Rjets (W+jets/Z+jets) :

Status ReportEvelin Meoni

On behalf of the Rjets group:G. Arabidze, C. Chavez Barajas, H. Beauchemin, M. Bona, G. Brandt, B.

Brau, N. Calace, S. Chouridou, M. Dunford, G. Fletcher, T. Hayashi, J.Huston, R. King, A. Meade, E. Meoni, M. Mondragon, J. Nielsen, J.B.

Sauvan, C. Sawyer, A. Tricoli

1st Ed Board Meeting23th January 20131

OutlineThis outline “roughly” represents the current skeleton of the Supporting Note with some differences to better

summarize the status of the work (what has been done/what we still have to do):

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•Motivation

•Measurements and Analysis Strategy

•Data and MC sample

• Event selection

• Detector level plots: - background estimation - overall systematics at detector level • Unfolding: - method - systematic uncertainties• Theoretical predictions

• Results

• Conclusions

For each point outlinedin red, work to be done and on-going activities( to do list summary at the end)

At the end few ideas/proposals about how synchronize the review paths of Rjets and Wjets papers

Motivations

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Boson + Jets measurements in general: - important bkg for new physics and test of the pQCD

Ratio measurement (W+jets)/(Z+jets) in particular:

- high precision test of pQCD reduced uncertainties both at experimental level (strongly reduced JES, LUMI) and theoretical level (significantly reduced dependence on PDFs) , but information about dynamics of V+jets production conserved in the ratio

- model-independent sensitivity to new physics : new physics preferentially coupling to W or Z could cause a deviation of the ratio in a particular kinematic regime

- useful tool for background predictions in searches mapping W/Z +jets in different regions Zee+jets We+je

ts

test similarity

ee

Met

PDFs uncertainties

Measurement

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Past measurement with 2010 dataset (Phys. Lett. B708 (2012),221-240):“A measurement of the ratio of the W and Z cross sections with exactly one associated jet in pp collisions at sqrt(s) = 7 TeV with ATLAS”: - measurement for the first time as a function of jet pT thr - measurement done for electron and muon channel and combination -comparison with LO +PS MCs (Pythia and Alpgen) and NLO calculations (MCFM): good agreement btw data and predictions

Goal for measurement with 2011 dataset:

Njets : inclusive and the ratio (njet/(njet-1) )Njets for pt_lead > 150 GeV: njet/(njet-1) ( Test scaling differences between W and Z)Jets: pT and y of 1st , 2nd ,3rd and 4th jet for Njets>=1,2,3,4

Dijets variables: m12,R12, 12, y12

Complex : HT and ST for Njets>=1,2,3,4 and for Njets==1,2,3,4 Distributions in VBF phase space (mjj>350 GeV, ||>3): pT and y of the 3rd jet

Comparison with LO MCs (Alpgen and Sherpa) and with NLO calculations (BlackHat+Sherpa)

Strategy (1/2)

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Measurement at detector level : - Data (2011 stat) and MC (mc11c, pileup reweighting applied, corrected for lepton momentum/energy scale and lep eff SF)- Signal measured as Data – BKGs:

Hadron level:-Correct for detector effect (trigger and reconstruction eff. and resolution) with Bayesian Unfolding (RooUnfold) in the same phase space of the detector level measurement with Alpgen (dressed leptons)

Comparisons of unfolded data with LO MCs+PS (Alpgen and Sherpa) and with NLO calculation (BlackHat+Sherpa) corrected

Parton level:NLO calculation corrected by NP effects (fragmentation and UE) and QED effects (born leveldressed)

Strategy (2/2)• Measurement done first for electron and muon in as similar as experimentally

possible phase space:

• Combination in the common generic phase space :

Correction of unfolded electron and muon results for space-phase done with Alpgen

• About Combination:

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Electrons (dressed level)Z: pT(e)>20 GeV ||<2.47 (crack excl), 66 < mZ < 116 GeVW: pT(e)>25 GeV ||<2.47 (crack excl), pT(v)>25 GeV, MT > 40 GeVJet : pT> 30 GeV |y|<4.4

Muons (dressed level)Z: pT()>20 GeV ||<2.4, 66 < mZ < 116 GeVW: pT()>25 GeV ||<2.4, pT(v)>25 GeV, MT > 40 GeVJet : pT> 30 GeV |y|<4.4

Combination (dressed level)Z: pT(l)>20 GeV ||<2.5, 66 < mZ < 116 GeVW: pT(l)>25 GeV ||<2.5, pT()>25 GeV, MT > 40 GeV

