Summary of Long-Baseline Systematics Session at CETUP*2014

0.32 MB·English

by  D. Cherdack

Summary of Long-Baseline Systematics Session at
CETUP*2014
Daniel Cherdack∗ and Elizabeth Worcester†
∗ColoradoStateUniversity
†BrookhavenNationalLaboratory
5
1 Abstract. Asessionstudyingsystematicsinlong-baselineneutrinooscillationphysicswasheldJuly14-18,2014aspartof
0 CETUP*2014.Systematiceffectsfromfluxnormalizationandmodeling,modelingofcrosssectionsandnuclearinteractions,
2 andfardetectoreffectswereaddressed.Expertspresentedthecapabilitiesofexistingandplannedtools.Aprogramofstudy
todetermineestimatesofandrequirementsforthesizeoftheseeffectswasdesigned.Thisdocumentsummarizestheresults
n
of the CETUP* systematics workshop and the current status of systematic uncertainty studies in long-baseline neutrino
a
J oscillationmeasurements.

1 Keywords: neutrinooscillation,systematicuncertainty
2 PACS: 14.60.Pq,13.15.+g

]
x
1. INTRODUCTION
e
-
p For discovery of CP violation, precise understanding of systematic uncertainty will be required. Until recently, the
e
expectedlevelofsystematicuncertaintyforalong-baselineexperimentatFermilab’sLong-BaselineNeutrinoFacility
h
(LBNF) has been estimated based on experience with existing experiments and estimates of the performance of the
[
next-generationdetectorsbeingdesignedforexperimentsatLBNF.Thesesystematicuncertaintiesareapproximated

1
insensitivitycalculationsbynormalizationuncertaintiesthatcovertheuncertaintiesinallofthemodelsusedinthe
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MC generation chain. These include the flux model, neutrino interaction cross section models, nuclear models, and
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modelsofthenearandfardetectorresponse.
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0 At the CETUP* workshop, our goal was to summarize existing knowledge of the the leading systematic effects
5 and to develop a program of study to determine a quantitative prediction for the size of each effect in a long-
0 baselineneutrinoexperimentatLBNF.Theultimategoalofthisprogramistoperformdetailedstudiesofeachsource
1. of systematic uncertainty that will determine detector design and analysis performance requirements to constrain
0 systematicuncertaintytotheprojectedlevels.Inthisdocument,thetoolsthathavebeendevelopedtostudysystematic
5 uncertaintyinLBNEaredescribedinSection3,thestatusofexistingstudiesisdescribedinSection4,andplansfor
1 futurestudiesaredescribedinSection5.ThestudiespresentedherewereperformedinthecontextofLBNE,butare
:
v largelyapplicabletothenewinternationalexperimentalcollaborationatLBNF[1].
i
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r 2. WORKSHOPDETAILS
a
The CETUP* 2014 systematics workshop had 21 registered participants, some of whom were participating in the
concurrent Near Detector workshop and some of whom were focused exclusively on the systematics workshop.
Additionally,severalexpertswhowereunabletoattendinpersongavepresentationsoverthephone.Eachdayofthe
workshopfocusedonaparticularsourceofsystematicuncertainty.Table1istheagendaforeachday.Eachday,there
wereapproximatelytwohoursofpresentationswithmostofthedayreservedforworkingtimeinwhichparticipants
discussedissuesarisingfromthepresentationsanddevelopedalistofspecificstudiesthatarerequiredtounderstand
eachsystematiceffect.Requirementsfordevelopmentoftoolsandacquisitionofexternalinputwerealsodetermined.
Detectorrequirementsweredeterminedwhenpossible,thoughgenerallythesewillbeanoutputofstudiesthathave
notyetbeenperformed.
