DØ Status Report

Frank Filthaut

18 December 2007

Tevatron

DØ

Physics

Nikhef Participation

Sijbrand de Jong Frank Filthaut Mike Kirby Axel Naumann

Pieter Houben Pieter van den Berg Cristina Galea Miruna Anastasoaie

Jeroen Hegeman Lucian Ancu Melvin Meijer Willem van Leeuwen

Nikhef Participation

Sijbrand de Jong Frank Filthaut

Projectruimte grant (Higgs, 1PhD Student + 1 Post-doc)will see (some of) us through2011. Post-doc to start 4/’08

Mike Kirbyleft

9/’07

Axel Naumannfinish

ingup

Pieter Houbenfinish

ingup

Pieter van den Bergfinish

ingup

Cristina Galeafinish

ingup

Miruna Anastasoaiedefe

nse2/’0

8

Jeroen Hegemanfinish

ingup

Lucian Ancuunti

l 3/’09

Melvin Meijerfrom

9/’07

Willem van Leeuwen

Tevatron

Luminosity upgrades have been very successful!

running in 2009 “guaranteed”, on track to& 6 fb−1 by end 2009

decision on running in 2010 in a fewmonths, depends mainly on experiments

3.4 fb−1

Detector Operation

Stable running throughout the year, DAQ efficiency ∼ 84%

Now recording at 100 Hz, data reconstruction moved to Grid (OSG),up to 12 M events/day

Biggest issue is tracking (and vertexing, b-tagging)

2 of 15Current Status: Global

Collaboration Meeting – December 7, 2007 Dmitri Smirnov

Installed new readout hardware: CFT timing information, beingcommissioned (Melvin)

Other refinements to reduce (reject) fake tracks

ProspectsRecommendation for running in 2010 will depend primarily on manpowersituation (besides physics case, see later)

Dzero MSU Wrokshop IB Meeting - P5 Panel Recommendations 888

Total FTE Total FTE PersonpowerPersonpower of the Experimentof the Experiment

This plot permits cross-check using 2006 Efforts Reports.Total FTE reported in Efforts Reports in 2006 is 407 FTE – match within errors.

MoUs do(!) have predictive power.

Sum FTE Total

354

474

437

357

184

272

0

50

100

150

200

250

300

350

400

450

500

CY2005 CY2006 CY2007 CY2008 CY2009

Calendar Year

FTE

Total experiment personpower based on MoUs2005-2007 – blue (MoU data collected in 2005)2007-2009 – red (MoU data collected in 2007)

Good agreement between MoUs preparedin 2005 and 2007 for year 2007

124 FTE (service)184 FTE (total)

= 67%

We believe that we can make this case, despite visible attrition:

stable detector operation

consolidation of reconstruction & object ID algorithms

well-understood institutional commitments

Physics

This is the time to harvest the Run IIb fruits! 33 publications submittedin 2006, 34 (as of last week) in 2007

Here, focus on a few high-pT topics of specific interest to Nikhef:

Top quark physics (Pieter H, Jeroen): top quark mass

Higgs searches (Mike, Cristina, Miruna, Lucian): SM Higgs bosonsearches, combination.See Lucian’s talk on the Z(→ µ+µ−)H channel

Not covered: searches for new phenomena (Pieter vdB)

mt

The systematics limits are not far off. . . yet there is steady progress!

1 Tevatron working group nowcombining many measurements,most of them updated to use 1fb−1

2 `+jets: Matrix Element methodworkhorse, largest weight in thecombination:

mt = 170.5±2.4(stat,JES)±1.2(syst)

Ideogram method (Pieter H) inprogress

3 Bare cross sectionmeasurements starting tobecome useful (Jeroen)

Mtop [GeV/c2]

Mass of the Top Quark (*Preliminary)Measurement Mtop [GeV/c2]

CDF-I di-l 167.4 ± 11.4

D!-I di-l 168.4 ± 12.8

CDF-II di-l 164.5 ± 5.6

D!-II di-l* 172.5 ± 8.0

CDF-I l+j 176.1 ± 7.3

D!-I l+j 180.1 ± 5.3

CDF-II l+j* 170.9 ± 2.5

D!-II l+j* 170.5 ± 2.7

CDF-I all-j 186.0 ± 11.5

CDF-II all-j* 171.1 ± 4.3

CDF-II lxy 183.9 ± 15.8

"2 / dof = 9.2 / 10

Tevatron Run-I/II* 170.9 ± 1.8

150 170 190

Many correlated uncertainties needto be accounted for (remember the

LEP EWWG?)

mt

The systematics limits are not far off. . . yet there is steady progress!

