minos: latest results and future plans - ppd · jeff hartnell university of sussex ral seminar,...
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JeffHartnellUniversityofSussex
RALSeminar,July22nd2009
MINOS:LatestResultsandFuturePlans
IntroducFon• MINOSphysicsgoals• NuMIneutrinobeam&MINOSdetectors
• Results:– PrecisemeasurementofΔm2
– MuonanF‐neutrinos– Searchforelectronneutrinoappearance– Searchforsterileneutrinos
• MINOSfutureplans
• AfewslidesonSNO+
2JeffHartnell,RALSeminar,July'09
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TheMINOSCollaboraFon
Argonne • Athens • Benedictine • Brookhaven • Caltech • Cambridge • Campinas • Fermilab Harvard • Holy Cross • IIT • Indiana • Minnesota-Twin Cities • Minnesota-Duluth • Otterbein
Oxford • Pittsburgh • Rutherford • Sao Paulo • South Carolina • Stanford • Sussex • Texas A&M Texas-Austin • Tufts • UCL • Warsaw • William & Mary
140 scientists 28 institutions
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MINOSOverview
735 km
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NeutrinoMassesandMixings
€
Δmatm2
€
Δmsol2
MINOSPhysicsGoals• Precisemeasurementsof|Δm2
atm|andsin2(2θ23)viaνμ disappearance
• Searchforsub‐dominantνμ‐>νeoscillaFonsviaνeappearance
• Searchforsterileν• CPT/LorentzviolaFon• Atmosphericneutrinoandcosmicrayphysics• StudyνinteracFonsandcrosssecFonsinNearDetector
• SearchforbothνμdisappearanceANDappearance• testthestandardneutrinomodel
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νμDisappearance
• Doνμandνμoscillateinthesameway?
• Ifnot,thencouldbeevidenceforCPTviolaFonornon‐standardinteracFons
€
Δmatm2
€
Δmsol2
€
ν 1
€
ν 2€
Δm atm2
€
Δm sol2
€
ν 3€
P(ν µ →ντ ) = sin2(2θ)sin2 1.27Δm2L
E
€
P(ν µ →ντ ) = sin2(2θ)sin2 1.27Δm2L
E
= ? Does
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νμAppearance• MINOShasobservedthedisappearanceof100sofνμ
– Doanyofthesereappearasνμ?– ConsideranexperimentallydrivenparametrisaFon:
– whereαisthefracFonofνμthattransiFontoνμ
• νμappearancepredictedbythestandardmodelatthe10‐18levelifneutrinosareMajorana:
P(νμ‐>νμ)~(mν/Eν)2
• AlsopredictedataverylowlevelbymodelswithalargeneutrinomagneFcmoment,neutrinodecayandotherexoFcprocesses(LangackerandWang,Phys.Rev.D58:093004)
€
P(ν µ →ν µ ) =α sin2(2θ)sin21.27Δm2L
E
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NuMINeutrinoBeam
• 120GeVprotonsstriketarget• 10μslongpulseof~3x1013protons
every2.2seconds(275kW)
• TwomagneFchornsfocussecondaryπ/K• decayofπ/Kproduceneutrinos
• Variableneutrinobeamenergy
Low Med. High
BeamFlavourComposiFon
• ThechargedcurrentinteracFonsintheNeardetectorcompriseof:o 91.7%νμ
o 7.0%νμ
o 1.3%νeandνe• Significantdifferenceinthe
energyspectrum:o νμpeakat3GeV
o νμpeakat8GeV
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Whyarethespectrasodifferent?
