effecve theory for deformed nuclei - uam/csic · effecve theory for deformed nuclei • eft...
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ThomasPapenbrock
and
EFTformanybodysystems Madrid1.16.2014ResearchpartlyfundedbytheUSDepartmentofEnergy
Effec%vetheoryfordeformednuclei
TP,Nucl.Phys.A852,36(2011);arXiv:1011.5026JialinZhangandTP,Phys.Rev.C87,034323(2013);arXiv:1302.3775
TPandH.Weidenmüller,arXiv.1307.1181ToñoCoelloandTP,inpreparaYon
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SeparaYonofscalesinnuclearphysics
Fig.:Bertsch,Dean,Nazarewicz,SciDACreview(2007)
ChiraleffecYvefieldtheory
EnergyorRe
soluYo
n
EffecYvetheoryofdeformednuclei
EffecYvetheoriesprovideuswithmodelindependence
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DeformaYonofatomicnuclei
Modelsrule!• BohrHamiltonian• GeneralcollecYvemodel• InteracYngbosonmodel
Rotors: E(4+)/E(2+) = 10/3 Vibrators: E(4+)/E(2+) = 2
EffecYvetheory!
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ModelsfornuclearrotaYons
1. BohrHamiltonian(1952),Bohr&Modelson’scollecYvemodel(1953).• fivequadrupoledegreesoffreedommodelsurfacedeformaYons
threeEuleranglesandtwoshapeparameters2. GeneralcollecYvemodel“Frankfurtmodel”[Gneuss,Mosel&Greiner
(1969);Hess,Maruhn,Greiner(1981)]3. Arima&Iachello’sInteracYngBosonModel(1976)
• sanddbosonaredegreesoffreedom;algebraicapproachwithsymmetriesimposedonHamiltonianinlimiYngcases
• TheexisYngmodelsdescribemanyaspectsofvastsetsofdataquitewell.
• TheyaredifficulttogeneralizeinatractablewayduetothedifficulYesincouplingofangularmomentaandthecomputaYonofmatrixelements.
• RenewedinterestincomputaYonallytractablemodels[M.A.Caprio,Phys.Rev.C68,054303(2003);D.J.Rowe,Nucl.Phys.A735,372(2004)]
ApproachwithinaneffecYvefieldtheorypossible.
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ξ
Ω
SeparaYonofscale:ξ<<Ω
Spectrumofadeformednucleus
g.s.‐band
γ‐band
“β”‐band
γγ‐band
“Complete”spectrumof168Er[Davidsonet al.,J.Phys.G7,455(1981)]
Keyfeatures:rotaYonalbandsontopof“vibraYonal”bandheadsTypicaldeformedeven‐evennuclei:lowestvibraYonalstatehasJπ=0+,2+
Similarlycomplete:spectrumof162DyA.Aprahamianet al.,Nucl.Phys.A764,42(2006)
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EFTforfinitesystemswith“emergentsymmetrybreaking”*ConsiderenergyscalesinanatomicnucleuswithmassnumberA
Radius
MomentofinerYa
RotaYonalenergy~
TypicalwavenumberofNGmode
Thus,forA>>1thereisaregimewhererotaYonalmoYonisacorrecYontoNGmodes
*Yannouleas&Landman,Rep.Progr.Phys.70,2067(2007)
Relatedwork:CorrecYonstoparYYonfuncYonsofinfinitesystemsfromfinitesimulaYons.[Horsch&vonderLinden,Z.Phys.B72,181(1988);H.Leutwyler,Phys.Led.B189,197(1987);Gasser&Leutwyler,Nucl.Phys.B307,763(1988);Hasenfratz&Niedermayer,Z.Phys.B92,91(1993),hep‐lat/9212022.]
CosetSO(3)/SO(2)ininfinitesystems:[Leutwyler,Phys.Rev.D49,3033(1994);Roman&Soto,Int.J.Mod.Phys.B13,755(1999);Hofmann,Phys.Rev.B60,388(1999);Bär,Imboden&Wiese,Nucl.Phys.B686,347(2004).]
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Keystep:singleoutthezeromode[Leutwyler,Phys.Led.B189,197(1987)]
Cosetspaceformoleculesanddeformednuclei:
ParameterizaYonintermsofYme‐dependentangles(α,β)andNambu‐Goldstonefields(x,y).
ProperYesofNGfields:
UponquanYzaYon,angles(α,β)restoresphericalsymmetry(goodangularmomentum)while(x,y)becomeintrinsicquanYzedexcitaYonmodes.