TABLE1. AgendaofCETUP*SystematicsWorkshop
Day Topic Presentation Speaker
1 Introduction Welcome BarbaraSzczerbinska
WorkshopGoalsandCharge ElizabethWorcester
ToolsforStudyingSystematicUncertainty DanCherdack
Flux FluxSystematicUncertainties PaulLebrun
NDFluxConstraints XinchunTian
ConstrainingtheNuMIFlux DebbieHarris
2 Crosssections NDCross-SectionConstraints(FastMC) XinchunTian
NDFluxandCross-SectionConstraints(VALOR) CostasAndreopoulos
Hadronization(GENIE/VALOR) CostasAndreopoulos
FDCross-SectionConstraints(FastMC) DanCherdack
SystematicEffectsfromQE,MEC,andRES RikGran
3 NuclearModel NearDetectorConstraints RobertoPetti
GENIEvsGiBUU MindyJen
ReducingEnergyResolutionUncertainty UlrichMosel
GENIEFSIModel/Systematics SteveDytman
4 FarDetector LArSimulationsandReconstruction TomJunk
ConstraintsfromTestBeamExperiments XinQian
AlternativeFDDesigns:ImplicationsforSystematics NunoBarros
TourofSURF4850-L
5 Discussion
3. TOOLS
Theworkpresentedheremakesuseofanumberoftools,someofwhicharecommonlyusedintheHEPcommunity
and others of which have been developed by the LBNE collaboration specifically for analysis of long-baseline
systematics and sensitivity calculations. GLoBES[2, 3] is a software package developed to calculate sensitivities
for neutrino oscillation experiments. The LBNE Fast Monte Carlo (Fast MC) is a simulation suite, combining flux
simulations from G4LBNE (a GEANT4[4]-based beam simulation), the GENIE[5] neutrino event generator, and a
parameterizeddetectorresponseusedtosimulatetheenergydepositionofeachfinal-stateparticle.TheNDFastMC
is an implementation of a fine-grained tracker (FGT) near detector (ND) in the Fast MC framework. My GLoBES
Tools(MGT)isananalysisframeworkusingGLoBESlibrariesthatcalculatesexperimentalsensitivity,includingthe
effectofsystematicvariations,usinginputsfromasimulationsuchastheFastMC.VALORisafittingframeworkthat
performsamaximumlikelihoodfitofneardetectordatatoconstrainsystematicuncertaintiesandthenappliesthese
constraintstooscillationparameterfitsoffardetectoreventsamples.LArSoft[6]isafulldetectorresponsesimulation
and reconstruction package for liquid argon TPCs, used by multiple experiments. Reconstruction algorithms within
LArSoft are under development. Once further development is complete, the LArSoft simulation will be used in
conjunctionwithwiththesamefluxandcrosssectionsimulationsasthecurrentFastMCtoprovidefullsimulations
ofaLArTPCfardetectoratLBNF.
4. CURRENTRESULTS
4.1. GLoBESStudies
Expected systematic uncertainties on the ν appearance samples in the three-flavor fit for LBNE are extrapolated
e
from the current performance of the MINOS [7, 8] and T2K [9] experiments, as shown in Table 2. The sensitivity
of long-baseline oscillation parameter measurements has been evaluated in GLoBES fits that account for statistical
uncertainties, oscillation parameter uncertainties, and these non-oscillation systematic uncertainties. The latter is
accomplished via eight normalization parameters; one each for the signal and background of four simultaneously
fit analysis samples (ν , ν , ν , ν ). These eight parameters are assumed to be completely uncorrelated, as any
e e µ µ
correlated uncertainty is expected to cancel. Estimates for these normalization uncertainties are 5% (1%) signal and
10%(5%)backgroundfortheν (ν )samples.Thesevaluesreflecttheuncorrelatedportionofthetotaluncertainty
µ e
projectionsforeachsample,includingconstraintsfromexternalandneardetectordata.Theportionofthesystematics
uncertaintiesthatarecorrelatedamongstanalysissampleareexpectedtolargelycancelincombinedfits.
The sensitivity of the mass hierarchy determination and the CP violation measurement to possible values for the
uncorrelated ν signal and background normalization uncertainties in the GLoBES-based calculation are shown in
e
Fig. 1. The impact of systematic uncertainty on the CP violation sensitivity is clear; the normalization of the ν
e
sample,relativetotheν ,ν ,andν samplesafterallconstraintsfromexternal,neardetector,andfardetectordata
e µ µ
havebeenapplied,mustbedeterminedatthe1-2%levelinordertoreach5σ sensitivityforexposureslessthan900
kt-MW-years. An important goal of the long-baseline community and the CETUP*2014 systematics workshop is to
individually evaluate the effect of individual systematic uncertainties from flux determination, neutrino interaction
cross section models, nuclear models, and near and far detector response rather than relying on these expected
normalizationuncertainties.
