(wisps) axions - idpasc...wisps in a nutshell axions. hypothe cal light pseudoscalar postulated to...
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Axions&ALPs(WISPs)
AlessandroDeAngelis,INFN/INAFPadovaandLIP/ISTLisboa
IDPASCSchool,Vipava,May2016
WISPs
ALPs
Axions
(Credits:D.Horns,S.Parker,G.Raffelt,A.Ringwald,M.Roncadelli)
Plentyofdarkma�er(DM)candi-datesspanninghugeparameterrangeinmassesandcouplings
Twoclassesstandoutbecauseoftheirconvincingphysicscaseandthevarietyofexperimentalandobserva�onalprobes:– WeaklyInterac�ngMassive
Par�cles(WIMPs),suchasneutralinos
– WeaklyInterac�ngSlim(=ultra-light)Par�cles(WISPs),suchasaxions
Plan:– Physicscaseforaxions,axion-like
par�cles(ALPs),WISPs– Probes(inthelab,inastropar�cle)
AlessandroDeAngelis 2Vipava2016
WISPsinanutshell Axions.Hypothe�callightpseudoscalarpostulatedtoexplainthestrongCP
problem(CPhasnota-priorireasontobeasymmetryoftheQCDLagrangian;however,CPappearstobeconservedinQCD).ASSBatavery-high-energyscale,givingrisetoanassociatedpseudo-scalarbosoncalledtheaxion,mightexplainit.Beingpseudoscalar(liketheπ0),theaxioncandecayintotwophotons.
Someconsequencesforcosmologicalphotonpropaga�on(seelater). ALPs.Anextensionofaxions,relaxingtheaboverela�onbetweenmassand
coupling. Ma�erinparallelbranes;ShadoworMirrorma�er.Sometheoriespostulatethe
presenceofma�erinparallelbranes,interac�ngwithourworldonlyviagravityorasuper-weakinterac�on.Intheoriespopularinthe1960s,a“mirrorma�er”waspostulatedtoformastronomicalmirrorobjects;thecosmologyinthemirrorsectorcouldbedifferentfromours,possiblyexplainingtheforma�onofdarkhalos.Thismirror-ma�ercosmologyhasbeenclaimedtoexplainawiderangeofphenomena.
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gaγγ ≈1M
; ma
1 eV~ 1
M/(6 x 106 GeV)
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WISPs:whyandhow
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Theaxion:originsinpar�clephysics
CPviola�ngterminQCDLagrangianimpliesneutronelectricdipolemoment:
Butmeasurementsplaceasevereconstraint:
“Simplest” solu�on: Introduce a U(1)PQ symmetry. This symmetry breaks at someenergyscale(fa);theassociated(pseudo)Goldstonebosonistheaxion,whichactsasadynamicalCP-conservingfield.
Whyistheneutronelectricdipolemoment(andthusθ)sosmall?ThisiscalledtheStrongCPProblem.
Couplingtoquarksandgluonsgivestheaxionmass:Couplingwithphotonsalsosuppressedbyg
“Weakly”interac�ng,smallmasspar�cle:WISP.
CPsymmetryisviolatedinelectroweakinterac�ons;noobviousreasontobeconservedinQCD
gaγγ ≈1M
; ma
1 eV~ 1
M/(6 x 106 GeV)
AlessandroDeAngelis 5Vipava2016
ISAPP,Heidelberg,15July2011
MechanismbyPecceiandQuinn,namebyWilczek
FrankWilczek
“Inamedthema�eralaundrydetergent,sincetheycleanup
aproblemwithanaxialcurrent.”(Nobellecture2004)
Theaxioncanbecold
Boththermalandnonthermalproduc�onmechanismsarepossible Thermaldecouplingmechanismshoulddominateform>10meV(HDM) Non-thermalproduc�onmechanismshoulddominateform<0.1meV(CDM)– DuringQCDphasetransi�on,freequarksformboundhadrons,andalongthataBosecondensateofaxionsisalsoformed(Weinberg1978,Wilczek1978)
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Axion/PhotonCouplingAxion-2photoncoupling:sameformalismasπ0->γγAxion-2photoncouplingprovidesveryimportantexperimentalandobserva�onalaccess(withminimalmodeldependence).
Bfieldcanactas2ndvirtualphotontoinduceaxion-photonconversion
Wanttotest/bindgaγγ
Axionmassdictatesphotonfrequency
AlessandroDeAngelis 8Vipava2016
Off-the-Beaten-TrackDarkMa�er,ICTP,Trieste13–17April2015
SN1987Aneutrinosignal
Late-�mesignalmostsensi�veobservable
Emissionofveryweaklyinterac�ngpar�clesmight“steal”energyfromtheneutrinoburstandshortenit.(Earlyneutrinoburstpoweredbyaccre�on,notsensi�vetovolumeenergyloss.)
