CERN University Wuppertal• Exchange of first luminosity detectors by new high-precision detectors...

Review of Final LEP Resultsor

A Tribute to LEPJ. Drees

CERN / University Wuppertal

So far more than 1100 scientific papers, many analyses arestill continuing. Main topics centre on the study of theproperties of the gauge and scalar bosons, of heavy fermionsand on searches for the Higgs and for new physics.

J. Drees Lepton - Photon 2001

Performance of LEP during 12 years of operation

Total luminosity above WW threshold ∼ 700 pb-1 per experiment.


LEP in 2000Record beam energy 104.4 GeV, more than foreseen. 200 days ofrunning, >130 pb-1 above 103 GeV, 100 pb-1 in last 110 days.


103 –103.49GeV

Superconducting cavities

Crucial for success of LEP2:S. Myers: For sc cavities the power needed is “only” proportionalto the 4th power of energy. To operate LEP at 103 GeV with coppercavities (P ∝ Ebeam8) would have needed 1280 cavities and 160MW of power! Impossible for many reasons.

1980 development program for 350 MHz niobium coated coppercavities, goal thermal stability at reduced costs.

2000: 272 Nb film and 16 Nb bulk SC’s.

Achieved: Average accelerating field 7.5 MV/m, Q > 3×109 at 4.5 K. Better than design value 6 MV/m. More than 80% of the Nb film SC’s had Q > 2.5×109 at 8 MV/m.



SC module installed in the LEP tunnel

4 cell Nb/Cu cavity inthe clean room

The Collaborations

ALEPH, DELPHI, L3, OPALMajor detector improvements during the years of data taking:

• Silicon micro vertex detectors for high resolution secondaryvertex measurements,

• Exchange of first luminosity detectors by new high-precisiondetectors able to measure small angle Bhabha scattering at alevel well below 1 0/00.

Creation of a new style of working together, the LEP WorkingGroups, e.g.

Electroweak Working Group (EWWG)Combination of the results from all LEP collaborations and from SLDtaking account of all systematic correlations between data.


Precision at the Z

Ecm [GeV]

σ had

[nb]

σ from fitQED unfolded

measurements, error barsincreased by factor 10

ALEPHDELPHIL3OPAL

σ0

ΓZ

MZ

10

20

30

40

86 88 90 92 94

J. Drees Lepton -Photon 2001

The 4 exps. collected 15.5million Z decays to quarksplus 1.7 million decays tocharged leptons, integratedL ≅ 200 pb-1 per exp.

The final hadronic crosssection, measured andQED deconvoluted.

Radiative corrections largebut v. well known.

The final result2⋅10-5 accuracy for one of the most fundamental constants:

mZ = 91.1874 ± 0.0021 GeVThis cannot be exceeded with any one of the future machines, noteven with a GigaZ Linear Collider!

Essential:- Beam energy measurement using the technique of resonant depolarisation plus careful control of all machine parameters, still dominant error of ±±±±1.7 MeV,- Close cooperation with theory.


1990-1992

91.1904±0.00651993-1994

91.1882±0.00331995

91.1866±0.0024average

91.1874±0.0021

mZ [GeV]91.185 91.19 91.195

The full setof nearly uncorrelated pseudo-observables from EWWG.

• Total Z width: ΓZ = 2.4952 ± 0.0023 GeV,

• Z peak cross section: 220 12

Z

hadee

Z

hadm Γ

ΓΓ⋅≡ πσ

,

• Ratios Rf0 ≡ Γhad/Γff for f = e,µ,τ; also Rq0 ≡ Γqq/Γhad for q = b,c,s,

• Forward backward asymmetries for f = e,µ,τ; b,c,s. At Z pole:

fef

FB AAA 4

3,0 ≡ 22

2

AfVf

AfVff gg

ggA

+≡

,

• τ polarisation: .


