cdf results for ichep 2008

CDF Results for ICHEP 2008

Chris Hays, Oxford University

Fermilab Wine and Cheese July 25, 2008

July 25, 2008 C. Hays, Fermilab Wine and Cheese 2

Tevatron Run II

Studying the Standard Model at an unprecedented

scale

Measurements build up the Standard Model

Searches probe for cracks


CDF Run II145145 publications in Run II

5252 new results since Moriond

Analyses with up to 3 fb-1 of data

Thanks to the accelerator division!


Building the Standard Model:

Light Quarks and Gluon


Proton-Antiproton Collisions

Non-perturbative QCD in every collision Probe by studying underlying event

Separate underlying event from perturbative process using Drell-Yan productionDefine regions relative

to boson pT :

toward, transverse,

away

Compare charged particle observables to model

predictions

PYTHIA tune "AW" models underlying event well

Standard HERWIG underestimates multiplicity

"away"

"transverse"

"toward"

pTZ

2.7 2.7

fbfb-1-1


Differential Cross Sections

Measure momentum & multiplicity distributions from inelastic collisions Unfold detector response and correct for diffractive background

0.5 0.5

fbfb-1-1


Diffractive W and Z Production

Focus on clean process of pomeron radiation from antiproton Study pomeron structure function using weak boson production

Roman pots measure outgoing antiproton momentum

Directly measure pz of neutrino from W boson decay

Single diffraction cross section / total cross section:

W's: 0.95 ± 0.05 ± 0.11% Z's: 0.85 ± 0.20 ± 0.11%

W,Z

p

p

pP

0.6 0.6

fbfb-1-1



Bottom Quark


B-meson Lifetime Measurements

Lifetimes predicted using heavy quark expansion

1.0 1.0

fbfb-1-1

GF2 mb

5 = 192 3

|Vcb|2 A0 + A2 +

A3([

QCDm

b

)2

(QCDm

b

)3

]

Bc c = 142.5 +15.8-14.8 ±

5.5 mWorld average c = 137.7 ± 11.0 m

New CDF method accounts for trigger bias using data Trigger requires tracks with large impact parameters

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Bc lifetime in J/ l

B± c = 498.2 ± 6.8 ± 4.5 m

Applied to B± → D0±

Use per-event acceptance function when calculating likelihood

Can reduce systematic uncertainties

J/Bc


b Lifetime MeasurementLifetime ratios predicted to O(1/mb

4): (b0)/(B0) =

0.88 ± 0.05Longstanding tension between prediction and measurements

World average (2006): 0.804 ± 0.049 Recent CDF measurement in J/ 2 above world

average

New CDF measurement uses c+- decay



1.1 1.1

fbfb-1-1

b c =

422.8 ± 13.8 ± 8.8 m

(b0)/(B0) =

0.922 ± 0.039

World's most

precise measurem

ent

b c

-


s Measurement

Complex Higgs-q-q Yukawa couplings give rise to CKM matrix

2.8 2.8

fbfb-1-1

Wolfenstein parametrization

Unitarity requires combinations of different columns to sum to zero Triangles in the complex plane

s

Not SM

Winter conferences:

DØ (2.8 fb-1): 2s = (-0.06, 1.20) at 90% CL (6.6%

consistency with SM)

CDF (1.4 fb-1): 2s = [0.32, 2.82] at 68% CL (15%

consistency with SM)

UTfit: "This is a first evidence of physics beyond the This is a first evidence of physics beyond the

Standard Model"Standard Model"

0802.4258

PRL 100,161802

(= 0.02 in SM

0803.0659


s Measurement in J/BBss mixing: mixing: Flavor eigenstates oscillate (Bs

0 ↔ Bs0) with frequency m

= 17.77 ps-1

Measure lifetime difference () and CP asymmetry (∝ sin2s) in

J/ decaysCP violation due to interference with and without mixingComplication: J/ not a CP eigenstate

Use angular distributions to separate longitudinal, parallel, transverse polarizations