Neutrinodiffusion
Neutrinosphere
Volumeemissionofnewpar�cles
Constraintsfromastrophysics
Off-the-Beaten-TrackDarkMa�er,ICTP,Trieste13–17April2015
Energyloss(PeriodChange)ofWhiteDwarfs
Neutrinos
Axions
Photons
Theobservableisnotverysensi�ve
AxionMass/PhotonCoupling
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FromaxionstoALPs
Non-minimalmodel Releasetheconstraintofpropor�onalitybetweenmassandcoupling
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ALPs
Axions
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FromALPstoWISPsexample:para-photonsinhiddensectorsDifferentSMextensionsintroduce“hiddensectors”ofpar�clesduetoaddi�onofextrasymmetries.Addi�onofextraU(1)symmetryinteractsveryweaklyviakine�cmixingofthegaugebosons.Consequence:Photon–HiddenSectorPhotonoscilla�ons
Broadrangeofallowablemassandcouplingstrength.CanbeformulatedasWISPDarkMa�er
Experimentalist’sapproach:It’slikeanaxionbutwithouttheneedforamagne�cfieldAndnospinformalismisneeded
WISPs
ALPs
Axions
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ProbingWISPs:laboratoryexperiments
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Off-the-Beaten-TrackDarkMa�er,ICTP,Trieste13–17April2015
ExperimentalTestsofInvisibleAxions
PierreSikivie:
MacroscopicB-fieldcanprovidealargecoherenttransi�onrateoverabigvolume(low-massaxions)
• Axionhaloscopes:Lookfordark-ma�eraxionsinacavity• Axionhelioscopes:LookattheSunthroughadipolemagnet
LightShiningThroughaWall(LSW)
Helioscopes
LASER DetectorB
B
B
Haloscopes(directsearch)Cavi�es(birefringence,dichroism)
B
op�cal
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LightShiningThroughaWall
Helioscopes
HaloscopesCavi�es
Op�calOSQAR(CERN)ALPS/ALPS-II(DESY)GammeV/REAPR(Fermilab)MicrowaveADMX(UW)CROWS(CERN)UWAYale
CAST(CERN)TSHIPS(DESY)Sumico(Tokyo)IAXO(?)
PVLAS(Legnaro/Trieste)WISPDMX(DESY)ADMX(UW)ADMX-HF(Yale)CAPP(IBS/KAIST)
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Axionhaloscopes
B
ρa–Axiondensity(~0.3GeV/cm3)ma–AxionmassB0–Magne�cfieldstrengthV–CavityvolumeC–Formfactor(E.Boverlap)Q–Cavityqualityfactor
Measurepowertoconstrainaxion-photoncoupling.
Expectedsignal(powerinW)
Cavityenablesresonantenhancementofconvertedphotonsignal
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Onemoregooduseofcavi�es Detectbirefringence/dichroismin“vacuum” PhysicssimilartoLSWexperiments;techniquesimilartohaloscopes
Note:birifringenceexpectedalsoinstandardQEDvacuum(butnotmeasured,yet)
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Off-the-Beaten-TrackDarkMa�er,ICTP,Trieste13–17April2015
Helioscopes:searchforsolaraxions
γγ a
Sun
Primakoffproduc�on
AxionHelioscope
γγMagnetS
Na
Axion-Photon-Oscillation
Ø TokyoAxionHelioscope(“Sumico”)(Resultssince1998,upagain2008)Ø CERNAxionSolarTelescope(CAST)(Datasince2003)
Axionflux
Experimentallimitsonsolaraxionfluxfromdark-ma�erexperiments(SOLAX,COSME,DAMA,CDMS...)
CAST@CERN
LHCtestmagnet
DecommissionedLHCtestmagnet(L=10m,B=9T) Movingpla�orm±8°V±40°H(toallowupto50days/yearofalignment) 4magnetborestolookforXrays 3Xraysdetectorprototypesbeingused. XrayFocusingSystemtoincreasesignal/noisera�o.