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BehaviorunderrotaYonsBehaviorofU=guunderrotaYonsr,with
(α,β)transformnonlinearly(likeanglesonthesphere). (x,y)areintrinsicvariablesandtransformlinearly(withacomplicatedangle)
Steps:• idenYfyinvariants• powercounYng:rotaYons<<vibraYons<<breakupscale(100keV<<1MeV<<3MeV)• Expansionoffields(x,y)innormalmodesandcanonicalquanYzaYon• QuantumNumbers:TotalangularmomentumJ,intrinsicprojecYonK• Keydifferencebetweennucleiandmolecules:Nucleiarepairedintheirgroundstate.Thisexcludeslow‐energyexcitaYonswithposiYveparityandoddK• Result:RotaYonalbandsontopofvibraYonal(spinK)bandheads
TPandH.Weidenmüller,arXiv.1307.1181(v2soon),Phys.Rev.C(2014)
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ConstrucYonofasimplereffecYvetheoryfordeformednuclei
StaywithinQM,considereffecYvetheoryforangles(α,β),andaddphysicsofintrinsicquadrupoledegreesoffreedomwithSSB.
Quadrupolefield• canbeviewedasoneofthenormalmodesoftheintrinsicfields(x,y)• takenfromphenomenologicalapproachbylookingatlow‐energystates
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1.IdenYfyrelevantdegreesoffreedom
Quadrupoledegreesoffreedomdescribespinsandparityoflow‐energyspectra
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2.IdenYfyrelevantsymmetriesandsymmetrybreaking
Symmetry:RotaYonalinvarianceVerylowenergyexcitaYons(“zeromodes”)indicateemergentsymmetrybreaking
ξ
Ω
SeparaYonofscale:ξ<<Ω
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NonlinearrealizaYonoftherotaYonalsymmetry:QuanYYeswithdefinitesymmetryproperYes
1. ExandEytransformasthexandy‐componentsofavectorunderrotaYons.(ThesearethevelocitycomponentsofaparYcleonthesphere)
2. The“covariantderivaYve”Dttransformsasthez‐componentofavectorunderrotaYons.(ThisisthecovariantderivaYveonthesphere)
AnyLagrangianconsisYngofcombinaYonsofEx,Ey,andDt(acYngonotherfields)thatisformallyinvariantunderSO(2)(i.e.axiallysymmetric)isindeedinvariantunderSO(3).
Weinberg(1967);Coleman,Wess,Zumino(1969);Callan,Coleman,Wess&Zumino(1969).Pedagogicalreviews:S.Weinberg,TheQuantumTheoryofFields,Vol.II,chap.19;C.P.Burgess,PhysicsReports330(2000)193;T.Brauner,Symmetry2,2010;arXiv:1001.5212.
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Physicsofzeromodes
RotaYonalbandsarequanYzedNambu‐Goldstonemodes.Low‐energyconstantC0ismomentofinerYaandfittodata.
Lagrangian
Hamiltonian
QuanYzaYon
Spectrum
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Nucleiwithnonzeroground‐statespins:WZtermsAfiniteground‐statespinbreaksYmereversalinvariance. ConsidertermsthatarefirstorderintheYmederivaYve NosuchtermsareinvariantunderrotaYons.BUT:AcYonremainsessenYallyinvariantunderoneparYcularcombinaYon(correspondstomagneYcmonopoleinsidesphere)
Lagrangian
Hamiltonian
EigenvaluesandeigenfuncYons(IdenYfyqwithground‐statespin!)
(WignerDfuncYons)
Chandrasekharan,Jiang,Pepe,&Wiese,Phys.Rev.D78,077901(2008)
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PowercounYngandbeyondleadingorder
Es%mates(naïvedimensionalanalysis)HLO~ξ
LagrangianatNLO
Powercoun%ngMainidea:higher‐odertermduetoneglectedcouplingsbetweenNGmodesandvibraYons.[C2/C0]=energy–2
Spectrum:AI(I+1)+B(I(I+1))2foreven‐evennuclei.(Bohr&Modelson)Ingeneral:
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173Yb:RelaYveerrorinLOandNLO
Smallparameter:ξ/Ω≈79/350≈1/4.5
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BeyondNGmodes:couplingtovibraYons
HigherenergeYcdegreesoffreedomneedtobeincluded.
Quadrupolefieldexhibitsspontaneoussymmetrybreaking.
5DoF–2NG=3DoF
ξ
Ω
SeparaYonofscale:ξ<<Ω
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CouplingstovibraYons:powercounYngLowenergyscaleξHighenergyscaleΩ>>ξ
Dimensionalanalysis
PotenYalexpandedaroundminiumum
PowercounYng:largeamplitudesφ0≈vrestorerotaYonalsymmetrybreakdownofEFT
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Leadingorder~O(Ω)Lagrangianatleadingorder:
Spectrum
LeadingorderLagrangianyieldsthebandheadsasharmonicvibraYons
LagrangianconsistsofEx,Ey,Dtφ0,Dtϕ2,φ0,ϕ2,andneedstobeformallyinvariantunderSO(2)(axialsymmetry)only.
βvibraYon γvibraYon
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Next‐to‐leadingorder~O(ξ)
Lagrangian
Hamiltonian(kineYcenergy)
Spectrum:harmonicvibraYons&rotaYonalbandoneveryvibraYonalbandhead
(CorrecYons~ξofbandheadsduetoanharmoniciYesinthepotenYalneglected.)