Combine with decay time and Bs0/Bs

0 tagging to obtain likelihood

for , and s

2.8 2.8

fbfb-1-1

PRL 97,242003

3166 Bs0 candidates

7% consistency with SM



Top Quark


Top Quark Cross SectionMeasurements in "lepton + jets" decay mode with and without b-jet tagging

2.8 2.8

fbfb-1-1

BR(lepton + jets) = 30%30% (lepton = e,)

No tagging:No tagging: Neural network separates tt from W + jets b-jet tagging:b-jet tagging: Based on either long b-hadron lifetimes

or semi-leptonic b-hadron decaystttt = 6.8 = 6.8 ± 0.4 (stat) ± 0.6 (sys) ±

0.4 (lum) pb pb

No tagging:No tagging: Lifetime-based Lifetime-based bb-jet tagging:-jet tagging:tttt = 7.2 = 7.2 ± 0.4 (stat) ± 0.5 (sys) ±

0.4 (lum) pb pb

tttt = 8.7 = 8.7 ± 1.1 (stat) +0.9-0.8 (sys) ±

0.6 (lum) pb pbbb → → XX tagging (2.0 fb tagging (2.0 fb-1-1):):

tttt = 7.8 = 7.8 ± 2.4 (stat) ± 1.5 (sys) ± 0.5 (lum) pb pb

bb → → eXeX tagging tagging (1.7 fb(1.7 fb-1-1):):


Top Quark Cross SectionMeasurements in "dilepton + jets" decay with and without lifetime-based b-jet tagging

2.8 2.8

fbfb-1-1

BR(dilepton + jets) = 5%5% (lepton = e,)

Combine with lepton + jets measurements

tttt = 6.7 = 6.7 ± 0.8 (stat) ± 0.4 (sys) ± 0.4 (lum) pb pb

No No taggingtagging::

With tagging:With tagging:tttt = 7.8 = 7.8 ± 0.9 (stat) ± 0.7 (sys) ± 0.5 (lum) pb pb

9% precision8% theory uncertainty


Top Quark MassTop quark loops contribute to the W & Z boson masses

mt2-dependent correction drowns ln(mH/mZ) Higgs

loop correctionNeed precise top mass measurement to constrain Higgs mass

Winter conferences: mt = 172.6 ± 1.4 GeV, mH = 87+36-

27 GeV

2.8 2.8

fbfb-1-1

Measurement in lepton + jets channel most precise (winter conferences:

mt = 172.7 ± 2.1 GeV)

Integrate matrix element over resolutions and unknowns to obtain unbinned likelihood Function of top mass and jet energy scaleNeural network separates signal from background

mmtt = 172.2 ± 1.0 (stat) ± 0.9 (JES) ± 1.0 (sys) GeV = 172.2 ± 1.7 = 172.2 ± 1.7 GeVGeV

Also: Updated measurement in dilepton + jets channel

Uses likelihood based on weighting events in 1-2 plane

mt = 165.1+3.3-3.2 (stat) ± 3.1

(sys) GeV

(Tevatron, 0803.1683)


Top Quark MassJet energy scale dominates systematic uncertainty in top mass reconstructionPursue alternative mass measurements largely independent of energy scale

b-jet lifetime:b-jet lifetime: proportional to b-quark pT

lepton plepton pTT:: dependent on W pT

1.9 1.9

fbfb-1-1

Combination: m mtt = 175.3 ± 6.2 (stat) ± 3.0 = 175.3 ± 6.2 (stat) ± 3.0 (sys) GeV(sys) GeV

Lifetime: mt = 176.7+10.0

-8.9 (stat) ± 3.4 (sys) GeV

Lepton pT: mt = 173.5+8.9

-9.1 (stat) ± 4.2 (sys) GeV


Single Top Production 2.7 2.7

fbfb-1-1

Top produced weakly in s-channel (tb = 0.9 pb) or t-

channel (tq = 2.0 pb)