• Majorityofνμcomefrom“neck‐to‐neck”low‐pTπ−thattraveldownthecentreofthehornswherethereiszeromagneFcfield
• νμspectrumdominatedbyfocusedhigh‐pTπ+
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π−
π+120GeVp+
Target FocusingHorns
2 m
675m
νμ
νμ
15m 30m
DecayPipe
12
MINOSDetectors
Far Detector
Near Detector
• Massive – 1 kt Near detector – 5.4 kt Far detector
• Similar as possible – steel planes
• 2.5 cm thick – scintillator strips
• 1 cm thick • 4.1 cm wide
– Wavelength shifting fibre optic readout
– Multi-anode PMTs – Magnetised (~1.3 T) JeffHartnell,RALSeminar,July'09
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MINOSEventTopologies(MC)νµCCEvent NCEvent νeCCEvent
long µ track+ hadronic activity at vertex
short, with typical EM shower profile
short event, often diffuse
3.5m 1.8m 2.3m
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AccumulatedBeamData
RUN I
1.27x1020 POT
Higher energy beam
0.15x1020 POT
RUN II
1.87x1020 POT RUN III
~4x1020 POT
First νµCC paper (2006) 2008 νµCC paper & latest results
Run III Analysis in progress
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MuonNeutrinoDisappearanceAnalysis
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ExperimentalApproach• TwodetectorexperimenttoreducesystemaFcerrors:
– Flux,cross‐secFonanddetectoruncertainFesminimised– MeasureunoscillatedνµspectrumatNeardetector
• extrapolateusingMC– ComparetomeasuredspectrumatFardetector
1 2
1
2
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AllowedRegion• Energy spectrum fit with
the oscillation hypothesis:
• Results:
|Δm232|=(2.43±0.13)x10‐3eV2
at68%C.L.
sin2(2θ23)>0.90
at90%C.L.
PRL 101 131802 (2008)
Most precise measurement of |Δm232| performed to date
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WhatabouttheMuonAn8‐Neutrinos…
νμ+Nμ++hadrons
νμ+Nμ‐+hadrons
SelecFngνμ
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• νμCCeventsare7%ofbeam
• SearchingforνμCCamongstalargesampleofotherevents:– Mis‐idenFfiedνμCCwhereμ
chargesigniswrong
– NeutralCurrent(NC)eventswhereanotherparFclefakesaμ+track
• NCeventswithatrackare~50:50,posiFve:negaFvechargesign
• DevelopcutstoremovecontaminaFon– Cuton3addiFonalvariables
All events with a positive curvature track
AddiFonalSelecFonVariables
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1) LikelihoodbasedCC/NCseparaFonparameterdevelopedforpreviousanalyses RemovesbothNCandmis‐idenFfiedνμCC
events
2) Trackfitchargesignsignificance3) RelaFveangle
– measureofwhetherthetrackcurvestowardsorawayfromthemagneFccoilhole,relaFvetoitsiniFaldirecFon
EfficiencyandContaminaFon
• A|erallcuts:– Neardetector
• Efficiencyof87%
• ContaminaFonof5%
– Fardetector• Efficiencyof82%• ContaminaFonof3%
• OpFmisedforphysicssensiFvitytoCPTconservingoscillaFons
– lowercontaminaFonispossiblebutatthecostofevents
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Monte Carlo
Monte Carlo
NearDetectorνμ• Unlikeforνμmovingtargetor
changinghorncurrentdoesnotprobethepT/pZspace– νμspectrumisthesameto10%in
allbeamconfiguraFons
• HadronproducFoninthebeamtargetismodeledbyFluka05– SparsehadronproducFondata– PredicFonuncertaintyis~20%
• FitNeardetectordatatoahadronproducFonmodel– Resultforπ+/π−raFogreatsuccess:
agreeswellwithnewNA49data• Eur.Phys.J.C49897(2007)
– Doesn’tsignificantlyaffecttheFardetectorpredicFon
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NeartoFarExtrapolaFon• Neardetectorspectrum≠Fardetector