θθθθθ

τ

ττ cos2cos1

cos2)cos1()(cos 2

2

e

e

AA

AAP

++++−=

Number of light neutrinos NννννOne of the questions asked by the LEPC before recommendingapproval of the experiments:

What is the expected accuracy for neutrino counting?

Best value from accurate measurement of Γ inv/Γll divided by Γνν/Γllfrom MSM; Γ inv = ΓZ -Γhad -Γll(3-δτ):

Average: Nν = 2.9841 ± 0.0083 (2 σ below 3).MeVxinv

7.15.17.2

+−−=Γ

Veltman ρρρρ-parameterFrom leptonic width Γll

ρlepteff = 1.0050 ± 0.00105 σ above tree-level value of 1, proves presence of genuine

ew radiative corrections, agrees with SM.J. Drees Lepton - Photon 2001

Z couplings to e, µµµµ, ττττ

-0.041

-0.038

-0.035

-0.032

-0.503 -0.502 -0.501 -0.5

gAl

g Vl

Preliminary

68% CL

l+l−

e+e−

µ+µ−τ+τ−

mt

mH

∆α


Contributions from LEP:• AFB at Z pole,• Partial widths Γff ∼ gVf2 + gAf2,• Longitudinal τ polarisation:

Aτ , Ae.

Contributions from SLD:• Asymmetry for left and right

handed e- polarisation: mostprecise Ae,

• AFBLR: Ae, Aµ , Aτ .

Z →→→→ quarks

0.16

0.17

0.18

0.19

0.214 0.216 0.218 0.22

R0b

R

0 c

Preliminary

68% CL

95% CL

SM


had

bbbR Γ

Γ≡0

had

cccR Γ

Γ≡0

Rb contains higher order ew.contributions ∼ mt2,nearly independent of QCD, QEDor other ew. corr.

Measurement of Rb requiresextremely high quality of btagging. → High resolution siliconmicrovertex detectors + multi-tagmethods + control of hemispherecorrelations …

Now Rb agrees with SM!

New analyses of A0,bFB

ALEPH, inclusive B-decays• 30% increase in data sample from neural network for b-tagging (b

hemisphere charge estimated by optimal merge of information fromprimary and secondary vertex charge, leading kaons, and jet charge).

A0,bFB = 0.1009 ±±±± 0.0031

DELPHI, v. high purity b-sample• Neural network (b hemisphere charge determined from vertex charge, jet charge, charge of leptons and kaons), self-calibration from double tagging.

A0,bFB = 0.0997 ±±±± 0.0042

Significant improvement, still significant deviation?J. Drees Lepton - Photon 2001

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

cos(Θthrust)

AF

B

b,di

ff

data

fit

92-95 differential asymmetry

(single+double tag)

DELPHI

AFB

0,bb_

LEPSummer 2001

= 0.0990 ± 0.0017

OPAL jet-ch ☞ 1991-95

0.1007 ± 0.0055 ± 0.0040

L3 jet-ch ☞ 1991-95

0.0949 ± 0.0101 ± 0.0055DELPHI NN

✍ 1992-950.0995 ± 0.0036 ± 0.0021

DELPHI jet-ch ☞ 1992-95

0.1004 ± 0.0047 ± 0.0014

ALEPH jet-ch ☞ 1991-95

0.1026 ± 0.0027 ± 0.0012

OPAL leptons ✍ 1990-95

0.0958 ± 0.0043 ± 0.0021L3 leptons

☞ 1990-950.0983 ± 0.0065 ± 0.0033

DELPHI leptons ✍ 1991-95

0.1041 ± 0.0057 ± 0.0022

ALEPH leptons ✍ 1991-95

0.0997 ± 0.0040 ± 0.0023

Include Total Sys 0.0007With Common Sys 0.0003

mt = 174.3 ± 5.1 GeV

∆αhad = 0.02761 ± 0.0003610 2

10 3

0.09 0.1 0.11

A0,bb_

mH

[GeV

]

150 200mt [GeV]

The 3.3 σσσσ discrepancysin2 θθθθeff from A0,bFB versus Al

Q: Are LEP meas. consistent? A: Yes!

