cern university wuppertal• exchange of first luminosity detectors by new high-precision detectors...
TRANSCRIPT
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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
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Performance of LEP during 12 years of operation
Total luminosity above WW threshold ∼ 700 pb-1 per experiment.
J. Drees Lepton - Photon 2001
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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.
J. Drees Lepton - Photon 2001
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.
J. Drees Lepton - Photon 2001
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J. Drees Lepton - Photon 2001
SC module installed in the LEP tunnel
4 cell Nb/Cu cavity inthe clean room
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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.
J. Drees Lepton - Photon 2001
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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.
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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.
J. Drees Lepton - Photon 2001
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
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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: .
J. Drees Lepton - Photon 2001
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
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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
J. Drees Lepton - Photon 2001
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
J. Drees Lepton - Photon 2001
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)
J. Drees Lepton - Photon 2001
Preliminary
Only quantitypreferring high mH
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gVb versus gAb, gRb versus gLbFrom Rb, Ab, and AFB
b, assuming lepton universality.
J. Drees Lepton - Photon 2001
-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
J. Drees Lepton - Photon 2001
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
J. Drees Lepton - Photon 2001
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)
J. Drees Lepton - Photon 2001
-
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
J. Drees Lepton - Photon 2001
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
J. Drees Lepton - Photon 2001
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
J. Drees Lepton - Photon 2001
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
J. Drees Lepton - Photon 2001
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
J. Drees Lepton - Photon 2001
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.
J. Drees Lepton - Photon 2001
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.
J. Drees Lepton - Photon 2001
-
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.
J. Drees Lepton - Photon 2001
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.
J. Drees Lepton - Photon 2001
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.
J. Drees Lepton - Photon 2001
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.
J. Drees Lepton - Photon 2001
-
Discussion
-
Distribution of cavity gradients (96 to 104 GeV)
At 104 GeV: Mean 7.5 MV/m
J. Drees Lepton - Photon 2001
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.
J. Drees Lepton - Photon 2001
-
sin2θefflept fromALRmeasurements(SLD) and fromA0,bFBmeasurements(LEP) versustime.
Situationunchanged sincemany years.
J. Drees Lepton - Photon 2001
-
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.
J. Drees Lepton - Photon 2001
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 .
J. Drees Lepton - Photon 2001
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).