We’ll publish just thecombination

Chi2 method : measurement of Ratio(e) and Ratio () first Combination of the 2 Ratios

Combination Code and References

Data and MC samples• 2011 Data: - period D-M

- GRL: data11_7TeV.periodAllYear_DetStatus-v36-pro10_CoolRunQuery-00-04-08_WZjets_allchannels.xml

- 4.64 fb-1 for each stream (EGamma and Muon)

- SMWZ D3PDs tag p833

• MC: -mc11c samples

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Process Generator

W Alpgen+Jimmy(0p..5p) and Sherpa v1.4

Z Alpgen+Jimmy(0p..5p) and Sherpa v1.4

We Alpgen+Jimmy(0p..5p) and Sherpa v1.4

Zee Alpgen+Jimmy(0p..5p) and Sherpa v1.4

Z Alpgen+Jimmy(0p..5p)

WW,ZZ,WZ Herwig

ttbar Alpgen+Jimmy (0p..5p)

Single top AcerMC

- Normalized to (N)NLO XS: https://svnweb.cern.ch/trac/atlasgrp/ browser/Physics/StandardModel/

Common/Winter2012/mc11c_p833_info.txt

-QCD estimated with data driven-techniques

TO BE DONE: some checks (see next slides)

-top : currently estimated via MC TO BE DONE: use Data-Driven

estimation(see next slides)

Rjets analysis tool on SVN : PhysicsAnalysis/StandardModelPhys/WZJets/Wzratio

Common W/Z baseline selection: https://twiki.cern.ch/twiki/bin/viewauth/AtlasProtected/WZElectroweakCommonTopics2011

Preselection: -trigger

- primary vertex (at least one good vertex with >=3 track ) -MET cleaning and LAr Hole Veto

Lepton selection:

Z selection: 2 OS leptons, 66 GeV< mll<116 GeV

W selection: MET > 25 GeV, mT(W) > 40 GeV

Jets selection:

Event selection

Electrons: Author 1or 3, Quality flag (OQ&1446 !=0) pT>25 GeV (W),20 GeV (Z) |n|<2.47 (excluding 1.37-1.52)

Muons:STACO Combined with cleaning cuts(MCP recommendations), pT>25 GeV (W),20 GeV(Z) |n|<2.4

Electrons: 2 OS medium electrons Muons: 2 OS muons, at least the 1st with d0sign (<3), z0(<10mm), isolation requ. (ptcone20 / pt < 0.1)

Electrons: 1 tight++ electron

Muons: 1 muon with d0sign,z0, isolation requ.

Electron TriggerW: e20_medium(D-I), e22_medium (K), e22vh_medium1 (L-M) Z : 2e12_medium(D-I), 2e12T_medium (K), 2e12Tvh_medium (L-M)

MuonTrigger:mu18_MG (D-I), mu18_MG_medium (J,M)

MET: MET_RefFinal, JES and lepton scale prop with MissingETUtility

Antikt4TopoEM at EM*JES scale pT > 30 GeV, |y| < 4.4 |JVF| > 0.75 ( for jets with |η| < 2.4) ΔR(jet-lepton) > 0.5

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QCD bkg estimation: electrons

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QCD mainly originated by light jets faking an electron

W channel: QCD template from data : loose trigger and events with loose electrons,passing at least one medium and failing tight isEM bit and anti-isolated - QCD normalization by fitting MET on data with QCD templ+ sign and other BKGs (from MC): - fit done in the MET region 10-100 GeV - fit done in exclusive jet bins up to 5 jets- Systematics :change of the fit range, change of the template (changing the electr. definition)-Note: estimation done separately for perD-K and perL-M (different pileup and trigger pre-scale) and sum up(Some checks on –going see conclusions and W+jets EdBoard of Friday)

Z channel

- QCD template from data : select events with>=2 loose electrons fails medium - QCD normalization by fitting mee with QCD templ + Signal and other BKGs (from MC): -fit done in the region 54-140 GeV- fine done in excluding bins up to 2jets - Systematic uncertainties : fit range, electron energy scale variation

Z Njets=0 Njets=1 Njets=2

Nominal (%) 0.31 0.36 0.62

Rel Uncert (%) 20.16 34.86 24.86

W Njets=0 Njets=1 Njets=2 Njets=3 Njets=4 Njets=5

Nominal (%) 6.35 18.09 17.97 16.72 11.50 6.11

Rel Uncert (%) 16.30 12.90 10.72 8.70 6.76 37.64

Njets=1

fQCD=QCD/Data

fQCD=QCD/Data

QCD bkg estimation: muons

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QCD mainly originated by muon coming from heavy flavour decays

