Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://zebu.uoregon.edu/~uochep/docs/docs02/review.pdf Äàòà èçìåíåíèÿ: Thu Mar 13 00:04:33 2003 Äàòà èíäåêñèðîâàíèÿ: Tue Oct 2 09:56:09 2012 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: m 5

David Strom 1 May 2002 University of Oregon

Lo oking back at LEP:

What were the weakest links?
· Electroweak physics from LEP 1 and LEP 2 (ALEPH, DELPHI, L3) · Electroweak physics from SLC (SLD)
Fermilab 1 May 2002

· Highlights from QCD · Searches 1
David Strom ­ Oregon


Intro duction · The LEP accelerator collided e+ e- b etween 1989 and 2000. ALEPH, DELPHI, L3 and OPAL (ADLO) recorded: > 200 pb-1 /exp eriment at the Z resonance (17 â106 visible decays) > 650 pb-1 /exp eriment at high energies ( Ecm < 208 GeV) · SLD recorded > 0.5 â106 p olarized Z decays at the SLC. · Total numb er of journal publication is more than 1000 and growing! Imp ossible to review everything in detail, esp ecially systematic errors · Premise of this Collo quium: Pick one weakest link p er measurement and discuss it in some detail. · Choices are very subjective · Concentrate on: · exp erimental challenges · theory errors which can't b e fixed later Ignore theory errors which can b e reduced later
Fermilab 1 May 2002

2

David Strom ­ Oregon


You b e the judge of how seriously to take this curve:

6

theory uncertainty
Da
0.02761±0.00036
(5) had

=

4

0.02747±0.00012

Dc
2 Excluded 20

2

0

Preliminary

100

400

mH [GeV]
For more details see "Precision Electroweak Measurements on the Z Resonance", to b e published in Physics Rep orts Fermilab 1 May 2002

3

David Strom ­ Oregon


Z Resonance Observables

[nb]



0

had



e+ Z

40
ALEPH DELPHI L3

f

30

OPAL

e e+ g e

f
20

Z

f
10
measurements, error bars increased by factor 10 from fit QED unfolded

f
M
Z

86

88

90

92

E
Example: Hadronic Cross Section

cm

[GeV]

94

Radiative corrections huge, but not weakest link (known to 3rd order see Berends, Neerven, Burgers/ Montagna, Nicrosini, and Piccinini / Jadach, Pietrzyk, and Skrzyp ek) Fermilab 1 May 2002

4

David Strom ­ Oregon


LEP Mo del (in)Dep endent Parameter Set (also called pseudo-observables) Total Error Z mass mZ 2.1 MeV (0.2 â 10
-4

Theory Error 0.3 MeV (0.03 â 10 0.2 MeV (0.8 â 10 0.022nb
-4

)

)

Z width

Z

2.3 MeV (9.2 â 10-4 )
12 e+ e- had m2 2 Z Z

-4

)

Hadronic cross section Ratio of leptons to hadrons Leptonic forward-backward asymmetry




0 had

0.037nb (8.9 â 10
-4

)

(5.3 â 10-4 ) 0.004 (1.9 â 10-4 ) 0.0001 (0.6%)

R



had

0.025 (12 â 10-4 ) 0.00095 (5.6%)

A0 FB



3 4

AeAf

Luminosity theory error: improvements difficult but p ossible to implement. Theory error for electrons is larger 0.024 (Re) and 0.0014 (A0 ) FB 5
David Strom ­ Oregon

Fermilab 1 May 2002


Psuedo observab els are expressed in terms of the effective couplings gVf and gAf
Lowest order differential cross section (ignoring masses and initial and final state QCD and QED corrections): 2s 1 d = 2 Nc d cos q
2 f

1 + cos2 + 2gAe gAf cos )} + 8gVe gAe gVf gAf cos ]

Photon Interference Z

-8Re{(s)qf (gVe gVf 1 + cos2
2 2 2 2 16|(s)|2 [(gVe + gAe )(gVf + gAf ) 1 + cos2

Where: · (s) =
GF m2 Z s 8 2 s-m2 +isZ /m Z
Z

· Nc is the numb er of "colors" for the final state.

In terms of the effective couplings we have:

f f =

GFNcm3 Z 6 2

f f RV gVf 2 + RAgAf 2 + QCD
Dep ends on ratio of couplings
for

g /gAf Af = 2 gVf gAf = 2 1+(Vf /g ) 2 2 gVf Af gVf +gAf

2

f f (RV and RA give corrections for final-state QED and QCD effects as well as quark masses, non-factorizable QCD effects.)

QCD

Fermilab 1 May 2002

6

David Strom ­ Oregon


Z mass: Weakest link Energy Calibration · Relative cross section measurements straight forward · Energy can b e measured to 0.2 MeV with resonant dep olarization (excite b eam with a magnetic field to precisely measure spin tune)

E [MeV]
44717
nitial

44718

44719

inal

/ Pi Pf

1 0.5 0

0.48

0.482

0.484

n - 101
Spin tune (precessions/turn) versus fractional change in p olarization. · Polarization calibration only done in dedicate runs at end of fills ­ Is the magnetic field seen by the electrons the same in collisions and p olarization runs? 7