Q: Are LEP and SLD results incompatible?

Ab(LEP only) = 0.891 ± 0.022 (last year 0.890 ± 0.024)

Ab(SLD) = 0.921 ± 0.020

Agree within 1.0 σσσσ !

Ab(LEP+SLD) = 0.899 ±±±± 0.013 (0.935 SM)


Preliminary

Only quantitypreferring high mH

gVb versus gAb, gRb versus gLbFrom Rb, Ab, and AFB

b, assuming lepton universality.


-0.35

-0.33

-0.31

-0.29

-0.54 -0.52 -0.50 -0.48

gAb

g Vb

Preliminary

68.3 95.5 99.5 % CL

SM

-0.12

-0.11

-0.10

-0.09

-0.08

-0.07

-0.45 -0.44 -0.43 -0.42 -0.41 -0.40

gLb

g Rb

Preliminary

68.3 95.5 99.5 % CL

SM

Strong anti-correlation of gVb, gAb due to constraint on sum of squaresfrom precise Rb. Deviation from SM mainly for gRb.

SM

Again sin2θθθθeff

102

103

0.23 0.232 0.234

Preliminary

sin2θlept

eff

m

H

[G

eV

]

χ2/d.o.f.: 12.8 / 5

A0,l

fb 0.23099 ± 0.00053

Al(Pτ) 0.23159 ± 0.00041

Al(SLD) 0.23098 ± 0.00026

A0,b

fb 0.23226 ± 0.00031

A0,c

fb 0.23272 ± 0.00079

0.2324 ± 0.0012

Average 0.23152 ± 0.00017

∆αhad= 0.02761 ± 0.00036∆α(5)

mZ= 91.1875 ± 0.0021 GeVmt= 174.3 ± 5.1 GeV


Prob. 2.5%

sin2θefflept from only leptons .23113 ± .00021 hadrons .23230 ± .00029

Either:- Statistical fluctuation,- unknown sources of systematic errors,- or evidence for new physics.

Note: Only average sin2 θeff consistent with mH O(100 GeV) .

2 fermion production above ZCompared to other processes cross-section still high.

10-4

10-3

10-2

10-1

1

10

80 100 120 140 160 180 200 220

σ [n

b]

s [GeV]

mH=114 GeV

e+e– → γ/Z → qq_(γ)

e+e– → HZ → qq_qq_

s' / s > 0.85

e+e–→ W+W−→ qq

_qq_

e+e–→ ZZ→ qq

_qq_

e+e– → e+e–hadronsWγγ > 5 GeV

L3preliminary

Agreement with SM, but hadronic cross-section 1.8 σ high.J. Drees Lepton - Photon 2001

Cut on √s’/sselectsinterestingevents.

Combined forhadrons, µµ,ττ , bb, ccby EWWG.

Cro

ss s

ectio

n (p

b)

√s

´/s

> 0.85

e+e−→hadrons(γ)e+e−→µ+µ−(γ)e+e−→τ+τ−(γ)

LEPpreliminary

√s

(GeV)

σ mea

s/

σ S

M

1

10

102

0.8

0.9

1

1.1

1.2

120 140 160 180 200 220

LEP2 µµµµ and ττττ asymmetries


Test of models with combined data:

• Additional Z′′′′, e.g. limit for mZ’ (zeromixing) in- LR model 0.80 TeV (95% CL),- χ model 0.68 TeV,

• Constraints on contact interactions- between leptons: gΛπ4 > 8.5 to

26 TeV,- between leptons and heavy

quarks. For eb: gΛπ4 > 2.2 to15 TeV.

Low scale quantum gravity, including e+e- data: Ms > 1 TeV.