Innext‐to‐leadingorder,theresultsoftherotaYonal‐vibraYonalmodelarereproduced.
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MulY‐phononexcitaYonsW.F.Davidsonet al.,J.Phys.G7,455(1981)
TheoryatNLOpredictsvibraYonalspectrumwithrotaYonalbandsontop(andconstantmomentofinerYas/rotaYonalconstants)
Data• VibraYonalbandheadsclearlynotharmonic• MomentsofinerYaexhibitsmaller,band‐head‐dependentvariaYons• Manybandheads(neg.parity)notaccountedfor(octupole,hexadecupole,…)
gsband
γband
βband
γγband
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MulY‐phononbandsindeformednucleiMulY‐phononγbandsunambiguously*observedin166,68Er,232Th
168Er[H.G.Börneret al.,Phys.Rev.Led.66,691(1991);M.Oshimaet al.,Phys.Rev.C52,3492(1995);T.Härtleinet al.,Eur.Phys.J.A2,253(1998).]
166Er[C.Fahlanderet al.,Phys.Led.B388,475(1996);P.E.Garredet al.,Phys.Rev.Led.78,4545(1997).]
232Th[W.Kortenet al.,Phys.Led.B317,19(1993);A.MarYnet al.,Phys.Rev.C62,067302(2000)].
EnergiesofrotaYonalbands
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• NonlineartermsinthevibraYonsonly(anharmoniciYes;sufficientparameters)• CouplingsbetweenrotaYonalandvibraYonaldegreesoffreedom
Methods:Fukuda’sinversionmethodforperturbaYveLegendretransformaYons
Result:rotaYonalconstantsarelinearlyintheexcitedvibraYonalquanta
PredicYonsingoodagreementfor168Er,fairagreementfor166Er,andcorrecttrendin232Th
Thetheory’saccountforsmallvariaYonsinthemomentofinerYaovercomesasmallerbutlong‐standingproblemoftheIBMandcollecYvemodels.Originofsuccess:couplingbetweenkineYctermsofrotorandvibraYons.
RotaYonalconstantsoftwo‐phononγγbandsfromNNLOcorrecYons
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ElectromagneYctransiYonsindeformednuclei
KeyfeaturesofgeometriccollecYvemodel
✓ RotaYonalbandsontopofvibraYonalbandheads✓ Strongin‐bandE2transiYons✓ Weakerinter‐bandE2transiYons
✗Inter‐bandtransiYonsarefactors2‐10toostrong[Garred,J.Phys.G27(2001)R1;Rowe&Wood“FundamentalsofNuclearModels”(2010)]
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CollecYvemodelconfrontsdata
25
x=B(E2,2g.s.0g.s.)
y=B(E2,200g.s.)
z=B(E2,2γ0g.s.)
Rowe &Wood, Fundamentals of nuclear models, World Scientific (2010)
++
++
++
2+
• Theproblemlieswiththeabsolutestrengthsofinter‐bandtransiYons.• RaYosofinter‐bandtransiYonsok• In‐bandtransiYonsok
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Lagrangianexpansioninpowersofξ/Ω
Ω(ξ/Ω)3/2
ξ
Ω
+ … Gaugingyields
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ElectromagneYctransiYons
27
• AddelectromagneYctermstotheLagrangian
• TheinteracYonHamiltoniandefinesthetransiYonoperatorsandtransiYonprobabiliYes
• ALegendretransformaYonyieldthecorrespondingHamiltonian
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GaugedHamiltonian
28
RicherelectromagneYcstructurethancollecYvemodels:“Radial”charge,and“angular”charge.
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Resultsfor168Er
0.0391
0.568
Adiaba%cBohrmodel 5.92
aBaglin,Nucl.DataSheets111,1807(2010)bLehmannetal.,Phys.Rev.C57,569(1998)cValueemployedtoadjustlow‐energyconstant
EffecYvetheory:
• GaugingofLagrangianyieldsEMcurrentsconsistentwithHamiltonian
• PowercounYngalsoforEMcouplings
• Richerstructurethangeometricmodel;moreparametersinasystemaYcexpansion
[ToñoCoelloandTP,inpreparaYon]
B(E2,if)ine2b2
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Summary
EffecYvetheoryfordeformednuclei
• EFTdevelopedforfinitesystem(singleoutthesymmetry‐restoringcosetmodes)
• rotaYonsarelarge‐amplitudezero‐modes
• vibraYonalstatesarequanYzedNambu‐Goldstonemodes
• exploitsseparaYonofenergybetweenrotaYonsandvibraYons• essenYallyreproducesspectraofphenomenologicalmodelsatNLO
• allowsforsmallvariaYonsinrotaYonalconstantsofbandheads
• predicYonsforrotaYonalconstantsofmulY‐phononγvibraYonsinreasonableagreementwithdata
• electromagneYccouplingviagaugingpromising:consistentandricherstructurethancollecYvemodels;improvedstrengthsofinter‐bandtransiYons