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HottopicsinModernCosmologySpontaneousWorkshopXIII
5-11May2019—IESC,Cargèse
Dedicatedexperimentsongravitationaleffectsonantimatterinspace
GiovanniMariaPiacentino,G.DiSciascio,A.Gioiosa,D.SHajdukovic,A.Palladino,G.Venanzoni.
PresentedbyG.M.Piacentino
MoonVillageScientificEnvironment
• At the future „Moon village” planned by theEuropeanSpaceAgency,itwouldbepossible,forthe first time in the human history, to performthe same experiment in laboratories withsignificantlydifferentgravitationalbackground.
• This presentation refers to a proposedexperimentontheinterferenceofgravitationonCPVthatiscompletelymodelindipendent.
• Nevertheless we will for euristic pourpose firstdescribe one of the possible models of thephenomenon
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OpenproblemsinAstrophysicsandCosmology
• The Standard Cosmological Model, even ifconcordantonwiththeexperimentonseveralPhenomena*, features an extremely strangestructure,withthe“Magic“ContributeofDarkMatter andDark Energy that reaches 96%ofthetotal.
*i.e. baryon acoustic oscillations (BAO), type-1a supernovae (SN1a)luminosity distance, primordial nucleosynt(hesis and cosmic microwavebackground(CMB))
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AcloserglancetotheopenproblemsinAstrophysicsandCosmology
i. In the observed Universe the matter prevails onantimatterevenifbotharealwayscreatedtogether;
ii. CMB is not anisotropic nor inhomogeneous enoughto be compatible with the Big Bangmodel withoutthe introduction of a still unknown interactiondrivingtheinflation;
iii. Giventhegravityweexpecta negativeaccelerationof the expansion. On the contrary that seems toaccelerate;
iv. Thegravitational fieldofGalaxies,clustersandevenof the Solar system seems much stronger that theoneduetothevisiblematter.
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PresentstateofPossiblesolutionsi. The mechanism suggested by Sakarov for matter/
antimatter asymmetry is connected to CPV butexperimentallythisphenomenonisfartooweak;
ii. Models have been proposed to justify inflation bysupersymmetric vacuum energy and SSB but atpresent no evidence for supersymmetry has beenfoundyet;
iii. DarkEnergyhasbeen introducedbyhand inorder togiveamotivationtotheacceleratedexpansionof theUniverse;
iv. Dark Matter has been introduced in order to give amotivation to the observed discrepancies betweentheoryandmeasurementsoftheorbitalspeedsofthestarsoftheexternalpartofthegalaxies.
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WHYSOMANYDIFFERENTMOTIVATIONS?
Fromthepointofviewoftheelegancethesituationisfarfrombeingsatisfactory:i. Asmanyhypothesisasproblems;ii. Mostofthemjustputbyhandintothetheory;iii. DarkMatterandDarkEnergyhypothesesare
artificial.
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Ockham'srazor• This “lex parsimoniae” Is due to the EnglishFranciscan Scholar Will iam of Ockahm( 1287-1347), who inspired the character ofWilliam of Baskerville in the Umberto Eco’snovel “The name of the Rose1”. It can bepresentedas:
• If thereare several competing Hypotheses inorder to explain a phenomenon or create atheory, The one that needs the fewestassumptionsandparametersshouldbeselected
• 1)Lecoseeiloronomi,ToraldoDiFranciaLaterza,1986
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CanwemasteralltheproblemswithasingleHypothesis?
• Let’sstartfromMatterAntimattersymmetry:
i. Matter is always produced with thecorrespondingantimatter;
ii. Matter seems todominate the landscapeoftheUniverse;
iii. NostableAntimatterseemstopopulateourGalaxynortheUniverseingeneral.
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Strong,WeakandelectromagneticInteractionsarelimitedinrange
• Atthescaleof106meventheelectromagneticinteraction is mostly screened and the onlyresidualinteractionisthegravity;
• At this scale no significant presence ofantimattercanbefind;
• Is there any connection between absence ofantimatterandpresenceofgravitation?
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Repulsion?• Antimatter particles correspond tonegativeenergysolution;
• Could this correspond to a negativegravitational mass and to a consequentgravitational repulsion between matterandantimatter?
