(WISPs) Axions - IDPASC...WISPs in a nutshell Axions. Hypothe cal light pseudoscalar postulated to...

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.

3

gaγγ ≈1M

; ma

1 eV~ 1

M/(6 x 106 GeV)

AlessandroDeAngelisVipava2016

WISPs:whyandhow


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)


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)


Axion/PhotonCouplingAxion-2photoncoupling:sameformalismasπ0->γγAxion-2photoncouplingprovidesveryimportantexperimentalandobserva�onalaccess(withminimalmodeldependence).

Bfieldcanactas2ndvirtualphotontoinduceaxion-photonconversion

Wanttotest/bindgaγγ

Axionmassdictatesphotonfrequency


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


Energyloss(PeriodChange)ofWhiteDwarfs

Neutrinos

Axions

Photons

Theobservableisnotverysensi�ve

AxionMass/PhotonCoupling


FromaxionstoALPs

  Non-minimalmodel  Releasetheconstraintofpropor�onalitybetweenmassandcoupling

AlessandroDeAngelis 12

ALPs

Axions

Vipava2016

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


ProbingWISPs:laboratoryexperiments



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


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)


Axionhaloscopes

B

ρa–Axiondensity(~0.3GeV/cm3)ma–AxionmassB0–Magne�cfieldstrengthV–CavityvolumeC–Formfactor(E.Boverlap)Q–Cavityqualityfactor

Measurepowertoconstrainaxion-photoncoupling.

Expectedsignal(powerinW)

Cavityenablesresonantenhancementofconvertedphotonsignal


Onemoregooduseofcavi�es  Detectbirefringence/dichroismin“vacuum”  PhysicssimilartoLSWexperiments;techniquesimilartohaloscopes

  Note:birifringenceexpectedalsoinstandardQEDvacuum(butnotmeasured,yet)



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



ParameterSpaceforALPs


NextGenera�onAxionHelioscope(IAXO)

  5.2mindiameterand25mlength.Magne�cfieldof5.4T  ConceptualDesignoftheInterna�onalAxionObservatory(IAXO),arXiv:1401.3233



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)


AnyLightPar�cleSearchII(ALPS-II)atDESY

ALPS(finished)

ALPS-IIb(2017)

ALPS-IIa(2016)

ALPS-IIc(2019)

ALPS-IITechnicalDesignReport,arXiv:1302.5647

Bl=468Tm

AlessandroDeAngelis27Vipava2016

WISPsandthecosmologicalpropaga�onofphotons


  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)

29

A�enua�onofγ-rays

γHEγbckàe+e-


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


31

  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.


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

33

TheEBLaffectsinpar�cularthesignalfromextragalac�csources


Fermi2FHLandgammahorizon


Anomalouseffectsoncosmologicalγpropaga�on

AreourAGNobserva�onsconsistentwiththeory?

–  ForeachAGNdetected,acorrespondinglowerlimitontheop�caldepthτiscalculatedusingaminimumEBLmodel

–  Nonparametrictestofconsistency–  Disagreementwithdata:overallsignificanceof4.2σ=>Understandexperimentallytheoutliers

(Horns,Meyer2011)


Areminder:EBLratherwellconstrained,andSEDextrapola�onfromFermiispossible

AlessandroDeAngelis36

PKS1424Ifz=0.6

PKS1424Ifz=0.8

Vipava2016

37

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�


38

AreourAGNobserva�onsconsistentwiththeory?

Selection bias? New physics ?

observed

spectralinde

x

redshi�

Measuredspectraaffectedbya�enua�onintheEBL:

~E-2

(DA,Galan�,Roncadelli;PRD2011) AlessandroDeAngelisVipava2016

VHEgammasourcesabovez=0.15


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


  g<10-10 GeV-1fromastrophysicalbounds  ma<0.02eV(directsearches)ifstandardaxion– ma<1keVingeneral– ma<(0.1-1)meVcouldbeCDM

AlessandroDeAngelis42

Vipava2016

Preferredvaluesform,g(DARMA)

AlessandroDeAngelis43Vipava2016

Futuregamma-rayexperimentssensi�vetoALPs:e-ASTROGAM

  ALPscaninducelocalisedO(10%)oscillatorymodula�onsinthespectraofphotonsourcespassingthroughastrophysicalmagne�cfields

  Ultra-deepobserva�onsofgalaxyclustersinthekeV-MeV-GeVcanspotgamma-rayspectralirregulari�esfromAGN

  e-ASTROGAM

44AlessandroDeAngelisVipava2016

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


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.


Minimalbibliography

AlessandroDeAngelis 48

  h�ps://dl.dropboxusercontent.com/u/44901481/BookAstropart/BookComplete28nov/Exercises/hea_deangelis_syllabus4.htm

  PageonaxionsandALPsinthePDG,andreferencestherein

Vipava2016

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(WISPs) Axions - IDPASC...WISPs in a nutshell Axions. Hypothe cal light pseudoscalar postulated to...

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