Flavor changing neutrino interactions and CP viola

arXiv:hep-ph/0210138v717Nov2003FlavorchangingneutrinointeractionsandCPviolationinneutrinooscillationsToshihikoHattori,a),1TsutomHasuike,b),2andSeiichiWakaizumic),3a)InstituteofTheoreticalPhysics,UniversityofTokushima,Tokushima770-8502,Japanb)DepartmentofPhysics,AnanCollegeofTechnology,Anan774-0017,Japanc)CenterforUniversityExtension,UniversityofTokushima,Tokushima770-8502,JapanAbstractWeinvestigatetheinterferenceeffectsofnon-standardneutrino-matterinterac-tions(NSNI)withthemass-inducedneutrinooscillations.TheNSNIiscomposedofflavor-changingneutrinointeractions(FCNI)andflavor-diagonalneutrinoin-teractions(FDNI).Bothoftheinteractionsareintroducedintheνμ−ντsectorandtheνe−νμsectorinordertostudytheireffectsinνμ→ντandνμ→νeoscillations,respectively.TheFCNIeffectprovestopossiblydominatetheCPviolatingeffectandsignificantlysurviveasafakeCPviolatingeffectintheneu-trinoenergyregionwherethepureCPviolatingeffect,ordinarymattereffectandFDNIeffectfall,forexample,above4GeVatthebaselineofL=730kmintheνμ→ντoscillationforthemaximumparametervaluesofFCNIandFDNIallowedbytheatmosphericneutrinooscillationdata.TheFCNIandFDNIeffectsonCPviolationinνμ→νeoscillationarenegligiblysmallduetothestringentconstraintsonFCNIfromtheboundsonleptonflavorviolatingprocessesandonFDNIfromthelimitsonleptonuniversalityviolation.1e-mail:[e-mail]2e-mail:[e-mail]3e-mail:[e-mail]1IIntroductionIntheframeworkofmassiveneutrinosandleptonicmixing,theatmosphericneutrinoanomaly[1]isresolvedbytheνμ→ντoscillationwithnearlymaximalmixing[2]andthesolarneutrinodeficit[3]isinterpretedbytheoscillationofνeintoanotherneutrinostatewithlargemixinganglesolution[4]intheMikheyev-Smirnov-Wolfenstein(MSW)mechanismofneutrinointeractionswithmatter[5]inthethree-neutrinoscheme,wheretheneutrinoflavoreigenstatesνα(α=e,μ,τ)areexpressedbyasuperpositionoftheirmasseigenstatesνi(i=1,2,3)withmassmiasfollows:να=3Xi=1Uαiνi,(1)whereUisthe3×3unitarymixingmatrix,whichiscalledasMaki-Nakagawa-Sakata(MNS)matrix[6].Thereactorexperimentofsearchfor¯νeoscillations,CHOOZ,givesanupperlimitontheelementUe3,whichisverysmallas|Ue3|0.22[7].Theliquidscintillationexperiment,LSND,claimsadiscoveryof¯νμ→¯νeoscillations[8],whichrequiresafourthsterileneutrino.Theabovesituationseemstoconvinceusofaschemeofmassiveneutrinosandleptonmixing.Inadditiontothisscheme,itisinterestingtoinvestigatenon-standardneutrino-matterinteractionsintheneutrinooscillationsinordertosearchfornewphysicsbeyondthestandardmodel.Thenon-standardneutrino-matterinteraction(NSNI)isoriginatedfromWolfenstein’swork[9]andtheflavor-changingneutrino-matterinteraction(FCNI)andflavor-diagonalneutrino-matterinteraction(FDNI)wereusedinordertostudythesolarneutrinoproblem,notbyrelyingonthemass-inducedneutrinooscillations[10][11],andthenbyconsideringthemassub-leadingeffectstothestandardmass-inducedoscillations[12].Fortheatmosphericneutrinoproblem,theFDNIalone[13]andbothoftheFCNIandFDNIwereapplied[14].ThemereNSNI,however,hasprovednottobeabletosolvetheatmosphericneutrinoproblem[15][16].2Afterthat,theFCNIhasbeenstudiedassub-leadingeffectstothestandardmass-inducedneutrinooscillationsbyconsideringFCNIinνμ−ντsectorandinνe−ντsector[16][17]anditsdetectabilityatafutureneutrinofactoryisdiscussedinRefs.[17][18][19].InRef.19,itisshownthattheFCNIdominatestheνeos-cillationprobabilityatsufficientlyhighneutrinoenergies.Moreover,theNSNIwiththenetrinomassescaninducesomefakeCPviolatingeffectinmatterinthelong-baselineoscillationexperiments[20].Therearealsocombinedanalyseswithnewflavor-changingneutrinointeractionsoccuringintheneutrinoproductionanddetectionprocessesinadditiontotheabove-mentionednon-standardinteractionswithmatterduringneutrinopropagation,ofwhicheffectsareenhancedbytheinterferencewiththeordinaryweakinteractionsintheoscillationphenomena[21].Inthispaper,weanalyzethenon-standardneutrino-matterinteractioneffects(NSNI)totheCPviolatingeffectsintheneutrinooscillationsbyconsideringtheminνμ−ντsectorandνe−νμsectorinthethree-neutrinoscheme.TheNSNIconsistsoftheabove-mentionedFCNIandflavor-diagonalneutrino-matterinteractions(FDNI).TheevolutionequationoftheneutrinoflavorstatesissolvedanalyticallybyusingArafune-Koike-Sato’sperturbativemethod[22]andwecalculatetheneutrinooscillationprobabilityforthegeneralνα→νβoscillation.WeapplythisanalyticexpressionoftheprobabilitytocalculatetheCPviolatingeffectsinνμ→ντandνμ→νeoscillations,i.e.thedifferencebetweentheneutrinoandtheantineutrinooscillationprobabilities.WefindthattheFCNImattereffectsurvivesanddominatestheCPviolatingeffectinνμ→ντoscillationevenafterboththepureCPviolatingeffectduetothephaseofUandthefakeCPviolatingonesduetotheordinaryandFDNImattereffectsfall.Thisshowsthatthenon-standardflavorchangingneutrino-matterinteractioncouldbedetectedintheCPviolatingeffectinνμ→ντoscillationattheneutrinoenergieswhereboththepureCPviolatingeffectandtheordinarymattereffectbecomesufficientlysmall3andundetectable.Forνμ→νeoscillation,theFCNIandFDNIeffectsontheCPviolatingeffectarenegligiblysmallduetothestringentconstraints[11][15][23]onFCNIfromthebou