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Supposethatgravitationalinteractionbetweenmatterandantimatterisrepulsive
• Thiscouldexplainmatterantimatterasymmetry;
• ThiscouldbethenatureofDarkEnergy;• RepulsioncouldhavepoweredtheInflaction;– Anequalmixofmatterandantimatterwouldgiveanetrepulsiveforce
– ThiscouldevenbethenatureoftheDarkMatter
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Theworkinghypothesis
• Even if the experiment we are proposing is completelymodel independent, we are fascinated by the workinghypothesisthat,bytheirnature,quantumvacuumfluctuationsarevirtual
gravitationaldipoles• This hypothesis permits to consider the well established
StandardModelmatter (i.e.mattermade fromquarks andleptonsinteractingthroughtheexchangeofgaugebosons)astheonlymatter–energycontentoftheUniverse;ofcourseacontentimmersedinquantumvacuum.
• Apparently there is no need to invoke dark matter, darkenergy,inflationfield…
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Fromthegravitationalpointofviewquantumvacuumisacontinuumofvirtualgravitationaldipoles
Therandomorientationofthegravitationaldipolesmakesthetotalgravitationalchargedensityofthevacuumequaltozero
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Aroundagalaxyoramassivebody
agravitationalpolarizationisinaction: An halo of the polarized
quantum vacuum acts as aneffective gravitational chargeon the on the boundarybetween the saturated zoneand the non-polarized areawhere a mass density arisesfrom
Sothatgravitationalpolarizationofthequantumvacuummightbethe true nature of what we call Dark Matter and the negativepressureofthepolarizedvacuumfluidcouldbethenatureofDarkEnergy.(thecompletetheoryhasbeenpresentedelsewherebyDraganHajdukovic)
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ρqv = −∇⋅
!Pg
Antimattergravitationalexperiments
• Whitteborn&Fairbanksattempttomeasuregravitationalforceonpositrons
• LosAlamos-ledteamproposed(1986)tomeasuregravitationalforceonantiprotonsattheCERNLowEnergyAntiprotonRing(LEAR)
• Projectsendedinconclusively• toovarioustodescribehere...• ManyH̅effortsinprogressatCERNAD(ALPHA,ATRAP,ASACUSA,AEgIS,GBAR)
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Worldleader:ALPHA*atCERNAntiprotonDecelerator
• Theymakeantihydrogenfromp-ande+inanoctupolartrapthenshutthemagnetand&seewhetherantihydrogenannihilateonthetoporatthebottom.
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Interference,atCERN(AEgIS)andproposedatFermilab(Phillips)
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TestingGravitywithMuoniumK.Kirch∗
PaulScherrerInstitut(PSI),CH-5232VilligenPSI,Switzerland
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AntigravityandCPVfromP.d.G.
• “DespitethephenomenologicalsuccessoftheKMCmechanism, it fails (byseveralordersofmagnitude) to accommodate the observedasymmetry [21].This discrepancy stronglysuggests that Nature provides additionalsources of CP violation beyond the KMmechanism.”
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CPVandGravity
• In the1958, eight yearsbefore thediscoveryof CPV, Philip Morrison published on theAmerican Journal of Physics a paper showingthat a strong difference in the gravitationalinteraction for matter and antimatter couldgenerateaCPVinneutralKaonssystem.
• The CPV in neutral Kaons has been discovered 8yearslater!!
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LetusrestricttoCPVintheKs-Klsystem
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ConsideranindirectCPV:
KL‘mixes’toKSbeforedecayINDIRECT
• IndirectCP:
The gravitational field is described by theacceleration g so the components ofantimatterandmatterofamesonaredividedbyadistancegrowingwiththetimethatcanbewrittenas:
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Δζ = gt 2
Thetimeusefulforthephenomenonisa fraction Ω-½ of the mixing time Δτwhere:
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Δτ = π!
Δmc2≈ 5.9x10−10 s ≈ 6τ s
WhereτsisthelifetimeofKs
Thedimensionof a Kmeson is about0.5fmor:
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ΔLk =
!mkc
Theratio: ΔζΔLk
Is the adimensionalc o n s t a n t t h a tcharacterizes thephenomenon
Sowehave:
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Ωg π 2!2
Δm2c4!mkc
=Ωπ 2! gmk
Δm2c3=Ωx0.88x10−3
AndobtaintheCPVparameteras:
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ε =Ωg π 2!2
Δm2c4!mkc
=Ωπ 2! gmk
Δm2c3=Ωx0.88x10−3
ThismeansthatgravitycouldberesponsibleforsomeoftheCPVintheneutralKseenontheEarth
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CPVandGravity
in1992GabrielChardinshowedthatgravityonEarthhastheright intensitytogenerateCPV inthemixingoftheneutralKandBmesons;Healsodemonstratedthat thephenomenonofantigravity for antimatter could be compatiblewith theGeneralRelativityandthat it couldbethe motivation of an instability of quantumvacuum in the presence of strong gravitationalfields,mimicoftheHawkingradiation.