4.2. Flux
Theuncertaintiesfromthegenerationofhadronsthatdecayintoneutrinos,whichareproducedoffthetargetand
bysecondaryandtertiaryinteractionsinthetargethallandthedecaypipe,areknowntobelarge(∼10%)andarethe
leading source of uncertainty in conventional neutrino beamlines. Studies of ND constraints are the best handle on
howtheresultingfluxuncertaintieswillbepropagatedtoFDmeasurements.
Toevaluatethecapabilitiesofproposedneardetectorstoconstraintheflux,initialstudieshavebeenperformedfor
a FGT ND design making use of the ND Fast MC. These studies demonstrate the capability of a FGT to constrain
theabsolutefluxusingfully-leptonicinteractionchannels,aswellasthefluxshapeandtheFD/NDfluxratio.Initial
TABLE2. Thedominantsystematicuncertaintiesontheνe appearancesignalpredictioninMINOS
andT2KandaconservativeprojectionoftheexpecteduncertaintiesinanexperimentatLBNF.Ineach
case,thequoteduncertaintyistheeffectontheνe appearancesignalonly.Theseuncertaintiesarethe
totalexpecteduncertaintiesontheνe appearancesignalwhichincludebothcorrelatedanduncorrelated
uncertaintiesinthethree-flavorfit.
Sourceof MINOS T2K ELBNF Comments
Uncertainty νe νe νe
FluxDetermination
BeamFlux 0.3% 2.9% 2% MINOSisnormalizationonly.
afterN/F ELBNFnormalizationandshape
extrapolation highlycorrelatedbetweenνµ/νe.
Neutrinointeractionmodeling
Simulation 2.7% 7.5% ∼2% Hadronizationmodelsarebetter
includes: constrainedintheELBNFLArTPC.
hadronization N/FcancellationlargerinMINOS/ELBNF.
crosssections X-sectionuncertaintieslargeratT2Kenergies.
nuclearmodels SpectralanalysisinELBNFprovides
extraconstraint.
Detectoreffects
Energyscale 3.5% included (2%) IncludedinELBNFνµ sample
(νµ) above uncertaintyonlyin3-flavorfit.
MINOSdominatedbyhadronicscale.
Energyscale 2.7% 3.4% 2% TotallyactiveLArTPCwithcalibration
(νe) includes andtestbeamdatalowersuncertainty.
allFD
effects
Fiducial 2.4% 1% 1% Largerdetectors=smalleruncertainty.
volume
Total 5.7% 8.8% 3.6% Uncorrelatedνeuncertaintyin
fullELBNF3-flavorfit=1-2%.
FIGURE1. ExpectedsensitivityofanexperimentatLBNFtodeterminationoftheneutrinomasshierarchy(left)anddiscovery
of CP violation, i.e. δCP (cid:54)= 0 or π, (right) as a function of exposure in kt-MW-years, assuming equal running in neutrino and
antineutrino mode, for a range of values for the residual νe and νe signal and background normalization uncertainties. The
sensitivities quoted are the minimum sensitivity for 100% of δCP values in the case of mass hierarchy and 50% of δCP values
inthecaseofCPviolation.Sensitivitiesarefortruenormalhierarchy;neutrinomasshierarchyisassumedtobeunknowninthe
CPVfits.Valuesoftheoscillationparametersandtheiruncertaintiesusedinthiscalculationaretakenfrom[10].
studies predict a 2% statistical uncertainty for neutrino-electron scattering which can be used to constrain the flux
below∼5GeV,anda3%statisticaluncertaintyforinversemuondecay,whichcanbeusedtomeasurethefluxabove
∼10 GeV. The low-ν method [11, 12, 13] can be used to constrain the shape of the flux as well as FD/ND shape
0
differencesandisexpectedtodosoatthe1-2%level.
