ＣＤＦの最新結果

筑波大学数理物質研究科

佐藤構二

「フレーバー物理の新展開」研究会2010

年 2月23日

Tevatron Run II

p – p collisions at

s = 1.96 TeV

(1.8 TeV in Run I).

Run II started in

Summer 2001.

Particle physics at

the highest energy!

CDF Collaboration

• ~600 people from 14 Countries.• Japanese collaboration

– KEK

– Osaka City University

– Okayama University

– University of Tsukuba

– Waseda University

Tevatron Run II — Luminosity Status

• Typical Peak Luminosity : 3 1032 cm2 s-1.

• Delivers 60 - 70 pb-1/week.

• Integrated Luminosity

– Delivered: 7.9 fb-1 ,Recorded: 6.7 fb-1.

• Recent analyses typically use up to 5 fb-1.

• Running in 2010. Possible running in 2011.

Run II since

Summer 2001

Collider Detector at Fermilab

Multi-purpose detector

Tracking in magnetic field.

Coverage |h|<~1.

Precision tracking with silicon.

7 layers of silicon detectors.

EM and Hadron Calorimeters.

sE/E ~ 14%/E (EM).

sE/E ~ 84%/E (HAD).

Muon chambers.

Contents• Top physics

– Pair production cross section

– Mass measurement

– Property measurements

– Single top observation

• Direct search for Higgs Boson

– Standard Model Higgs

Top Physics

Top Physics at Tevatron

• Top quark was observed at TEVATRON in 1995.

• Top is still the least studied observed particle.

• Any deviation from SM might suggest new physics!!

• Top mass is unexpectedly heavy ~35mb.

– Special role in EWSB? p

p t

b

W-

q

q’

t b

W+

l+

n

X

Production cross-section

Resonance production

Production kinematics

ttbar Spin correlation

Top Mass W helicity

|Vtb|

Branching Ratios

Rare/non SM Decays

Anomalous Couplings

CP violation

Top lifetime

Top Charge

Top Width

_ _

_

_

BR (%) Bkgd.

Di-lep. 5 Low

L+jets 30 Moderate

All had. 44 High

+X 21 -ID hard

ttbar decay modes:

Top Pair Cross Section (L+jets)

~85% ~15%

• Top quark is mostly produced in pairs at Tevatron.

Event selection:

• 1 lepton Pt>20, |h|<2.0

• MET>25

• ≥3 jets with Pt>20 , |h|<2.0

• ≥ 1 jet b-tagged

stt = 7.14 ± 0.34 (stat.) ± 0.58 (syst.) ± 0.14 (theory) pb (4.3 fb-1)

stt = 7.04 ± 0.34 (stat.) ± 0.55 (syst.) ± 0.43 (lumi.) pb

The dominant luminosity systematic can be canceled out by

measuring ratio stt /sZ.

s(NLO) = 7.4 +0.5-0.7 pb

Top Pair Cross Section• Cross section is sensitive to both

production and decay anomaly.

• The difference between different

decay modes might indicate new

physics.

• CDF measures xs with various decay

modes/methods, and the results are

consistent with SM.

L+jets Top Mass Measurement with

Matrix Element Method• Construct likelihood for Mt

and Jet Energy Scale (JES) with Signal Matrix Element calculation.

– JES had been the dominant systematic source.

• Simultaneously fit Mtop and JES.

– JES constrained by hadronically

decaying W→qq’ in candidate events.

t

t

q

q

g

g

b

b

W+

W-

l+

n

q’

q15% 85%

100%

100%

Constrain

Dijet mass

To MW

mt = 172.6±0.9 (stat.)±0.7 (JES)±1.1 (syst.) GeV/c2

= 172.6 ± 1.6 (total) GeV/c2

Top Mass Tevatron CombinationUse only best analyses from each

decay mode, each experiment.

Mhiggs < 157 GeV/c2 (95% CL) .

Mhiggs < 186 GeV/c2 w/ LEP direct search limit.

Before Run II results

(Spring 2004):

Mtop = 178.0 4.3 GeV/c2

mhiggs251 GeV/c2 (95% CL)

Mtop = 173.1±1.3 GeV/c2

(winter 2009)

Search for tt Resonance

• Cross section limit on neutral vector resonance.• Top color assisted technicolor

predicts leptophobic Z’ with strong coupling to 3rd generation quarks.

Limit on Z’ with G=1.2%xMZ’

MZ’ > 805 GeV (2.8 fb-1)

t

tq

q

b

b

W+

W-

q’’’

q’’q’

q

?

Analysis in all hadronic channel.

No significant

excess

Forward Backward Assymmetry

• L+jets analysis.

• Measure rapidity yhad of

hadronically decayed top.