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CPVandGravityonTheMoon
i. Thegravitationalaccelerationonthesurfaceofthe
Moon(1,62m/s2)isaboutsixtimesmallerthanthatoneonthesurfaceoftheEarth. Hence,itwouldbepossible to perform historical experiments in asignificantlydifferentgravitationalfield;
ii. Inthepastinalltheparticleexperimentgravitationainteractionhasnotbeenconsideredi.eitisageneralsystematicnevermeasurednorextimate;
iii. We argue that it is feasible to repeat on theMoonthe famous Nobel Prize winning experiment thatrevealedtheCPviolationinaneutralkaonsystem.
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ParticlebeamontheMoon
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�CRprotonandheliumspectraobtainedfromthebestfitoftheFermiLATMoongamma-raydata. The fit was performed using the MP lunar surface model. The results of the fit(continuous black and red lines) are compared with the proton measurements taken byPAMELA[39]in2008(bluepoints)and2009(purplepoints)andwiththeAMS-02proton[5](cyanpoints)andheliumdata[6](violetpoints).
�PHYSICALREVIEWD93,082001(2016)�(FermiLATCollaboration)
AMS
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CPVandGravity
• On a square target of 70 cm of side, about1.4x 104 protons per secondwill impact, Theenergy of the cosmic protons ranges from afewMeVto∼200GeVwiththemaximumfluxaround 1 GeV and several smaller localmaxima at 5, 13, and 31GeV. This spectrumcan produce the neutral Kaons. The totalnumber of K mesons decays over a spacemission lifetime (> 2 years) will yield therequiredphysicalmeasurement.
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AdedicateddetectorontheMoon
• Wesuggesttheuseofadedicateddetectrotobeinstalled on the Moon surface as part of theMoonVillageprogram;
• The apparatus should have an active target, amagneticspectrometer,trackerandcalorimeter
• Active Target: We simulated the production oftheKl“long”(longdecayneutralmesons)andKs(“short”) mesons by the cosmic protons on anappropriatetarget
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ActiveTarget
TrackerLayersPermanentMagnet
ECAL28/04/19 g.m.piacentino 34
TheTargetsystem
• �We performed Geant4 simulations using theangular and energy spectrum of the incidentcosmic protons as measured by AMS-02spectrometer. We simulated incident protonswith θmax = 45◦ over a target surfacecorrespondingtoaπ=4solid-angleacceptance.
• We considered an active target consisting ofalternating layers of Tungsten and scintillatingcrystals(Stolzite,PbWO4)foratotaldepthof18cm),tobereadwithphotodiodes
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• G.M.Piacentino,A.PalladinoandG.Venanzoni,``Measuring• gravitationaleffectsonantimatterinspace,''• Phys.DarkUniv.{\bf13}(2016)162
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Kaonsthatdecayinthedetectorvolume
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N KLdecays( )year
�Number of KL that decay within various tracking region volumes 50 cmdownstreamofthetarget(50<z<150cm,r<50cmorr<100cm),withandwithoutakinematicalcutontheaxialmomentumattheKS;Ldecayvertex.
Criticalparameters
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�Criticalparametersnecessaryfor3σand5σmeasurementsofagravitationalmodulationin the levelofCPviolation (85%change inR) alongwith thevaluesobtained fromourMonteCarlosimulation.TheresultstakeintoaccountabasicgeometricaleventselectionofKS;Ldecayverticeswithina1m×1mcylindricaltrackingvolume50cmdownstreamofthetarget(50<z<150cm,r<50cm),andaxialmomentumattheKS;Ldecayvertexofpz<0:5GeV/c.Thesevaluesassumea100%detectionefficiency,2%(4%)statisticaland2%(4%)systematicfractionaluncertaintiesfor5σ(3σ).
conclusions• Wehaveproposedapossible testof thegravitationalbehaviorof
antimatterbymeasuring the rateof theCPviolatingdecay in thegravitationalenvironmentoftheMoonsurface.Weestimatethat:
• 5σmeasurementofapossiblechangeintheCPviolationparameterεcouldbeobtainedwithina years,dependingonthedetectionefficiency,fewdayswitha100%efficiency.
• Anydifferencebetween theamountofCP violationon theMoonwith respect to the level of CP violation on the Earth’s surfacewouldbeanindicationofthenatureofthegravitationalinteractionbetweenmatterandantimatter.
• A positive resultmay offer an explanation for the cosmic baryonasymmetry andmay offer a contribution to the observed effectsthoughttocomefromdarkmatteranddarkenergy
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