Fermilab 1 May 2002

David Strom ­ Oregon


Main energy systematics Tides and other ground motion:
100

Trains
L EP
IP 5 IP 4 IP6 Versoix River Lausanne Geneva lake

D

E/E

0

(ppm) -100 0:00 100 4:00 8:00 11 November 1992 12:00 16:00 20:00 24:00 4:00

IP 3 IP 7 IP 2

SPS
IP 8 I P1

Railway

D

E/E

0

(ppm) -100 10:00 14:00 18:00 29 August 1993 22:00 2:00 6:00 10:00 14:00

CERN Meyrin Zimeysa
airport

Geneva Cornavin

Bellegarde
100

1 0.5 0
11 October 1993 12:00 16:00 20:00 24:00 4:00 8:00 12:00

1 km

DE

/E

0

(ppm) -100 8:00

-0.5 -1

1

2

3

4

5

6

7

8

Daytime

Correlation versus IP

Use tidal mo del and b eam p osition monitors to correct for orbit changes

Use NMR prob es and thermal mo del to extrap olate energy during fills

Fermilab 1 May 2002

8

David Strom ­ Oregon


Energy sawto oth
DE

D E [MeV]

CM

[MeV]: 15.8

1.0

9.2

-1.0

40

· Energy dep ends on lo cation exp eriments around the ring. · Correct for misalignment of RF cavities

of

20

e

e

0

-20

-40

*
L3 ALEPH

*

*
DELPHI

*
L3

OPAL

Bottom line: Energy error on mZ Energy error on
Z

1.7 MeV 1.2 MeV

resonant dep olarization uncalibrated fills dip ole field changes tidal mo del e+ difference corrector fields RF sawto oth disp ersion

error on mZ MeV 0.4 0.5 1.7 0.0 0.2 0.2 0.4 0.2

error on MeV 0.5 0.8 0.6 0.1 0.1 0.1 0.2 0.1

Z

Fermilab 1 May 2002

9

David Strom ­ Oregon


Z Mass Results by running p erio d (calibration metho d) by exp eriment

1990-1992 91190.4 ±6.5 1993-1994 91188.2±3.3 1995 91186.6±2.4 average 91187.4±2.1

Mass of the Z Boson Experiment ALEPH DELPHI L3 OPAL
2

MZ [MeV] 91189.3 ± 3.1 91186.3 ± 2.8 91189.4 ± 3.0 91185.3 ± 2.9 / dof = 2.2 / 3 91187.5 ± 2.1 1.7 91187 MZ [MeV] 91192

LEP common error

91.185

91.19

mZ [MeV ]

91.195

91182

Fermilab 1 May 2002

10

David Strom ­ Oregon


Z Width ( Z )
Total Z Width Experiment ALEPH DELPHI L3 OPAL
2

Z [MeV] 2495.9 ± 4.3 2487.6 ± 4.1 2502.5 ± 4.1 2494.7 ± 4.1 / dof = 7.3 / 3 2495.2 ± 2.3 1.2

LEP common error 10
3

Nof f -peak Z Non-peak
1993 pb-1 1994 pb-1 65 0 1995 pb-1 20 20

MH [GeV]

10

2

S = 0.118±0.002 linearly added to Mt = 174.3±5.1 GeV

Peak Off-p eak

20 20

10 2.483

2.495 Z [GeV]

2.507

· Weakest links Energy (see mZ ) calibration and inter-year normalization 11

Fermilab 1 May 2002

David Strom ­ Oregon


Measuring cross section and rates is harder:
0 had 0



12 e+ e- had m2 2 Z Z
2 12 e+ e- m2 2 Z Z



Nhad L N L Nhad N

R

had 0 had

Only two of these are indep endent (

and R are in the LEP parameter set)

·

0 had

and

0

eg e+

Weakest link luminosity measurement, L, using small angle Bhabhas. 1 3 · Use highly granular Si-W calorimeters or Si trackers
ee



· Lumi theory error (
Fermilab 1 May 2002

0.05%) , could b e improved in future. 12
David Strom ­ Oregon


For a typical LEP luminosity monitor a measurement at the 1/1000 level (e.g. Nhad 106 ) requires that inner acceptance edge b e known to 10 µrad. Radial metrology to << 25 µm Axial metrology to << 1mm (10 â b etter achieved) · Reconstruction bias with test b eam.
OPAL
Entries 4256 RMS 1.32

Entries/0.5mm

700 600 500 400 300 200 100 0 -15 -10 -5 0 5

10

Half-Layer Fit Residual Distribution
OPAL
10
-1 a)

15 (mm)

Second order effects controlled with data: · · · · Energy mo deling Beam parameters mo deling Trigger Reconstruction

10

-2

10

-3

10

-4

10

-5

10

-6

0.4

0.6

0.8

1

1.2

1.4

Measured Energy/ Beam Energy

Exp erimental systematic errors 0.03% to 0.09%
Fermilab 1 May 2002

13

David Strom ­ Oregon


Weakest link for R is lepton acceptance systematic for hadron acceptance is almost complete (94.8 99.5 %)

L3

e+e- ô e+e-(g) peak-2

Lepton limited

acceptance
1

peak peak+2

Edge in cos must b e precisely known Systematic errors of muons: 0.1% to 0.4%.

d s / d cos q [nb]

0.5

0

-1

-0.5

cos q

0

0.5

1

Background in selection not negligible

Fermilab 1 May 2002

14

David Strom ­ Oregon


Experiment ALEPH DELPHI L3 OPAL

Hadronic Pole Cross Section s

0 had

[nb]

Ratio of Hadronic to Leptonic Width Experiment Rl = had / l ALEPH DELPHI L3 OPAL
2

41.559 ± 0.057 41.578 ± 0.069 41.536 ± 0.055 41.502 ± 0.055 c / dof = 1.2 / 3
2

20.729 ± 0.039 20.730 ± 0.060 20.809 ± 0.060 20.822 ± 0.044 / dof = 3.5 / 3 20.767 ± 0.025 0.007

