CP-even neutrino beamCP甚至中微子束.ppt

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1、IntroductionIffinitevalueofq13isNOTfoundinthenextroundneutrinoexperiments,weneedMorepowerfulsuperbeamNeutrinofactoryMuon-basedneutrinofactoryBeta-beamWeliketoaddonemoreoptiontoneutrinofactory,whichwouldbenefitCPphasemeasurement.ConceptofCP-evenneutrinobeamId

2、ealneutrinobeamforCPphase(d)measurement:Purebeamsofneutrinoandanti-neutrino.Mono-energetic.Fluxisknownandiscomposedofneutrinoandanti-neutrinoinverselyproportionaltotheircrosssections.CPphasemaybedeterminedjustcountingthenumberofm+/-Weproposetousebound-stateb

3、eta-decay(bb)togeneratemono-energeticanti-neutrinoinadditiontoelectroncapture(EC)neutrino.Thisideaisanextensionofbeta-beamandECbeam.Point2Point1Point3OscillationProbabilityAppearanceexperimentisneededtoobserveCP.Mattereffectisnegligibleatlowenergy.Foranti-ne

4、utrino,the3rdtermreversesitssign.P(ne)+P(ne)issensitivetoq13whileP(ne)-P(ne)toCPphased.Point1OscillationprobabilityandCPasymmetrySin22θ13=0.1,0.05,0.01Atthe1stoscillationpeak,E/L=600MeV/310km.Bound-stateβ-decayIftheparentatomsare(fullyorpartially)ionized,ele

5、ctronsemittedfromordinarybetadecaymaybecapturedinavailableatomicorbits.Inthiscase,anti-neutrinobecomesmono-energetic.Bound-statebeta-decayhasbeenstudiedtheoreticallyforlongtime,butexperimentallyitwasprovenratherrecently.Point2TheoreticalstudiesbyR.Daudeetal:

6、Comptes.Rend.224,1427(1947)R.M.Shrk:Phy.Rev.84,591(1949)J.H.Bahcall:Phy.Rev.124,495(1961)QvalueBoundbetaratioTheratioisbiggerforlargeZandsmallQ.Ratioofbound-to-continuumbetadecayUnfortunatelyrequirementofshortlifetimemeanslargeQandcontradictswiththelargeboun

7、d-to-continuumratio.ExperimentalstudiesThefirstexperimenttodemonstratethebound-statebetadecaywasdonein1992atGSI.Forexample,fullyionized187Re(thegalacticchronometer)lifetimeisshortermorethan109timesthantheneutralRe.Theexperimentshownhereistomeasurethebound-to

8、-continuumratioof207Th.208Pbfromtheheavyionsynchrotron(SIS)hitaproductiontarget;208Tlwasselectedbythefragmentsseparator(FRS),andstoredintheexperimentalstoragering(ESR);thedaughternucleiwasidenti