– Projectdifferentsolidangles– Non‐pointsourceforNeardetector– π/KdecaykinemaFcs
• averageneutrinoenergyvarieswithangle
Far Detector Decay Pipe
π+/− Target
Near Detector
p
Eν ~ 0.43Eπ / (1+γπ2θν2)
BeamMatrixExtrapolaFon
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• AbeammatrixtransportsmeasuredNearspectrumtoFar– νμandνμareextrapolatedindependently
• MatrixencapsulatesknowledgeofmesondecaykinemaFcsandbeamlinegeometry– MatrixelementMijreflectstheprobabilityofobtainingaFareventwith
energyEjgiventheobservaFonofaNeareventwithenergyEi• MCusedtocorrectforenergysmearingandacceptance
Monte Carlo
SystemaFcUncertainFes• Errorsthatarethesameastheνμanalysis
– Normalisa8on:±4%– RelaFvereconstrucFoneff.,detectorliveFmeandmass
– Muonenergy:range±2%,curvature±4%• (ErrorfromcurvatureincreasedslightlyduetoexiFngtracks)
– Beamextrapola8on:1σerrorbandfrombeamfit
– Rela8veshowerenergy:±3%– Absoluteshowerenergy:±10%
• Errorsthatarespecificforthisanalysis– Decaypipeproduc8on:±40%– Background:±50%
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TotalSystemaFcUncertaintyonFarDetectorPredicFon
• AddedsystemaFcuncertainFesinquadrature
• Overalluncertaintyis<10%acrossallenergies– significantlylessthan
staFsFcalerror
• Dashedlineshowsthe4%normalisaFonuncertainty
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TheFarDetector…
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PredictedFarDetectorSpectrum
• PredictedeventswithCPTconservingoscillaFons:– 58.3±7.6(stat.)±3.6(syst.)
• PredictedeventswithnulloscillaFons:– 64.6±8.0(stat.)±3.9(syst.)
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FarDetectorSpectrum
• Observe42eventsintheFardetector
• FirstdirectobservaFonofνμinanacceleratorlong‐baselineexperiment
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• PredictedeventswithCPTconservingoscillaFons:– 58.3±7.6(stat.)±3.6(syst.)
• PredictedeventswithnulloscillaFons:– 64.6±8.0(stat.)±3.9(syst.)
StaFsFcalContext• ComparedtotheCPT‐
conservingoscillaFonhypothesiswehaveadeficitof16.3events
• UsingnormalisaFoninformaFonalonethisisa1.9sigmaeffect
• Astudyusing100,000fakeexperimentsincludingsystemaFcsgavetheprobabiliFesinaccordancewithexpectaFons
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Resultsoffits
1.)Disappearance:oscilla8onmodel
2.)Appearance:fracFonofeventstransiFoningfromνμtoνμ
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AllowedRegion• Contoursobtainedusing
Feldman‐Cousinstechnique,includingsystemaFcs
• NulloscillaFonhypothesisexcludedat99%
• CPTconservingpointfromtheMINOSneutrinoanalysisiswithin90%contour
• νμbestfitisathighvalue,duetodeficitathighenergy
• Unshadedregionaroundmaximalmixingisexcludedat99.7%C.L.
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ComparisontoGlobalFit
• Globalfittopreviousdata– Super‐Kamiokandedominates
– IncludesSK‐IandSK‐IIdata– M.C.Gonzalez‐Garcia&Michele
Maltoni,Phys.Rept.460(2008)
• MINOSdataexcludespreviouslyallowedCPTviolaFngregionsofparameterspace
• Atmaximalmixingexclude:– (5.0<Δm2<81)x10‐3eV2(90%C.L.)
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Resultsoffits
1.)Disappearance:oscillaFonmodel
2.)Appearance:frac8onofeventstransi8oningfromνμtoνμ
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ResultsofSearchforνμAppearance• MINOSobservesno
appearanceofνμintheNuMIbeam
• 1‐parameterfitforαusingsimpleparameterisaFon
(θandΔm2settoCPTconservingcase)
• Uncertaintyfromνμ/νμcrosssecFonraFo
• Result:limitfracFon,α,ofeventstransiFoningfromνμtoνμ:o α<0.026(90%C.L.)