StudiesusingtheVALORanalysistechniquetoconstrainsimulateddataderivedfromtheFastMCeventsamples
also demonstrate the significant ability of a FGT ND to constrain the flux rate and shape. As shown in Fig. 2, the
post-fituncertaintyinmostfluxbinsforasampleVALORfitislessthan5%,whichisconsistentwiththeuncorrelated
ν signalnormalizationuncertaintyassumedbythesensitivitycalculations.Sincethefluxfortheν (ν )appearance
µ e e
and the ν (ν )-disapearance analysis samples are identical, the unceratinties are 100% correlated; i.e., the ν (ν )
µ µ µ µ
sampleconstrainsthefluxfortheν (ν )sample.
e e
Systematicuncertaintyinthefardetectorfluxarisingfromuncertaintiesinpositionsofbeamlineelementsinduce
significantreductioninsensitivityintheabsenceofneardetectorconstraints,butpreliminarystudiesindicatethatthe
neardetectorwillsignificantlyconstraintheflux,sotheseeffectsarenotexpectedtobealeadingsourceofsystematic
uncertainty.Furthermore,theseuncertaintieshavebeenevaluatedusingbeamsimulationsandthequadraturesumof
theuncertaintypropagatedtotheND/FDratioisdeterminedtobeatthe1%level.
4.3. CrossSectionsandNuclearInteractions
AsseeninFig.3,atLBNFthefardetectoreventsampleswillcontainsignificantcontributionsfromquasielastic,
resonance production, and deep inelastic scattering (DIS) interactions, so it is important to understand systematics
arising from uncertainty in the cross-section models for each of these neutrino interaction processes. Results from
MGT using Fast MC inputs show that a fit to all four far detector samples (ν , ν , ν , ν ) significantly constrains
e e µ µ
cross-section systematic uncertainty even in the case where multiple cross-section parameters are allowed to vary
simultaneouslywithintheirGENIEuncertainties.Forexample,fitsareperformedinwhichMQE andMRESforcharged
A A
current(CC)interactionsarebothallowedtovarywithintheirGENIEuncertaintiesof∼±20%.Thisessentiallyallows
theconstituentsamplenormalizationsinthereconstructedenergyspectratovaryby∼20%.Asseenintheexample
fitshowninFig.4,thislevelofallowedvariationresultsinadramaticreductioninsensitivityifonefitsonlytheν
e
s
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nti 0.3 Prior uncertainties
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t Postfit uncertainties
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_fhc_flux_numu0_fhc_flux_numu0_fhc_flux_numu0_fhc_flux_numu0_fhc_flux_numu0_fhc_flux_numu0_fhc_flux_numu0_fhc_flux_numu0_fhc_flux_numu0_fhc_flux_numu0c_flux_numubar0c_flux_numubar0c_flux_numubar0c_flux_numubar0c_flux_numubar0f_fhc_flux_nue0f_fhc_flux_nue0f_fhc_flux_nue0_rhc_flux_numu0_rhc_flux_numu0_rhc_flux_numu0_rhc_flux_numu0_rhc_flux_numu0_rhc_flux_numu0_rhc_flux_numu0c_flux_numubar0c_flux_numubar0c_flux_numubar0c_flux_numubar0c_flux_numubar0c_flux_numubar0c_flux_numubar0c_flux_numubar0f_rhc_flux_nue0f_rhc_flux_nue0f_rhc_flux_nue0f_ccqf_cc1pif_cc1pif_ccotf_nf_nuecc_numuc
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FIGURE 2. Example of prior uncertainties (blue) compared with post-fit uncertainties (red) on binned flux normalization
parameters from a VALOR fit of simulated near-detector data. In this fit, the true values of all the FHC νµ flux parameters are
settobe10%greaterthannominalandthetruevaluesoftheotherparametersaresettobenominal.Nostatisticalfluctuationsare
applied.Near-detectorefficiencyparametersareincludedinthenear-detectorfitbutarethenmarginalized.Thepost-fituncertainties
intheRHCνe fluxparametersareidenticaltotheprioruncertaintiessincethereisnoRHCνe sampleincludedinthisfit,which
meansthattheseparametersarenotconstrainedbythisfit.
