dØ results from run 2 · yuri gershtein d0 results from run 2: wine & cheese, july 26, 2002 3...

DDØØ Results from Run 2Results from Run 2

Yuri GershteinBrown University

for the DØ collaboration

Yuri Gershtein D0 Results from Run 2: Wine & Cheese, July 26, 2002 2

A Truly International Collaboration

Totals:18 countries

Europe, Asia, and North, Central and South Americas

73 institutions & labs

33 US40 non-US

646 physicists334 US312 non-US


Run 2 and our Physics Program Started March 2001

Ecm=1.96 TeVPeak L = 2.1·1031

Delivered ~ 50 pb-1

Detector commissioning almost completeFirst physics results from ~10 pb-1 at new Ecm

Physics ProgramTop, W, HiggsNew PhenomenaB-physicsQCD

Tevatron

Chicago↓

p

p CDF DØ

You Are HereYou Are Here


DØ Detector


DØ Detectormuon system

shielding electronics


DØ Detector

Central Calorimeter

SolenoidFiber Tracker

Silicon


Detector Performance: Tracking

KS → π+π-

p-side pulse-height (ADC)

n-si

de p

ulse

-hei

ght (

ADC

) p-side pulse-height (ADC)

Silicon cluster charge1 mip ~25 ADC #Noise < 2 ADC #

track pseudorapidity

fiber light yield

Scintillating Fiber Tracker (CFT)first time in a collider detector

• performs as expected • ε > 98% (including dead channels)• good light yield• reconstruct tracks Silicon (SMT)

• good S/N• 95% detectors are working• Clusters are being understood• ε>97% (incl. dead)

zero is suppressed


Detector Performance: Tracking

Impact Parameter

KS → π+π-

track

x

y

Secondary Vertices

mass π+π-

Almost on target with• no CFT alignment• 1st pass SMT alignment

DØ Run 2 Preliminary

width =36µbeam ~30µ

DØ resolution:~20µ


)2

mass (GeV/c1 1.5 2 2.5 3 3.5 4 4.5 5

2N

eve

nts

/ 10

0 M

eV/c

0

10

20

30

40

50

60

Run 2 Preliminary∅D

-e+ e→ ψJ/J/ψ→e+e-

Muon System

Calorimeter

J/ψ and ψ’

E/P0 0.5 1 1.5 2 2.5 3

Eve

nts

/ 0.0

50

50

100

150

200

250Chi2 / ndf = 0.5317 / 4

156.4 ±p0 = 105.6

490.4 ±p1 = -411.3

459.2 ±p2 = 530.6

141.7 ±p3 = -192.2

26.31 ±N = 147.6

0.01741 ±Mean = 1.031

0.02659 ±Sigma = 0.165


candidate eventsν e→W

>20 GeVmissT>20 GeV, Eel

TP

E/P Chi2 / ndf = 0.5317 / 4

156.4 ±p0 = 105.6

490.4 ±p1 = -411.3

459.2 ±p2 = 530.6

141.7 ±p3 = -192.2

26.31 ±N = 147.6

0.01741 ±Mean = 1.031

0.02659 ±Sigma = 0.165

W→eν

E(cluster)/p(track)

2GeV/c3.5 3.55 3.6 3.65 3.7 3.75 3.8 3.85

0

10

20

30

40

50

mass -µ +µ mass -µ +µ Combine tracking with other systems

Detector Performance

Z→µ+µ-

~170 evts


[GeV]jjM200 300 400 500 600 700

[nb/

GeV

]2η

d1η

d jjpa

rtia

lly c

orre

cted

dN

/LdM

10-4

10-3

10-2

10-1

Cone algorithm, R = 0.7

| < 0.41,2η |

| < 0.71,2η 0.4 < |

DØ preliminary

Jet Physics

Only statistical errorsLuminosity L = 5.8 pb-1 (±10%)Preliminary jet energy scale

30-50% syst. error in cross section

Not fully corrected(for unsmearing, efficiencies)

