SearchforX-rayphoton-photonelasticscatteringwithaLaue-casebeamcollider

TomohiroYamajiT.InadaA,T.YamazakiA,T.NambaA,S.Asai,T.KobayashiB,K.TamasakuC,Y.TanakaD,

Y.InubushiE,K.SawadaC,M.YabashiC,T.IshikawaC,T.TakahashiF,S.WatanabeF,G.SatoG

TheUniv.ofTokyo,ICEPPA,KEKB,RIKEN/SPring-8C,Univ.ofHyogoD,JASRIE,ISAS/JAXAF,Univ.ofWasedaG

LNPC’17@yokohama21th,April,2017 1

Photon-photonscattering

initialphotons

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virtualelectron

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elasticallyscatteredphotons

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4th-orderQEDprocess

uPhoton-photonscattering・QuantumElectroDynamics(QED)predictselasticscatteringofphotonsinvacuum(1936)=nonlineareffectofvacuum

・Thecontributionofvirtualphotonscatteringisinclusivelyobserved:Delbruckscattering,e/μ anomalousmagneticmoment・Thescatteringofrealphotonshasnoteverbeenobserved→importantverificationofQED

・Ifunknownparticleswhichmediatethescatteringexist,scatteringcrosssectioncanbeenhancedbythepredictionofQED→newphysicsex)Axion LikeParticles(ALP)

2

・crosssection(QED)isproportionalto6th powerofphotonenergy

・Allpreviousexperimentsusevisibleorinfraredsources・Thebestupperlimitis18ordersofmagnitude worsethanthepredictionofQED

3

Bernard2000

Moulin1996

Hughes1930

crosssectionlog10σ[m2]

1eV 100eV 1MeV10keVvisibleregion

log-logplot

photonenergyωcm@centerofmasssystem

Summaryofpreviousexperiments

1018

・X rayshave4ordersofmagnitude higherenergythanvisiblephotons→Crosssectionisenhancedby24ordersofmagnitude・X-raydetectorswithhighenergyprecisionimproveS/Nratio・Xrayshavesmallerdiffractionlimit→ beamscanbefocusedmorestrongly・X-rayregion(~10keV)isnewtoparticlephysicsexperiments→interesting!

104

1024

4

Bernard2000

Moulin1996

Hughes1930

crosssectionlog10σ[m2]

1eV 100eV 1MeV10keVvisibleregion X-rayregion

NewexperimentusingX-ray sourcelog-logplot

photonenergyωcm@centerofmasssystem

5

・thestrongestX-rayFreeElectronLaser(XFEL)intheworld

◆Specs・pulsedsourcewiththephotonfluxof~6×1011photon/pulse andthedurationof<10fs・beamwidth:200μm(FWHM),and1μmcoherentfocusingisavailable→suitableforscatteringexperimentswithhighluminosity・repetition:30Hz@2015November・X-rayenergy:10.985keVwiththebandwidthof80eV

X-raysource:SACLA

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・X-raydiffractionisusedtosplitX-raybeamsandtomakethemcollideThistechniqueisdevelopedinX-rayinterferometryregion◆X-raybeamcollider・Laue-caseX-raydiffractionatsiliconcrystalisused・Thecolliderconsistsofthreeblades(t0.2mm)manufacturedonasinglemono-crystal

X-raydiffraction@Si(440)

injectedXraystransmitted

Xrays

reflectedXrays

θB

θB

θB

Sithincrystal

thinblades(t0.2mm)

spacing:50mm

beamcollider

X-raycollisionsystem(1/2)

latticeplane

7

Gedetector

X-raycollision

50mm

collidervertical(up)direction

monochro Xrays~108 photon/pulse(11keV)

X-raydiffractionacceptablebandwidth:100meV

signalXrays18~20keV

X-raycollisionsystem(2/2)

72°

・ X-raycollisionisspatiallyandtemporallyguaranteedbyageometricalsymmetry・Thepulse-by-pulseintensityofcollidingbeamsaremeasuredbyPINphotodiodes

SACLArawbeam1011photon/pulse

diffractionefficiency:~2%→106 photon/pulse

monochromator80eV→ 60meV

PIN

TR

RR

8

・Signalsareveryweakeveniftheyexist→ suppressionofstrayXrays isessential!・TosuppressstrayXraysfromatmosphericmolecules,colliderisinstalledintoavacuumchamber・CollimatorsareinstalledalongtheX-raypathtocutthepathofstrayXraysscatteredbythecollider→ThedetectionrateofstrayXraysisreducedto10-13ofinjectedXrays,andmeasurementwithoutpseudosignalsisachieved!

innerchamber

collider

collimator

Xrays

collisionpoint

experimentalsetup@SACLA

Gedetector

vacuumchamber

goniometer

signalXrays

220mm

SuppressionofstrayXrays:vacuumchamber

Xrays

Measurementofbeamwidths

PIN

goldenwire

collidingbeam

aportionofbeamisshielded 9

・Beamwidthsismeasuredbyedgescan1)vertical(notfocused):astainlessrod2)horizontal(1μmfocused):φ200μmgoldenwire