LEP common error 10
3

41.540 ± 0.037 0.028

LEP common error 10
3

[GeV]

10

2

MH [GeV]

10

2

M

H

aS = 0.118±0.002 linearly added to Mt = 174.3±5.1 GeV

S = 0.118±0.002 linearly added to Mt = 174.3±5.1 GeV

10 41.45

41.55 0 s had [nb]

41.65

10 20.65

20.75 Rl

20.85

Fermilab 1 May 2002

15

David Strom ­ Oregon


Physics from absolute cross sections Ratio of invisible to leptonic widths: inv = Z - had - 3 B r(Z inv) = B r(Z + - ) inv = 5.943 ± 0.016 SM = inv 12 R 0 m2 had Z
1 2

-R -3

LEP or

= 5.9736 ± 0.0048

N = 2.984 ± 0.008

2 (0.53 ± 0.27)% low

Same "trend" as NuTeV, /
SM

= 0.9884 ± 0.0026(stat.) ± 0.0032(sy s.) (1.16 ± 0.41)% low

b enefits from the improved Bhabha theory error (Jadach, Placzek, Richter-Was, Ward,Z. Was/ Montagna, Moretti, Nicrosini, Pallavicini, Piccinini) Indep endent of s , mt and mh = N 3 S M


inv

Fermilab 1 May 2002

16

David Strom ­ Oregon


Determination of s from Rl 1 +
(take mh = 100GeV for the following)

s

...

s (mZ ) = 0.1224 ± 0.0038 and surprisingly from 0 (
2 ) Z

+0.0033(mh =900 GeV) -0.0000 (mh =100 GeV)

1 - 1.4 s ...
+0.0026(mh =900 GeV) -0.0000(mh =100 GeV)

s (mZ ) = 0.1180 ± 0.0030

Grand LEPEWG fit and private corrections: s (mZ ) = 0.1190 ± 0.0027(E X P ) ± 0.0011(QC D) (See Sop er and hep-ex/0105076 for a discussion of the QCD error.) PDG 2000 average NNLO average (no LEP) s (mZ ) = 0.1181 ± 0.002 s (mZ ) = 0.1178 ± 0.0034

(S. Bethke J. Phys. G 26(2000) R27-R66) 17

Fermilab 1 May 2002

David Strom ­ Oregon


Leptonic Forward-Backward Asymmetries · Measure separately for electrons, muons and taus · Correct for large contribution from Z- interference · Weakest link: subtraction of t-channel and s-t interference terms in the electron channel.
e+ Z e e+ ee-

Forward-Backward Pole Asymmetry Experiment ALEPH DELPHI L3 OPAL

A

0,l FB

0.0173 ± 0.0016 0.0187 ± 0.0019 0.0192 ± 0.0024 0.0145 ± 0.0017 / dof = 3.9 / 3
2

LEP common error 10
3

0.0171 ± 0.0010 0.0003

2
g
MH [GeV]

+
e+

10

2

Based on comparisons b etween TOPAZ0 and ALIBABA (see W. Beenakker and G. Passarino,
PLB425, 199.)
10 0.013 0.017 0,l A FB

had= 0.02761±0.00036 linearly added to
(5)

Mt = 174.3±5.1 GeV

0.021

Bhabha theory error is 0.0014 ­ further dilutes contribution of electrons to average.
Fermilab 1 May 2002

18

David Strom ­ Oregon


Tau Polarization

(+ - Polarization is P (+ +- ) where - ) is for p ositive(negative) helicity.

+(-)

Pt

ALEPH

· Angular dep endence (Born level) is P (cos - ) = with P P (1 + cos2 - ) + 8 AFB cos 3 p ol (1 + cos2 - ) + 8 AFB cos 3
- -

Universality No-Universality

= -A and AFB = - 3 Ae p ol 4

· The decay pro ducts of the tau leptons are analyzed to determine average p olarization as a function of cos

Fermilab 1 May 2002

19

David Strom ­ Oregon


Weakest link: detector systematics ­ must b e able to tell tau decay pro ducts apart (e.g. from e) and accurately reconstruct directions and momenta of 0 s.
0.7 0.6 0.5 0.4 0.3

p

r

d G /d x

dG/dw

pn

1.4 1.2 1 0.8 0.6 0.4 0.2

r

Monte Carlo exp ectation for · x=
E,µ E

0.2 0.1

· = 'optimal observable'
Includes all decay angles and momenta
1

0

0

0.2

0.4

0.6

0.8

x

1

0

-1

-0.5

0

0.5

p

w

1

r

dG/dw

d G /d x

0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0

a

m

0.1

0.08 0.06 0.04 0.02 0 -1 -0.5 0

a

Helicity=+1 Helicity=-1

1

mnn

0.5

w

1

0

0.2

0.4

0.6

0.8

a

1

x

1

m

Fermilab 1 May 2002

20

David Strom ­ Oregon


Errors largely uncorrelated b etween exp eriments ­ largest common systematic error is from hadronic mo deling in A .
Experiment ALEPH DELPHI L3 OPAL LEP
3

Average Tau Polarisation

A

t

Forward-backward Tau Polarisation Experiment ALEPH DELPHI L3 OPAL LEP
3

A

e

0.1451 ± 0.0060 0.1359 ± 0.0096 0.1476 ± 0.0108 0.1456 ± 0.0095 c / dof = 0.9 / 3 0.1439 ± 0.0043 hadronic model <0.0025
2