appearancesignalwithoutconstraintfromtheν andν /ν samples.Incontrast,forafour-samplefit,thesamelevel
e µ µ
of allowed fluctuations lead to a significantly smaller degradation of the CPV sensitivity. Comparing the fraction of
δ values for which a 3σ discovery of CP violation can be made with an exposure of 245 kt-MW-years, i.e., 3σ
CP
CPVcoverage,betweenthetwofits,wefinda54%reductionin3σ CPVcoveragefortheν appearance-onlyfitis
e
reducedtoa2%reductionin3σ CPVcoverageforthefour-samplefit.Thisresultincludesa10%uncertaintyinthe
ν/ν cross-sectionratioanda2.5%uncertaintyintheν /ν cross-sectionratio.PreliminarystudiesfromVALORand
e µ
theNDFastMCdemonstratesignificantconstraintoncross-sectionsystematicsfromtheneardetectoraswell.
Nuclearmodelsenterintothesimulationofneutrinointeractionsboththroughmodelingofinitial-stateinteractions,
i.e.,interactionsbetweentheinitialstateofthenucleonsandvirtualparticleswithinthenucleuswiththeneutrino,and
modelingoffinal-stateinteractions(FSI),i.e.,interactionsoftheparticlesexitingtheprimaryinteractionvertexwith
thenuclearmedium.Uncertaintiesininitial-stateinteractionsduetonaivemodelingoftheenvironmentofthenucleus
have thus far been taken into account through inflation of the uncertainties on the free nucleon or quark interaction
model,suchasMQE.Final-stateinteractionscanaltereventreconstructionintwodistinctways.Thefirstisasmearing
A
ofthetotalenergyavailabletobedepositedinthedetector.Thesecondisthemisidentificationofeventtopologiesused
toclassifytheneutrinoflavorandinteractionmode.Uncertaintiesinselectionefficienciesandevent-samplemigrations
duetointranuclearrescatteringcanbestudiedwiththeFastMCandhavebeenimplementedinVALOR.
FIGURE3. ExampleνeappearancespectrumatLBNF.EventsareseparatedbyinteractiontypeusingFastMCsignalselection
criteria.
FIGURE4. TheCPviolationsensitivityforthenominal245kt-MW-yearsofexposurecalculatedusinginputsfromtheFastMC
inafittoallfour(νe,νe,νµ,νµ)samples(red)andafittotheνe appearancesampleonly(blue),forthecaseofnosystematic
uncertainty(solid)andthecaseinwhichbothMQE,CCandMRES,CCareallowedtovarywitha1σ uncertaintyof20%(dashed).
A A
4.4. DetectorEffects
Methods to estimate far detector properties, such as single-particle energy resolutions, missing hadronic energy,
energy-scale uncertainties, event selection efficiencies, and background rejection rates have been implemented in
the Fast MC. The parameters that control these effects are determined by GENIE event kinematics, typical event
selectioncriteria,ICARUS[14,15]andT2K[16]results,andLArSoft-basedsimulations.CurrentFastMCsensitivity
calculationsreflectthenominalinputvaluesfortheenergyresolutionsandmissingenergy.
5. PLANNEDWORK
AttheCETUP*2014systematicsworkshop,wedevelopedalistofstudiesthatwouldinformthestudyofsystematic
uncertaintyinalong-baselineneutrinooscillationanalysis.Inthissection,wedescribethestatusofin-progressand
plannedstudies.Inmanycases,thisworkisacollaborationamongmultipleexperimentalefforts,phenomonologists,
andsimulationgroups.Animportantpartofthisprogramissupportfortheeffortsofphenomonologistsandsimulation
groupstoimplementarangeofmodelsintoneutrinoeventgeneratorsforcomparisontoexperimentalresults.
5.1. GLoBESStudies
The developers of GLoBES have implemented more sophisticated treatment of systematic uncertainty into an
unreleased version of the software, which has been used in [17, 18, 19]. This updated version of GLoBES has been
madeavailabletoLBNEcollaboratorsandisbeingincorporatedintofuturesensitivitystudies.
5.2. Flux
Initialstudiesofneutrino-electronscattering,inversemuondecay,andthelow-ν method,whichcurrentlypredict
0
absolute flux normalization at the 2-3% level and relative normalization and ND/FD ratio at the 1-2% level, must
be followed up with more detailed treatment of systematic uncertainties affecting these results. For example, event
selections for purely lepton interactions rely heavily on the angle of the final-state lepton, and uncertainties of the
angular dispersion of the beam must be included to validate the current results. Such studies are planned and in
progress.
