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

The rstpointfollowsimmediatelyfromthefactthattheSMneutrinosappearinSU(2)ingtheupperboundsonτ →µ M(M=π0,ρ0,η)andτ →µ e+e weconstrain,inamodel-independentway,thestrengthofthe avorchangingneutrinoscatteringreactionνµf→ντftobeatmostattheone-percentlevel(comparedwithGF).Fortheuniquecaseofanintermediatescalarsingletwederiveasevereconstraintonthenon-universal avordiagonalneutrinointeractionsusingtheupperboundonleptonuniversalityviolation.

Theconstraintsweobtainedfortheparametersthatdescribethenewneutrinointer-actionsarenotconsistentwiththevaluesthatarerequiredtoexplaintheANanomalyintermsofFCNIs.Thusweconcludethatsuchasolutionisruledout.Onecouldevadeourboundsby ne-tuningseveralnewphysicscontributions,butwedonotconsidersuchascenarioasveryattractive.Nevertheless,wewouldliketostressthatultimatelyanyalter-nativeexplanation[39]oftheANanomalyshouldbetestedbytheexperimentaldataitself.Forthetimebeing“standard”neutrinooscillationswithmassiveneutrinosremainthemostplausibleandelegantsolution.

ACKNOWLEDGMENTS

WethankK.S.Babu,J.Erler,Y.NirandS.Pakvasaforhelpfuldiscussions.Y.G.issupportedbytheU.S.DepartmentofEnergyundercontractDE-AC03-76SF00515.D.M.P.issupportedunderDepartmentofEnergycontractDE-AC02-98CH10886.