For

war

d-B

ackw

ard

Asy

mm

etry

√s

´/s

> 0.85

e+e−→µ+µ−(γ)e+e−→τ+τ−(γ)

LEPpreliminary

√s

(GeV)

A

FB

mea

s -A

FB

SM

0

0.2

0.4

0.6

0.8

1

-0.2

0

0.2

120 140 160 180 200 220

W+W- ProductionFocus of SM tests at LEP2: Measurement of mW, investigation ofstructure of triple boson couplings.

Each LEP experiment has collected about 10000 W+W- events.Five decay classes: Fully hadronic (45.6%), 3 semileptonic (each 14.6%),fully leptonic (10.6)%.

Powerful tools to separate four fermion events originating from Wproduction from background, e.g. neural networks.Typical efficiency for WW selection 85% at v. high purity.J. Drees Lepton - Photon 2001

CC03diagrams

σσσσ(e+e- →→→→ W+W- →→→→ 4 fermions)

0

5

10

15

20

160 170 180 190 200 210

Ecm [GeV]

σWW

[pb]

LEP Preliminary08/07/2001

no ZWW vertex (Gentle 2.1)only νe exchange (Gentle 2.1)

RacoonWW / YFSWW 1.14

σσσσmeas/σσσσtheory (RacoonWW) = 1.000 ±±±± 0.009 (√s > 180 GeV)J. Drees Lepton - Photon 2001

Combined results of the 4collaborations

Obvious: All t- and s-channel contributions, needed to understand the data.

Subtle: Comparison with new MC generators with improved radiative corrections, DPA for virtual O(α) corrections in resonant W-pair production (plus all other QED corr.) needed for 0.5% accuracy.

W mass

Before crossing W-pair threshold precise mW value from Z datausing SM relations. Updated indirect value using measured mt :

mW = 80.373 ±±±± 0.023 GeV .

Small error sets scale for direct mass measurements.

In SM mW depends on mt, mH and ∆α (complete 2-loop, Freitas et al.):

...)105924.0

(081.1)100

ln(05613.0)1)3.174

((5235.03767.80 2 −+−∆−−−+= αHtWmm

m

Significant deviation of direct meas. from indirect value wouldindicate new physics and existence of new fundamental particles.

At LEP2 two independent methods:

• Meas. of the total cross-section near threshold at ECM = 161 GeV:

mW = 80.40 ± 0.21 GeV. (Estimated error for GigaZ: ∆mW = 0.006 GeV)


Direct mW measurementsFrom invariant mass distribution of detected decay products(constrained by energy and momentum conservation):

m /GeV

Eve

nts

qqqq

OPAL 183-209 GeV ∫ L dt = 677 pb-1

Signal

Combinatorial b/g

Other b/g

0

50

100

150

200

250

300

60 65 70 75 80 85 90 95 100 105

Systematic uncertainties of mW:• 29 MeV for semileptonic, (fragmentation, beam energy, detector

systematic, initial and final state photon radiation, …)• 54 MeV for fully hadronic, (colour reconnection, BE).

Consistency: MeVlqqqqqqmW 449)( ±+=−∆ νJ. Drees Lepton - Photon 2001

qqqq

0

10

20

30

40

50

60

70

80

50 55 60 65 70 75 80 85 90 95 100

MW (GeV/c2)

Eve

nts

per

1 G

eV/c

2

ALEPH Preliminaryµνqq selection

√s > 202 GeV

Data (Luminosity = 217 pb-1)

MC (mW = 80.31 GeV/c2)

Non-WW background

µνqq

SM formW=80.42 GeV

Results

LEP: mW = 80.450 ± 0.026 ± 0.030 GeV, weight of 4q channel 26%.