Ithasbeenproposedthatcoherentpionproduction,whichhasthesamecrosssectionfromneutrinosandantineu-
trinosanddoesnotsufferfromnucleareffects,willhelptoconstraintheν/ν¯ fluxratio.Alternatemodelsofcoherent
production[20,21,22,23],whichareknowntovarygreatlyintheirpredictionofthecoherentinteractioncrosssec-
tions,areexpectedtobeincludedinanupcomingGENIErelease,allowingfordetailedstudyofthisproposal.
More work is needed to asses the impact of hadronization model uncertainties, which are the leading source of
uncertaintyinthefluxprediction.Minerva[24]measurementsoftheNuMIfluxhavebeenobtainedintheformofa
flux correlation matrix[25]; flux uncertainties based on this data are being implemented in the Fast MC and will be
propagated to LBNF analyses. Since the NuMI and LBNF beams share many key properties, this technique should
providereasonablyaccurateresults.AfluxdriverwithMinervafluxre-weightingtoolsisalsobeingimplementedin
GENIEtoallowreweightingofeventsbasedonthesetofinteractionsthatproducedtheneutrino.Oncethesetoolsare
available,additionalstudieswillbeperformedtodeterminetheprecisionwithwhichtheabsoluteflux,fluxshape,and
ND/FDfluxratiocanbemeasuredgivenrealisticuncertaintiesinthehadronizationmodel.
Extrapolation of the flux at the near detector, measured using the methods described above, to the far detector
willrequireunderstandingoftherelativeenergyscalebetweenthenearandfardetectors.Todeterminetherequired
precisionontherelativeenergyscale,whichweassumewillbedominatedbythefardetectorenergyreconstruction,
wewillexplorethevariationinphysicssensitivityforarangeofvaluesformuonenergybiasandresolution,hadron
energy resolution, and energy reconstruction bias from undetected and mis-identified particles. Undetected particles
includeneutronsandparticlesbelowthreshold.
5.3. CrossSectionsandNuclearInteractions
CurrentstudiesbasedonFastMCsamplesaddresscross-sectionparametervariationsforwhichGENIEreweights
areavailable.Toevaluatecross-sectionuncertaintiesbeyondthoseconsideredbyGENIE,wewillmakecomparisons
between observables from the Fast MC generated using the nominal GENIE and with alternate versions of GENIE.
Thesealterationsincludeadjustingnon-reweightableparametersandtheuseofadditionalandalternatecross-section
models.Inparticular,modelsthatdescribeinitial-stateinteractions,includingmodelsoflong-andshort-rangecorrela-
tionsamongstnucleons[26,27],randomphaseapproximation(RPA)effects,meson-exchangecurrents(MEC),2p-2h
effectsinCCQEinteractions[28,29,30,31],andextensionsofthesemodelstoresonanceproductioninteractionsmust
beimplemented.Theeffectivespectralfunctionmodel[32]includesalloftheseeffectsbytuningtoelectronscattering
data.ThesemodelsareallinvariousdevelopmentstagesforGENIE.ImplementationsoftheAlvarez-Ruso[21,22,23]
andBerger-Sehgal[20]modelsofcoherentpionproductionarealsoexpectedinupcomingversionsofGENIE.These
modelscanbecomparedwiththefluctuationsthatareallowbyuncertaintiesineffectiveparameterslikeMQE,which
A
havesubsumedtheuncertaintiesinducedbynucleareffects.Wecanalsocomparesystematicerrorcoverageagainst
recentdata(e.g.Minervaresults)andalternategenerators(e.g.NuWro[33]andGiBUU[34]).
An alternate model for DIS interactions[35] will also be implemented in GENIE and predictions from this new
model will be compared to the current implementation based on Bodek-Yang to determine if the two models are
consistent within their uncertainties. Models of DIS interactions predict only the bulk properties of the final-state
hadronic system; other models are required to predict the particle content of the hadronic system as well as the
momentaofeachfinal-statehadron.InGENIEthisisdonewiththeAGKYmodel,whichisdifficulttoreweight.To
testtheuncertaintiesintheAGKYmodel,newGENIEsamplesaregeneratedinwhichallofthetunableparameters
areadjustedbytheir±1σ uncertainties;anyparametervariationresultinginsignificantchangestotheenergyspectra
willbestudiedfurtherusingaparameterizedreweightfunction.Uncertaintiesintheformationlength,thedistancea
hadrontravelswithinthenucelusbeforeitcaninteractwiththenuclearmedium,willalsobestudied.