0.1504 ± 0.0068 0.1382 ± 0.0116 0.1678 ± 0.0130 0.1454 ± 0.0114 c / dof = 3.1 / 3 0.1498 ± 0.0049
2

10

10

[GeV]

[GeV]

10

2

Da(5)d= ha 0.02761±0.00036 linearly added to Mt = 174.3±5.1 GeV

10

2
(5) Dahad= 0.02761±0.00036 linearly added to

H

M

M

H

10

0.12

0.15 At

0.18

10

Mt = 174.3±5.1 GeV

0.12

0.15 Ae

0.18

Fermilab 1 May 2002

21

David Strom ­ Oregon


ALR ­ Ae from longitudinal p olarized b eams at SLC

ALR

1 Pe

l - r = Ae l + r

r and l are cross section with left and right p olarization

· In contrast to LEP radiative and interference corrections are very small. Errors: · Statistics (

1.3%) (Financial problem)

· Polarization (0.5%) weakest link · Energy dep endence ( 0.4%, based on energy scan)
Fermilab 1 May 2002

22

David Strom ­ Oregon


Polarization Measurement
Unpolarized Cross Section 1. 0 0. 8 0. 6
e+

532 nm Frequency Doubled YAG Laser e­ Mirror Box

50 40 30 20 10 0

[mb/cm]

Circular Polarizer
Focusing and Steering Lens Mirror Box (preserves circular polarization) Compton Back Scattered e­

0. 4 0. 2 0. 0 -0 . 2 -0 . 4 -0 . 6 6

Scattering Asymmetry

Channel 6 Respons e

SLD

Laser Beam Analyzer and Dump "Compton IP"
Analyzing Bend Magnet

8 10 12 14 16 18 Transverse Distance from Neutral Beamline [cm]

20

Cerenkov Detector

Polarized Gamma Counter

Quartz Fiber Calorimeter

d dx

=

d dx

[1 - P Pe A(x)]

x = photon energy fraction A(x) = Compton asymmetry function

Polarization must b e extrap olated to SLD IP (0.15% systematic) Polarization systematic at Compton IP (0.50%)
Fermilab 1 May 2002

23

David Strom ­ Oregon


Measurement Summary Polarization Systematics
Effect Laser p olarization Detector linearity Analyzing p ower calib. Electronic noise Total Pe /Pe (%) 0.10 0.20 0.40 0.20 0.5
92 93 94-95 96 97-98 Average
0.10 0.12 0.14 0.16

0.100 ± 0.044 ± 0.004 0.1656 ± 0.0071 ± 0.0028 0.1512 ± 0.0042 ± 0.0011 0.1593 ± 0.0057 ± 0.0010 0.1491 ± 0.0024 ± 0.0010 0.15138 ± 0.00216 c /DOF=7.4/4 Prob.=11.4%
2

Including extrap olation to IP, interference uncertainties, and typical systematic error is 0.65%. statistical error is 1.3%

A

0 LR

Corresp onds to
lept sin2eff = 0.23097 ± 0.00027

where 1 g lept sin2eff (1 - V ) 4 gA

Fermilab 1 May 2002

24

David Strom ­ Oregon


From p olarized forward-backward and forward-backward asymmetries
dZ d cos

events events

= f Z (s ) â (1 - PeAe)(1 + cos2 )+ (Ae - Pe)(A 2 cos ))

2000 1750 1500 1250 1000 750 500 250 0

SLD e+e-ôe+e- 97-98
left polarized e- beam right polarized e- beam

600 500 400 300 200 100

SLD Z0ôm+m- 97-98

events

SLD obtains: Ae = 0.1544 ± 0.0060 Aµ = 0.142 ± 0.015 A = 0.136 ± 0.015

0 500

left polarized e- beam right polarized e beam

SLD Z ôt t 97-98

0

+-

400 300 200 100 0

left polarized e- beam right polarized e- beam
-0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8

cosq

Fermilab 1 May 2002

25

David Strom ­ Oregon


Combined results for gA and gV

Fermilab 1 May 2002

26

David Strom ­ Oregon


Contact interactions
preliminary
Ô

Forward-Backward Asymmetry

Cross section (pb)

10

2

s'/s > 0.85

LEP

1 0.8 0.6 0.4 0.2 0 0.2 0

preliminary

Preliminary LEP Combined

s /s' > 0.85

LEP

L

-

L

+

LL 9.8 16.5 RR 9.4 15.8 VV 16.5 26.2 AA 14.0 21.7 LR 8.5 11.2 RL 8.5 11.2 V0 13.5 22.9 A0 13.2 15.6

10

1 1.2 1 0.9 0.8 120

e s(g) e e e ôt t (g)

+e ôhad- on r ++ e ôm+ m (g) +-

++e+e- ôm+ m (g) e e ôt t (g)

ll

+-

meas/sSM

30. L (TeV)

0

30. + L (TeV)

Ameas-A

1.1

SM

FB

FB

s

-0.2 120 140 160

See LEP2FF01/02
s (GeV)
180 200 220

140

160

s (GeV)

180

200

220

g2 L= 2 (1 + )
i,j =L,R

¯ ij ei µ ei fj µ f ¯

j

limits for g 2 /4 = 1

· High energy b ehavior as exp ected · No evidence for contact interactions or anomalous Z - interference · No evidence for Z (weakest limit is 436 GeV at 95% C.L. for mo dels) c.f. London and Rosner, PRL D30 (1984) 1470.
Fermilab 1 May 2002

27

David Strom ­ Oregon


Heavy Quark Elecroweak Results e+e- bb and e+e- cc can b e identified in many different ways:
1600 1400
Candidates / 3 MeV/c2

D

+

ALEPH

1200 1000 800 600 400 200 0 1.8 1.85 1.9 1.95 2 2.05

Full reconstruction of charm · hadrons (e.g. D0, D+, D+, c, s D+), etc.

