MiniBooNEOscillation Searches SteveBrice(Fermilab) - - PowerPoint PPT Presentation

MiniBooNEOscillation Searches

SteveBrice(Fermilab) fortheMiniBooNECollaboration Neutrino2008

Neutrino2008 SteveBrice(FNAL) 2

Outline

• ElectronNeutrinoAppearance

– OscillationResult – π0 RateMeasurement – CombiningAnalyses – CompatibilityofHighm2 Measurements – LowEnergyElectronCandidateExcess – DatafromNuMI Beam

• MuonNeutrinoDisappearance
• Anti-ElectronNeutrinoAppearance
• Summary

Neutrino2008 SteveBrice(FNAL) 3

2NationalLaboratories,14Universities,80Researchers

TheMiniBooNECollaboration

UniversityofAlabama Bucknell University UniversityofCincinnati UniversityofColorado ColumbiaUniversity Embry-RiddleAeronauticalUniversity FermiNationalAccerator Laboratory UniversityofFlorida IndianaUniversity LosAlamosNationalLaboratory LouisianaStateUniversity UniversityofMichigan PrincetonUniversity SaintMary’sUniversityofMinnesota VirginiaPolytechnicInstitute YaleUniversity

Neutrino2008 SteveBrice(FNAL) 4

TesttheLSNDindicationofanti-electronneutrinooscillations KeepL/Esame,changebeam,energy,andsystematicerrors

P(ν→νe) =sin22θsin2(1.27m2 L/Ε)

neutrinoenergy(E): MiniBooNE:~500MeV LSND:~30MeV baseline(L): MiniBooNE:~500m LSND:~30m

Booster

• targetandhorn

detector dirt decayregion absorber

primarybeam tertiarybeam secondarybeam

(protons) (mesons) (neutrinos)

π+

ν→ν???

TheMiniBooNEStrategy

e

98.1%, 0.6%, 1.2%, 0.03%

• ν

ν ν ν = = = =

Eventrates:

Neutrino2008 SteveBrice(FNAL) 5

541metersdownstreamoftarget 3meteroverburdenofdirt 12meterdiametersphere Filledwith800tofpuremineraloil (CH2--density0.86,n=1.47) Fiducial volume:450t 1280inner8” phototubes-10%coverage, 240vetophototubes (Lessthan2%channelsfailedduringrun)

TheMiniBooNEDetector

Neutrino2008 SteveBrice(FNAL) 6

trackbasedanalysis: CountingExperiment:475<Eν<1250MeV data:380events expectation:358±19(stat)± 35(sys) significance:0.55 σ

OscillationAnalysisResults:April2007

Noevidenceforν ν ν ν

• →ν

ν ν νe appearance intheanalysisregion

Phys.Rev.Lett.98,231801(2007)

Neutrino2008 SteveBrice(FNAL) 7

Measuring ν NCπ0and Constrainingνe MisIDs

• largestν NCπ0 sampleevercollected!

arXiv:0803.3423,acceptedbyPhys.Lett.B

28,600π0 events mπ ~20MeV/c2

π0 ratemeasuredtoafewpercent Criticalinputtooscillationresult→ withoutit,π0 backgrounderrorswouldbe~25%

Neutrino2008 SteveBrice(FNAL) 8

Twoalgorithmswereused:

• “track-basedlikelihood” (TBL)

Usesdirectreconstructionofparticletypes andlikelihoodratiosforparticle-ID

• “boosteddecisiontrees” (BDT)

Setoflow-levelvariablescombinedwith BDTalgorithm->PID“score”

• Intheend,theTBanalysishadslightly

bettersensitivity,sowasusedforprimaryresults.

• OscillationAnalysisStrategy

Neutrino2008 SteveBrice(FNAL) 9

CombiningνeBDT+νeTBLSamples

Limitsfromfitstoopendata

10%-30%improvementin90%C.L.limitbelow~1eV2.