1 Tevatron working group nowcombining many measurements,most of them updated to use 1fb−1

2 `+jets: Matrix Element methodworkhorse, largest weight in thecombination:

mt = 170.5±2.4(stat,JES)±1.2(syst)

Ideogram method (Pieter H) inprogress

3 Bare cross sectionmeasurements starting tobecome useful (Jeroen)

(GeV)topM150 155 160 165 170 175 180 185

JES

0.94

0.96

0.98

1

1.02

1.04

1.06

1.08

1.1 -1913pb0+1+2 Tags

Calibrated 2D LikelihoodD0 RunII Preliminary

(mt, JES scale factor) contour fore+jets

mt

The systematics limits are not far off. . . yet there is steady progress!

1 Tevatron working group nowcombining many measurements,most of them updated to use 1fb−1

2 `+jets: Matrix Element methodworkhorse, largest weight in thecombination:

mt = 170.5±2.4(stat,JES)±1.2(syst)

Ideogram method (Pieter H) inprogress

3 Bare cross sectionmeasurements starting tobecome useful (Jeroen)

4 dilepton (e/µ) final states:insufficient kinematicconstraints, but kinematics stillaffected by mt:

mt = 173.7± 5.4(stat)± 3.4(syst)

5 Mass measurements usingpurely hadronic final statesongoing. . .

Resulting Constraints

By now, constraints on MH clearly limited by MW measurement!

80.3

80.4

80.5

150 175 200

mH [GeV]114 300 1000

mt [GeV]

mW

[G

eV]

68% CL

∆α

LEP1 and SLDLEP2 and Tevatron (prel.)

Higgs Boson Searches: Generalities

Search channels entirely determined by MH dependence of productioncross sections and decay branching fractions

1

10

10 2

10 3

100 120 140 160 180 200

qq → Wh

qq → Zh

gg → h

bb → h

gg,qq → tth

qq → qqh

mh [GeV]

σ [fb]

SM Higgs production

TeV II

low MH: H→ bb̄

high MH: H→WW(∗)

Associated Production: WH

Significant analysis improvements (Miruna, FF):

NN b-tagging

maximized efficiency

NN selection (small gaincompared to looking at mjj

spectrum)

NN output - 2 tags

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Even

ts

0

20

40

NN output - 2 tags

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Even

ts

0

20

40

DØ Preliminary-1L = 1.7 fb W + 2 jets / 2 b-tags

Data W + jets QCD

tt bWbother

WH115 GeV (x10)

NN output - 2 tags

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Even

ts

0

20

40 )2 (GeV/cHm105 110 115 120 125 130 135 140 145

)bb!

BR(H

×W

H)!p

(p"

Lim

it /

0

10

20

30

40

50

60

70

-1DØ Preliminary, L=1.7 fbb b# l !WH

Observed LimitExpected Limit

single/double b-taggingconsidered separately

here, ` = e, µ: analysis ofW(→ τν)H in progress

Plus a similar performance in theZ(→ νν̄)H channel (also includes

undetected leptons from W decays)

High-Mass Higgs Searches

tH W

+

W−

dilepton mode (relatively)background free

discrimination mainly on basisof kinematics: significant gainwhen using NN over∆φ(`+, `−)

nicely complemented byWH→WWW channel: lowstatistics but almostbackground free (like-signdileptons)

9

Neural Network Output 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

-210

-110

1

10

210

Higgs 160 GeV (After Cuts 1-6) data

ee!Z

"" !Z

QCD fakes

W W# l!W

WZ/ZZ

e e!tt 160 GeV Higgs

Higgs 160 GeV (After Cuts 1-6)

a) e+e− DØ Run II

Preliminary

Neural Network Output 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

-210

-110

1

10

210

Higgs 160 GeV (After Cuts 1-6) data

"" !Z

QCD fakes

W W

# l!W µ e!tt

µµ !Z

WZ/ZZ 160 GeV Higgs

Higgs 160 GeV (After Cuts 1-6)

b) e±µ∓ DØ Run II

Preliminary

NN

-0.4 -0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4

-110

1

10

NN

-0.4 -0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4

-110

1

10

Higgs 160 ""!Z

QCD

ZZ

tt

WZ

µµ!Z

#µ!W

WW

Data

H160

c) µ+µ−DØ Run IIa

Preliminary

NN

-0.4 -0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4

-210

-110

1

NN

-0.4 -0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4

-210

-110

1

Higgs 160 ""!Z

QCD

ZZ

tt

WZ

µµ!Z

#µ!W

WW

Data

H160

d) µ+µ−DØ Run IIb

Preliminary

FIG. 4: Distribution of the Neural Network Output after the final selection in the in the (a) e+e−, (b) e±µ∓, (c) µ+µ− Run IIaand (d) µ+µ− Run IIb final states. The expected signal for the Standard Model Higgs of mass 160 GeV is also shown.

Finally, the theoretical cross-section uncertainty on WW production is ∼ 4%. The systematic uncertainty on thenormalization factor is a sum of a combination of the PDF uncertainty (4%), the uncertainty on the NNLO Z/γ∗ → ""cross section (4%) and the statistical uncertainty (2 − 4%) on the data-to-MC normalization factor. The uncertaintydue to the trigger efficiency is conservatively taken to be 5% .

