Outline• TheCMSgroupatWayneState• ThestandardmodelofparticlephysicsandtheHiggsBoson
• TheCMSExperiment• SearchesforNewPhysics• Confirmationanddiscussionofimplications
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CompactMuonSolenoid(CMS)• WayneStategroupconsistsof– Profs.PaulKarchinandRobHarr– ResearchengineerAlfredoGutierrez– PostdocDr.JustinSturdy– PhDstudents:ChrisClarke,KevinSiehl,Prakash Thapa,ShawnZaleski,Nabin Poudyal
• Weinteractwiththetheorygroupof– Profs.AlexeyPetrov, GilPaz,andNausheenShah
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TheStandardModel• Thestandardmodelofparticlephysicsisthetheoryforthebehaviorofthefundamentalparticlesofnature.
• Itisextremely wellestablished.• TheHiggsBosoncompletedthemodel.• Wearenowlookingforphenomenabeyondwhatisinthestandardmodel:– supersymmetry,extradimensions,righthandedcurrents,preons,axions,andmany,manymore
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StandardModel• TheSMisbuiltonprinciplesofgaugeinvariance.– physicsnotchangedbyashiftofpotentialenergy– slightlymorecomplexinparticlephysics
• Masstermsbreakgaugeinvariance– startwithmasslessparticlesand– usesymmetrybreakingtogeneratetherequiredmassterms.
• Soundscrazy,butthatiswhythere’saHiggs.18Nov.2013 PHY6991 7
GaugeTransformations• Thestandardmodelofparticlephysicsisbuiltontheideaofgaugesymmetries.– Recallfromelectromagnetismthatthescalarandvectorpotentialcanbetransformedaccordingto:
– TheMaxwellequationsremainunchanged.
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GaugeTransformations(2)• ThesameprocessisusedinQFT
• Aµ canbethefieldforphotons,gluons,orweakbosons(WandZ).
• ButtheWandZhavemass,andmasstermsbreaktheinvariance
• Symmetrybreakingcangenerateamassforaninitiallymasslessfield(c.f. superconductivity).
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Aµ ! Aµ + @µ⇤
mAµAµ
SymmetryBreaking• SymmetryisbrokenbyaHiggspotentialwhosegroundstatehasnon-zerofield– commonlypicturedwiththemexican hatpotential
• PredictstheexistenceofaHiggsBoson.18Nov.2013 PHY6991 10
ManyQuestionsRemain• Whatisdarkmatter?darkenergy?• Whataccountsforthepredominanceofmatterintheuniverse?
• Howdowesolvethehierarchyproblem?• Howmanygenerationsofquarksandleptons?• Aretheknownparticlesfundamentalorcomposite?• Arethereextradimensions?• Doessupersymmetryexist?Wherearethesuper-partners?
• AreneutrinosMajorana orDiracparticles?18Nov.2013 PHY6991 11
NoteonApparatus• LHCoperationispausedfromDecember2018toMarch2020.
• Improvementstotheacceleratorcomplexwillenableahigherrateofcollisions.
• TheWayneStategroupisworkingon– (Karchin)addingnewdetectorstothemuonsystemforcoverageatverysmallangles(nearthebeampipe),
– (Harr)buildinganewtrackertoreplacetheexistingone.
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TwoWaystoSearch:• DirectSearch– Produceaparticleandobserveitsdecay.– Advantageofdirectlystudyingtheparticle.
• IndirectSearch– Observeeffectsproducedbynewparticlesinpreciselypredictedandmeasuredquantities.
– Advantageofsensitivitytomanykindsofnewparticlesinasinglemeasurement
– Thereisalonghistoryofindirectevidencefornewparticles
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TevatronWHandZHResults
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EvidenceforHiggsatabout3s
SensitivetotheHiggscouplingtobquarks.
SearchingforNewPhysics• Directsearchesarespecific,indirectsearchesarebroad.
• Todate,allresultsfromtheLHCareconsistentwiththestandardmodel.
• IwillsummarizetheworkgoingonbytheWayneStategroup.
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ContactInteractions• Karchinandstudentsaresearchingforsignsofnewinteractionsbetweenquarksandgluonsatveryshortdistances.
• Theylookforanexcessofµ+µ- pairswithveryhighinvariantmass.
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TripleandQuarticGaugeCouplings• W,Z,andg havetripleandquarticcouplings.• TheSMcouplingsarerestrictive,andnon-SMcouplingsaresignsofnewphysics.
• ThesisprojectforK.Siehl,N.Poudyal
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ExclusiveWBosonDecays• Wà ln hasamissingneutrino.• NoexclusiveWdecayhaseverbeenreconstructed!• SearchforWà csdecay.– triggeronDdecay– lookfor3tracks,netchargeof1,lowmass
• Usetomeasuremassandwidthdirectly.
• Veryspeculative18Nov.2013 PHY6991 31
Summary• SearchesfornewphysicsinCMSdata.• Bothdirectandindirectsearchesarepossible.• Wà J/y Ds maybethefirstexclusiveWdecaytobereconstructedandwillmakepossibleinterestingmass,width,andpolarizationmeasurements.
• TriplegaugecouplingsaresensitivetonewphysicsthateffectsthegaugeBosons
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