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€
P(ν µ →ν µ ) =α sin2(2θ)sin2 1.27Δm2L
E
90%
Futureplans
a.)Updateanalysiswithmorethandoublethedataset
b.)Dedicatedνμrun
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• PlantoreversecurrentinNuMImagneFchornstofocusπ−fromSeptember
• createaνμbeam
• MINOScandirectlyobserveνμ disappearanceat7σwith5x1020POT
• rapidlyreducetheuncertaintyonΔm2
32
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DedicatedνμRunning
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ElectronNeutrinoAppearanceAnalysis
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νµ→νeOscillaFonSearchOverview• Sub‐dominantneutrinooscillaFons
– LookforνeappearanceatFardetector• P(νµ→νe)≈sin2θ23sin22θ13sin2(1.27Δm2
31L/E)
– alsoCPvandma�ereffects:notshownherebutincludedinfit
– Electronneutrinoeventsonly2%oftotal(atChoozlimit)
• Selecteventsw/compactshower,typicalEMprofile– MINOSopFmisedforνµ– νesignalselecFonisharder
• Steelthickness2.5cm=1.4X0• Stripwidth4.1cm~Molièreradius(3.7cm)
• UsetheNeardetectortodeterminethebackground
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SelecFngνeEvents
• 11variableschosendescribinglength,widthandshowershape
• ANNalgorithmachieves:• signalefficiency41%• NCrejecFon>92.3%• νμCCrejecFon>99.4%• signal/background1:4
at Chooz limit
Area Normalised
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MCEventComposiFonin2Detectors
• PrimarybackgroundfromNCevents,also• high‐yνµCC,beamνe,oscillatedντatFardetector
• Rightplot:purpleshowsanappearancesignalattheChoozlimit(sin22θ13=0.15)
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NearDetectorData• O(20%)data/MC
differencesinNeardet.– notsurprising,strong
backgroundrejecFonleavesjusttailsofdistribuFons
– suchdifferencesareexpectedfromtheuncertainFesintheMCsimulaFonofthehadronisaFonmodel
• tunedtosparseexternaldata
• UseadatadriventechniquetomeasureNeardetectorbackground– comparehornon/offdata
• fitforCCandNCcomponents
Use measured Near detector background and MC to extrapolate to the Far detector
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PreliminaryUncertainFesonBackground
• StaFsFcalerrordominates
• SystemaFcerrorprimarilyfromextrapolaFngNeardetectormeasurementofbackgroundtoFardetector
PreliminaryUncertain8es Sizeoferror
1.)ExtrapolaFonsystemaFc 6.4%
2.)Hornon/offsystemaFc 2.7%
3.)Hornon/offstaFsFcal 2.3%
Total(suminquadrature) 7.3%
Sta8s8calerror(data) 19%
JeffHartnell,RALSeminar,July'09 44
FarDetectorEnergySpectrum
• Ablindanalysiswasperformed:– allproceduresfor
calculaFngbackgroundandsignalwerefinalisedbeforetheFardetectordatawerelookedat
Fit the data to the oscillation hypothesis, obtain the signal prediction for the best fit point
• Expectedbackground: 27±5(stat)±2(sys)• Observedevents: 35
• A1.5σexcessoverbackgroundpredicFon
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AllowedRegion• AFeldman‐Cousins
methodwasused
• Fitsimplytothenumberofeventsfrom1‐8GeV
• Bestfitand90%C.L.limitsareshown:• forbothmass
hierarchies
• atMINOSbestfitvalueforΔm2
32 & sin2(2θ23)
Allowed region (Δm2>0)
• Results:Normalhierarchy(δCP=0):
sin2(2θ13)<0.29(90%C.L.)
Invertedhierarchy(δCP=0):
sin2(2θ13)<0.42(90%C.L.)
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InterpretaFon
• A1.5sigmaexcessiswellwithintherealmsofastaFsFcalfluctuaFon
• Futureνeappearanceanalysis:– updatedMCandreconstrucFon– usemorethandoublestaFsFcs
– otheranalysisimprovementstoo– aimtorelease2ndresultearlynextyear
• Watchthisspace!
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NeutralCurrentAnalysis
‐Lookingforsterileneutrinomixing‐
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• GeneralNCanalysisoverview:– AllacFveneutrinoflavours
parFcipateinNCinteracFon
– Mixingtoasterile‐νwillcauseadeficitofNCeventsinFarDet.