X-rayfocussingop�cs
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Off-the-Beaten-TrackDarkMa�er,ICTP,Trieste13–17April2015
ParameterSpaceforALPs
Off-the-Beaten-TrackDarkMa�er,ICTP,Trieste13–17April2015
NextGenera�onAxionHelioscope(IAXO)
5.2mindiameterand25mlength.Magne�cfieldof5.4T ConceptualDesignoftheInterna�onalAxionObservatory(IAXO),arXiv:1401.3233
Off-the-Beaten-TrackDarkMa�er,ICTP,Trieste13–17April2015
Off-the-Beaten-TrackDarkMa�er,ICTP,Trieste13–17April2015
Recent“shining-light-through-a-wall”orvacuumbirefringenceexperiments:
• ALPS • BMV• BFRT• GammeV• LIPPS• OSQAR• PVLAS
Photonregenera�onexperiments(LSW)Ehretetal.(ALPSCollabora�on),arXiv:1004.1313
(DESY,usingHERAdipolemagnet)(LaboratoireNa�onaldesChampsMagné�quesIntens,Toulouse)(Brookhaven,1993)(Fermilab)(JeffersonLab)(CERN,usingLHCdipolemagnets)(INFNTrieste/Legnaro)
Off-the-Beaten-TrackDarkMa�er,ICTP,Trieste13–17April2015
AnyLightPar�cleSearchII(ALPS-II)atDESY
ALPS(finished)
ALPS-IIb(2017)
ALPS-IIa(2016)
ALPS-IIc(2019)
ALPS-IITechnicalDesignReport,arXiv:1302.5647
Bl=468Tm
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WISPsandthecosmologicalpropaga�onofphotons
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γ-raysareeffec�velyproducedinEMandhadronicinterac�ons– EnergyspectrumatsourcesE-2
areeffec�velydetectedbyspace-andground-basedinstruments
effec�velyinteractwithma�er,radia�on(γγàe+e-)andB-fields
Theinterac�onwithbackgroundphotonsintheUniversea�enuatesthefluxofgammarays
The“enemies”ofVHEphotonsarephotonsneartheop�calregion(Extragalac�cBackgroundLight,EBL)
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A�enua�onofγ-rays
γHEγbckàe+e-
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Galac�cCentre(9kpc)
DeAngelis,Galan�,Roncadelli2011withFranceschiniEBLmodeling
30GeV100GeV
redshi�z
γrayenergy(TeV)
τ=1(GRH)
τ >1regionofopacity
),(emobs )(),( zEeEzE τ−×Φ≡Φ
γVHEγbck → e+e-
Maxfor:
σ(β)~
CenA(3.5Mpc)
1/nσ
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Thediffuseextragalac�cbackgroundlight(EBL)isalltheaccumulatedradia�onintheUniversedueessen�allytostarforma�onprocesses Thisradia�oncoversawavelengthrangebetween~0.1and600µm(considertheredshi�andthereprocessing)
A�ertheCMB,theEBListhesecond-mostenerge�cdiffusebackground
TheunderstandingoftheEBLisfundamental Toknowthehistoryofstarforma�on TomodelVHEphotonpropaga�onforextragalac�cVHEastronomy.VHEphotonscomingfromcosmologicaldistancesarea�enuatedbypairproduc�onwithEBLphotons.Thisinterac�onisdependentontheSEDoftheEBL.
Therefore,itisnecessarytoknowtheSEDoftheEBLinordertostudyintrinsicproper�esoftheemissionintheVHEsources.
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Mea
n Fr
ee P
ath
The γ horizon: nuisance and resource
100 TeV 10 TeV 1 TeV 100 GeV 10 GeV 1 EeV 100 PeV 10 PeV 1 PeV 10 EeV 100 EeV
1 Mpc 100 kpc 10 kpc
10 Mpc
1 Gpc 100 Mpc Mrk 421
Cen A M 31 GC
z=5 z=1
CMB
UV NIR
FIR
Radio
3C 279
Can be used to measure: - EBL - EG magnetic fields - vacuum energy (search for axions) - Cosmological parameters… Data from existing detectors give many hints but are not conclusive Ground
-based detectors
γ + γ à e++ e-
(AdA,Roncadelli&Galan�2013)
EBL
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TheEBLaffectsinpar�cularthesignalfromextragalac�csources
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Fermi2FHLandgammahorizon
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Anomalouseffectsoncosmologicalγpropaga�on
AreourAGNobserva�onsconsistentwiththeory?
