Neutrino Interactions Neutrino Interactions with Nucleons and Nucleiwith Nucleons and Nuclei

Tina Leitner, Ulrich Mosel

LAUNCH09

Contents and MotivationContents and Motivation

Neutrino Detectors contain nucleons and Neutrino Detectors contain nucleons and nuclei nuclei have to understand interactions have to understand interactions of neutrinos with nucleons and nucleiof neutrinos with nucleons and nuclei

LBL experiments: mixing parameters are LBL experiments: mixing parameters are intimately linked with the neutrino energy intimately linked with the neutrino energy in the oscillation formula. BUT: neutrino in the oscillation formula. BUT: neutrino energies are not ‚sharp‘, but widely energies are not ‚sharp‘, but widely distributed distributed have to reconstruct have to reconstruct neutrino energy from final hadronic stateneutrino energy from final hadronic state

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Neutrino oscillation Neutrino oscillation searchsearch

P(º¹ ! ºe; t) = sin22µsin2Ã

¢ m2L4Eº

!

Flux: obtained from Event-Generatorsfor hadronic production and subsequentweak decay

Energy must be reconstructed from hadronic final state

Neutrino nucleon cross Neutrino nucleon cross sectionsectionQE single ¼

P.

Lip

ari

, N

ucl.

Ph

ys.

Pro

c.

Su

pp

l. 1

12,

27

4 (

20

02

)

¼N N'

Quasielastic scatteringQuasielastic scattering

axial form factors • related by PCAC

• dipole ansatz with MA= 1 GeV

vector form factors • related to EM form factors by CVC• BBBA-2007 parametrization

J ¹QE =

µ°¹ ¡

q=q¹

q2

¶F V

1 +i

2MN¾¹ ®q®F V

2

+°¹ °5FA +q¹ °5

MNFP

Axial Formfactor of the NucleonAxial Formfactor of the Nucleon

Recent Data give significantly larger values for MRecent Data give significantly larger values for MAA

One difference: One difference: all old data use H (or D) as targetall old data use H (or D) as target

all new data use nuclei (C, O, Fe) as targetall new data use nuclei (C, O, Fe) as target

MiniBooNE @NUFACT09:MA = 1.35 GeV, Pauli problem

Resonances: Hadronic currentsResonances: Hadronic currents

Spin 3/2 resonances:Spin 3/2 resonances: PP3333(1232)(1232), D, D1313(1520), D(1520), D3333(1700), (1700),

PP1313(1720)(1720)

R+R++ (I=3/2)p

J ®¹3=2 =

·CV

3

MN(g®¹ q=¡ q®°¹ ) +

CV4

M 2N

(g®¹ q¢p0¡ q®p0¹ ) +CV

5

M 2N

(g®¹ q¢p¡ q®p¹ )

+µ

CA3

MN(g®¹ q=¡ q®°¹ ) +

CA4

M 2N

(g®¹ q¢p0¡ q®p0¹ ) + CA5 g®¹ +

CA6

M 2N

q®q¹¶

°5

¸8<

:

°5

1

9=

;

CV (Q2) from electroproduction (MAID), CA(Q2) modelled,fit to (very few) old data

Pion production through Pion production through ¢¢

avera

ged o

ver A

NL fl

ux, W

< 1

.4

GeV

New V, old A

New V, new A

Pion production off nucleonsPion production off nucleons

main mechanism: main mechanism: excitation and subsequentexcitation and subsequentdecay of decay of Delta resonanceDelta resonance

dominant channel:dominant channel:

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Complications from Nuclear TargetsComplications from Nuclear Targets(K2K, MiniBooNE, T2K, MINOS, Minerva, ….(K2K, MiniBooNE, T2K, MINOS, Minerva, ….

‚Data‘ for any given channel contain admixtures of other channelsNeeds state-of-the-art treatment of fsi

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Low-EnergyNuclear Reactions and Structure determine responseof nuclei to neutrinos

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what is GiBUU? what is GiBUU? semiclassical coupled channels transport model semiclassical coupled channels transport model

general information (and code available): general information (and code available): http://theorie.physik.uni-giessen.de/GiBUU/http://theorie.physik.uni-giessen.de/GiBUU/

GiBUU describes (within the same unified theory and code)GiBUU describes (within the same unified theory and code) heavy ion reactions, particle production and flow heavy ion reactions, particle production and flow pion and proton induced reactionspion and proton induced reactions low and high energy photon and electron induced low and high energy photon and electron induced

reactionsreactions neutrino induced reactionsneutrino induced reactions

…………..using the same physics input! And the same code!..using the same physics input! And the same code!