Cross section directly measures Vtb magnitude

Unique test of CKM unitaritySingle top cross section overwhelmed by W + jets backgroundAdvanced techniques required to separate signal from backgroundtt-channel likelihood function: -channel likelihood function: 7 (10) input variables for 2- (3)-jet

final states

ss-channel likelihood function: -channel likelihood function: 6 input variables for 2-jet final

state


Single Top Production 2.7 2.7

fbfb-1-1

Matrix-element Matrix-element probabilityprobability: :

Combines s & t channels

Boosted decision tree:Boosted decision tree:Four trees: 2 or 3 jets with 1

or 2 tags

Neural network:Neural network:Four networks:

2 or 3 jets with 1 or 2 tags





Leptons and Electroweak Bosons


W Boson Mass 2.4 2.4

fbfb-1-1

W mass precision the primary limitation on indirect Higgs mass constraint Also constrains other scalars with weak charge (e.g.,

superparticles)

Published measurement with 200 pb-1 has 48 MeV uncertainty (world's best)Dominant uncertainties expected to scale with square root of luminosity Now analyzing 12x data:

PRL 99,151801 PRD 77,112001

97k Z → ll 97k Z → ll eventsevents

1.4M W → l1.4M W → l eventsevents

Expect total Expect total uncertainty < 25 MeVuncertainty < 25 MeV

Z → Z → W → eW → e



The Higgs Boson


The Higgs Boson 3.0 3.0

fbfb-1-1

The last unobserved particle in the standard model Only fundamental scalar

Gives fermions and weak bosons their masses Responsible for generational mixing

Narrow allowed mass region

Direct 95% CL limit: mmHH > 114 GeV > 114 GeV

Indirect 95% CL limit: mmHH < 160 GeV < 160 GeVHiggs boson at the Tevatron:

(pb)

Higgs boson at CDF:All dominant channels updatedNew channels added All include improvements: scale better than luminosity


Higgs Searches (mH ≲130 GeV)

2.7 2.7

fbfb-1-1

Use W/Z + H production at low mass Significantly suppresses background

Leptonic boson decays provide further suppression Balance loss in cross section with large H → bb BR

WHWH → → llbbbbNeural network

approach:Six categories based on lepton type and number

of b-tags

QuickTime™ and aTIFF (LZW) decompressor


mH = 115 GeV:

< 5.0 x < 5.0 x SM SM

(5.8 x SM expected)

winter conferenc

es: < 7.1 x

SM expected



Added trigger to extend Added trigger to extend muon coveragemuon coverage

Matrix element probability +

boosted decision tree:

ME likelihoods among 21 inputs

< 5.8 x SM < 5.8 x SM (5.6 x SM expected)





2.4 2.4

fbfb-1-1

ZHZH → → llbbllbb2-dimensional neural network:

13 input variables separate ZH from tt and Z+jets

mH = 115 GeV:


winter conferences: < 16 x SM

expected

Matrix element probability:

mH = 120 GeV:


Less data and lepton coverageBetter sensitivity for overlap sample



2.1 2.1

fbfb-1-1

ZHZH → → bb + WHbb + WH → → llbbbb

mH = 120 GeV:

< 38 x SM < 38 x SM (40 x SM expected)


are needed to see this picture.Added H1 algorithm

using charged-particle tracks to

improve jet energy resolution

mH = 115 GeV:


winter conferences: < 8.3 x SM

expected

7 inputs to neural network

WH + ZHWH + ZH → → qqbb qqbb Matrix element procedure



ME discriminant

CDF Run II Preliminary


Higgs Searches (mH ≳130 GeV)

3.0 3.0

fbfb-1-1

Traditionally focus on direct Higgs production High branching ratio to WW

H → WW → ll low-background final state

Additional sensitivity with new modes

HH → → WWWW

Neural network:Uses matrix element

likelihood as a discriminant in events

with no jets

Large boson branching ratio to quarks

Provides 30% additional acceptance

qqH

WH + ZH + qqHWH + ZH + qqH → →

qqWWqqWWmH = 160 GeV:


winter conferences: < 2.5 x SM

expected


Combination: < 1.6 x SM< 1.6 x SM

(1.8 x SM expected)

