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Current Knowledge of Neutrino Cross-Sections and Future Prospects. D. Casper University of California, Irvine. Outline. Why do we care? What do we know from past experiments? What are current experiments telling us? Outlook for future experiments. “Normal”. “Inverted”. 3. 2. 1. 2. 3. - PowerPoint PPT Presentation
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Current Knowledge ofNeutrino Cross-Sections
and Future Prospects
D. CasperUniversity of California, Irvine
OutlineWhy do we care?What do we know from past experiments?What are current experiments telling us?Outlook for future experiments
Neutrino Oscillation: GoalsProbe fundamental parameters of Standard Model:
Precision measurement of |m223|
Precision measurement of 23
Measurement of unknown angle 13
Determination of mass hierarchy sgn(m223)
Search for leptonic CP violating phase Measurements involve probabilities
Need number of oscillated neutrinos and number of starting neutrinos
Next generation experiments, starting with MINOS, will have impressive statistical power from high luminosity beams and massive detectors
Systematic uncertainties must be controlled at a level comparable to the statistical errors to take full advantage
12
312
3
“Normal” “Inverted”
Expt. DatesBeamPower(MW)
Det.Mass(kt)
K2K1998-2005
0.005 22.5
MINOS 2005+ 0.25 3.3
J-PARC I 2008+ 0.7 22.5
NOA ? 0.4 ~35
Neutrino Oscillation: Requirements
Neutrino energy resolution for CC interactions
K2K/T2K: Quasi-elastic channelMINOS/NOA: Calorimetry (Evis E)
Control energy-scale systematics for high E-resolution sample at few percent level
EfficiencyContamination
Control near/far beam flux and energy spectrum differences at few percent levelControl background for e appearance signature at few per-mille level
Beam e, CC, NC contributionsControl neutrino/anti-neutrino systematics at percent level for mass hierarchy and CP studies
C. Walter, NUINT02
K2K
NOA(13 nearCHOOZ bound)
NormalHierarchyInverted
Hierarchy
Neutrino Oscillation: RealitiesOnly well-known neutrino interaction cross-section is for electron scattering
Unfortunately useless for oscillation experiments with accelerators
Available data for few-GeV reactions:Old (Early ’70s to mid 80’s)
Normalized to quasi-elastic measurements, using obsolete form factor parameters, and introducing complicated correlated errorsBeam spectrum and flux based on dubious hadron production modelsUndocumented and inconsistent corrections for nuclear targets
SparseEnergy, hadronic mass reach limitedNuclear targets not applicable to common detector materialsAlmost no data on > 1 exclusive channelsAnti-neutrino data even worse
Low-statisticsNeutral current 1 data based on a few dozens of events
Mutually inconsistent
What About a Near Detector?Near detectors are important, but not a panacea flux and spectrum differs far vs. near
Not identical even without oscillation, due to extended sourceCC backgrounds and contamination extrapolate differently than NC+beam, due to oscillationOptimal sensitivity dictates that far detector is at oscillation maximum, making the difference as large as it can be
Near/Far detectors usually not identicalFar detector must be large, coarse-grainedIf identical, near detector has similar resolution and not suited to measure cross-sectionsK2K/T2K solution: two near detectors…
Maximum physics reach requires:Near detector similar in composition, performance and resolution to far detectorGood model/measurements of parent hadron beamGood understanding of exclusive neutrino cross-sections
NOAP()
Nuance
K2K Near Detectors
Extrudedscintillator(15t)
Multi-anodePMT (64ch)
Wave-lengthshifting fiber
EM calorim
eter
1.7m
3m
3m
SciBar SciFi
E (GeV)
MiniBooNE
(H. Tanaka, WG2)
CC Quasi-Elastic ScatteringDominant reaction up to ~1 GeV energyEssential for E measurement in K2K/T2KThe “well-measured” reaction
Uncertain to “only” 20% or so for neutrinosWorse in important threshold region and for anti-neutrinos
Axial form-factor not accessible to electron scattering
Essential to modeling q2 distributionRecoil proton reconstruction requires fine-grained design - impractical for oscillation detectorsRecent work focuses on non-dipole form-factors, non-zero Gn
E measurements
K2K and MiniBooNE CCQE RatesK2K and MiniBooNE rates agree with MC for CCQEOnly shape is measured, not absolute cross-sections
Same data is used to measure the neutrino flux!
