With Neutrino Masses Revealed, Proton Decay is the

arXiv:hep-ph/9811442v123Nov1998UMD-PP99-052WITHNEUTRINOMASSESREVEALED,PROTONDECAYISTHEMISSINGLINK1JogeshC.PatiPhysicsDepartment,UniversityofMaryland,CollegePark,MD20742,USAOctober,1998ABSTRACTBywayofpayingtributetoAbdusSalam,IrecalltheideasofhigherunificationthatheandIinitiated.Idiscussthecurrentstatusofthoseideasinthelightofrecentdevelopments,includingthoseof:(a)gaugecouplingunification,(b)discoveryofneutrino-oscillationatSuperKamiokande,and(c)ongoingsearchesforprotondecay.Itisremarkedthatthemassofντ(∼1/20eV)suggestedbytheSuperKresultseemstoprovideclearsupportforanunderlyingunityofforcesbasedontheideasof(i)SU(4)-color,(ii)left-rightsymmetryand(iii)supersymmetry.Thechangeinperspective,pertainingtobothgaugecouplingunificationandprotondecay,broughtforthbysupersymmetryandsuperstringsispresented.Thebeneficialrolesofstring-symmetriesinaddressingcertainnaturalnessproblemsofsupersymmetry,includingthatofrapidprotondecay,arenoted.Inthelastsection,attentionisdrawntotherecentjointworkswithK.BabuandF.Wilczek,wheretheinfluenceofneutrinomassesandthusofthenewSuperKresultonprotondecayarenoted.Inthiscontext,itisremarkedthatwithneutrinomassesandcouplingunificationrevealed,thediscoveryofprotondecay,thatremainsasthemissinglink,shouldnotbefarbehind.1BasedinpartonatalkdeliveredattheAbdusSalamMemorialMeeting,ICTP,Trieste,November1997.1I.SalaminPerspectiveAbdusSalamwasagreatscientistandahumanitarian.Hisdeathwasindeedalosstoscienceandespeciallytothegrowthofscienceinthethirdworld.Hewillsurelyberememberedforhiscontributionstophysics,someofwhichhaveproventobeoflastingvalue.TheseincludehispioneeringworkonelectroweakunificationforwhichhesharedtheNobelPrizeinphysicsin1979withSheldonGlashowandStevenWeinberg.Contributionofthiscalibreisrare.ButIbelievehismostvaluablecontributiontoscienceandhumanity,onethatisper-hapsunparalleledintheworld,isthesacrificehehasmadeofhistime,energyandpersonalcomfortinpromotingthecauseofscienceindifferentcornersoftheglobe,inparticularthethirdworld.Hislifelongeffortsinthisdirectionhaveledtothecreationofsomeoutstand-ingresearchcentres,includingespeciallytheInternationalCentreforTheoreticalPhysics(ICTP)atTrieste,Italy,2anInternationalCentreforGeneticEngineeringandBiotech-nologywithcomponentsinTriesteandDelhi,andanInternationalCentreforScienceandHighTechnologyinTrieste.SalamdreamedofcreatingtwentyinternationalcentresliketheICTP,spreadthroughouttheworld,emphasizingdifferentareasofscienceandtechnology.Approachingdevelopedaswellasdevelopingnations,forfundingofsuchinstitutions,Salamoftenusedthephrase:”scienceisnotcheap,butexpendituresonitwillrepaytenfold”[1].IfonlySalamhadlivedafewmoreyearsingoodhealth,manymoresuchinstitutionswouldhavesurelycometofruition.Salamwasalsoastrongsupporterofworldpeace,andthusofnucleardisarmamentandPugwash.Thus,inadditiontohisnumerousawardsforhiscontributionstophysics,includingtheNobelprize,healsoreceived,somemajorawardsforhiscontributionstopeaceandinternationalcollaboration,includingtheAtomsforPeaceAwardin1968andthe”EttoreMajorana”-ScienceforPeaceprizein1989.Itishardtobelievethatasingleindividualcanaccomplishsomuchinonelifetime.Inthissense,Salamwasindeedarareindividual—aphenomenon.IwasespeciallyfortunatetohavecollaboratedwithSalamcloselyforoveradecade.Ofthisperiod,Itreasuremostthememoryofmanymomentswhichweremarkedbythestruggleandthejoyofresearchthatwebothshared.Needlesstosay,Salamplayedacentral2Nownamed(atthismeeting)theAbdusSalamInternationalCentreforTheoreticalPhysics.2roleinthegrowthoftheideaswhichweinitiated.LetmetouchupononeaspectofSalam’spersonality.Duringthetenyearperiodofourcollaboration,therehavebeenmanyletters,faxes,argumentsoverthephoneandinpersonandevenheatedexchanges,abouttastesandjudgementsinphysics,butalwaysinagoodnaturedspirit3Inourdiscussions,Salamhadsomefavoritephrases.Forexample,hewouldsometimescomeupwithanideaandgetexcited.IfIexpressedthatIdidnotlikeitforsuchandsuchreason,hewouldgetimpatientandsaytome:”Mydearsir,whatdoyouwant:Blood?”Iwouldsometimesreplybysaying:”NoProfessorSalam,Iwouldlikesomethingbetter”.WhetherIwasrightorwrong,henevertookitill.Itisthisattitudeonhispartthatledtoahealthycollaborationandastrongbondbetweenus.Mostimportantforme,byprovidingstrongencouragementfromthebeginning,yetoftenarguing,hecouldbringoutthebestinacollaborator.ForthisIwillremaingratefultohim.BywayofpayingtributetoSalamtherefore,Iwouldfirstliketorecallbrieflytheideasonhigherunificationwhichweinitiated(Sec.2),andthenpresenttheircurrentstatusinthecontextofsubsequentexperimentalandtheoreticaldevelopments(Secs.3,4,and5).Theexperimentsofspecialrelevanceare:(a)recentobservationofneutrinooscillationatSuperKamiokande,(b)theprecisionmeasurementsofthegaugecouplingsatLEP,and(c)ongoingsearchesforprotondecay.InSection3,Idiscusshowtherecentdiscoveryofatmosphericneutrino-oscillationatSuperKamiokande4,especiallythemassofντsuggestedbytheSuperKresult,ontheonehandagreeswellwiththegaugecouplingunificationrevealedbytheextrapolationoftheLEPdata,andontheotherhandprovidesclearsupportfortheroutetohigherunificationbasedontheconceptsofS