• SM predicts at NLO:

Afbpred. = 0.05 0.015

t

t

q

q

g

g

b

b

W+

W-

l+

n

q’

q

yhad

Ql

Afb = 0.193 +- 0.065 (stat) +- 0.024 (syst) (3.2fb-1)

~2s effect!

y<0 y>0

Spin Correlation• Top does NOT hadronize (unique about top quark).

– SM prediction : top~0.4x10-24 s << 1/LQCD10-23 s

• Spin information will be inherited by decay products.

Signal: SM predicts k~0.8.

Bkgd:

k= 1 k= -1

-0.455<κ<0.865 (68% C.L.)

2.8 fb-1

Single Top Production• Top quark is sometimes singly produced Tevatron.

0.884±0.11 pb (NLO)

1.98±0.25 pb (NLO)

• 1 lepton, MET, 2 or 3 jets

• S/B separation by Matrix Element (ME)

|<2.8

Signal MEbkgd ME

st+s-chan = 2.5 +0.7-0.6 pb (3.2 fb-1)

4.3 seffect

t-channel

Vtb

Vtb*

s-channel

Vtb

Vtb*

5.0 sobservation!!

t-channel

Vtb

Vtb*

Single Top Combined Result

st+s-chan = 2.3 +0.6-0.5 pb

st-chan = 0.8±0.4 pb

ss-chan = 1.8+0.7-0.5 pb

|Vtb| = 0.91 ± 0.11 (exp.)

± 0.07 (theory)

s-channel

Vtb

Vtb*

0.884±0.11 pb (NLO) 1.98±0.25 pb (NLO)

Direct Search

for SM Higgs Boson

Production Cross Sections

recently observed

by CDF!

SM Higgs Properties at Tevatron

bb WW• mH<135 GeV (low mass):

– gg→H→bb is difficult to see.

– Look for WH/ZH with leptonic vector boson

decays.

• mH>135 GeV (high mass):

– Easiest to look for H→WW with one or two W

decaying to lepton.

WHlnbb (low mass)

• S/B separation by NN.

• Four tagging categories, using 3 algorithms

(including NN tagger).

• New NN b-jet energy correction

See Nagai’s presentation!

• 3 b-tag categories with 2 algorithms.

• S/B separation by NN.

• Improved lepton coverage with forward EM clusters.

• Dominant backgrounds:– Z+jets, top, diboson

ZH ll+bb (low mass)l

l

tight 2 b-tag

1 b-tag

(mH=120 GeV)

WH/ZHMET+bb (low mass)

• Target process: ZHnnbb

– Also complementary to WHlnbb and ZHllbb searches.

• 3 b-tag categories with 2 algorithms.

• S/B separation by NN.

• Dominant backgrounds:– QCD with MET miscalculation

– W/Z+jets, top, diboson

(mH=115 GeV)

tight 2 b-tag + loose 2 b-tag

H WW*l+n l-n (high mass)• Opposite sign 2 leptons.

– Lepton acceptance improved by using isolated tracks.

• S/B separation by NN.

– Matrix element calculation result input to NN.

• Newly including low Mll channel.

• Dominant background

– DY, Diboson, top

(mH=165 GeV)

Summary of Higgs Search

• Elaborate analyses are already there for most promising channels.

• Striving for further improvement.

• New channels are being explored.

CDF Combination

mH (GeV) CDF

115 3.12 x sSM

165 1.18 x sSM

Tevatron Combination

mH (GeV) CDF CDF+D0

115 3.12 x sSM 2.19 x sSM

165 1.18 x sSM 163-166 GeV

excluded

B Physics

See Miyake’s presentation!

Summary• TEVATRON and CDF Run II are operating pretty well!

– CDF has already collected ~6.7 fb-1 of data.

• Possible running in 2011.

• CDF keeps producing impressive physics results.

– Top properties are studied closely.

• Top pair cross section precision is 6.5% (better than theory).

• Single top production has been observed.

• Top mass precision is 0.7 %.

– Higgs boson is intensively searched for, with increasing sensitivity.

• 163<MH<166 GeV mass region has been excluded.

• No obvious signs of new physics so far, but stay tuned!

– CDF is keeping a heavy challenge on SM.

TEV status Backup

Tevatron Status

Tevatron FY2011 Projection

FY11 start

Real data for FY02-FY09

12.0 fb-1

10.0 fb-1

Highest Int. Lum

Lowest Int. Lum

FY10 start

0

1

2

3

4

5

6

7

8

9

10

11

12

13

Higgs Backup

WH WWW*l±n l±n +jets(high mass)

• Same sign 2 leptons.

– Lepton acceptance improved by

using isolated tracks.

• S/B separation by NN.

• Dominant background

– DY, Diboson, W+jets

CDF Higgs Sensitivity Projections

• S/B separation by NN.