W-Boson Mass [GeV]

mW [GeV]

χ2/DoF: 0.0 / 1

80 80.2 80.4 80.6

pp−-colliders 80.454 ± 0.060

LEP2 80.450 ± 0.039

Average 80.451 ± 0.033

NuTeV/CCFR 80.25 ± 0.11

LEP1/SLD/νN/APV 80.363 ± 0.032

LEP1/SLD/νN/APV/mt 80.373 ± 0.023


Still agreement betweenindirect and directmeasurements within 1.9 σ.

Final LEP: ∆mW ≅ 35 MeV

ΓW from direct reconstruction:ΓW = 2.150 ± 0.091 GeV

agrees with SM.

Charged gauge couplings

• Tools: σWW, cosθW- distribution, W± helicities analysed via fermion decay angles, e+e- → eνW andννγ production.

C and P conservation plus constraints from low energy data leaves:g1

Z, κγ, λγ (1,1,0 within SM).One parameter fit precision:

δg1Z = ± 0.026, δκγ = ± 0.066, δλγ = ± 0.028.

CP violating couplings studied by ALEPH, OPAL. Within errors no deviation fromSM. Quartic gauge couplings (ALEPH, L3, OPAL): limits available.

No evidence for any anomalous W boson coupling!J. Drees Lepton - Photon 2001

W+ electromagnetic moments:

Magnetic dipole moment µW = (e/2mW) (1 + κγ + λγ),

Electric quadrupole moment qW = -(e/mW2) (κγ - λγ).

ZZ production• New test of SM. Search for existence of anomalous neutral gauge

boson couplings (ZZZ, ZZγ).

0

0.5

1

1.5

170 180 190 200

Ecm [GeV]

σZZ

NC

02

[p

b]

LEP Preliminary08/07/2001

±2.0% uncertainty

ZZTO

YFSZZ


Combined results (NC02, only t-and u-channel exchange).

All experiments analyse ZZ → qqqq(4 jets), qqνν (2jets + missingenergy), qql+l- (2jets + 2 isolatedleptons),4 lepton final states; statistic v. limited.

Anomalous neutral gauge couplings

• SM tree level → no neutral TGCs,• Tools to search for anomalous neutral TGCs:

- Total cross section for ZZ and γZ (increase?),- cos θZ, cos θγ, and Eγ distributions

(deviations at large θ?).

New results from all LEP collaborations,examples of averages (95% CL):

f5Z [ -0.36, +0.38]

h3γ [ -0.08, +0.14]

No evidence for any anomalous boson coupling!J. Drees Lepton - Photon 2001

γγγγ

γγγγ*, Z*

f4γ,Z, f5

γ,Z Z

Z

γγγγ*, Z*hiγ,Z

i = 1,4Z

SM

LEP Preliminary

68% CL95% CL

h3Z

h 4

Z

Budapest 2001

-0.7

-0.35

0

0.35

0.7

-0.7 -0.35 0 0.35 0.7

Consistency test of SMmW from LEP and Fermilab versus mt from Fermilab

80.2

80.3

80.4

80.5

80.6

130 150 170 190 210

mH [GeV]114 300 1000

mt [GeV]

m

W

[G

eV

]

Preliminary

68% CL

∆α

LEP1, SLD, νN, APV DataLEP2, pp

− Data


Indirect and directmeasurementsfavour low mH !

80.2

80.3

80.4

80.5

80.6

130 150 170 190 210

mH [GeV]113 300 1000

mt [GeV]

m

W

[G

eV

]

Preliminary

68% CL

LEP1, SLD, νN DataLEP2, pp

− Data

Statussummer2000

Predicting mH


MSM fit to• all data from LEP1 and SLD,• mt , mW,• sin2θW from CCFR, NUTEV,• APV.

0

2

4

6

102

mH [GeV]

∆χ2

Excluded Preliminary

∆αhad =∆α(5)

0.02761±0.000360.02738±0.00020

theory uncertainty

mH

Contributions to CKM


Many tools available at LEP:

• W branching ratios,

• High Z →bb statistics,∼ 4 M events,

- Fast moving B-hadrons,- B decay particles well

separated from QCD rest,- Particle identification,- Full reconstruction of B0s,- Experience of 12 years.