W channel- QCD template from data : inverting d0sign cut (d0sign>3.0)- QCD normalization fixed by fitting MET on data with QCD templ. + signal and other BKG (from MC): fit in 10-100 GeV, fit done in excl jet bins up to 4 jets and inclusive for njets>=5Z channel: - QCD template from data: inverting isolation -QDC norm fixed by fitting di-muon mass on data with QCD temp.+ signal and other BKG (from MC): fit in 45-150 GeV; fit done in excl jet bins up to 2 jets and inclusive for njets>=3 Systematics : Fit Range, Fit variable, alternate QCD template

W Njets=0 Njets=1 Njets=2 Njets=3 Njets=4 Njets>=5

Nominal (%) 4.22 14.42 13.45 13.06 10.93 8.28

Rel Uncert (%) 23.9 10.35 13.43 19.57 37.19 44.80

Z Njets=0 Njets=1 Njets=2 Njets>=3

Nominal (%) 0.33 0.53 0.92 0.81

Rel Uncert (%) 9.48 10.73 63.78 91.33

fQCD=QCD/Data

Njets=1

ttbar data-driven estimation

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Njets=3

Njets=5

Currently detector level plots and Unfolded plots done with ttbar from MC, in the next switch to data-driven. Here just few words (more details in EdBoard of Friday for W+jets paper; W+Jets and Rjets group joined in one group sharing codes/results)

ttbar template from Data:

Independent variable to fit the normalization:Fit on transverse sphericity the ttbar template subtracted by W+jets (h.f and light jets) contributions estimated with from MC template

Systematics currently : different W MC templates (Alpgen vs Sherpalarge contribution in the Njet=3 bin region currently), subtraction of W template(25% variation considered), statistical uncertainty on the fitOngoing activities syst. from: fit variable (Mtop and MET), fit range

Work to be finalized

Still to be includedin the analysis framework

Selected events with :>=2 jets , MET and MT cutRequired at least 1 b-jets

Detector level : Njets (exclusive)

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Systematic band:

JET: Jet Energy Scale and Jet Energy resolution ;

Leptons: Muons :Reconstruction, Trigger Efficiency, Momentum scale and resolution Electrons: Reconstruction and Identification, Trigger Efficiency, Energy scale and resolution

MET

Bkgs: unc on XS for Normalization for bkg taken from MC; for QDC from data-driven estimation

(Tag of the package in bkup slides)

Here shown the style of our detector level plots (what kind of information are in)

Systematics on detector level plots: Njets (exclusive)

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Here shown the style of our detector level systematicsplots

TO BE DONE:On going checks on few small differences betweenelectron and muon channel

In the Supporting Note: for each variable shown detector level plot and systematic plots for W and Z for muon and electron. A few of the results in the main text (for sure Njet, leading pT and y) , the rest in the appendices

W- e ch W- ch

Z- e ch Z- ch

Unfolding

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Unfolded W and Z in each channel (e,) separately Performed R() and R(e) Comb

Unfolding technique: Bayesian iterative unfolding with RooUnfold, implemented a- “match method” (2010 and 2011 Z+jets group method): applied a match reco-truth jets (best R match regardless pT order). - build : response matrix and fake correction (to account for un-matched reco jets) respecting the truth pT ord. - fake correction applied as a bin-by-bin external correction before unfolding - “unmatch method” (similar not identical to 2010 W+jets group method): -no match reco-truth jets - build fake correction (to account for reco jets in events not passing the truth selection) -fake correction applied as a bin-by-bin external correction before unfolding Currently all the results shown in the supporting note are based on “match approach” with a fixed number of iteration (3 it) regardless the variable.