StudiestodetermineifthereweightableparametersintheGENIEintranuclearrescatteringmodeladequatelycover
themodeluncertaintieswillcomefromcomparisonswithexternaldata,eg:[36,37,38],andcomparisonswithalternate
models, in this case GiBUU. Additionally, tests in which tunable, but currently non-reweightable, parameters in the
GENIEintranuclearrescatteringmodelarefluctuatedwithinreasonablerangeswillberequiredtodetermineifthey
willleadtouncertaintiesonoscillationparametermeasurements.Theeffectofuncertaintyintheamountofundetected
energy is being studied in the Fast MC and will be used to determine the neutron response calibration required
to achieve the necessary energy resolution for accurate determination of CPV. Measurements and simulations by
CAPTAIN[39]willbeextrapolatedtodetermineiftherequiredlevelofenergyresolutionispossiblewiththecurrent
FDdesign.
There is concern that it will be difficult to isolate nuclear reinteraction uncertainties from flux, cross-section, and
detector model uncertainties, especially with regard to ν/ν differences. This could lead to differences in the ν and
e
ν appearanceenergyspectrathatcouldbemistakenforCPV.Amethodtocombatthisbycomparingtheν andν
e e e
samplestotheν andν samples,whereCPVeffectsinoscillationprobabilitiesarenegligible,hasbeensuggested.
µ µ
However, this requires that the hadronic final states in the appearance and disappearance samples are comparable.
Furtherworkisneededtodevelopthismethodandevaluatethepotentialreductioninrelatedsystematicuncertainties.
5.4. FarDetectorEffects
Propagation of uncertainty in energy scale and energy resolution inputs into the Fast MC sensitivity calculations
is in progress. The initial plan of study is to determine required constraints on these effects using the Fast MC and
to interact with the various near-term short-baseline neutrino and test-beam experiments to ensure that the required
constraintswillbeavailable.Inthelongerterm,moresophisticatedsimulationandanalysisalgorithmswillbeincluded
intheFastMCandtherequirementsandsensitivitieswillbere-evaluatedasmoreinformationbecomesavailable.
DevelopmentofaMicroBooNE[40]configurationoftheFastMCandLArSoftstudiesofsingleparticleresponse
will allow for some level of validation of the single-particle energy resolutions, missing hadronic energy, energy-
scaleuncertainties,eventselectionefficiencies,andbackgroundrejectionrateswhichareinputtotheFastMC.Future
improvementstotheseestimateswillcomefromdataanddata-MCcomparisonsfromtheLBNE35-tprototype,the
CERNNeutrinoPlatform[41]prototypes,MicroBooNE,LAr1-ND[42],LArIAT[43],andCAPTAIN.
6. CONCLUSION
TheCETUP*2014systematicssessionwasavaluableopportunityfordetailedandproductivediscussionofsystematic
uncertainty in long-baseline physics measurements. The primary result of the workshop is an understanding of
availabletools,thepresentstatusofuncertaintystudies,andadetailedplanoffurtherstudythatisneeded.Asummary
oftheseresultsisprovidedinthisdocument;detailedreportsonspecifictopicsareavailableinothercontributionsto
theCETUP*2014proceedings.
ACKNOWLEDGMENTS
WewouldliketothankCETUP*(CenterforTheoreticalUndergroundPhysicsandRelatedAreas)foritshospitality
and partial support during the 2014 summer program. In addition, we would like to thank the CETUP* organizers,
Baha Balantekin and Barbara Szczerbinska, for their efforts to organize this valuable opportunity for collaboration
andallofthespeakersandparticipantsintheCETUP*2014systematicssessionfortheircontributions.Thisworkis
supportedinpartbytheUnitedStatesDepartmentofEnergy,includingcontractDE-SC0012704.
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