higgs

HUNTING THEgSeSGS _——, PREHISTORIC humans long knew about manifestations Lodestones,rocksthatexert -ancient times. Likewise, itwas known that R fursometimes makes sparks when itis be rubbedandthatlightning attimeslightsupbe thesky.Anofcoursephotons—or thelight LfA)waves thattheycomprise, aformofelectro- A=magnetic radiation—are detected allthe etime bythehuman eye zB ri sibleforcertain forms ofradioactive decay,ae |(eG tp tooklate19th-century sclence. Studyingo% x Pa ’ themindetailrequired thetechnology of—— (Sy |] thelatterpartofthe20thcentury. Y i Yetwhentheoretical understanding ofthe .«\ ; weakinteractions finallydawnedinabout ~%rs \ s/1970withtheriseofthestandardmodelof & i particlephysic,itbecamecleathatelctro- » \ sidesofthe same coin, Inthe very early Unie gFf % ‘equallypowerfulandprominent.Theditfer- ; fs, RisRitRoap ‘encebetween themarosespontaneouslyy It'sthemissing piece ‘whentheUniverseexpandedandcooled. Pe eae NWS Whatdoesthismean,inplainlanguage? .puzzle, anditCould tell—NorthPoeiscold,whilecentralAftica,on a ol :theequator ishot. Thisisnotbecausethere :USagreat deal ADOUt —isaninnerentaitferenceberweentheNorth Inivelers PoleandAfrica.Rather,itresultsfromthe theUniverse Welivein.gert’smotion.heEarsclimatedeterLeading theoretical minedbythewayitrevolves around the physicists Gordon Kane motion, theNorthPoleisfrigidandthe (left) and Edward Witten “ropursuetheanalogy, wemightthinkof (above) explain why basicparticlesthattransmittheweakinter they'reconvinced thatenoleaeConeamope theHiggs particle is oflight.Inthestandard modelofparticle justwaiting tobe buildingblocks,suchaselectronsand quar.ere Forcesbetweenparticlesaretransmitted by discovered otherparticles, suchasphotons, thecarrier tices, thebasic particles that transmit the knowin about light. Bycontrat, theNorth Re PoleandtheeffectsoftheWandZparticles 30March2002NewScents«wa newscentscom 2» x Pa 5 sophisticated particle accelerator that .atagl}( theNorthPoleasbeingfrigidandhardto aeaaas4 ae ticlephysics,thedifferencecomesbecauseof Rae afterPeterHiggs, oneoftheoriginators of :AGES reGuanaofaireSelacalledeeHlggs DER ~ field)wtiichwaszerointheveryeatlyUni- : \ , Universe cooled—fust asthemotion ofthe +|¢i <4) dustandgassurroundingtheearlySun, SS, a theWandZ—areinaccessible,andwhich raS ‘one—the photon—is obvious indailylife. i \\ mustreallybesomethinginnaturethatplays 23 i i theroleoftheproposed Higgsparticle >) \)ae According tothestandard model, theHiggs A ‘ ‘onesbecause ofitsroleindetermining what ” particlesandforcesarepostulatedtodothe $jobthattheHiggsparticledoesinthestan- “S is lekpertmerit ecidesthisquertod =. rarilardicncdel pieture ofelataicaal tiles ri . sy aspectsofthestandard model,apartfrom “iiadadsaeFiche theHiggsparticle,havebeenspectacularly work forall theparticle, while other app- § effective starting point forunified field 3 * . theories, andstring theories, thatseektoi ¢ 4 Thesetheories areattractive butunproven. iS rOurhopeisthat,alongwithdiscovering the y deeper eve Thestandard model istested mostdirectly ae byaccelerating particles toveryhighener- [au . laboratories inEurope (CERN, andDESY in B& Hamburg), theUS(especially SLAC inCali i bis Japan (the KEK laboratory. particles,thetopquark,andthetauneu- fe- ii . ‘trino,Also,numerous standard modelpre- KG eli \ dictionsfordetailsofelementary particlere- /ie i . Large Electron Positron (LEP) acceleratorat I Ci ge a CERN.Theybehaved inaccordwiththe MMMM = q as standardmodeltoaveryhighdegree BZ,h >»he G2 z thetheoryplusotherexperiments.thisisaaaia4 yytyUypossible Because the standard model isaQAM Se/YYYj. mathematicaltheory thatdescribes many a /i\ Wwe Tave alreadybeendone / ¥ Wy ‘experiments havealreadybeendone J Yi liderthatdiscoveredtheWandZparticles, MAA MMMA (CERNknew just what energy was necded theory pus experimentsalready performed. GeV respectively them, Finally, thetests ofthestandard model = ’ actually domuch morethanweavesofar Mam Sp,5a suggested.Toexplainwhy,wemustexplain Ee2 thethird reason forsurmising thatthe © BP standard modeltheoryoftheHiggsparticle CY aed pointforunifyingtheforcesofnature. te: ‘ThestandardmodeldescribesthreeoftheXO i j Hy forcesofnature:electromagnetism, the <Q Sie A teractions andchemcafore. AY WWea] — omitsonlygravity. Withthehelpofthe \ \\ We / theelectromagnetic andweakinteractions j NN (Canwegofurtherandbuildaunifiedfield }| \\if . theoryofallthreestandardmodelforces?A ip) i\fh beautiflstrategyfordoingsowasproposed ip) almost30yearsagointhe“grandunified 1h) theory’ofHowardGeorgiandSheldon All \_— | Glashow,whichdrewoneatllerworkby ANY|\)eaeFr JogeshPatiandAbdusSalam,Theprecise SS Mi ste, ‘measurements performed sincethenhave :ofthe three standard model forces are just theHiggsparticle weighs lessthanabout THERE |SVERY tighttomakegrandunificationwork200GeV,andlessthanabout160GeVwith ] Buttheresacatch:grandunificationonlyhighconfidence. Dietexperiments have GOOD INDIRECT snakessenseithestandardmodelconcept swept through roughlyhalfoftheexpected EVIDENCE, ANDA.ofthetiggsparticiisright.Soeitherthisis orendprobablyaaFotgoalof0a HINT OFDIRECT tiicecoupingstrengthshowninthePare piri rec 2g MIDI: =see Howfarhas experiment current reached? nature onunwary physicist.reetepenentlboundontgs THATHIGGS "Anirsnoteonlyxe,orgrand particlemassisthattisatteat 1138Gev, PARTICLES DOEXIST’ unificationtowork,oneatsoneedsto assumesumingthevalidityofthestandardmodel supersymmetry. Toexplainsupersymmetry‘Thismeasurement wasmadebytheextra-present,thehighestenerglesintheworldare_propelyisasubjectforanotherarticle.But ordinarily successful LPcollider which also attained atthe Tevatron collider atFermilab, inbrlf, supersymmetry isanenrichment Carried outmany ofthemost accurate which recently resumed operation afteranofElnstln’s theory ofspecial relativity to Standard model ets. When thefinalstageofupgradetoprovidemoreIntenseparticleincludequantumvariableinthestructureof LEPwasbuilt wasexpected tosearch for beams, Ifitperforms asplanned, itwillbespace-time. Itrelates thequarks andelectrons Higgs particles uptoanenergy ofabout 108 abletodiscover Higgs particles uptoabout tothe particles thattransmitthe ores. ItpreGeVBystrainingeverythingtothelimit,LEP180GeVwithinseveralyears,andhopefully dietsnewparticles,partnersfortheparticlesengineerswereabletooperatethemachine confirmorexcludeby2004thehintfromLEP._wealeadyknow,thatshouldbediscoveredatbeyond itsdesign, making itpossible to Beyond theTevatron, thenextbigstepinthe Tevatron andLHCandfuture facilities search fortheHiggs upto113.5GeV. energy willcome withthecommissioning suchasalinea electron collider. Itoffers aFamous,intheclosingstageoftheLEPoftheLargeHadronCollider(LHC)atCERN,windowtograndunification andbeyond programme,ahintwasfoundofadiscovery scheduledfor2006,Itisexpectedtohavethattotheevenmoreambitiousstring bftheHiggs particle with amass ofvery roughly seven timesthe energyoftheTevatrontheory,whichmayunifygravityalongwith neatly118GeV.Unfortunately, LEPdidnotandconsiderably moreintenseparticlebeams.theotherforces.Supersymmetry affectsthe {gite have theenergy andintensity toestab- TheLHC willcoverthewholerangeofHiggs_detallsofsearchesforHiggsparticlesbutnot ishthisconclusively orruleitout.Sowewillparticlemasses upto200GeVand{farbeyond, thegeneralidea.hvetoawait future experiments. ndshould findtheHiggs particle, orwhat- Ifsupersymmetry 1sdiscovered, itwill “Thus themotivation forproving the everdoesthejobthatItssupposed todo, putphysics onanewlevel. ItwillenableexistenceofHiggsparticlesIsassongorwhetheritsthestandardmodeltheoryofexperimenters tomakemanyimportantandStrongerthanever,andthereIsverygoodtheHiggsparticlethatprovestobecomector excitingmeasurements andgiveaboostto tvidence, that theydoinfactexst.JustasFindingandstudyingtheHiggsparticleanddeeperinsightsbeyondthat. a direct observation ofthetopquarkremained exploring thestandard model atyethigherelusiveuntilfalitieswithsuficientenergyenergiesmakesanexcitingmission.AndtheGordonKaneiatheUniversoMichigan, and intensitywereavallable,soItsnowforpropertiesoftheHiggsparticlewilpoint10.janarbor Higgs particles. fewdevelopments. There lsagood chance Edward witen sate Intute forAdvancedWhereillthenextresultscomefom?AtthattheLH,andpossiblytheTevatron,willStd,Princeton,NewJersey