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Update on the Diphoton + MET Analysis

Update on the Diphoton + MET Analysis. Bruce Schumm, channeling Ben Auerbach (Argonne), Osamu Jinnouchi (Tokyo Tech), Susan Fowler (Penn), Brig Williams (Penn), Khilesh Mistry (Penn), Ryan Reese (SCIPP), Sheena Schier (SCIPP) UC Santa Cruz / SCIPP 22 April 2014 SUSY Background Forum Meeting.

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Update on the Diphoton + MET Analysis

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  1. Update on the Diphoton + MET Analysis Bruce Schumm, channeling Ben Auerbach (Argonne), Osamu Jinnouchi (Tokyo Tech), Susan Fowler (Penn), Brig Williams (Penn), Khilesh Mistry (Penn), Ryan Reese (SCIPP), Sheena Schier (SCIPP) UC Santa Cruz / SCIPP 22 April 2014 SUSY Background Forum Meeting

  2. Conference Note public in early January: Search for Supersymmetry in Diphoton Events with Large Missing Transverse Momentum in 8 TeV pp Collision Data with the ATLAS Detector ATLAS-CONF-2014-001 List of Tasks generated to move from note to paper…

  3. Analysis Strategy (lower reach of Wino-Bino limits) Also: require ET > 75 GeV for each of the two photons • Low-mass winos lead to limited • Photon ET • MET • Overall energy scale • -MET • Efficiency may fall off faster than cross section rises leading to a lower limit on the wino mass scale • Appears to be below 300 GeV (lowest mass simulated) • Lower masses being simulated (almost done!)

  4. WP2 One-Sided Significance Levels Low statistics signal point; still excluded

  5. WP1 One-Sided Significance Levels

  6. MC Generation/Simulation Tasks • There were several issues to address that required more MC • Low mass wino  Extend grid from 300 GeV down to 100 GeV •  This is high cross-section/low-efficiency regime; required working out filtering mechanism • Low mass bino  Extend explored bino mass reach down from 50 GeV to 10 GeV for all gluino, squark, and wino masses  Requires care to avoid metastable states, direct gravitino decays (our model requires decay through bino) • Nearly degenerate case for EW production (M_bino close to M_wino)  Add points with m of 25 and 10 GeV Again need to watch for pathologies • Full set submitted and running; should be done very soon

  7. Analysis Tasks • Increase jet ET cut from 20 to 40 GeV (M_eff reconstruction)  very little change to anything • Evaluate pT dependence of e   fake rate •  play role in determination of EW background •  evaluated with “tag and probe” method •  No significant pTdependence observed • Check grids developed for other signatures •  DISCUSS

  8. Background Studies • Estimate H   background •  Use existing H   MC sample •  Pass through all 5 analysese •  Contributions at 10-2 level or less • Re-evaluate jet-MET uncertainty •  Inclusion of overflow bin made diphoton and control distributions much more similar •  Reduce uncertainty accordingly (small change in overall background uncertainty • Re-examine QCD/EW background overlap uncertainty •  25% of EW backgrounds do not involve an e fake •  MC truth enumeration of processes suggested they might instead be included in QCD background •  ± 25% uncertainty adopted •  Do more explicit study to determine overlap; perhaps reduce 25% uncertainty (Underway; not considered necessary)

  9. Signal Systematics • Include photon ID systematics correlations  Done! • Explore differences between ATLFAST and full sim •  Several point in EW have both •  differences at few percent level •  No action taken; new points in full sim but we intend to use either with impunity

  10. Interpretation/Limits • Redo gluino/bino contour (changes very slight, except extension to Mbino < 50 • Set limit in squark/bino plane, including low bino mass • Set limits in wino/bino plane, including lower limits (additional MC needed; hope to submit soon • [Depending on manpower: Set limits in constrained SPS8 model (signal MC already in place)] • Since last update squark/bino limits done except low bino mass; awaiting completion of other steps, especially, MC simulation.

  11. Wrap-Up • Most of proposed work towards paper completed • Major focus for paper now is MC generation (low-mass bino; lower limits on wino mass • Might be a gap between LHC and LEP wino mass limits  if so will want to think about re-consideration of 1 fb-1 analysis? • Look at other signal grids with our analysis? • Most of changes documented in new backup note in SVN; not yet in CDS. Personnel issue: While many are working, most of core analysis was done by Ben, who is leaving ATLAS for the private sector immediately. We will need some time to regroup.

  12. BACKUP

  13. Analysis Strategy Continued 5 fb-1 analysis required ET > 50 GeV and Not good • 1 fb-1 analysis required • ET > 25 GeV • MET > 125 GeV • These will likely place lower limits on the wino mass than those of the 8 TeV analysis (which are still being determined) • Estimate of lower wino limit for 1 fb-1 analysis underway… but can we really include that in a paper? DISCUSS

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