CP-even neutrino beamCP甚至中微子束

2007/3/8SasaoNeutrinoTelescope1IntroductionIffinitevalueofq13isNOTfoundinthenextroundneutrinoexperiments,weneedMorepowerfulsuperbeamNeutrinofactoryMuon-basedneutrinofactoryBeta-beamWeliketoaddonemoreoptiontoneutrinofactory,whichwouldbenefitCPphasemeasurement.2007/3/8SasaoNeutrinoTelescope2ConceptofCP-evenneutrinobeamIdealneutrinobeamforCPphase(d)measurement:Purebeamsofneutrinoandanti-neutrino.Mono-energetic.Fluxisknownandiscomposedofneutrinoandanti-neutrinoinverselyproportionaltotheircrosssections.CPphasemaybedeterminedjustcountingthenumberofm+/-Weproposetousebound-statebeta-decay(bb)togeneratemono-energeticanti-neutrinoinadditiontoelectroncapture(EC)neutrino.Thisideaisanextensionofbeta-beamandECbeam.Point2Point1Point32007/3/8SasaoNeutrinoTelescope3OscillationProbabilityAppearanceexperimentisneededtoobserveCP.Mattereffectisnegligibleatlowenergy.Foranti-neutrino,the3rdtermreversesitssign.P(ne)+P(ne)issensitivetoq13whileP(ne)-P(ne)toCPphased.2131322222231323121212131223Attheoscillationmaximumof,42theoscillationprobabilityatlowenergyisgivenby()sin(2)sin(2)sin()sin()sin(2)sin(2)sinemLEPscJJcmdnnqqdqq2121312(2),4mLEdqPoint12007/3/8SasaoNeutrinoTelescope4OscillationprobabilityandCPasymmetrySin22θ13=0.1,0.05,0.01Atthe1stoscillationpeak,E/L=600MeV/310km.2007/3/8SasaoNeutrinoTelescope5Bound-stateβ-decayIftheparentatomsare(fullyorpartially)ionized,electronsemittedfromordinarybetadecaymaybecapturedinavailableatomicorbits.Inthiscase,anti-neutrinobecomesmono-energetic.Bound-statebeta-decayhasbeenstudiedtheoreticallyforlongtime,butexperimentallyitwasprovenratherrecently.Point2TheoreticalstudiesbyR.Daudeetal:Comptes.Rend.224,1427(1947)R.M.Shrk:Phy.Rev.84,591(1949)J.H.Bahcall:Phy.Rev.124,495(1961)2007/3/8SasaoNeutrinoTelescope6QvalueBoundbetaratioTheratioisbiggerforlargeZandsmallQ.Ratioofbound-to-continuumbetadecay222203007/2000e(0)1(,)(,):numberoffreeplaces,(0):Wavefucntionofatomicstateatthenucleus,(,):Fermiintegral(1):availableenergyinunitsofmfbnbfcfnnQZnWfZWnfZWnfZUnfortunatelyrequirementofshortlifetimemeanslargeQandcontradictswiththelargebound-to-continuumratio.2007/3/8SasaoNeutrinoTelescope7ExperimentalstudiesThefirstexperimenttodemonstratethebound-statebetadecaywasdonein1992atGSI.Forexample,fullyionized187Re(thegalacticchronometer)lifetimeisshortermorethan109timesthantheneutralRe.Theexperimentshownhereistomeasurethebound-to-continuumratioof207Th.208Pbfromtheheavyionsynchrotron(SIS)hitaproductiontarget;208Tlwasselectedbythefragmentsseparator(FRS),andstoredintheexperimentalstoragering(ESR);thedaughternucleiwasidentifiedbytheFourieranalysisofthefrequencychange.PRL95,052501(2005)2007/3/8SasaoNeutrinoTelescope8BoundDecayBranchingTheresultagreesverywellwiththetheoreticalexpectation.2007/3/8SasaoNeutrinoTelescope9Betabeam&ECbeamThebasicideaofbetabeamistoaccelerateandstorebetaunstablenuclides.Thensharplyfocusedhighenergyneutrinosareobtainedintheforwarddirection.MeritsofbetabeamPureneutrinobeamKnownenergyspectrumKnownintensityMeritsofECbeamMonoenergetic66231818109eeHeLieNeFenn1481486665*eDyTbnJ.Sato:PRL95,131804(2005)J.Bernabeuetal:hep-ph/0605132;J.Bernabeuetal:JHEP0512,14(2005)Zucchelli:PLB532,166(2002)Point32007/3/8SasaoNeutrinoTelescope10CERNschemeforbeta&ECbeam10^14ions/decayringVolpehep-ph/06050332007/3/8SasaoNeutrinoTelescope11Sensitivitytoq13J.E.CampagneetalHep-ph/06031722007/3/8SasaoNeutrinoTelescope12SensitivitytodThereddashedcurveiswhenbetaintensityis½ofthedesign.Thustheintensityisthekeyparameter.2007/3/8SasaoNeutrinoTelescope13CP-evenbeamanditsvariants(Pure)CP-evenbeamConsistsofsingleisotopewhichhasbothECandbound-statebetadecaychannels.Needadetectorcapableofm+/m-discrimination.Examples:108Ag,110Ag,114In,104RhMixedCP-evenbeamTwoseparateisotopes,withECorbound-statebetadecay.Needtostorebothbeamssimultaneouslyinaringorstoretheminatime-sharingmode.Examples:122Cd(bb)&152Yb(EC)2007/3/8SasaoNeutrinoTelescope14Propertyof108Ag１0847Ag10848Cd10846Pd1016keV,1.76%1649keV,95.5%1484keV,0.26%1918keV,2.35%97.15%2.85%ｔ1/2=2.37minb-decayECNeutral108AghasbothECandb-decaymodes.Hydrogen-like108Ag46+hasbound-stateb-decayinaddition.2007/3/8SasaoNeutrinoTelescope15Hydrogen-like108Aglife2.37min-2.36min2007/3/8SasaoNeutrinoTelescope16~0.32007/3/8SasaoNeutrinoTelescope17RateEstimateBoosting108Ag46+withg=180produces(anti)-neutrinobeamofEn=600-700MeV.Thischoiceofenergyismadeconsideringthecrosssectionandmulti-pionproductionrates..Referencerate1014ions/ring(sameasthebeta-beam)100ktontargetatL=310km.4mono-chromaticlinesareincluded.2QEevents/year:toosmall!2007/3/8SasaoNeutrinoTelescope18MixedCP-evenbeamForECbeam,betterisotopeis152Yb.Lifetime:3sec.En4988keVg60EC/(EC+b+)=0.3Rate=1400(QE)events/yearThisrateisworthfurtherstudy.2007/3/8SasaoNeutrinoTelescope19MixedCP-evenbeam(2)Forbbbeam,betterisotopeis122Cd.Lifetime:5.24sec.En3031keVbb/(bb+cb)=0.01Rate=12events/year2007/3/8SasaoNeutrinoTelescope20SomecommentsECnuclidecandidates:152Yb;Lifetime