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

17 June 2014 SUSY Background Forum Meeting

17 June 2014 2

Conference Note public in early January:

Search for Supersymmetry in Diphoton Events with Large MissingTransverse Momentum in 8 TeV pp Collision Data with the ATLASDetector

ATLAS-CONF-2014-001

List of Tasks generated to move from note to paper…

17 June 2014 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 scaleAppears to be below 300 GeV (lowest mass simulated)

Lower masses now simulated… will be analyzed soon.

17 June 2014 4

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

Now done; awaiting analysis

17 June 2014 5

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 pT dependence observed

• Check grids developed for other signatures DISCUSS

17 June 2014 6

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)

17 June 2014 7

Background Studies: New Issue

• New developments on W background calculation (Kaplan, Haas) Our “enhancement factor” of ~3 is relative to Alpgen Kaplan/Haas implement VBFNLO; see that Bozzi et al. NLO is consistent with Alpgen Expect no need for enhancement factor

Bozzi et al. Kaplan/Haas

17 June 2014 8

Background Studies: New Issue Cont’d

• On the other hand, our W background estimate based on e control sample. Our “enhancement factor” of ~3 is relative to Alpgen Is this incompatible with Kaplan/Haas (phase space..) Have we missed some background to the e control sample? Can just expand error to include Kaplan/Haas result (but we do simultaneous fit… so need to understand how to do that!)

Includes x3 enhancement factor

17 June 2014 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

17 June 2014 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)]

• Squark/bino limits done except low bino mass

17 June 2014 11

Wrap-Up• Most of proposed work towards paper completed

• Major issue is loss of Ben Auerbach; are recovering. Cut flow now matched by Osamu; Reese/Schier almost there too.• Osamu working on getting up to speed on fitting/limit-setting.

• If expanding systematic error on W background felt to be necessary, then will need to figure out how to do that with simultaneous fitting of W and signal.

• Changes so far documented in new backup note

<http://cds.cern.ch/record/1700554>

22 April 2014 12

BACKUP

17 June 2014 13

5 fb-1 analysis required ET > 50 GeV and

Analysis Strategy Continued

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

Not good

17 June 2014 14