|Dh, Df < 0.006, DpT < 20%) • Overall match prob is higher in data. • KS probability for data and MC e distributions is 8%. • Also mu pT spectrum diff. • Once understood, uncertainty/disagreement will propagate to limit

  8. Work underway and plan • Background estimate (we see no bgd, but need an estimate in order to be sensitive to signal) • Turns out to be nontrivial – we have looked at mass dependence as a function of h, use of vertices in material, use of jet triggers etc. • Looks like we’ll look at reduction in data yield as cuts are tightened, accounting for simple correlations between variable distributions, hopefully not incurring large errors in the process – being looked at. • Goal is to finalize analysis in time for summer publication with at least up to period I data.

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