M(Kpp) (GeV/c2)

·

Identification of low pt pions from D+ D +

Fermilab 1 May 2002

28

David Strom ­ Oregon


· Electrons and muons from decays of b and c-hadrons ( b X , b cX X and c X )
15000 12500

L3
Data uds c fake l bô l bô cô l

6000

L3
Data uds c fake l bôl bôcôl

Number of muons

10000 7500 5000 2500 0

Number of muons
50

4000

2000

10

Muon momentum (GeV/c)

20

30

40

0

0

Muon transverse momentum (GeV/c)
35 -1 : r: ro 44, 996 Run En ssi EVEN 06:05 Data ergy CDC ng 12 T 6476

1

2

3

4

5

6

Ru 27 So Tr Be

n u i a

AP rc gg m

3 R e e C

Pol: R Hadron 15252296

Track Properties

Reconstructed vertices and im· pact parameters from finite b and c-hadron lifetimes

y z x

Fermilab 1 May 2002

29

0

4.000

David Strom ­ Oregon
8.000

centimeters


No. of Hemispheres

Distinguishing e+e- bb and e+e- cc: 3500
3000 2500 2000 1500 1000 500 0 0

SLD
Data MC

b-hadron mass · c-hadron mass

5 GeV 1.8 GeV

b c
uds
1 2 3 4 5

Mass (GeV/c )

2

6

1/Nhad dND*/dxD

0.012 0.01

*

OPAL
D* signal D* signal fit bôD* côD* fit bôD* fit gôcc

0.008 0.006 0.004 0.002 0

Charm from b-hadrons app ears · at low x = pD/pbeam

0

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 xD*

Use charge of reconstructed hadrons, leptons as well as momentum weighted to jet charge to tell q from q
Fermilab 1 May 2002

30

David Strom ­ Oregon


Heavy Quark Fit Parameterize Rb = b , Rc = c , Ab b Ac b, Ab, Ac in terms of 14 f f had had inputs for the mix of b and c-hadrons at LEP, e.g.:


· branching ratios, B r(b ) B r(b c ), B r(c ) · B0 mixing · pro duction probabilities ( f (D0), f (Ds), ...)

Go o dness of fit: Including systematics 2 = 47/(99 - 14) Statistical errors only 2 = 87/(99 - 14) Consistent with individual systematic errors b eing set by statistics limited checks.
Fermilab 1 May 2002

31

David Strom ­ Oregon


Rb = b and Rc = c had ha · Rb from double tag measurement fsingle = fdouble =
b Rb + dbR + b b c Rc + dbR + c c





d

uds db uds

Ruds Ruds

Relation b etween single and double tags: db = (1 + (correlation)f ) 2 Eliminates dep endence on one efficiency (e.g. b) Can b e extended to multiple tags. Weakest link: Dep endence on charm data: Systematics comparable to statistical errors ( 0.3%). · Rc Uses double tags, semi-inclusive/exclusive tags, charm counting and lepton tags.

Fermilab 1 May 2002

32

David Strom ­ Oregon


Rb has a vertex contribution from top:

But with current Tevatron mt there is little sensitivity to Standard Mo del parameters
0.19
Preliminary

R

Z

t t W

b b

0.18
0 c

SM 68% CL 95% CL

0.17

0.16 0.214

0.216

0 Rb

0.218

0.22

Fermilab 1 May 2002

33

David Strom ­ Oregon


Forward-backward Ab b = f

and p olarized forward-backward asymmetries 3 A A , Ac = 3 A A (LEP) and fb 4eb 4ec Ab, Ac (SLD)

Determine the quark direction from thrust axis and: · Jet charge and/or Vertex Charge (SLD) · lepton charge · charm quark typ e (e.g. D0 or D0 )

Weakest link: QCD corrections for quark direction ( Not an inclusive measurement
Must graft hadronization and acceptance corrections from JETSET onto QCD calculation; reduces effect by 50-70% see D. Abbaneo, et al., EPJC4
(1998) 185
ô ­ ô

-4%)
ô

T

b

T

b

e b

+

eb
­

e+

(a) No gluon

(b) Soft gluon

T

ô

T

2nd order Alteralli and Lamp e calculation now
-

b b b
­

e

+

eb
­

e+

sup erseded by Ravindran and van Neervan, Catani and Seymour.

(c) Hard gluon

(d) Thrust forward, quark backward

Fermilab 1 May 2002

34

David Strom ­ Oregon


Ab b = 3 AeAb f 4
ALEPH leptons DELPHI leptons
-1991-95 -1991-95

A

_ 0,bb FB

0.0995 ± 0.0038 ± 0.0017 0.1015 ± 0.0052 ± 0.0020 0.1002 ± 0.0060 ± 0.0035 0.0938 ± 0.0040 ± 0.0022 0.1015 ± 0.0025 ± 0.0012 0.1011 ± 0.0044 ± 0.0015 0.0995 ± 0.0036 ± 0.0022 0.0953 ± 0.0101 ± 0.0056 0.1028 ± 0.0049 ± 0.0046 150 200 [GeV] mt
_ 0,bb FB

· Favors large mh (mh sensitivity from Ae and not Ab ) · Systematics (0.7%) << Statistical (1.5%) · Entire effect of QCD correction similar to error