TO BE DONE/On going activities :-Check full set of results with “un-match method” if working use it as nominal method- Fix the convergence criterium to define the proper number of iteration for each variable (on going study , close to the end, see backup slides)

Unfolding matrix

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W+ jets

Z + jets

Muons

Muons

Electrons

Electrons

Here shown the style of our matrices representation in the supporting note:

Each bin normalized tothe Hadron level entries ofthe corresponding ColumnShown migration & efficiency in the same plot

In the supporting note, plan to put all the matrices in an appendix

MC details:-Used Alpgen signal sample to unfold data-Closure test done with Sherpa emulating the data

Closure test

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Sherpa (used to emulate Data) Unfolded with Alpgen

Bayesian method with different number of iterations provide optimal closure in the region with high statistics, some differences observed in the region with low statisticsuncertainty term relating to unfolding (see next slides) should cover this effects

W+ jets

W+ jets

Z + jets

Z + jets

Muon Channel

Systematics on unfolded results (1/3)

For each source varied signal (matrix and fake correction) and bkg estimated with MC (for unfolding unc source moved Signal only, for bkg unc source moved bkg only)

Experimental Systematics: JET, MET, Muon, Electron, BKGS as for detector level plotsUnfolding Systematics: Method: Bayesian vs. Bin-by-bin ; Modeling: Unfolding with Alpgen vs. Sherpa Statistical Uncertainty (to be implemented): Toy MCs to fluctuate the MC inputs (matrix and distributions)

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Z + jetsW + jets

To Do List: -Produce uncertainty plots on unfolded results also for electron channel (debugging on going)-In muon channel to be added the statistical-uncertainty on unfolding

)

Z + jetsW + jets

Ratio

Systematics on unfolded results (2/3)

Ratio is a very precise measurement at low multiplicity, at high multiplicity (Njets>=4) precision limited by BKGs uncertainty :different level of top bkg in W and Z it doesn’t cancel in the ratio (needed ttbar data-drivenestimation with an uncertainty <10% for Njets>=4 )

For each systematics source, the corresponding unfolded result for W and Z taken to form the varied Ratio

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Systematics on unfolded results (3/3)

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Systematics drasticallyreduced in the ratio

Systematics suffer fromstatistical fluctuationsof MC

TO BE DONE:Apply a partial rebin ofsome variables in the regionwith low statistics (use firstfinal Z+jets binning)

In particular for RapitidyPlots: show absolute valueResults

Z + jetsW + jets

Ratio

Predictions• NLO pQCD preditions with BlackHat+Sherpa : CT10 PDFs , ren and fact scale at HT/2

(scalar sum of all particles/partons in final state)

• Corrections :

• Nominal correction derived from Alpgen+Herwig (Auet2-cteq6l1 tune )syst estimated with Alpgen+Pythia (Perugia2011C)(UE and hadronization) and Sherpa (QED corrections)

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W W W

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Predictions

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For Z+jets used same prediction of Z+jets paper, for W+Jets used resultsproduced in the same way :-pdfs uncertainties computed using the complete eigen vector set, impact of s evaluated, scale uncertainty evaluate varying it by a factor of two W+Jets full sets results arrived this Monday TO BE DONE:Work of the uncertainties of the prediction (scale , pdfs and QED and acceptance Corrections varying correlated uncertainties in parallel calculating the ratio)

Currently on supporting note just shown central value for the predictions

Ratio vs Njets exclusive

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Discrepancy of Data/MC in the Ratio at high multiplicity seemsan issue related with unfolding in W (data/MC at detector level agree well) in a region with low statisticsand large migrations

Effect covered by the large uncertainties at high Multiplicity

W Z RATIO

W Z RATIO

Muons Muons Muons

EleEle EleMuon channel all syst in

Electron channel:just unf sys in (TO BEUPDATED)

Z.Ch results fully consistentWith Z+jets paper results

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W Z RATIOLeading jetpT

Muons Muons Muons

EleEle

Ele

Significant deviations Between Data and Predictions(mainly in muo ch)

Shapes seems rather consistent

Investigation through the double ratio (vs inclusive)

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Significant deviations betweenData and Predictions

Shapes seems rather consistent

Investigation throughthe double ratio (vs inclusive)

Just overall normalization Improved Data/MC agreement

Currently in Supporting Note shown Ratio of Absolute XS. For some distributions we want to showDouble ratio (just overall normalization). List to be defined

W Z RATIO

Muons MuonsMuons

Double Ratio

Leadingjet y

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W Z RATIO

W Z Significant deviations Between Data and Predictions

Shapes seems rather consistent

Muons Muons Muons

EleEle

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W Z RATIO

W Z

Muons Muons Muons

Double Ratio

Just overall normalization

Improved Data/MC agreement

Conclusions

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Rjets is a very high precision measurement and with 2011 statistics we are able tosignificantly extend the 2010 measurement to a larger number of observables.

Some good agreement of data with NLO and LO MCs+PS and some deviations larger than uncertainties in the Ratio provide very useful information for QCD Wait for the finalization of the different parts of the analysis for final Statements.