Testing pQCD at new energy2x cross section for ET>400 GeV

Structure functions at large xCompositeness, W’, Z’, etc…

[GeV]Tp50 100 150 200 250 300 350 400

[nb/

GeV

]ηd

Tpa

rtial

ly c

orre

cted

dN

/Ldp

10-4

10-3

10-2

10-1

1

10

Cone algorithm, R = 0.7

| < 0.4η |

| < 0.7η 0.4 < |

DØ preliminary

Inclusive jet pT spectrum

Dijet mass spectrum


0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

1

10

102

Graph

B Physics

20 30 40 50 60 70 80 90 10010-4

10-3

10-2

10-1

1

Run 2 Preliminary Data

MC

R = 0.5 Cone Jets

| < 0.6jetη|

> 4 GeV/cµTp

| < 0.8µη|

) < 0.7µR(jet, δ

EJet [GeV]T

d[n

b/10

GeV

]d/

σE

T

DØ Run 2 PreliminaryDataPYTHIA

New tracking in 2 Tesla fieldMuon triggers up to |η|< 2

b-quark Production Cross SectionNew ECM

Luminosity ~5 pb-1

Jet |η| < 0.6muon tag only, b-content from pT

rel fits

J/ψ Cross Section MeasurementLuminosity ~5 pb-1

First measurement in this rapidity region and ECM

J/ψ pseudorapidity

pT( J/ψ ) > 5 GeVpT( J/ψ ) > 8 GeV

cros

s se

ctio

n, a

u


) [GeV]+,K-µ,+µM(5 5.1 5.2 5.3 5.4 5.5 5.6 5.7

0

2

4

6

8

10

0.021 GeV±Mean = 5.277 0.014 GeV±Sigma = 0.057

D0 Run 2 Preliminary

+(-) KΨ J/→ +(-)B

B Physics

Proper decay length (cm)-0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25 0.3

mµE

ven

ts/5

0

1

10

102

103

Proper decay length (cm)-0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25 0.3

mµE

ven

ts/5

0

1

10

102

103

Data

Background from sidebands

ψBackground + prompt J/

B lifetime signal

Signal+background

D0 Run II Preliminary

+ X)ψ J/→Average B lifetime (B Proper B decay length (B J/ψ+X)DataBackground from sidebandsBackgrounds from prompt J/ψB-lifetime signalSignal + background

mass (µ+µ-K±)

B lifetime measurement from inclusive J/ψ

• Measured lifetime consistent with the world average

• Track errors (esp. from large SMT clusters) are being understood

Exclusive B reconstruction

• B±→J/ψ K±

• First time in DØ• Expect more soon!

~5 pb-1


Electroweak PhysicsHigh priority measurements

W→eν cross-section

25 30 35 40 45 50 55 60 65 70 75

0

100

200

300

400

500

600

0 10 20 30 40 50 60

0

100

200

300

400

500

600

700

800

25 30 35 40 45 50 55 60 65 70 75

0

100

200

300

400

500

600

30 40 50 60 70 80 90 100 110 120

0

100

200

300

400

500

ET

/GeV

T/GeVM

DO Run2 Preliminary

ET

/GeV

pT/GeV

a)

c)

b)

d)

dots: Datadots: Datahistogram: MChistogram: MC

Di-Electron Mass (GeV)0 20 40 60 80 100 120

Ev

en

ts /

2 G

eV

0

20

40

60

80

100

Number of Entries: 604

Peak Mass: 90.8 +- 0.2 GeV

Width: 3.6 +- 0.2 GeV

D0 Run II PreliminaryET ETe

MT pTw

diEM Invariant mass (GeV)

Z→e+e- cross-section


W and Z Production Cross Section

Data Sample:Luminosity ~ 7.5 pb-1

No. of W→e: 3493±75±296No. of Z →ee: 186±14±10

First measurements of the cross sections at 1.96 TeV!

10 2

10 3

1Center of Mass Energy (TeV)

σ W, Z

× B

(pb)

DØ Run2 Preliminary

Center of Mass Energy (TeV)Center of Mass Energy (TeV)

pp_ → W+X → lν+X

pp_ → Z+X → ll+X

DØ(e) Run2DØ(e)CDF(e) CDF(µ)UA1 UA2

DØ(µ)

DØ

pb 212020266)(

lumisyststat

Z eeZB±±±

=→×σ

nbeWB lumisyststatW 27.033.006.067.2)( ±±±=→× νσ

NNLO Van Neerven et al


W and Z Production Cross sectionSince we can measure both: Ratio of cross sections

Most of the systematic effects cancel out

W boson width can be calculated from the above formulaUsing σ(W)/σ(Z) from theory and BR(Z ee) from LEP

In good agreement with world average

ΓW = 2.135±0.069 GeV

WZ

ZWsyststat

Z

W

eeZeW

eeZBeWBR

Γ→Γ⋅Γ→Γ⋅

=±±=→⋅→⋅

=)()(6.08.00.10

)()(

σνσ

σνσ

GeV 04.013.018.026.2 theorysyststatW ±±±=Γ


2GeV/c20 40 60 80 100 120

0

2

4

6

8

10

12

14e+jets data

multijet background

DØ Run 2 PreliminaryW + >= 2 jets

W/Z boson + jets eventsJet multiplicity distributions

W+≥ 2jetsTransverse massspectrum

•Top Physics: W+≥3jets, Z+≥2jets•Higgs Physics: W/Z +≥ 2jets

•Need excellent b-jet identification•Secondary vertex recons.•Soft leptons in jets