L3 leptons OPAL leptons DELPHI jet-ch ALEPH jet-ch

+1990-95 -1990-95

+1991-95 +1992-95 -1992-95

DELPHI NN OPAL jet-ch

L3 jet-ch

+1994-95 +1991-95

Winter 2002

LEP

> = 0.0994 ± 0.0017
0.0007 0.0004

Include Total Sys With Common Sys

mH [GeV]

mt = 174.3 ± 5.1 GeV Da
10
2

· QCD error is

0.4%

had

= 0.02761 ± 0.00036

QCD Correction

· OPAL and Delphi numb ers still not final!
Fermilab 1 May 2002

0.09

A

_ 0,bb FB

0.1

0.11

35

David Strom ­ Oregon


Ac and Ab SLD uses flavor tags to extract b and c events and uses p olarization and cos to extract Ac and Ab.

dZ (1 - PeAe)(1 + cos2 ) + (Ae - Pe)(2Af cos ) d cos Ac 0.670 ± 0.026 0.634 ± 0.033 0.653 ± 0.020 0.668 Ab 0.922 ± 0.020 0.893 ± 0.022 0.901 ± 0.013 0.935 2.6

SLD LEP from Af b and Ae Combined Standard Mo del

Fermilab 1 May 2002

36

David Strom ­ Oregon


lept sin2eff
Assume Standard Mo del dep endence of
lept Ab on sin2 eff , eg.

A

0,l fb

Preliminary 0.23099 ± 0.00053 0.23159 ± 0.00041 0.23098 ± 0.00026 0.23218 ± 0.00031 0.23220 ± 0.00079 0.2324 ± 0.0012
c2/d.o.f.: 10.6 / 5

Al(Pt) Al(SLD) A
0,b fb 0,c fb

ef f gVf = (T 3 - 2Qf sin2W ) 3 T gAf = g /gAf Af = 2 1+(Vf /g )2 gVf Af
T
3

A

Average
10
3

0.23149 ± 0.00017

e.g.

+1/2 for u, -1/2 for d, effective 1

value of

mH [GeV]

is third comp onent of weak isospin,

Probability ~ 5%

Possible problem: probability for 2 to b e 10.6/5 or higher is 5%. Weakest links are a small fraction of errors.
Fermilab 1 May 2002

10

2

Da(5)d= 0.02761 ± 0.00036 ha mZ= 91.1875 ± 0.0021 GeV mt= 174.3 ± 5.1 GeV

0.23

si

lept n2qeff =

0.232

(1 - gVl/gAl)/4

0.234

Higgs constraint will improve as had is b etter measured.
37
David Strom ­ Oregon


W and Z measurements (ab ove the Z p ole)
08/07/2001

LEP
20

Preliminary
[pb]

1.5

LEP
±2.0% uncertainty YFSZZ ZZTO

Preliminary

08/07/2001

[pb]

ZZ NC02

WW

15

1

s

10

5

RacoonWW / YFSWW 1.14 no ZWW vertex (Gentle 2.1) only ne exchange (Gentle 2.1)

s
0.5
0 160 170 180
cm

E

[GeV]

190

200

210

0 170

180

Ecm [GeV]

190

200

Fermilab 1 May 2002

38

David Strom ­ Oregon


Mass from e+e- W W qq
Summer 2001 - LEP Preliminary

· Events easy to identify

m

Y

n
X
2 0 0 . cm . 5 10 20 5 0 GeV 0 . 0000 , 0 . 0000 , 0 . 0000 )

Z

Ce n t r e o f s c r e e n i s (

· Use kinematic fit to improve mass measurement · Weakest link: tion Energy calibra-

0 0 0 0 0 0 0 0 0

ALEPH [1996-2000]

DELPHI [1996-2000] L3 [1996-2000]

OPAL [1996-1999] LEP

LEP working group 80.0

. . . . . . . . .

1 9 8 7 6 5 4 3 2 1 0 08123456789 8 808888880. 1 . 000000. ......
80.456 ± 0.060 80.414 ± 0.089 80.314± 0.087 80.516± 0.073 80.448 ± 0.043 81.0 MW [GeV] (non-4q)

correl. with 4q = 0.28

(includes final state)

Fermilab 1 May 2002

39

David Strom ­ Oregon


Energy Calibration at LEP 2

· Energy scale and determined by ­ resonant dep olarization + NMR / flux lo op ­ sp ectrometer ­ Qs versus accelerating voltage ­ radiative returns

Fermilab 1 May 2002

40

David Strom ­ Oregon


Energy Calibration: Standard Metho d
E
Be a m

(GeV)

Resonant dep olarization used to calibrate NMR prob es at low energy ( > 60 GeV) Use flux lo op calibrations to check NMR prob es. Neither the flux lo op measurement or the NMR prob es see all of the B field seen by the b eam. Beam energy error: 20 MeV 17 MeV on mW
41

from RDP

Beam Energy in Physics

n tio ola p tra Ex
60 50 40
Simultaneous Measurements

445

555

66 5

B

10 00
N MR

(Gauss)

B

FL

(Gauss)
1000

Note: Wiggles NOT to Scale

n tio ola p tra Ex
665 555 445
Fit B in this region
FL

?

vs. B

N MR

445

555

66 5

B

10 00
N MR

(Gauss)

Fermilab 1 May 2002

David Strom ­ Oregon


Sp ectrometer Concept:
Bend Angle BPM Triplet LEP Dipole BPM Triplet

Radiative Returns ( e+e- Z ) Use Z mass and final state fermion angles
Example from OPAL
DEb /MeV 2000

1500

OPAL

preliminary
1000

Hadrons Muons Taus Electrons

Realization:
Quad
Wire Position Sensors

500

Steel Dipole

Synchrotron Absorbers

Quad

0
1998 data

-500
BPM Pickups NMR Probes 0m 10m
1997 data

1999 data 2000 data

-1000

180

185

190

195

200

205 L E

EP

210 /GeV

(needs micron precision) Exp ected Error: 20 MeV
Fermilab 1 May 2002

E = -31 ± 40 ± 36MeV
42
David Strom ­ Oregon


Mass from e+e- W W qqqq · Events more difficult to identify

Summer 2001 - LEP Preliminary

· Weakest link: Hadronization and color reconnection systematics.