Thecombinationofthetwoνe samples givesanincreaseincoverageinthe regionm2<1eV2. Differencesinthedetailsareduetothe specificfluctuationsinthedatasamples andtheinterplaywithcorrelations amongthem.

Thecombinationyields aconsistentresult.

paperatdraftstage

Preliminary

Neutrino2008 SteveBrice(FNAL) 10

GlobalDataAnalysis

• Combineresultsfromseveralexperiments--

LSND,MiniBooNE,Karmen andBugey

• Compatibility

– Howprobableisitthatallexperimentalresultscomefromthesame underlying2-ν osc.hypothesis? – Assessedbycombiningtheχ2 surfaceofeachexperiment

• Allowedregions

– Indicatewhereoscillationparameterswouldlie,atagivenCL, assumingallexpt.resultscanariseinaframeworkof2-ν osc. – Thecompatibilityisthemetricforthevalidityofthisassumption.

arXiv:0805.1764[hep-ex],submittedtoPhys.Rev.D

Neutrino2008 SteveBrice(FNAL) 11

GlobalFitstoExperiments

0.012 0.221 27.37

X X X

0.147 0.052 73.44

X X

0.023 0.253 2.14

X X X

0.256 0.072 16.00

X X

0.023 0.242 3.94

X X X X

0.256 0.072 25.36

X X X

Sin22θ θ θ θ

• m2

Max. Compat % Bugey MB

KARMEN2

LSND

Neutrino2008 SteveBrice(FNAL) 12

GlobalFitResults-2DFits

• LSND,KARMEN2&MiniBooNE

– 25.36% compatibilityatm2 =0.072eV2,sin22θ = 0.256

• LSND,KARMEN2,MiniBooNE&Bugey

– 3.94% compatibilityatm2 =0.242eV2,sin22θ = 0.023 Colorsrepresentχ 2

Neutrino2008 SteveBrice(FNAL) 13

reconstructedneutrinoenergybin(MeV) 200-300300-475475-1250 Data375±19369±19380±19 totalbackground 284±25274±21358±35 νeintrinsic2667 229 ν induced258207129

• Nosignificantexcessat

higherE,whereνebkgd dominates.

• Largestbackgroundsat

lowerEare ν-induced, inparticular:

• NC π
• NC→Nγ
• Dirt

Preliminary

LowEnergy νe Candidate Excess

Neutrino2008 SteveBrice(FNAL) 14

UpdatestoLowEnergyνe Prediction

Nearingtheendofacomprehensivereviewoftheνe appearancebackgroundsandtheiruncertainties → NotQuiteReadyforReleaseYet

Neutrino2008 SteveBrice(FNAL) 15

UpdatestoLowEnergyνe Prediction

• Includedphotonucleareffect

Arrowsindicatewhethereffectistoincreaseordecreasethelowenergydataexcess Theeffectshavedifferentmagnitudesdespitethearrowsallbeingthesamesize

Nearingtheendofacomprehensivereviewoftheνe appearancebackgroundsandtheiruncertainties → NotQuiteReadyforReleaseYet

• Photonuclearabsorption

removesoneofthegammas fromaν-inducedNCπ0 → γγ

– Photonuclearabsorptionwas missingfromourGEANT3 detectorMonteCarlo – Reducessizeofexcess

Effectofphotonuclearinteractions

Neutrino2008 SteveBrice(FNAL) 16

UpdatestoLowEnergyνe Prediction

• Includedphotonucleareffect

– AbsentfromGEANT3– createsbackgroundfromπ0s

• Morecomprehensivehadronic errors

– e.g.uncertaintiesinfinalstatefollowingphotonuclearinteraction

Arrowsindicatewhethereffectistoincreaseordecreasethelowenergydataexcess Theeffectshavedifferentmagnitudesdespitethearrowsallbeingthesamesize

Nearingtheendofacomprehensivereviewoftheνe appearancebackgroundsandtheiruncertainties → NotQuiteReadyforReleaseYet

