the LEP Electroweak Working Group + and the SLD Heavy Flavou

This note presents a combination of published and preliminary electroweak results from the four LEP collaborations and the SLD collaboration which were prepared for the 1999 summer conferences. Averages are derived for hadronic and leptonic cross sections,

EUROPEANORGANIZATIONFORNUCLEARRESEARCH

CERN-EP-2000-016January21,2000

ACombinationofPreliminaryElectroweakMeasurementsandConstraintsontheStandardModel

TheLEPCollaborations ALEPH,DELPHI,L3,OPAL,

theLEPElectroweakWorkingGroup

andtheSLDHeavyFlavourandElectroweakGroups

PreparedfromContributionsoftheLEPandSLDexperiments

tothe1999Summerconferences.

Abstract

ThisnotepresentsacombinationofpublishedandpreliminaryelectroweakresultsfromthefourLEPcollaborationsandtheSLDcollaborationwhichwerepreparedforthe1999summerconfer-ences.Averagesarederivedforhadronicandleptoniccrosssections,theleptonicforward-backward

cpartialwidthsandforward-backwardasymmetries,theτpolarisationasymmetries,theb

asymmetriesandtheq

TheLEPCollaborationseachtakeresponsibilityforthepreliminarydataoftheirownexperiment.

D.Abbaneo,J.Alcaraz,P.Antilogus,P.Bambade,A.Barczyk,T.Behnke,G.Bella,A.Blondel,S.Blyth,D.Bourilkov,D.G.Charlton,R.Clare,P.deJong,G.Duckeck,M.Elsing,F.Filthaut,D.Glenzinski,M.W.Gr¨unewald,A.Gurtu,J.B.Hansen,R.Hawkings,J.Holt,R.W.L.Jones,T.Kawamoto,R.G.Kellogg,N.Kjaer,M.Kobel,http://n¸con,W.Lohmann,A.Macchiolo,C.Mariotti,M.Martinez,G.Martinez,C.Matteuzzi,M.N.Minard,J.Mnich,K.M¨onig,P.Molnar,S.Olshevski,U.Parzefall,Ch.Paus,M.Pepe-Altarelli,B.Pietrzyk,G.Quast,D.Reid,P.Renton,H.Rick,J.M.Roney,E.Sanchez,C.Sbarra,R.Sekulin,D.Strom,R.Tenchini,F.Teubert,M.A.Thomson,J.Timmermans,M.Verzocchi,H.Wahlen,C.P.Ward,N.K.Watson,P.S.Wells.

J.Brau,N.deGroot,P.C.Rowson,M.Swartz,D.Su.

This note presents a combination of published and preliminary electroweak results from the four LEP collaborations and the SLD collaboration which were prepared for the 1999 summer conferences. Averages are derived for hadronic and leptonic cross sections,

1Introduction

ThefourLEPexperimentshavepreviouslypresented[1]parametersderivedfromtheZresonanceusingpublishedandpreliminaryresultsbasedondatarecordeduntiltheendof1995.Sincethenadditionalresultshavebecomeavailable.Toallowaquickassessment,aboxhighlightingtheupdatesisgivenatthebeginningofeachsection.Since1996LEPhasrunatenergiesabovetheW-pairproductionthreshold.In1998thedeliveredluminositywassigni cantlyhigherthaninpreviousyears,andthustheknowledgeofthepropertiesoftheWboson,especiallyitsmass,hasbeensigni cantlyimproved.TheseresultsaredenotedasLEP-IIresults.

TheLEP-Idata(1990-1995)consistofthehadronicandleptoniccrosssections,theleptonic

cpartialwidthsandforward-backwardasymmetries,theτpolarisationasymmetries,theb

forward-backwardasymmetriesandtheqbandc

fproductionatenergiesabovetheZ;

Section4τpolarisation;

Section5ALRmeasurementatSLD;Section6Heavy avouranalyses;

Section7Inclusivehadronicchargeasymmetry;

Section8Wbosonproperties,includingmW,branchingratios,WWproductioncrosssectionsand

triple-gauge-bosoncouplings;Section9ZZproductioncrosssections;

Section10Interpretationoftheresults,includingthecombinationofresultsfromLEP,SLD,neu-trinointeractionexperimentsandfromCDFandDØ;Section11Prospectsforthefuture.

This note presents a combination of published and preliminary electroweak results from the four LEP collaborations and the SLD collaboration which were prepared for the 1999 summer conferences. Averages are derived for hadronic and leptonic cross sections,

2ZLineshapeandLeptonForward-BackwardAsymmetries

Updateswithrespecttolastsummer:

Allexperimentshaveupdatedtheirresults.ALEPHhavepresented nalvalues.Manyrecenttheo-reticaldevelopmentshavebeenincludedintheresultsand ts.

2.1ResultsfromtheZPeakData

TheresultspresentedherearebasedonthefullLEP-Idataset.Thisincludesthedatatakenduring

√

theenergyscansin1990and1991intherange1|

s mZ|<1.8GeV)andthe

peakrunningin1994.ThetotalstatisticsandthesystematicerrorsontheindividualanalysesofthefourLEPcollaborationsaregiveninTables1and2.DetailsoftheindividualanalysescanbefoundinReferences4–7.

q

’90-’91’93prel.’95prel.

+

’92’94prel.

total

77

75

202

66

500

343127

81

1724

ALEPH

433

630

1310

735

370536

58

79

657

526

406658

293

DELPHI

697

646

1585

2572

L3416

OPAL733

2600LEP1660

Table1:LEPstatisticsinunitsof103eventsusedfortheanalysisoftheZlineshapeandleptonforward-backwardasymmetries.

FortheaveragingofresultstheLEPexperimentsprovideastandardsetof9parametersdescribingtheinformationcontainedinhadronicandleptoniccrosssectionsandleptonicforward-backwardasymmetries[2,10].Theseparametersareconvenientfor ttingandaveragingsincetheyhavesmallcorrelations.Theyare:

ThemassandtotalwidthoftheZboson,wherethede nitionisbasedontheBreit-Wignerdenominator(s m2Z+isΓZ/mZ)(s-dependentwidth)[11]. ThehadronicpolecrosssectionofZexchange:

σh≡

12π

Γ2Z

.(1)

HereΓeeandΓhadarethepartialwidthsoftheZfordecaysintoelectronsandhadrons.

This note presents a combination of published and preliminary electroweak results from the four LEP collaborations and the SLD collaboration which were prepared for the 1999 summer conferences. Averages are derived for hadronic and leptonic cross sections,

’93

Lexp.(a)σhadσµAµFB

0.067%

0.069%

0.16%

0.11%

0.18%0.0012

0.0005

0.0007

’95

prel.

0.080%0.073%

0.46%

0.11%

0.60%0.0026

0.0005

0.0020

’94

prel.

0.09%0.11%

0.52%

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