0. 0. 0. 0. 0. 0. 0. 0. 0.
LEP

ALEPH [1996-2000]

DELPHI [1996-2000] L3 [1996-2000]

OPAL [1996-1999]

LEP working group 80.0

1 9 8 7 6 5 4 3 2 1 0 08123456789 8 808888880. 1 . 000000. ......
80.507± 0.070 80.384± 0.084 80.478 ± 0.093 80.408± 0.120 80.457± 0.062 81.0 MW[GeV] (4q)

correl. with non-4q = 0.28

Fermilab 1 May 2002

43

David Strom ­ Oregon


hadronization pp W

· Mass shift dep ends on "color reconnection". · Work continues to limit size of "color reconnection" effects based on event kinematics and reconstructed masses. Present preliminary Errors for qqqq state: Effect Color Reconnection Bose-Einstein Corr. Hadronization MeV 40 25 17

Z/g pp W KK color reconnection BE

W Mass SK1- Standard Jetset (MeV/c2)

300 250 200 150 100 50 0 -50

SK-I W Mass Bias Comparison
ALEPH- Error on points 0 to 17 MeV DELPHI - Error on points 0 to 6 MeV L3 - Error on points 0 to 15 MeV OPAL - Error on points 0 to 13 MeV

0

10

20

30

40

50

60

70

80

90

100

Fermilab 1 May 2002

44

David Strom ­ Oregon

% Reconnected Events


Experiment

Mass of the W Boson

M

W

[GeV]

No evidence for mass difference b etween qqqq and qq mo des

ALEPH DELPHI L3 OPAL
2

80.471 ± 0.049 80.401 ± 0.066 80.398 ± 0.069 80.490 ± 0.065 c / dof = 32.5 / 39 80.450 ± 0.039

mW (qqqq) = +9 ± 44MeV

LEP
3

10

[GeV]

Preliminary average (same as summer 2001)

10

2

mW = 80.450 ± 0.026(stat.) ± 0.030(syst.)
10 80.2 80.4 MW [GeV]

Da(5)d= ha 0.02761±0.00036 linearly added to Mt = 174.3±5.1 GeV

M

H

80.6

Fermilab 1 May 2002

45

David Strom ­ Oregon


W Mass Summary
W-Boson Mass [GeV]
pp-colliders LEP2 Average NuTeV LEP1/SLD LEP1/SLD/mt
80 80.2
-

NuTeV deviates by

3 :

80.454 ± 0.060 80.450 ± 0.039 80.451 ± 0.033
c2/DoF: 0.0 / 1

In NuTeV has a large correlation b etween and sin2W Deviation could b e explained by a non-Standard Mo del deviation. · Other effects p ossible: Structure functions?
(see hep-ex/0203004 ) Not as well understo o d as QED

80.136 ± 0.084 80.372 ± 0.033 80.379 ± 0.023

mW [GeV]
=1-

80.4

80.6

sin W

2

on-shell

m2 W m2 Z

Many trials? Electroweak with all data including mt, APV, NuTeV gives

mh < 196 GeV (95%C.L.)
but 2/dof (Prob.) is 28.8/15 (1.7%) Higgs limit not sensitive to inclusion of NuTeV in average
Fermilab 1 May 2002

46

David Strom ­ Oregon


LEP Electroweak Summary

Fit to Z p ole data and mW , Fit Prediction

W

Exp er. Constraint

mt GeV mh GeV
s

181+11 -9 121
+166 - 65

174.3 ± 5.1 > 114 0.1181 ± 0.002

0.1185 ± 0.0027

2 (Prob.) 18.5/12 (10%)

Fermilab 1 May 2002

47

David Strom ­ Oregon


Some QCD results
m2~ 2E E ( 1 - cos f )
12

y=

m2 >y E 2is v

cut

JADE jet finder

Relatively easy to define jets, but many schemes: JADE, CAMBRIDGE, DURHAM, GENEVA, etc Weakest link: Lack of 3rd order (NNLO) calculations for event shap es and jet rates.
Fermilab 1 May 2002

48

David Strom ­ Oregon


Running of s · 30 - 190 GeV (OPAL and JADE) · Visible in fraction of three jet events "R3"
R3 [%] R3 [%]

28 26 24 22 20 18 16 14 12 10

R

3 JADE scheme, ycut=0.08 Parton level

s(MZ)=0.1243, xµ=1 s(MZ)=0.1086, xµ=0.063

20 40 60 80 100 120 140 160 180 200 s [GeV]

· Many different jet finds to cho ose from, Jade, Cambridge, Durham, cone. · s from jet related observables:
0034 s(mZ ) = 0.1187+0..0019 -0
Fermilab 1 May 2002

40 37.5 35 32.5 30 27.5 25 22.5 20 17.5

R

3 Cambridge scheme, ycut=0.01 Parton level

s(MZ)=0.1137, xµ=1 s(MZ)=0.1123, xµ=0.464

20 40 60 80 100 120 140 160 180 200 s [GeV]