K2K SciBar2-ring QE(70% purity)
MiniBooNE
(88% purity)
CC Resonant Single-Pion Production
Existing data inconsistent (factor 2 variations)Treatment of nuclear effects unclearRenewed theoretical interest with JLAB data
Sato et al. Dynamical Model
K2K/MiniBooNE CC Pion Production
1-kton: Study of 0 proton decay backgroundMiniBooNE: 85% purity for CC ± sample(no results, in progress)
1-kton0 candidates
Normalizedto total events
NC Single-Pion ProductionHistorical samples of NC single pion production:
ANL p n + (7 events) n n 0 (7 events)
Gargamelle p p 0 (240 evts) n n 0 (31 evts)
Crucial background for e appearance searches!
K2K/MiniBooNE NC 0 ProductionK2K(Preliminary)
( )( ) ( )
( )( )
0
0
K2K 1-kton cross-section measurement:
(NC 1 )0.065 0.001 stat 0.007 syst
(NC 1 )0.064 NEUT
For K2K beam spectrum ( E =1.3 GeV)MC
CC
CC
m
m
n
s p
s n
s p
s n
= ± ±
=
MiniBooNE:Shape comparison only
Deep-Inelastic ScatteringOne area with lots of data and a clear theoretical framework, but uncertainties remain:
Nuclear effects?Low-q2 regimeConnection/overlap with resonant production
Quark/Hadron DualityRecent JLAB data have revived interest in quark/hadron dualityBodek and Yang have shown that DIS cross-sections can be extended into the resonance regime, and match the “average” of the resonant cross-section
Bodek and Yang
Nuclear Effects (QE/Resonant)
1ktonSciFi
SciBar MiniBooNE
All currently running detectors seeanomalous suppression at low-Q2
One anomaly or two?
Nuclear Effects (DIS)
0.7
0.8
0.9
1
1.1
1.2
0.001 0.01 0.1 1
EMCNMCE139E665
shadowing
original
EMC finding
Fermi motion
x sea quark valence quark
-
LH on
LH off
+
Hadron formation lengtheffects
E = 5 GeV(NEUGEN)
Bound nucleon structure functions
Final-State Interactions
Renewed theoretical interest, plus new data from JLAB
NEUTMC
“Hope is on the way…”HARP data (next talk)
Hadron production measured with K2K, MiniBooNE targets at CERNWill provide essential data for neutrino fluxes, aid absolute cross-section measurements
MINERA at NuMI (2006?)T2K Near Detectors (2009?)
280m: Fine-grained (design not finalized)2km: Water Cherenkov + fine-grained (not yet approved)Potential to measure cross-sections around few GeV, if independent flux prediction available
MINERA at a GlanceScintillating strip design leverages DZERO, K2K, MINOS experience
Modular construction, good spatial resolution, 3d-tracking, fast timing and dE/dx measurement at attractive cost
Fully-active central volume surrounded by magnetized “calorimeters”
Inner fiducial mass > 3 tonsIron + Lead planes upstream to vary nuclear target
Parasitic operation within current NuMI/MINOS run-plan yields 1.25M neutrino events/ton
Broad neutrino energy reachMINOS near detector can substitute for downstream muon rangerMIPP will measure NuMI hadron production within ~few percent, allowing precision absolute cross-section measurements
MINERA CCQE Measurements
Full simulated analysis, including realistic detector simulationand reconstruction
MINERA Resonant Pion Production
Errors statistical only, assuming 50% efficiency
Coherent Pion ProductionNeutral-current reaction important background for e appearance search
Realistically, 100% uncertainties in rate for oscillation experimentsTheoretical models vary significantlyCC reaction (easier to measure) closely related to NC
No data on light nuclei in energy region of relevance
K2K and MiniBooNE may help at low energies, but NC background to e appearance feeds down from high energiesEasier to distinguish with proton reconstruction and (for CC reaction) dE/dx
MINERASimulatedMeasurements
ConclusionsFew-GeV neutrino interaction physics is (finally) leaving the “Dark Ages”Multiple, synergistic lines of attack are beginning to peel back our ignorance:
Data from K2K and MiniBooNEElectron scattering dataHEP/Nuclear collaboration (NUINT workshops)Revived theoretical attention to different questions
MINERA and T2K can provide another quantum leapIndependent knowledge of fluxes are vital for absolute measurements
Continued progress on cross-sections will be invaluable for future oscillation experiments
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