VII. RESULTS

A summary of the background contributions together with signal expectations and events observed in the dataafter the final selection is shown in the Tables III-V. Since after all selection cuts the remaining candidate events areconsistent with a background observation, limits on the production cross section times branching ratio σ ×BR(H →WW ∗) are derived for the Neural Network Analysis. Limits are calculated at 95 % confidence level using the modifiedfrequentist CLs approach with a Poisson log-likelihood ratio (LLR) test statistic [23]. The value of CLs is definedas CLs = CLs+b/CLb, where CLs+b and CLb are the confidence levels for the signal-plus-background hypothesisand the background-only hypothesis, respectively. The CLs method used in this analysis utilizes the binned NNdistributions (see Fig. 4) rather than simply the total number of events per channel. The expected background final

Analyses in all 3 (e/µ) dileptonmodes (W → τν ongoing),1.1 – 1.7 fb−1

“lucky” in all cases!

These analyses are clean and largelystatistics limited. . .

Combined Higgs Limit

17Gregorio Bernardi / LPNHE-Paris / W&C Dec. 07

Final variables used for the Combination

Final variables

(used to construct

likelihood ratio) for

“some” channels

Combined Higgs Limit

Significant work in combining results: understanding correlations, profilelikelihood, coverage tests. Now nearing SM at 160 GeV!

24Gregorio Bernardi / LPNHE-Paris / W&C Dec. 07

Lepton-Photon 2007 + latest updates

Higgs Analysis Projection

Beyond mere luminosity increase, expect improvements from varioussources:

more efficient lepton ID

additional channels (e.g.W → τν)

low MH: improved mjj

resolution (undetectedν, radiation)

27Gregorio Bernardi / LPNHE-Paris / W&C Dec. 07

Median expected Higgs sensitivity

Assumes two experiments

2010

2009

Projection: DØ X

2

By the time LHC produces Physics (end 2009) Precision EW measurements+ Tevatron could allow SM Higgs only with mass between 118 and 145 GeVdefinitely only a light Higgs boson, which will take several years to be foundat LHC (needs 5 fb-1) ! LHC/Tevatron complementarity H" !! vs H" bb

“Realistic” projections for 2009 and 2010

Conclusions

Steady advances in most analyses

Looking forward to next round of Higgs results!

Awaiting FNAL decision concerning running in 2010

Limit Setting Procedure

Adopted the CLs method and its likelihood ratio test statistic from LEP:

CLs =CLs+b

CLb, Q ≡

Nch∏i=1

Nbin∏j=1

(sij + bij)dij e−(sij+bij )/dij !

bdij

ij e−bij /dij !

The big issue (and difference with LEP):systematics! Fortunately, profilingtechniques help to reduce the effects ofsystematics (e.g., mjj sidebands in low-masssearches)

Systematics modeled as

bij → bij

∏k

(1 + f kij σksk)

with sk modeled according to standardGaussians, σk a priori uncertainties

2Gregorio Bernardi / LPNHE-Paris / W&C Dec. 07

Constraining Systematics Uncertainties with Data

“Profiling” AKA side band fittingNuisance parametersintroduced in the chi2 ofthe fit allow shifting ofcentral value of thebackground estimation

Systematic uncertaintywidth gets also constrained

Shape of the systematic isalso taken into account

Background prediction+ uncertainty

High-mass Higgs Search

Selection criteria for e±µ∓:1 two leptons, p

(1)T > 15 GeV,

p(2)T > 10 GeV, remove

Z→ e+e−, µ+µ− candidates

2 /ET > 25 GeV, /ET/∆(/ET) > 7

3 meµ < MH/2

4 min`=e,µ mT(`, /ET) > 65 GeV(for MH = 160 GeV)

5 ∆φ(e, µ) < 1.25 (forMH = 160 GeV)

6 HT ≡∑

jεjets pT,j < 70 GeV

Variables entering the e±µ∓ NN(after cut (1)):

p(1)T

p(2)T

meµ

∆φ(e, µ)

/ET

∆φ(e, /ET)

∆φ(µ, /ET)

min`=e,µ mT(`, /ET)

p(1)T + p

(2)T + /ET

MW

Blind measurement on 1 fb−1 of W → eν data ongoing

Ingredients:

e± measurement

underlying event

recoil

Emphasis on recoilmodeling (infer fromZ→ e+e− events):

in hard scatter

add’l interactions inthe same pp̄ collision

add’l pp̄ collisions

Underlying event in the electron cluster

measured in data should be modelled in the fast MC

the green is the underlying event that slips under the electron window

generate by fast MC

Underlying event energy measuredaway from the electron cluster and addedto the electron ..but zero suppression !

Aiming for ∼ 30 MeV overall systematic uncertainty. Compare with CDFmeasurement [PRL 99 (2007) 151801]:MW = 80413± 34(stat.)± 34(syst.) MeV