Few examples:

��Vcs�� from Br(W→→→→lνννν)

�=

++=→⋅ cui

ijs V

lWBr ,

2)1(1

)(3

1

πα

ν

Results:

��Vij�² = 2.039 ±±±± 0.025

unitarity not needed,

��Vcs�� = 0.996 ±±±± 0.013assuming world average forother Vij.

tbtstd

cbcscd

ubusud

VVV

VVV

VVV

( )

��Vub��Strategy: Inclusive reconstruction of b→ulν fraction:

bbuub lXBBRV γτν /)(2 →= γb uncertainty known.

V. difficult to separate charmless b decays from dominant b → cbackground. In a new analysis OPAL uses 7 kinematic variablesas NN input to enrich B → Xu sample.


LEP average from Vub�WG:310)52.067.1()( −− ×±=→ lulXbBR ν

with world average B hadron lifetimeτb = (1.564 ± 0.014) ps:

359.069.0 10)04.4(

−+− ×=ubV

incl. theoretical uncertainties (QCD, mb).BR(B → Xu l υ) x 103

LEP Average 1.67 ± 0.31 ± 0.42

L3 3.3 ± 1.3 ± 1.5

DELPHI 1.57 ± 0.51 ± 0.49

ALEPH 1.73 ± 0.56 ± 0.55

0 1 2 3 4 5 6

OPAL 1.63 ± 0.57 ± 0.52

B0s -B0s oscillations

Main interest:

ξ2 of O(1) known to 5-6%. Analysis technique amplitude method (ALEPH):

0/00 ))cos(1(

2

1)( sB

t

sss etmABBPτ−

∆−=→

Amplitude A fitted to data for various ∆ms.

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

3

0 2.5 5 7.5 10 12.5 15 17.5 20 22.5 25

∆ms (ps-1)

Am

plit

ude

data ± 1 σ 95% CL limit 14.3 ps-1

1.645 σ sensitivity 15.4 ps-1

data ± 1.645 σdata ± 1.645 σ (stat only)

LEP average (prel.)

2

2

td

ts

B

B

d

s

V

V

m

m

m

m

d

s ξ=∆∆

Present world limit, including SLDand CDF and new data from DELPHI

∆∆∆∆ms > 14.6 ps-1 (95% CL)

��Vtd��/��Vts��< 0.22

J. Drees

LEP only

Contributions to QCDClean environment, hadronic cm. energy well defined, well collimatedjets, enough statistics to investigate even rare topologies.

Typical early topics:- Tests of QCD, measurements of αs, understanding of fragmentation,

Later: Global studies (up to which level can the accurate data be described).

Ew precision quantities depend on αs:

��

�

�

��

�

��

��

�−��

��

�++⋅=→Γ→Γ=

32

1594.0045.11934.19)(

)(

πα

πα

πα sss

lept leptonsZ

hadronsZR

With final Rlept = 20.767 ± 0.025:)(),(002.0.)(exp004.0124.0)( 003.0 001.0 QCDmmm tHZs

+−±±=α

Best measurement?• Relies on electroweak sector of MSM,• Convergence, at mZ αs3-term ≅ 63% of αs2-term.


ααααsNeed to measure αs from infraredsafe shape variables like jet rates,thrust, etc. not depending on Zcouplings to quarks.

From event shapes(LEP QCD Working Group)

But all these quantities are calculatedin O(αs2) matched with NLLA → renormalisation scale uncertainty.


0.1

0.11

0.12

0.13

0.14

0.15

50 100 150 200Ecm[GeV]

α s(E

cm)

0.1

0.11

0.12

0.13

0.14

0.15

50 100 150 200

ADLO (preliminary)DLO (preliminary)L3Jade

LEP/Jade 35...207GeVNLLA+O(αs

2) log(R)

All LEP ααααs measurements

For this fig.: Theoretical uncertainties for all αs from event shapesevaluated from change in renormalisation scale µ by factor 2.