Neutrino2008 SteveBrice(FNAL) 17

UpdatestoLowEnergyνe Prediction

• Includedphotonucleareffect

– AbsentfromGEANT3– createsbackgroundfromπ0s

• Morecomprehensivehadronic errors

– e.g.uncertaintiesinfinalstatefollowingphotonuclearinteraction

• Betterhandlingofbeamπ+ productionuncertainties

– Errorspropagatedinmodel-independentway

Arrowsindicatewhethereffectistoincreaseordecreasethelowenergydataexcess Theeffectshavedifferentmagnitudesdespitethearrowsallbeingthesamesize

Nearingtheendofacomprehensivereviewoftheνe appearancebackgroundsandtheiruncertainties → NotQuiteReadyforReleaseYet

Neutrino2008 SteveBrice(FNAL) 18

UpdatestoLowEnergyνe Prediction

• Includedphotonucleareffect

– AbsentfromGEANT3– createsbackgroundfromπ0s

• Morecomprehensivehadronic errors

– e.g.uncertaintiesinfinalstatefollowingphotonuclearinteraction

• Betterhandlingofbeamπ+ productionuncertainties

– Errorspropagatedinmodel-independentway

• Improvedmeasurementofν inducedπ0s

– e.g.finermomentumbinning

Arrowsindicatewhethereffectistoincreaseordecreasethelowenergydataexcess Theeffectshavedifferentmagnitudesdespitethearrowsallbeingthesamesize

Nearingtheendofacomprehensivereviewoftheνe appearancebackgroundsandtheiruncertainties → NotQuiteReadyforReleaseYet

Neutrino2008 SteveBrice(FNAL) 19

UpdatestoLowEnergyνe Prediction

• Includedphotonucleareffect

– AbsentfromGEANT3– createsbackgroundfromπ0s

• Morecomprehensivehadronic errors

– e.g.uncertaintiesinfinalstatefollowingphotonuclearinteraction

• Betterhandlingofbeamπ+ productionuncertainties

– Errorspropagatedinmodel-independentway

• Improvedmeasurementofν inducedπ0s

– e.g.finermomentumbinning

• IncorporationofMiniBooNEπ0 coherent/resonantmeasurement

– Nolongerneedtorelyonmoreuncertainpastresults

Arrowsindicatewhethereffectistoincreaseordecreasethelowenergydataexcess Theeffectshavedifferentmagnitudesdespitethearrowsallbeingthesamesize

Nearingtheendofacomprehensivereviewoftheνe appearancebackgroundsandtheiruncertainties → NotQuiteReadyforReleaseYet

Neutrino2008 SteveBrice(FNAL) 20

UpdatestoLowEnergyνe Prediction

• Includedphotonucleareffect

– AbsentfromGEANT3– createsbackgroundfromπ0s

• Morecomprehensivehadronic errors

– e.g.uncertaintiesinfinalstatefollowingphotonuclearinteraction

• Betterhandlingofbeamπ+ productionuncertainties

– Errorspropagatedinmodel-independentway

• Improvedmeasurementofν inducedπ0s

– e.g.finermomentumbinning

• IncorporationofMiniBooNEπ0 coherent/resonantmeasurement

– Nolongerneedtorelyonmoreuncertainpastresults

• Betterhandlingoftheradiative decayofthe resonance

– Comprehensivereviewofhowthe0,+ radiative decayrateisinferred fromthemeasuredπ0 rate

Arrowsindicatewhethereffectistoincreaseordecreasethelowenergydataexcess Theeffectshavedifferentmagnitudesdespitethearrowsallbeingthesamesize

Nearingtheendofacomprehensivereviewoftheνe appearancebackgroundsandtheiruncertainties → NotQuiteReadyforReleaseYet

Dirteventstendtobeatlargeradius, headinginward Addanewcuton“DistancetoWall backward” toreducethese.

s h

• w

e r

dirt

Inlowenergyregionthereisa significantbackgroundfromneutrino interactionsinthedirtoutsidethetank