• 3 b-tag categories with 2 algorithms.

• Improved lepton coverage with forward EM clusters.

• Dominant backgrounds:– Z+jets, top, diboson

ZH ll+bb (low mass)

l

l

tight 2 b-tag

loose 2 b-tag

1 b-tag

(mH=120 GeV)

WH/ZHMET+bb (low mass)

• Target process: ZHnnbb

– Also complementary to WHlnbb and ZHllbb searches.

• S/B separation by NN.

• 3 b-tag categories with 2 algorithms.

• Dominant backgrounds:– QCD with MET miscalculation

– W/Z+jets, top, diboson

(mH=115 GeV)

tight 2 b-tag loose 2 b-tag 1 b-tag

H WW*l+n l-n (high mass)

• Opposite sign 2 leptons.

– Lepton acceptance improved by

using isolated tracks.

• S/B separation by NN.

– Matrix element calculation result

input to NN.

• Newly including low Mll events.

• Dominant background

– DY, Diboson, top

(mH=165 GeV)

Mll <16 GeV channel

Tools Backup

Ttbar diagram

t

t

q

q

g

g

b

b

W+

W-

l+ ,

n , q’

q

15% 85%

100%

100%

l- ,

n ,q’’’

q’’

B-Tagging

• B-jet tagging by secondary

vertex displacement from the

primary vertex.

• B-tagging reduces wrong jet-

parton assignment as well as

background events.

B-tag 2

Jet Probability Algorithm (1)

Jet Probability Algorithm (2)

Top Mass Backup

L+jets Top Mass Measurement with

Matrix Element Method• Construct likelihood for Mt and Jet Energy Scale (JES) with Signal Matrix

Element calculation.

– JES had been the dominant systematic source.

• Simultaneously fit Mtop and JES.

– JES constrained by hadronically

decaying W→qq’ in candidate events.t

t

q

q

g

g

b

b

W+

W-

l+

n

q’

q15% 85%

100%

100%

Constrain

Dijet mass

To MW

mt = 172.6±0.9 (stat.)±0.7 (JES)±1.1 (syst.) GeV/c2

= 172.6 ± 1.6 (total) GeV/c2

CDF Top Mass Measurements

TEVATRON Top Mass Comb.

Top Mass Tevatron CombinationUse only best analyses from each

decay mode, each experiment.

Mhiggs < 157 GeV/c2 (95% CL) .

Mhiggs < 186 GeV/c2 w/ LEP direct search limit.

Mtop = 173.1±1.3 GeV/c2

(winter 2009)

Top Mass Tevatron CombinationUse only best analyses from each

decay mode, each experiment.

Mhiggs < 157 GeV/c2 (95% CL) .

Mhiggs < 186 GeV/c2 w/ LEP direct search limit.

Before Run II results

(Spring 2004):

Mtop = 178.0 4.3 GeV/c2

mhiggs251 GeV/c2 (95% CL)

Mtop = 173.1±1.3 GeV/c2

(winter 2009)

L+jets Top Mass Measurement with

Matrix Element Method• Construct likelihood for Mt and Jet Energy Scale (JES) with

Signal Matrix Element calculation.

Signal Matrix Element

detector response function

x: parton level quantities

y: observed quantities

Incoming parton PDFs

normalization acceptance24 permutations of parton↔jet assumption

L+jets Top Mass Measurement with

Matrix Element Method

Systematic sourceSystematic uncertainty

(GeV/c2)

Calibration 0.1

MC generator 0.6

ISR and FSR 0.3

Residual JES 0.5

b-JES 0.4

Lepton PT 0.2

Multiple hadron interactions 0.1

PDFs 0.2

Background modeling 0.5

Color reconnection 0.3

Total 1.1

CDF L+jets Template Method (3)

JES syst 2.5 compared to 3.1

wo/ in situ calibration

Likelihood fit looks for top mass, JES and background fraction that

describes the data Mtop distribution best (template fit).

L = 318 pb-1Mtop distributions :

2tag 1tagT

1tagL 0tag

mtop = 173.5 +2.7/-2.6 (stat) 3.0 (syst) GeV/c2

A slide from

summer 2005.Effect of in-situ calibration!!

Others

Single Top Combined Result5 different L+jets analyses (3.2 fb-1)

combine

MET+jets analyses (2.1 fb-1)

combine

st+s-chan = 2.5 +0.7-0.6 pb

st-chan = 0.8±0.4 pb

ss-chan = 1.8+0.7-0.5 pb

|Vtb| = 0.91 ± 0.11 (exp.)

± 0.07 (theory)

Spin correlation frame

ttbar rest frame

Measured in top/tbar rest frame

MSSM Higgs with bbb final state