Studies of• gauge structure of QCD,• running b-quark mass,• colour coherence,• hadronisation models,• power corrections as

alternatives to hadronisationmodels,

• differences between quarkand gluon jets,

are all consistent with QCDpredictions.

αs(MZ)0.11 0.115 0.12 0.125 0.13

Indi

rect

(L

EP)

Dir

ect (

from

ES,

LE

P)

EW fit (5 Param. to LEP data)

Γhad/ΓleptRτ

4-jets O(αs3)

3-jet like O(αs2)+PC

3-jet like O(αs2)+Models

3-jet like NLLA

3-jet like NLLA+O(αs2) log(R)

PDG 2001 0.1181±0.0020

Daniel Wicke

Before LEP

What was known or expected in summer 1989 before start of LEP(G. Altarelli; LP, Stanford and R. Barbieri; EPS, Madrid):

Quantity Expected error AchievedmZmWNν

A0,µFBA0,bFB

Aτ

50 to 20 MeV100 MeV

0.30.00350.00500.0110

2.1 MeV39 MeV0.0080.00130.00170.0043

In the end, all measurements are much more precise. SMcontinues to be in good shape.


mZ = 91.12 ± 0.16 GeVsin2θW = 0.227 ± 0.006

mW = 80.0 ± 0.36 GeVNv = 3.0 ± 0.9

Why was LEP so successful?

• Dedicated machine group, excellent performance of LEP,low background,

• Good performance of detectors from beginning until end ofdata taking,

• Effective division of work between CERN and outsidelaboratories,

• Close cooperation• between the 4 collaborations and also between LEP and

SLD (without avoiding competition),• with the machine group,• with theory groups.

Many analyses continuing, still more to be expected.


Discussion

Distribution of cavity gradients (96 to 104 GeV)

At 104 GeV: Mean 7.5 MV/m


0

5

10

15

20

25

30

4 4,2 4,4 4,6 4,8 5 5,2 5,4 5,6 5,8 6 6,2 6,4 6,6 6,8 7 7,2 7,4 7,6 7,8 8 8,2 8,4 8,6 8,8 9 9,2 9,4

Accelerating field [MV/m]

Nu

mb

er o

f ca

viti

es

96 GeV100 GeV104 GeV

Can we trust A0,bFB ?Breakdown of errors for the combined LEP result:

• Statistics: ∆A0,bFB = 0.00156• Systematic:

Uncorrelated 0.00061 Correlated 0.00039

Total systematic 0.00073

Small correlated uncertainty. Main contributions to correlatedsyst. uncertainty from physics:

- QCD correction (0.00030), - Light quark fragmentation (0.00013), - Semileptonic model b → l decays (0.00009),

- Gluon splitting g →bb (0.00007), etc.

Conclusion: No reason to consider the A0,bFB results as unreliable.


sin2θefflept fromALRmeasurements(SLD) and fromA0,bFBmeasurements(LEP) versustime.

Situationunchanged sincemany years.


Measurement Pull (Omeas−Ofit)/σmeas-3 -2 -1 0 1 2 3

-3 -2 -1 0 1 2 3

∆αhad(mZ)∆α(5) 0.02761 ± 0.00036 -.35

mZ [GeV]mZ [GeV] 91.1875 ± 0.0021 .03ΓZ [GeV]ΓZ [GeV] 2.4952 ± 0.0023 -.48σhad [nb]σ

0 41.540 ± 0.037 1.60RlRl 20.767 ± 0.025 1.11AfbA

0,l 0.01714 ± 0.00095 .69Al(Pτ)Al(Pτ) 0.1465 ± 0.0033 -.54RbRb 0.21646 ± 0.00065 1.12RcRc 0.1719 ± 0.0031 -.12AfbA