・horizontalwidth(σ):0.962±0.037μm(RR)0.992±0.044μm(TR)

verticalwidths:144±12μm(RR)124±7μm(TR)

knife-edgescan

wireposition[μs]

transmittedintensity[arb.]

horizontalscan Theshapeofspectrum=integralofGaussianbeamThetransmittedintensityisfittedbyanerrorfunction

s]µTiming [1− 0.5− 0 0.5 1

Ener

gy[k

eV]

0

5

10

15

20

25

30

・newestmeasurement(Phys.Lett.B763(2016)454)・measurementperiod:30Hz×~38 hourDAQ=4.1× 106 X-raypulses・timingwindow:detectortimingresolution±5σ=±0.4μs・Nosignificantsignalisobserved

MeasuredX-rayspectrum

MeasuredX-rayspectrum(scatterplot)○:1event

X-raytiming(0:SACLAX-raypulse)[μs]

X-rayEn

ergy[keV

]

NoeventstrayXrays(11keV)

environmentalXrays

◆Potentialsourceofpseudosignals1)pileupsoftwostrayXrays(<22keV)2)accidentalcoincidentofenvironmentalXrays(18~20keV)・pseudosignalsareexpectedto<1event

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・upperlimit(PLB2016)onthecrosssection:1.9× 10-27 [m2]@6.5keV(95%C.L.)

・Thisistheunique/moststringentupperlimitinX-rayregion

Bernard2000

Moulin1996

Hughes1930

photonenergyωcm@centerofmasssystem

cross-sectionlog10σ/m2

1eV 100eV 1MeV10keV

PLB732(2014)356PLB734(2016)454

11

visible X-rayregion

Results

・Theupperlimitis20ordersofmagnitude worsethanQEDprediction・InordertoenhancethesensitivityandapproachtotheQEDprediction,itisessentialtochangetheexperimentalsetupdrastically・Diffractionefficiencyisverysmall(~10-5 ofrawbeam→ 10-10 sensitivityreduction)→Experimentwithoutdiffractionisneeded!

Bernard2000

Moulin1996

Hughes1930

photonenergyωcm@centerofmasssystem

cross-sectionlog10σ/m2

1eV 100eV 1MeV10keV

PLB732(2014)356PLB734(2016)454

~1020

12

visible X-rayregion

Results

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・ExperimentwithoutdiffractionrequiresanadditionalX-raysource・IfanotherSACLAexistsinfrontofSACLA,canphoton-photonscatteringbeobserved?(thoughtexperiment)

・head-oncollisionofX-raypulseswith1012 photon/pulse・50nmfocusing(horizontal/vertical)canbeusedforhead-oncollision→1 photon-photonscatteringper60Hz2dayDAQ

・Inprinciple,X-raycollisioncanbeobservedbyhead-oncollisionof2XFELs→ultimategoalofscatteringexperimentsinX-rayregion

X-raybeams

head-oncollision

dreamplan:SACLA+SACLAhead-oncollision

dreamSACLA

realSACLA

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EH5

◆SACLA+SPring-8head-oncollision・SACLAEH5:simultaneoususageofSACLAandSPring-8BL32Synchronizedoperationwillbedevelopedinthenearfuture→ realisticsetup・SPring-8:~103 photon/pulse,40MHz,40ps(pulseintensityis10-9 ofSACLA)

・Thehead-oncollisionexperimentwith50nmfocusingatEH5→sensitivityenhancementof1011 by60Hz2dayDAQ(109 worsethanQEDprediction)・morerealisticthanSACLA+SACLA:nextstep

realisticsetup:SACLA+SPring-8

・currentupperlimit:20ordersofmagnitude worsethanQEDprediction

・SACLA+SACLA:QEDpredictioncanbeverified(inprinciple):ultimategoalofphoton-photonscatteringexperimentintheX-rayregion・head-oncollisionofSACLAandSPring-8:sensitivitycanbeenhancedby1011

光子エネルギー

1eV 100eV 1MeV10keV

15

visible X-ray

SACLA×2

SACLA+SPring-8

Summaryofprospectscrosssectionlog10σ[m2]

photonenergyωcm@centerofmasssystem

PLB734(2016)454

・Weareperformingparticleexperimentsusingphotons・Photon-photonscatteringofrealphotonshasnoteverbeenobserved:importantverificationofQED・WehaveperformedfirstscatteringexperimentinX-rayregion・X-raydiffractionisusedtosplitXraysandmakethemcollide・BackgroundXraysaresuppressedtoperform0-pileupexperiment・Theupperlimitoncrosssectionis1020 worsethanQEDprediction:drasticchangeofexperimentalsetupisnecessary

・SACLA+SACLA:sensitivitycanapproachtoQEDpredictioninprinciple:ultimategoalofX-rayphoton-photonscatteringexperiment・head–oncollisionofSACLAandSPring-8:sensitivityisenhancedby1011:nextstep

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Summary