– Assumeonesterileneutrinoandthatmixingbetweenνμ,νsandντoccursatasingleΔm2
• SurvivalandsterileoscillaFonprobabiliFesbecome:
(αμ,s=mixingfracFons)
SimultaneousfittoCCandNCenergyspectrayieldsthefracFonofνμthatoscillatetoνs:
NeutralCurrentAnalysis
[Previousresult:PRL101221804(2008)]fs < 0.55 (90% C.L.)
TestsofLorentz/CPTViolaFonusingNearDetectorEvents
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TestsofLorentz/CPTViolaFon• SMextensionssuggestthatneutrinoscoupletoaLorentzfieldin4Dspace– neutrinos’interacFonwiththefielddependsonthedirecFonoftravel
• TerrestrialneutrinobeamswouldshowvariaFonsonthescaleofasiderealday:
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• Results:– rateandFFTconsistentwithconstantvalue
– limitsonSMextensionparameters1‐3ordersofmagnitudelowerthanpreviouslimitsPRL101151601(2008)
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SNO+
• Fundamentallydifferentapproach– Searchforneutrinolessdoublebetadecayusingkilo‐tonscalescinFllatordetector
– FilltheexisFngSudburyNeutrinoObservatory(SNO)detectorwith800tonsofliquidscinFllator
– 0.1%loadingisO(1ton)ofneodymium– gives50kgof150Nd(~5%naturalabundance)
– Canprobe• Absoluteneutrinomassscaleintheinvertedhierarchyscenario(50meV)
• Majorana/Diracnatureofneutrinos(ownanFparFcle?)
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Oneyearwith0.1%ofnaturalNd‐loadedliquidscinFllatorinSNO+:
Example: Test <mν> = 0.150 eV Klapdor-Kleingrothaus et al., Phys. Lett. B 586, 198, (2004)
Better suppress 208Tl and enhance loading (or enrich) to increase sensitivity further
small but statistically significant distortion
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PotenFaltobeWorldBeaFngExpt.
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Furthermore…amulFfacetedExpt.• First/bestmeasurementofsolarpepneutrinos
– excellentprobeofneutrino‐ma�erinteracFon
• Geo‐neutrinos– measureradiogenicporFonofEarth’sheatflow– inputtomodelsofEarth’schemicalorigin/composiFon
• Nuclearreactorneutrinos– improveknowledgeofneutrinooscillaFonparameters
• Supernovaneutrinos– informaFononcorecollapseandoscillaFons
JeffHartnell,RALSeminar,July'09 56
SNO+Status• Full Canadian funding (CFI) approved last
month– project will definitely go ahead
• UKPRDfundingrequestsubmi�edinOctober…awaiFngSTFCdecision– wesFllintendtosubmitafullproposalin2010,giventhatdetectorturn‐onisexpectedin2011
• SignificantUKinvolvement:– 9faculty:Sussex,Oxford,LeedsandQMUL(alsoLiverpoolpossibly)
Conclusions• MINOShasanalysed3.2x1020POTofbeamdata(7.6x1020POTdatanowtaken)
• Muonneutrinodisappearance– |Δm2
32|=(2.43±0.13)x10‐3eV2(68%C.L.)– sin2(2θ23)>0.90(90%C.L.)
• FirstdirectobservaFonofνμinanacceleratorlong‐baselineexperiment
• Searchforelectronneutrinoappearance– 1.5σexcessoverbackgroundpredicFon
• Searchforsterile‐νmixingfracFon:fs<0.55(90%C.L.)
• DedicatedνμruntocommenceinSeptember• ExciFngprospectswithSNO+
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Backupslides
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A. Strumia, F. Vissani, Nucl. Phys. B 726 (2005) 294-316
FarDetectorDistribuFons
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Focusedμ−fromνμ De‐focusedμ+fromνμ
FarDetectorEventProperFes• Thehigheraverageenergyofνμ
meanthatalargefracFonexitthebackofthedetector
• Eventsaretypically100‐200planeslong
• ShapesofdistribuFonsconsistentwith42events
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