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Fully differential W' production and decay at next-to-leading order in QCD

We present the fully differential production and decay of a W' boson, with arbitrary vector and axial-vector couplings, to any final state at next-to-leading order in QCD. We demonstrate a complete factorization of couplings at next-to-leading order in bot

Fullydi erentialW′productionanddecayatnext-to-leadingorderinQCD

ZackSullivan

TheoreticalPhysicsDepartment,FermiNationalAcceleratorLaboratory,Batavia,IL,60510-0500

(July23,2002)Wepresentthefullydi erentialproductionanddecayofaW′boson,witharbitraryvectorandaxial-vectorcouplings,toany nalstateatnext-to-leadingorderinQCD.Wedemonstrateacompletefactorizationofcouplingsatnext-to-leadingorderinboththepartialwidthoftheW′boson,andinthefulltwo-to-twocrosssection.WeprovidenumericalpredictionsforthecontributionofaW′bosontosingle-top-quarkproduction,andseparateresultsbasedonwhetherthemassoftheright-handedneutrinoνRislightenoughfortheleptonicdecaychanneltobeopen.Thesingle-top-quarkanalysiswillallowforanimproveddirectW′masslimitof525–550GeVusingdatafromrunIoftheFermilabTevatron.Weproposeamodi edtolerancemethodforestimatingpartondistributionfunctionuncertaintiesincrosssections.

arXiv:hep-p

Fully differential W' production and decay at next-to-leading order in QCD

h

Fully differential W' production and decay at next-to-leading order in QCD

/0207290v1 23 Jul 2002

I.INTRODUCTION

Sincetheintroductionofthestandardmodel,manyextensionshavebeenproposedthatinvolveenhancedgaugesymmetries.Onecommonfeatureofthesemodelsisthepredictionofadditionalgaugebosons,genericallycalledW′andZ′bosons.Innon-universalandtop- avormodels,theW′gaugebosonarisesfromanewSU(2)Lsectorthatdistinguishesbetweengenerationsoffermionsandmaytreatquarksandleptonsdi erentlyTheW′bosoncouldbethelowestKaluza-KleinmodeoftheWboson[7],oraheavymasseigenstateinnon-commutingextendedtechnicolor[8].Inaleft-rightsymmetricmodeltheW′andstandard-modelWbosonsareremnantsofabrokenSU(2)L×SU(2)RsymmetryTheresultingleft-rightmixingmaybenaturallysuppressedbyorbifoldbreakingoftheleft-rightsymmetryorbysupersymmetricinteractionsWhileindirectboundsmaybeplacedonthemassesandcouplingsofthesevariousW′bosonswithinthecontextoftheirexplicittheories,itisalwaysadvantageoustosearchforthesenewparticlesdirectly.Inordertofacilitateadirectexperimentalsearch,andtoachievethemostgeneralcontactwiththeory,wecalculatethefullydi erentialnext-to-leadingordercrosssectionfortheproductionanddecayofaW′bosontoany nalstatewitharbitraryvectorandaxial-vectorcouplings.

ThemostgeneralLorentzinvariantLagrangiandescribingthecouplingofaW′tofermionsmaybewrittenas

L=

g2

whereζisaleft-rightmixingangle,andωisaCP-violatingphasethatcanbeabsorbedintoVR.Inthisnotation,

aregeneralizedCabibbo-Kobayashi-Maskawa(GCKM)matrices.gR(L)aretheright(left)gaugecouplings,andVfR,Lifj

InmodelswheretheWandW′mix,themixingangleζisusuallyconstrainedtobesmall(|ζ|<afew×10 5–10 2[16]).Hence,thesearchforpurelyright-orleft-handedstatesappearswellmotivated.

ManydirectsearchesforW′bosonshavebeenperformedathadroncolliders.Mostexperimentalanalyseshaveconsideredleft-orright-handedW′bosons,withstandard-model-likecouplings,thatdecayintoleptonic nalstates.

′′

Left-handedWLbosons,orright-handedWRbosonsinwhichthedecayintoaright-handedneutrinoνRiskinemati-callyallowed,areconstrainedtohavemassesmW′>786GeVIfmνR>~mW′thedecaytoνRisnotallowed,′

andtheright-handedWRbosonsareonlydirectlyconstrainedbypeaksearchesinthedijetdata.UnlesstheW′hasgreatlyenhancedcouplingstolightquarks,thedijetdataarelimitedbyQCDbackgroundstoprovidingamasslimitof420GeVTheonly nalstatenotmeasuredbyoneoftheexperimentslistedaboveinvolvesthedecayofaW′toasingletopquark.InRefs.itwaspointedoutthatadeviationofmeasuredthesingle-top-quarkcrosssectionfromthe

′ L

√fiγµgReiωcosζVfRWfj+H.c.,PP+gsinζVLRLfffijij

(2)

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