To Do List (1/2)

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QCD data-driven: QDC estimation in W increases compared to 2010 in both ch (3xele,4xmuon)(differences in evt selection, different level of pileup) needed some investigation (check heavy-flavor component in e-ch, try estimation per periods also in m ch, Cross-check with incl. group results)

ttbar data-driven: Finalize the results (work on systematics) Include in the analysis results

Detector level plots: complete (just some on-going checks on the systematics)

Unfolding: -Check the impact of the method without matching truth-reco -Finalization of convergence criterium -Electron channel: Propagation of the systematics on unfolded results -Muon channel: Add last missing systematics: statistical uncertainty on unfolding - Missing in both channel a few variables ( scaling: (njets+1)/njets)

Predictions: Complete set of results just arrived , work on uncertainty estimation

Combination: Code ready, we need to complete systematics propagation in ele chan to show results

To do list (2/2)

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Documentation: Supporting note already in place. The svn location is: https://svnweb.cern.ch/trac/atlasphys/browser/Physics/StandardModel/WZPhysics/Analyses/RatioJets/RjetsInternal5fb

Expected to be a very extended supporting note(basically 3 times the Z+jets one)

Currently 250 pages and a lot of material still missing

What is there?-Basically the full set of results (plots) we currently have : detector level plots with syst ones, unfolded result and syst ones (matrices, closure), Prediction correctionsfor almost the full set of variables-About the text :first part is the more documented:MC and data samples, selection, QDC bkg,minimal on the rest (expecially on the unfolding)

-We should prefer to improve it before invite you to read it (maximum one week)In order to clean it , make it more organic and readable (a lot of material is it, but it need to be organized) This should facilitate and speed the things at the end

Rjets and Wjets papers

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In December at the time we required an EdBoard for Rjets ,the W+jets analysis had a longer time scale

In extended discussions (with SM convernors , W/Z convenors and among the 2 groups) we felt it was important to publish the W+jets results on the same time scale (Z+Jets paper will give the open presentation next week). So:-R+jets and W+jets agreed to work together to accelerate the W +jets publication (with reduced in scope to realistically meet the new timeline)- W+jets and R+jets will be 2 publications with the same EdBoard to facilitate this goal

Having same EdBoard and being the same group of persons for both the analyses, if possible tryto optimize the work/time:- Do we want maintain the EdBoard meetings separated or do we want joined Ed Board meetings? As analysis group we should prefer joined meetings-Do we want 2 separated supporting notes (one for each paper) or one supporting note for both papers? Different opinions within the analysis group, we think the choice has to be driven by preference of the EdBoard in line with the convenors (this option has not been discussed before with them)

BACKUP

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Technical remarks

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MC specific corrections: -Pileup: PileupReweighting-00-02-01 -Leptons:

MC/data :

Systematics: -Leptons: previous packages -JETs: ApplyJetResolutionSmearing-00-00-03, JetResolution-00-07-14, JetUncertainties-00-07-04 - MET: previous package

Electrons:-Correct for Energy scale and reconstruction, ID and trigger efficiencies: : egammaAnalysisUtils-00-02-76

Muons:-Correct for: momentum scale, resolution, reconstruction and trigger efficiencies: MuonEfficiencyCorrections-02-01-00 MuonMomentumCorrections-00-07-00 TrigMuonEfficiency-00-01-10

JETS: ApplyJetCalibration-00-01-06 MET:MissingETUtility-01-00-09

Detector level: leading jet pT

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Converge criteria for unfolding

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Convergence criterium, 3 method under evaluation:

1) 2011 Z+jets paper approach:

2) (close to) 2010 W+jets paper approach:

3) Best iteration is the one for which the unfolding uncertainty on XS results is minimal

€

Conv= 1N

bins

|Unf(i)−Truth(i) |2

σTruth( i )

2i=1

Nbins

∑Used Sherpa to emulate the data and Alpgen to unfold

€

Conv2(i)= 1N

bins

|UnfK(i)−Unf

K(i+1) |

σK ,Unf ( i )

K =1

Nbins

∑Stop iterations when difference on 2 consecutive is smaller of the statistical unc

I meth Z

II meth Z

III meth Z

Predictions• NLO pQCD preditions with BlackHat+Sherpa : CT10 PDFs , ren and fact scale at HT/2

(scalar sum of all particles/partons in final state)

• Corrections :

• Nominal correction derived from Alpgen+Herwig syst estimated with Alpgen+Pythia (UE and hadronization) and Sherpa (QED corrections)

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ZZ

Z