– ForeachAGNdetected,acorrespondinglowerlimitontheop�caldepthτiscalculatedusingaminimumEBLmodel
– Nonparametrictestofconsistency– Disagreementwithdata:overallsignificanceof4.2σ=>Understandexperimentallytheoutliers
(Horns,Meyer2011)
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Areminder:EBLratherwellconstrained,andSEDextrapola�onfromFermiispossible
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PKS1424Ifz=0.6
PKS1424Ifz=0.8
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Explana�onsfromthestandardones– veryhardemissionmechanismswith
intrinsicslope<1.5(Stecker2008)– VerylowEBL,plusobserva�onalbias,plus
acoupleof“wrong”outliers
toalmoststandard– γ-rayfluxesenhancedbyrela�velynearby
produc�onbyinterac�onsofprimarycosmicraysorνfromthesamesource
topossibleevidencefornewphysics
– Oscilla�ontoalightpar�clecoupledtothephoton?
Ifthereisaproblemob
served
spectralinde
x
redshi�
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AreourAGNobserva�onsconsistentwiththeory?
Selection bias? New physics ?
observed
spectralinde
x
redshi�
Measuredspectraaffectedbya�enua�onintheEBL:
~E-2
(DA,Galan�,Roncadelli;PRD2011) AlessandroDeAngelisVipava2016
VHEgammasourcesabovez=0.15
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ShiningTeVGammaRaysthroughtheUniverse
FigurefromM.Meyer(Hamburg)
Thecosmologicalphoton-axionmixing
Magne�cfield1nG<B<1fG(AGNhalos).Cellsof~1Mpc
Photons-ALPmixingcouldenhancethetransparencyoftheUniverse:– Photon/ALPmixingintheintergalac�cspace(DA,Roncadelli&MAnsu�[DARMA],PRD2007)– Conversionintoaxionatthesource,reconversionintheMilkyWay(Hooper,Simet,Serpico
2008)Axionemission(Simet+,PRD2008)– Acombina�onoftheabove
γ
γ*
a
γ*
γ
γ*
…
γ*
γ a a
Laγγ = gaγ
E ⋅ B ( )a
!!
Pγ →a ≈ NP1
P1 ≈gaγ2 BT
2s2
4≈ 2 ×10−3 BT
1nGs
1Mpcgaγ
10)10GeV)1
'
( )
*
+ ,
2
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g<10-10 GeV-1fromastrophysicalbounds ma<0.02eV(directsearches)ifstandardaxion– ma<1keVingeneral– ma<(0.1-1)meVcouldbeCDM
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Vipava2016
Preferredvaluesform,g(DARMA)
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Futuregamma-rayexperimentssensi�vetoALPs:e-ASTROGAM
ALPscaninducelocalisedO(10%)oscillatorymodula�onsinthespectraofphotonsourcespassingthroughastrophysicalmagne�cfields
Ultra-deepobserva�onsofgalaxyclustersinthekeV-MeV-GeVcanspotgamma-rayspectralirregulari�esfromAGN
e-ASTROGAM
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45AlessandroDeAngelis
CTA
Vipava2016
Summary Axions(andWISPs)areeconomical(intheOccamsense)darkma�ercandidates Laboratoryandspaceexperimentscurrentlyprobingviableparameterspace Somehints,mostlybyexperimentsingammaastrophysics(anomalousgammapropaga�on) S�llnocompellingsignal,butalotofac�vityforeseen– IAXO,ALPS2arethenext“bigthings”– CTA,(Fermi)andnextgamma-rayexperimentsinspace(e-ASTROGAM)mightfurthertesthints
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Exercises γγ->e+e-.Computetheenergythresholdforthisprocessasafunc�onoftheenergyofthetargetphoton,andcompareittotheenergyforwhichtheabsorp�onofextragalac�cgamma-raysismaximal.Analyzeinpar�cularthecaseofthesca�eringagainsttheCMB,assumingadensityof400photons/cm3forthebackgroundCMBphotons
Mixingphotonswithparaphotons.Theexistenceofaneutralpar�cleof�nymassm,theparaphoton,coupledtothephoton,hasbeensuggestedtoexplainpossibleanomaliesintheCMBspectrumandinphotonpropaga�on(themechanismissimilartotheonediscussedtothephoton-axionmixing,buttherearenocomplica�onsrelatedtospinhere).Callingφthemixinganglebetweenthephotonandtheparaphoton,expresstheprobabilityofoscilla�onofaphotontoaparaphotonasafunc�onof�me(note:theformalismisthesameasforneutrinooscilla�ons).Supposingthattheparaphotonissterile,computeareasonablerangeofvaluesfor φ andmthatcouldexplainanenhancementbyafactorof2forthesignaldetectedat500GeVfromtheAGN3C279atz~0.54.
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Minimalbibliography
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h�ps://dl.dropboxusercontent.com/u/44901481/BookAstropart/BookComplete28nov/Exercises/hea_deangelis_syllabus4.htm
PageonaxionsandALPsinthePDG,andreferencestherein
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