Update on the Diphoton + MET Analysis Basckground

Bruce Schumm, Osamu Jinnouchi (Tokyo Tech), Ryan Reese

(SCIPP), Sheena Schier (SCIPP)

26 August 2014 SUSY Background Forum Meeting

26 August 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…

26 August 2014 3

Analysis Strategy (lower reach of Wino-Bino limits)

Also: require ET > 75 GeV for each of the two photons

26 August 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

26 August 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

26 August 2014 6

Background Studies

• Estimate H background Use existing H MC sample Pass through all 5 analysese Contributions at 10-2 level or less DONE

• 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 DONE

• Explore Wgg-background control region (l sample) for non-Wgg backgrounds This required developing the analysis from scratch since the sudden departure of Ben Aurebach Also want to add tt background just in case… Nominal subject of this talk

26 August 2014 7

New Wrinkle

• Comment on current version of Internal Note request that we update our analysis using BCH Cleaning

• In addition, we discovered that we had been unintentionally vetoing events containing identified muons, which was contrary to our intent

Are updating analysis, but need to see if this will have an appreciable effect on the backgrounds.

Note that this latter issue should not affect the Wgg analysis, since that explicitly requires events with muons, so no veto was applied.

26 August 2014 8

Wgg Background Studies

• 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

26 August 2014 9

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 l 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

W control region

From CONF Paper Internal Note

26 August 2014 10

Ed Board Request: Look for Z contamination in W control sample

Idea is to take l control sample, divide it into low and high MET (below and above 50 GeV) and look at the following quantities:

•PT(e), PT()

•M(e1), M(e2), M(e), M(), M(l)

•(MET,l), (MET,e), (MET,)

But….

26 August 2014 11

Re-Assessing the W Control Analysis

Re-inventedAnalysis

Although signal selection was validated, lepton selection was notSignal and MC down by x2 relative to CONF NOTE analysisExploring reasons for thisHave included tt; does not make much differenceX3 enhancement factor still consistent with data (see 3, expect 4.5), but based on 3 events rather than 8, so little statistical significance.

26 August 2014 12

Summary

• Our tools for doing analysis and selecting events are largely back in place.

• While we seem to be able to reproduce our sample, our l sample has not been reproduced.

• If we decide current analysis is correct, could lower photon pT cut to get more statistics in control sample

• One bug (muon veto) and one analysis improvement (BCH cleaning) force us to recalculate backgrounds once again, but changes should be small. Should be quickly followed through upon once we work out the l problem.

22 April 2014 13

BACKUP

17 June 2014 14

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 15

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 16