Also: WH → WWW → lll

< 33 x SM < 33 x SM (33 x SM expected)


Breaking the Standard Model:

Supersymmetry

±


Stop and Sbottom Production

2.7 2.7

fbfb-1-1



mgluino - msbottom = 20 GeV





QuickTime™ and a decompressor


QuickTime™ and a decompressor


Supersymmetry solves the hierarchy problem, predicts coupling unification, has

a dark matter candidate, and is required by string theory Superpartners of every particle, differing in spin by 1/2

Searches for stop and gluino-mediated sbottom production


Chargino + Neutralino and Sneutrino Production

2.0 2.0

fbfb-1-1

Chargino + neutralino searchSpin 1/2 partners of gauge and Higgs bosons mix to form charginos and neutralinos

Limits set in m0-m1/2 plane of constrained SUSY

Sneutrino searchResonant production if R-parity violated

e, e, final states

m > 586 GeV

(e)487 GeV

(e)484 GeV

()for

couplings 0.05-0.1



Neutral Resonances

'


Resonance Decays to Dimuons

2.5 2.5

fbfb-1-1

New U(1) symmetry ubiquitous in models: versions of supersymmetry, unified theories Excited graviton states predicted in warped extra dimension theoriesBoth predict resonances decaying to dileptons, likely at Electroweak mass scale

'

Winter conferences: dielectron search showed excess at mass around 240 GeV

0.6% probability to be a background fluctuationNew search in dimuon channel: similar sensitivity to a resonance with this massProbe 1/m spectrum: resolution constant vs 1/m

Most significant excess at 103 GeV6.6% probability to be due to background

Set mass limits on Z' and gravitons



A Fourth Generation

'

'


Fourth Generation Top Quark

2.8 2.8

fbfb-1-1

t' can lead to large s and D0 mixing (Hou, Nagashima, and Soddu, PRD

76, 016004)

Search for t' in lepton + jets final stateReconstruct hypothesized t' mass and search in plane of mass vs total transverse energy

'

1% consistency between data and SM at this mass mt' > 311 GeV


CDF Run II:ICHEP 2008

Reaching the peak of the physicsReaching the peak of the physicsBroad program with many exciting Broad program with many exciting resultsresults

New results not shown today:New results not shown today:Z + jets cross sectionInclusive photon cross sectionX(3872) mass measurementSearch for narrow resonances below the Search for Bs/d → eGluon fusion fraction of top productionW helicity measurement combinationLimits on top decay to non-SM final statesAnomalous single top production

Search for charged Higgs in top decaysAnomalous ZZZ couplingsSearch in photon + missing pT + jet

Search in photon + missing pT + b-jet

Search in photon + missing pT + b-jet + lepton

Maximal-flavor-violation in same-sign top productionTechnirho productionLeptoquark production

See See http://www-cdf.fnal.gov/physics/S08CDFResults.htmlhttp://www-cdf.fnal.gov/physics/S08CDFResults.html for more details for more details


The Standard Model at ICHEP 2008

Closing in on the final pieceClosing in on the final pieceAre we seeing a new wrinkle?Are we seeing a new wrinkle?


Backup


Top Quark Pair ProductionStandard Model predicts 85% qq annihilation and 15% gluon fusion

2.0 2.0

fbfb-1-1

Leptons go in same direction when J = 0

J = 1

J = 0

t spin: t spin:

ll++ momentum: momentum:

Top quark decays via W+: left-handed top decays to right handed l+ t spin: t spin:

ll-- momentum: momentum:

Measure gluon fusion fraction through lepton azimuthal correlation

qq annihilation

gluon fusion

Distribution

sculpted by event selection

gluon fusion

fraction:5353+36+36

-38-38%%


Anomalous ZZZ Couplings1.9 1.9

fbfb-1-1

cdf results for ichep 2008

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chris hays

oxford universityfermilab

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