JetsN0 2 4 6

Eve

nts

1

10

102

Events with

Jets N≥no. of Jets

candidates-µ +µ →0Z

DØ Run II Preliminary

Z→µ+µ-

W→eν

Multi jet BGMulti jet BG


WW productionSearch for ee+ET eventsA lot of interest in this channel (tri-linear couplings, New Phenomena)Exotic Higgs Models:

4th SM family enhance Higgs cross sections by a factor of ~8.5 for Higgs mass between 100-200 GeV

Fermiophobic/Topcolor Higgs: BR(H WW) >98% for mH ≥ 100 GeV

Backgrounds due to misidentified objects.Azimuthal opening angle between the leptons

Require good e+e- Require good

e+e- , missing ET,

no jets

luminosity8.8 pb-1

/


Search for New Phenomena

eta

4.7

0

-4.7

1 2

3

-1 -2

-3

phi180

0

360

ET(GeV)

10

Run 152415 Event 603157 Wed Jun 19 07:23:52 2002

y

x

ET scale: 7 GeV

-1.5 1.5

Run 152415 Event 603157 Wed Jun 19 07:24:01 2002

An eeµ candidate

Tri-lepton signaturesOne of cleanest signatures of SUSY for example from chargino+neutralino production

Analyses in progress:Likesign dielectronsJets+Missing Et


GMSB SUSY

XGG

ZWgauginospp

++→

+→→~~

,, 01

01

γγ

χχγ

0 10 20 30 40 50 60 70 80 90 100

10-1

1

10

Missing Transverse Energy, GeV

Phenomenology:Light Gravitino (<<eV) is LSP, NLSP can be neutralino or slepton

If neutralino NLSP:

⇒inclusive search for γγET + XBackgrounds:

QCD: γγ, γ+j (w/ jet misidentified γ)

Wγ →eνγ (track is lost)WW, WZ, DY,

Sensitivity is still too low to exclude SUSY points“Model Independent” Limit

Missing Transverse Energy


γγ

QCD+DY

CLpb %[email protected]<σ


St [GeV]0 100 200 300 400 500 600 700 800 900 1000

Nev

ents

/25G

eV

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5 DØ Run 2 Preliminary

Data

Background

LQ (100 GeV)

LQ (140 GeV)

St = scalar sum of Et of 2e2j

Leptoquarksparticles with properties of both quarks and leptonsSignature: eejj events

MLQ > 113 GeV/c2

at 95% CL, for β=1

β2×C

ross

Sec

tion

[pb]

Consistent with Run1 result

8.8 pb-1

Data : 6 eventsBackground : 6.9 ± 2.9 eventsLQ (m = 100 GeV) : 13.8 ± 1.8 eventsLQ (m = 140 GeV) : 2.9 ± 0.3 events

BG from QCD and DY

LQ Mass, GeVΣET of electrons and jets, GeV


Extra DimensionsSearch for large extra spatial dimensions via virtual graviton effects e+e-, γγ and µ+µ- events

Run2 Preliminary Limit:MS(GRW) > 0.92 TeV (ee,γγ)

DØ Run 1 limits:MS(GRW) > 1.2 TeVProspects for Run 2:

1.5-2.5 TeV (2fb-1)2.1 – 3.5 TeV (20 fb-1)

SM

SM+ED

DATA

instrumental background (from data)


Future ProspectsContinue to Search for New Physics

SUSY, strong dynamics, extra dimensions, etc…

Measurements of cross sections at 1.96 TeVW and Z boson production, jet cross sectionsb-quark production, top quark production

Measure W/Z Properties (AFB, W mass to 30 MeV)Rich program of B-physics Comprehensive study of Top quark Properties (2fb-1)

Cross section(7%), Mass (2 GeV) spin correlations, charge, top-gauge boson couplings

Precision measurements of Top quark and W Boson mass ⇒constrain the Higgs BosonDirect Searches for the Higgs Boson

Run 2A: MH > 115 GeVRun 2B: MH > 180 GeV or see signal


ConclusionFirst physics results at 1.96 TeV

W and Z production cross sectionsfirst generation LQ limit, limit on Large Extra Dimensions, manymore analyses in the works

Enormous progress made over the last year detector performance optimizationdeveloping analysis tools

Improvements in store:optimization of event reconstruction and selection procedures triggers and DAQ performancescalibration and alignment of the detectors

Looking forward to large integrated luminosity!

dØ results from run 2 · yuri gershtein d0 results from run 2: wine & cheese, july 26, 2002 3...

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