UpdatestoLowEnergyνe Cuts

Removingdirtevents

Neutrino2008 SteveBrice(FNAL) 22

RemovingDirtEvents

MCupgradesandnewcutshavenoappreciableeffectabove475MeV

“DistancetoWallBackwards” cut:- Reducesdirteventsby~80% Reducesνe eventsby~20% Plothasnodirtremovalcuts

Neutrino2008 SteveBrice(FNAL) 23

NuMI eventrates:

ν ν ν ν

• :81%ν

ν ν νe:5%ν

ν ν ν

• :13%ν

ν ν νe:1% ThebeamatMiniBooNEfromNuMIis significantlyenhancedin νfromKdecay becauseofthe110mrad off-axisposition. MiniBooNEis745mfromNuMI target

NuMIEventsinMiniBooNE

WorkincollaborationwithMINOS

Neutrino2008 SteveBrice(FNAL) 24

PRELIMINARY PRELIMINARY

Goodagreementbetween dataandMonteCarlo:the MCistunedwell. Verydifferentbackgrounds comparedtoMB(Kaons vs Pions) Ongoingefforttoreduceν ν ν ν ν ν ν νe

e

CCQE samplesystematics 1.26σ excess<900MeV

PRELIMINARY PRELIMINARY

NuMI ν ν ν ν

• andν

ν ν νe Data ν ν ν ν

• CCQE

sample

ν ν ν νe

CCQE

sample

paperatdraftstage

Neutrino2008 SteveBrice(FNAL) 25

MiniBooNEν Disappearance Sensitivity

• MiniBooNEdata90%CL

sensitivity(NOT limitfrom data)

• CDHS

CCFR90%CL

• Combinedanalysiswith

SciBooNE datawill significantlyimprovethis sensitivity

Preliminary

Neutrino2008 SteveBrice(FNAL) 26

MiniBooNEPresentandFuture

• Taken~6.6x1020 POTinneutrinomode

– Makingsuiteofcross-sectionmeasurements – Searchingforvariousneutrinooscillations – Publicationscomingout

• Taken~2.5x1020 POTinanti-neutrinomode

– Makingsuiteofcross-sectionmeasurements – Searchingforanti-neutrinodisappearance

• InNov2007requestgrantedforextrarunningfor

ananti-nue appearancesearch

– LSNDresultwasanindicationofanti-nue appearance – Extra~2.5x1020 POT(makinggrandtotalof~5x1020 POT) – ShouldtakeFY2008andFY2009running

Neutrino2008 SteveBrice(FNAL) 27

Anti-nue AppearanceSensitivity

Regionallowedat90%C.L. byjointanalysisof LSNDandKARMEN

Onlyantineutrinosallowedtooscillate

Preliminary

Neutrino2008 SteveBrice(FNAL) 28

Summary

• ElectronNeutrinoAppearance

– CombiningAnalyses

• Setsatighterlimit

– CompatibilityofHighm2 Measurements

• Highm2 experimentscompatiblewith2vosc.atonly3.94%level

– LowEnergyElectronCandidateExcess

• Fullupdatecomingthissummer

– DatafromNuMI Beam

• SamplecomplementarytoMBflux,onlysmallsignificanceLE

excessseenwithcurrentuncertainties

• MuonNeutrinoDisappearance

– Resultthissummer

• Anti-ElectronNeutrinoAppearance

– DoublingcurrentPOTforresult

Neutrino2008 SteveBrice(FNAL) 29

Backups

Neutrino2008 SteveBrice(FNAL) 30

• CCπ+

– 2papersexpected

• CCπ0

– Reconstructionchallengesovercome – 1paperexpected

• NCπ0

– 1papersubmittedPLB – Coherent/resonantinnuandanti-nu modes – Fluxaveragedcross-section measurement – 2furtherpapersexpected

• NCElastic

– Fluxaveragedcross-section measurement – 1paperexpected

• ν-eElastic

– Numag.Mom – 1paperexpected.