0,b 0.0990 ± 0.0017 -2.90AfbA

0,c 0.0685 ± 0.0034 -1.71AbAb 0.922 ± 0.020 -.64AcAc 0.670 ± 0.026 .06Al(SLD)Al(SLD) 0.1513 ± 0.0021 1.47sin2θeffsin

2θlept(Qfb) 0.2324 ± 0.0012 .86m(LEP) [GeV]mW 80.450 ± 0.039 1.32mt [GeV]mt [GeV] 174.3 ± 5.1 -.30m(TEV) [GeV]mW 80.454 ± 0.060 .93sin2θW(νN)sin

2θW(νN) 0.2255 ± 0.0021 1.22QW(Cs)QW(Cs) -72.50 ± 0.70 .56

Summer 2001

Test of SM

χ2/dof = 23/158.5%

Comparison with SM prediction as function of mHfor quantities sensitive to mH

Combined LEP and SLD measurements

102

103

2.49 2.5

ΓZ [GeV]

m

H

[G

eV

]

102

103

0.015 0.02

A0,lFB

m

H

[G

eV

]

102

103

41.4 41.5 41.6

σ0 had [nb]

m

H

[G

eV

]

102

103

80.2 80.4

mW (LEP) [GeV]

m

H

[G

eV

]

102

103

20.7 20.8

R0l

m

H

[G

eV

]

Preliminary

Measurement

∆αhad= 0.02761 ± 0.00036∆α(5)

αs= 0.118 ± 0.002

mt= 174.3 ± 5.1 GeV

102

103

0.14 0.15

Al(A0,lFB )

m

H

[G

eV

]

102

103

0.095 0.1 0.105

A0,bFB

m

H

[G

eV

]

102

103

0.14 0.15

Al(Pτ)

m

H

[G

eV

]

102

103

0.06 0.07 0.08

A0,cFB

m

H

[G

eV

]

102

103

0.14 0.15

Al (SLD)

m

H

[G

eV

]

Preliminary

Measurement

∆αhad= 0.02761 ± 0.00036∆α(5)

αs= 0.118 ± 0.002

mt= 174.3 ± 5.1 GeV

Example of a global study

0.06 0.08 0.1 0.12 0.14 0.16 0.18

αS (MZ2)

EECAEECJCEF1-ThrOCBMaxBSumρHρSρDD2E0

D2P0

D2P

D2Jade

D2DurhamD2Geneva

D2Cambridge

w. average : αS(MZ2) = 0.1168 ± 0.0026χ2/ndf = 6.2 / 17ρeff = 0.635

DELPHIxµ exp. opt.


αs(mz) from 18 shapes consistent ifrenormalisation scale experimentallyoptimised (∼ same as PMS or ECH).

BUT: How to quote theoretical uncertainty?

Note: Between ∼ 20 to 200 data points perdistribution with typically a few % error foreach fit, χ2/ndf ≅ 1!

��Vcb��1. Inclusive, from semileptonic width plus recent evaluation of

theoretical uncertainties.

bbccb lXBBRV γτν /)(2 →=

��Vcb��Working Group takes LEP1 average.))%(17.0.)(07.058.10()( syststatXlbBR l ±±=→ −ν

and world average B hadron lifetime τb = (1.564 ± 0.014) ps.

2. Exclusive, from B0d→D*lν diff. width 22 )()(/ cbVFKdd ωωω=Γ .


30 32 34 36 38 40 42 44 46 48

Vcb (10-3)

LEP average 40.6±1.9

Vcb Inclusive 40.7±0.5±2.0

Vcb Exclusive 40.5±1.9±2.3

Vcb Working Group

Theoreticaluncertaintiesdominate

Uncertainty of γb knownfrom HQET

Κ(ω) known phasespace term , F2(ω)estimated from HQETat ω =1 (q2 = 0).

CERN University Wuppertal• Exchange of first luminosity detectors by new high-precision detectors...

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