42.5 40 37.5 35 32.5 30 27.5 25 22.5

R

3 Durham scheme, ycut=0.01 Parton level

s(MZ)=0.1127, xµ=1 s(MZ)=0.1097, xµ=0.31

20 40 60 80 100 120 140 160 180 200 s [GeV]

49

David Strom ­ Oregon


Determination of s and color factors QCD color factors give the relative probability for CA q q g CF g g g TF g qq
1 .4 1 .2 1 .0 0 .8 0 .6

2

3

2

3

1

2

1
O PA L results 9 5 % C .L . 6 8 % C .L . S U (3 ) Q C D lig h t g lu i n o

4

Use jet-rates and angles from energy order jets in four jetevents
B N
Z

P re v i o u s re s u l t s A L E P H ( 6 8 % C .L .) D E L P H I ( 6 8 % C .L .) O PA L (68% C .L .)

Bengtsson-Zerwas
R SW

= (p1 - p2 ), (p3 - p4 )
Nachtmann-Reiter

K

=

((p1 â p4 ), (p2 â p3 ) +(p1 â p3 ), (p2 â p4 ))
K¨ orner-Schierholtz-Willro dt

1 2



3, 4

= (p3 , p4 ) 50

T R /C

F

= (p1 â p2 ), (p3 â p4 )

0 .4 0 .2 0 .0 -0.2 1 .0

1 .2 5

1 .5

1 .7 5

2 .0

C A /C

2 .2 5

2 .5
F

2.75

3 .0

3 .2 5

3 .5

Fermilab 1 May 2002

David Strom ­ Oregon


Running b-quark mass Measure the ratio of 3 jet events in bb events to the ratio in light quark events
b R3 udsc R3

mb(Q ) [GeV]

5 4.5 4 3.5 3 2.5 2 1.5 1

B3 =

Use lifetime information to tag b-events. According to the renormalization group equations, the M S bquark mass is
mb (Q2 ) = mb · ^ 1+
s (Q2 ) 12/23 · Q2 1.175 · s ( ) s (Q2 ) 3

Ô

2

PDG (Production threshold) OPAL ALEPH Brandenburg et al (SLD) DELPHI
10 10 Q= s [GeV]
2

+ 1.500 ·

s (Q2 ) 2 4

+

0.172 ·

+ O s (Q2 )

Fermilab 1 May 2002

51

David Strom ­ Oregon


Some examples from searches · At LEP 2 we were generally able to put stringent limits on anything which was pro duced at a reasonable rate. · There is no time for a general review of searches, but I give a couple of examples which bump ed against the limits of our detectors · A few weakest links:

· SUSY Sleptons

· Generalized Higgs searches

· Charged Higgs
Fermilab 1 May 2002

52

David Strom ­ Oregon


Sleptons · Weakest link: slepton decays to very heavy or very light neutralino
s = 183-208 GeV Selectrons Smuons Staus
Ml < M
R

Mc (GeV/c )

ADLO Preliminary

100 80 60 40

2

c

Typically valid for M > 2 to 15 GeV. · Searches limited to sleptons decaying to visible particles with pt of > 0.05Ebeam 5.0 GeV.

20 0

Observed Expected Excluded at 95% CL
(m =-200 GeV/c2, tanb=1.5)

50

60

70

80

90

100 Ml

R

LEPSUSYWG/01-01.1

Fermilab 1 May 2002

53

David Strom ­ Oregon


Charged Higgs Preliminary
Br(Hôtn)
1

· Predicted by two-doublet extensions to the Standard Mo del · Search for H + cs and H + + Weakest link: Background from e+e- W+W-

Expected Limit
0.8

0.6

0.4

Excluded

LEP 189-209 GeV

0.2

0 60 65 70 75

charged Higgs mass (GeV/c )

80

85

90

95 2

LHWG 2001-5

Fermilab 1 May 2002

54

David Strom ­ Oregon


Generalized Higgs searchs
Ratio of cross section to SM

· Most extreme, OPAL decay mo de indep endent scalar (eg Higgs) search in e+e- ZS0 Weakest link: based primarily on leptonic decays of the Z, needs more luminosity/exp eriments

Preliminary

OPAL Ô
1

s = 91, 183-209 GeV

10

-1

Observed Expected background

(CL=95%)

10

-2

10

-6

10 20 30 40 50 60 70 80 90 100
mS0 (GeV)

Preliminary
Ratio to SM rate

· Completely invisible Higgs (LEP combination) is easier. · 95% C.L. for SM pro duction rate 114.4 GeV.

Observed Median Background 1

10

-1

90

95

100

105

110

115 120 MH, GeV/c2

Fermilab 1 May 2002

55

LHWG 2001-06 David Strom ­ Oregon


Conclusion
Ap ologies to:

· Weakest links are not very weak
· tau physics

· Decide for yourself if LEP systematic errors are sufficiently well understo o d to b e treated as Gaussian · Final LEP 1 results far b etter than exp ected at outset · Still lots of work to finish to LEP 2 analysis and final combinations ­ can we do as well?
Sp ecial thanks to Martin Gr¨newald, Dick Kellogg, Eric u Torrence and Kevin McFarland Fermilab 1 May 2002

· 2- physics · photon structure function · B mixing · fragmentation studies · excited lepton · H · SUSY charginos and neutralinos · SUSY Higgs · Anomalous triple and quartic gauge couplings · single W's, Compton Z's

56

David Strom ­ Oregon