• Oscillation

– RefinedNue appearance – Nuebar appearance – Numu andnumubar disappearance – 1PRL,~3furtherpapersexpected

• LowEnergyExcess

– Bigeffort – 2+papersexpected

• AlternativeOscillations

– Phenomenology – CPviolation,Lorentzviolation,... – 3+papersexpected

• NuMI Events

– LargeeventratefromNuMI beam – Checkonosc.andLowE – 1paperbeingwritten

• CCQE

– 1PRL,2furtherpapersexpected

BroadRangeof Analyses

• Noorganizationalseparationbetweenneutrinoandantineutrinomode
• 12PhDStudents+6graduated

=PhDStudent(6alreadygraduated)

Neutrino2008 SteveBrice(FNAL) 31

ν NCElastic

NCEL

Results(from10%nusample):

• NCelastic diff.crosssection

(pernucleon,n+p averaged,fluxaveraged)

• FluxIntegratedCross-Section

=8.8±0.6(stat)±2.0(syst)x10-40cm2

• Measuredaxialmass(NC)

=1.34+0.38–0.25GeV

• workofChrisCox,IndianaU.,Ph.D.2008
• furtheranalysisonfullnudatasetandwithgoalof

reducingsystematicerrorsinprogress (D.Perevalov,Alabama)

• eventualanalysisgoal:

NC/CCQEratiomeasurementandantinu data

Neutrino2008 SteveBrice(FNAL) 32

GlobalDataAnalysis

• Dataprovidedaspointson2-D

m2- sin22θ grid

• Eachpt=agreementbetweendata&2-ν

hypothesisatthatpoint

• Datainln(L),ln (L),χ2 grids

χ

• Mustuseχ2 gridsinthisanalysis

Neutrino2008 SteveBrice(FNAL) 33

TwoMethods

• Createχ2 gridsin2ways
• 2-Dgridusesglobalbestfitpointto

calculatetheχ2 ateachpoint

– Prob toobserveallexpt resultsifnaturehas 2-ν osc inthisentirem2 region

• 1-D(RasterScan)useslocalbestfitpoint

ateachm2 toproduceχ2

– Compat ateachm2,ifnaturetrulyhad2-ν

• sc atthatspecificm2

Neutrino2008 SteveBrice(FNAL) 34

CompatibilityCalculation

• Constructaχ2 gridforeachexpt.

– eachpt=localvalue- bestfitvalue

• Sumindividualχ2 grids
• Compatibility=χ2 prob.ofminimumof

summedgrid,usingareducedNDF

– Σ(indep.α)- (#indep α estimatedfromdata) – ex:MB+LSND=4- 2=2NDF

Neutrino2008 SteveBrice(FNAL) 35

AllowedRegion

• Eachexpt’s χ2 gridconvertedintoχ2 probgrid

usingstandardNDF(2,1)

• Multiplyχ2 prob gridstogether,producex
• Allowedregions=closedcontoursinspace
• Exclusionbands=non-closedcontours

– ValuestoRareexcludedatagivenCL

!"#$%

Σ

1 J! x|lnj(x)|

J=0 n-1

P(x)=

Neutrino2008 SteveBrice(FNAL) 36

LSND,MB,Bugey,± KAR2

• 2.14%vs 3.94%!
• Bestfitpoint=0.242

eV2 ,0.023sin22θ

• IncludingKARMEN2

increasestheNDF usedtocalculateprob, butprovidesno increaseinsensitivity!

Neutrino2008 SteveBrice(FNAL) 37

AnomalyMediatedBackground

• “Anomalymediatedneutrino-photon

interactionsatfinitebaryondensity.”

• StandardModelprocess

⇒ Underactiveinvestigation,predictionof ~140(gω/10)4 events,wheregω is10to30.

• Canusephotonenergyandangletocheck

prediction. (Harvey,Hill,andHill,arXiv:0708.1281[hep-ph])