incoming energy crucial for your physics result, but only badly known (~50%) incoming energy crucial...
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Incoming energy crucial for your physics result, but only badly known (~50%)
Beam composition not fully known Beam diameter ~ 0.5 m at its source Beamline ~ 300 – 1000 km Beam diameter ~ 600 m at the
detector Cross sections ~ 10-11 mb Only a small part of the final state
known
Winter Park 2011
The Impossible Experiment
1300 km
Winter Park 2011
Soudan Mine,Nova
770 kmHomestake Mine
Dusel
Long Baseline Experiments
T2K: JPARC-Kamioka ~ 300 km, OPERA: CERN –Gran Sasso ~730 km
Long baseline experimentsM
. Wascko
Winter Park 2011
Neutrino oscillation search
neutrino oscillations: probability for 2 flavors:
Crucial parameter: neutrino energy E
Need to understand ‚classical‘ hadronic interactions
P(º¹ ! ºe; t) = sin22µsin2Ã
¢ m2L4Eº
!
Flux: obtained from Event-Generatorsfor hadronic production and subsequentweak decay
Energy must be reconstructed from hadronic final state
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Neutrino nucleon cross section
QE
P. L
ipari
, N
ucl.
Ph
ys.
Pro
c.
Su
pp
l. 1
12
, 2
74
(2
00
2)
10-38 cm² = 10-11 mb
R+
¼N N'
‚ DIS
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QE is used for energyreconstruction
Quasielastic scattering
axial form factors • FA FP and FA(0) via PCAC• dipole ansatz for FA with • MA= 1 GeV:
W, Z
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Axial Formfactor of the Nucleon
neutrino data agree with electro-pion prod. data
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MA ¼ 1.02 GeV world average MA ¼ 1.07 GeV world average
Axial Formfactor of the Nucleon
Recent Data give significantly larger values for MA
One difference: all old data use H (or D) as target
all new data use nuclei (C, O, Fe) as target
MiniBooNE (2010):MA = 1.35 GeV
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MA Problem
Old neutrino experiments used H and D as targets
All modern experiments use heavy nuclei
Quasielastic scattering kinematics is used to reconstruct neutrino energy also in oscillation experiments
Problem to identify QE on nuclear targets Winter Park 2011
QE Identification
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Need event generator to reduce data to true QE event
what is GiBUU? semiclassical coupled channels transport model
general information (and code available): http://theorie.physik.uni-giessen.de/GiBUU/
GiBUU describes (within the same unified theory and code) heavy ion reactions, particle production and flow Pion, proton and antiproton induced reactions low and high energy photon and electron induced
reactions neutrino induced reactions……..using the same physics input! And the same code!
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GiBUU transport
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CC nucleon knockout: nm56Fe m- N X
w FSI
w/o FSI
p
p n
n
E = 1 GeVD
ram
atic
FSI
Effe
ct
Detector Types: QE Identification
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Tracking detector (Sci-BooNE, K2K, SciFi)
Cerenkov detector (MiniBooNE, K2K 1kt)
Too high QE: misidentifies about 20%, pion-induced fakes
QE identification is clean, but 30% of total QE cross section ismissed
measured
measured
Detector Sensitivities: T2K
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T2K has different detector types:1. Tracking for near detector2. Cherenkov for far detectorNear Detector sees only about 50% of all QE events
Energy Reconstruction and Detector Thresholds
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Energy reconstruction sensitive to the detector pion thresholds
Energy reconstruction via CCQE
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Rms energy deviations S
~15% energy uncertainty fromquasifree qe kinematics alone
~21% uncertainty forCerenkov detectors, error grows with neutrino energy
~16% uncertainty fortracking detectors
Errors in reconstructed º energies larger than expected
Energy reconstruction via CCQE
Energy uncertainties affect mixing masses,Event identification affects mixing angles
P(º¹ ! ºe; t) = sin22µsin2Ã
¢ m2L4Eº
!
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±CP with LBNE
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Event reconstruction hampers determination of CP violating phase
Wilson, LBNE workshop
Uncertainties at the oscillation maximum due to detector as large as dependence on CP violating phase
Experiments have to rely heavily on event-generators to identify QE events needed for energy reconstruction
Quasielastic scattering events contain admixtures of Delta excitations excitations affect nucleon knockout, contaminate QE experiments
Energy reconstruction good up to 15 – 20%. Combined error from near and far detectors ~ 20 – 30%. Experiments
want 5%! Challenge for event generators!
Extraction of axial mass (1 GeV) strongly affected by nuclear structure (RPA correlations), difficult to get
both absolute height and slope.
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Physics Summary
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Low-Energy Nuclear Physics determines responseof nuclei to neutrinos
Need excellent event generatorsTo extract fundamental science
Need for Low Energy Nuclear Physicsin Neutrino Physics