GiBUU transport for FSIGiBUU transport for FSI

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time evolution of spectral phase space density time evolution of spectral phase space density (for (for i = Ni = N, , ,, ,, ,, …) …) given by BUU equationgiven by BUU equation

one equation for each particle species (61 baryons, 21 one equation for each particle species (61 baryons, 21 mesons) mesons)

coupled through the potential coupled through the potential UUSS and the collision integral and the collision integral IIcollcoll

Cross sections from resonance model (and data) for W < Cross sections from resonance model (and data) for W < 2.5 GeV2.5 GeV

at higher energies (W > 2.5 GeV) particle production at higher energies (W > 2.5 GeV) particle production throughthrough string fragmentation (PYTHIA) string fragmentation (PYTHIA)

Well tested for many different reaction types: heavy ions, Well tested for many different reaction types: heavy ions, protons, pions, electrons….protons, pions, electrons….

Model Ingredients: Model Ingredients: FSIFSI

one-particle spectral phase space density for particle species i

df i

dt= (@t + (r ~pH )r ~r ¡ (r ~r H)r ~p) f i (~r;~p;¹ ;t) = I coll [f i ; f N ; f ¼; f ¢ ; : : :]

f i (~r;~p;¹ ;t)

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Neutron Knockout: Final state effectsNeutron Knockout: Final state effects

Without FSI With FSI

12C1 GeV

CC º + A A + n + X

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Effects of FSI on pion kinetic energy spectrum at Effects of FSI on pion kinetic energy spectrum at EE = 1 = 1 GeVGeV strong absorption in strong absorption in region region side-feeding from dominant side-feeding from dominant into into channelchannel secondary pions through FSI of initial QE secondary pions through FSI of initial QE

protonsprotons Significant distortion of spectra by FSISignificant distortion of spectra by FSI

CC pion production: CC pion production: 5656Fe Fe --

X X

0

0+

Entanglement of QEEntanglement of QE and CC 1 and CC 1 Production Production

MiniBooNE K2K

0 ¼ + X

0 ¼ + 1 p + X

Pion ProductionPion Production

‚Data‘ before FSI

1:1/0 after FSI2: 1/0 p after FSI3: 1/QE after FSI

4: 1/QE before FSI (‚Data‘)5: 1/QE in vacuum

MiniBooNE CCQEMiniBooNE CCQE CCQE cross section

compared to MiniBooNE background corrected QE ‚data‘ , underestimate by ~35%

T. Katori, NUINT09

Neutrino Fluxtoo high by 30% ?

MiniBooNE CCQEMiniBooNE CCQE CCQE Q² distributionCCQE Q² distribution

full GiBUU in-med mod., no parameter tuningfull GiBUU in-med mod., no parameter tuning MMAA = 1 GeV = 1 GeV in addition: in addition: RPA correlationsRPA correlations by Nieves et al. PRC 73 by Nieves et al. PRC 73

(2006)(2006) compared to MiniBooNE „data“:compared to MiniBooNE „data“:

Fermi gas Fermi gas with „modified Pauli blocking“ and with „modified Pauli blocking“ and MMAA = 1.35 = 1.35 GeVGeV

describes shape but not absolute cross sectiondescribes shape but not absolute cross section

Grey Band: Data

Pion production in Pion production in MiniBooNEMiniBooNE

Data comparable with calculation without FSI, same shape Flux too high?? BNL data correct?

Energy reconstruction via CCQEEnergy reconstruction via CCQE

reconstruction viareconstruction viaquasifree kinematicsquasifree kinematics

EB = 34 MeV

CCQE-like = muon, but no pion

Rms deviation ~ 15-20%Shift towards lower energiesdue to misidentified events

Energy reconstruction via Energy reconstruction via CCQECCQE

Energy uncertainties affect oscillation mininum and mixing angles

ConclusionsConclusions Transport theory shows intimate entanglement of Transport theory shows intimate entanglement of

QE scattering and pion production, difficulty to QE scattering and pion production, difficulty to isolate elementary processes from in nuclear targetsisolate elementary processes from in nuclear targets

Experimental (MiniBooNE, K2K) QE and pion nuclear Experimental (MiniBooNE, K2K) QE and pion nuclear cross sections about 30% too high, compared with cross sections about 30% too high, compared with theory, inconsistency with NOMAD theory, inconsistency with NOMAD deficiency of deficiency of experimental event generators? too large neutrino experimental event generators? too large neutrino flux assumed?flux assumed?

Energy reconstruction has tendency to lower Energy reconstruction has tendency to lower energies, uncertainty about 20%, translates into energies, uncertainty about 20%, translates into errors for mixing angleserrors for mixing angles

Conclude: state-of-the-art physics-based, well tested Conclude: state-of-the-art physics-based, well tested event generator is essential to extract meaningful event generator is essential to extract meaningful cross sections and neutrino energiescross sections and neutrino energies