Can lepton flavor violating interactions explain the atmosph(2)

We investigate whether flavor changing neutrino interactions (FCNIs) can be sufficiently large to provide a viable solution to the atmospheric neutrino problem. Effective operators induced by heavy boson exchange that allow for flavor changing neutrino sca

I.INTRODUCTION

Severalatmosphericneutrino(AN)experiments[1–4]observeananomalousratioνe/νµintheatmosphericneutrino ux.Thislong-standingANproblemhasbeencon rmedbytherecentSuper-Kamiokandehigh-statisticsobservations[4],whichgivestrongevidencethatthestandardmodel(SM)descriptionoftheneutrinosectorisincomplete.ThestandardsolutiontotheANanomalyintermsofneutrinooscillationsrequiresthatneutrinosaremassive,andthatthereismixingintheleptonsector.Then,νµ→ντoscillationscanexplaintheatmosphericneutrinodataprovidedthattherelevantmass-squareddi erenceis AN～10 3eV2andthemuonandtauneutrinoshavelargevacuummixingangles,sin2θAN

Recently,～1.analternativesolution,wheretheANanomalyisinducedbynon-standardneutrinointeractionshasbeenproposed[5–8].Inthisscenariotheneutrinosareassumedtobemassless,buttheyaresubjecttonon-standardinteractions.Forneutrinopropagationinmatter, avorchangingneutrinointeractions(FCNIs)induceano -diagonalterminthee ectiveneutrinomassmatrix,whilenon-universal avordiagonalinteractionsgeneratetherequiredsplittingbetweenthediagonalterms.Apriorisuchascenarioiswellmotivated,sincemanyextensionoftheSMpredictnewneutrinointeractions.Moreover,itiswellknownthatonecannotexplaintheatmospheric[9],solar[10]andLSND[11]neutrinoanomalieswiththreelightneutrinos.Thus,ratherthanignoringoneoftheresultsorintroducingaforth,lightsterile-neutrino[12],itisinterestingtoinvestigatewhetherFCNIscanexplainanyofthethreeneutrinoanomalies[13].

Thetwoe ectiveparametersthatdescribethenon-standardinteractionsofνµandντare[14,15,6–8]

fGfνµντ

ν≡G,(1.1)

F

whereGfνανβ(α,β=µ,τandf=u,d,e)denotesthee ectivecouplingofthefourfermion

operator

Ofν≡(