Neutrino Interactions with Nucleons and Nuclei Tina Leitner, Ulrich Mosel LAUNCH09 TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: AAAA A

Contents and Motivation Neutrino Detectors contain nucleons and nuclei  have to understand interactions of neutrinos with nucleons and nuclei Neutrino Detectors contain nucleons and nuclei  have to understand interactions of neutrinos with nucleons and nuclei LBL experiments: mixing parameters are intimately linked with the neutrino energy in the oscillation formula. BUT: neutrino energies are not ‚sharp‘, but widely distributed  have to reconstruct neutrino energy from final hadronic state LBL experiments: mixing parameters are intimately linked with the neutrino energy in the oscillation formula. BUT: neutrino energies are not ‚sharp‘, but widely distributed  have to reconstruct neutrino energy from final hadronic state LAUNCH09

Neutrino oscillation search neutrino oscillations: probability for 2 flavors: neutrino oscillations: probability for 2 flavors: Crucial parameter: neutrino energy E Crucial parameter: neutrino energy E Need to understand ‚classical‘ hadronic interactions Flux: obtained from Event-Generators for hadronic production and subsequent weak decay Energy must be reconstructed from hadronic final state

Neutrino nucleon cross section QEsingle ¼ P. Lipari, Nucl. Phys. Proc. Suppl. 112, 274 (2002) R+R+ ¼ N N'

Quasielastic scattering axial form factors related by PCAC dipole ansatz with M A = 1 GeV vector form factors related to EM form factors by CVC BBBA-2007 parametrization

Axial Formfactor of the Nucleon Recent Data give significantly larger values for M A One difference: all old data use H (or D) as target all new data use nuclei (C, O, Fe) as target M A = 1.35 GeV, Pauli problem

Resonances: Hadronic currents Spin 3/2 resonances: P 33 (1232), D 13 (1520), D 33 (1700), P 13 (1720) Spin 3/2 resonances: P 33 (1232), D 13 (1520), D 33 (1700), P 13 (1720) R+R+ R ++ (I=3/2) p C V (Q 2 ) from electroproduction (MAID), C A (Q2) modelled, fit to (very few) old data

Pion production through ¢ averaged over ANL flux, W < 1.4 GeV New V, old A New V, new A

Pion production off nucleons main mechanism: excitation and subsequent decay of Delta resonance dominant channel: main mechanism: excitation and subsequent decay of Delta resonance dominant channel:

LAUNCH09 Complications from Nuclear Targets (K2K, MiniBooNE, T2K, MINOS, Minerva, …. Complications from Nuclear Targets (K2K, MiniBooNE, T2K, MINOS, Minerva, …. ‚ Data‘ for any given channel contain admixtures of other channels Needs state-of-the-art treatment of fsi

LAUNCH09 Low-Energy Nuclear Reactions and Structure determine response of nuclei to neutrinos

LAUNCH09 what is GiBUU? semiclassical coupled channels transport model what is GiBUU? semiclassical coupled channels transport model general information (and code available): general information (and code available): 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 reactions pion and proton induced reactions low and high energy photon and electron induced reactions low and high energy photon and electron induced reactions neutrino induced reactions neutrino induced reactions ……..using the same physics input! And the same code! GiBUU transport for FSI

LAUNCH09 time evolution of spectral phase space density (for i = N, , , , …) given by BUU equation time evolution of spectral phase space density (for i = N, , , , …) given by BUU equation one equation for each particle species (61 baryons, 21 mesons) one equation for each particle species (61 baryons, 21 mesons) coupled through the potential U S and the collision integral I coll coupled through the potential U S and the collision integral I coll Cross sections from resonance model (and data) for W < 2.5 GeV Cross sections from resonance model (and data) for W < 2.5 GeV at higher energies (W > 2.5 GeV) particle production through string fragmentation (PYTHIA) at higher energies (W > 2.5 GeV) particle production through string fragmentation (PYTHIA) Well tested for many different reaction types: heavy ions, protons, pions, electrons…. Well tested for many different reaction types: heavy ions, protons, pions, electrons…. Model Ingredients: FSI Model Ingredients: FSI one-particle spectral phase space density for particle species i

Photo-hadronproduction data from TAPS as test Photo-hadronproduction data from TAPS as test Necessary check for exclusive cross section: Photoproduction  0  ->2  0  ->  Pion reaction Xsect.

LAUNCH09 Neutron Knockout: Final state effects Without FSIWith FSI 12 C 1 GeV CC º + A  A + n + X

CC pion production:  56 Fe   -  X effects of FSI on pion kinetic energy spectrum at E = 1 GeV effects of FSI on pion kinetic energy spectrum at E = 1 GeV strong absorption in  region strong absorption in  region side-feeding from dominant   into   channel side-feeding from dominant   into   channel secondary pions through FSI of initial QE protons secondary pions through FSI of initial QE protons   Spectra determined by ¼-N-¢ dynamics

LAUNCH09 Effects of FSI on pion kinetic energy spectrum at E = 1 GeV Effects of FSI on pion kinetic energy spectrum at E = 1 GeV strong absorption in  region strong absorption in  region side-feeding from dominant   into   channel side-feeding from dominant   into   channel secondary pions through FSI of initial QE protons secondary pions through FSI of initial QE protons Significant distortion of spectra by FSI Significant distortion of spectra by FSI CC pion production:  56 Fe   -  X 00 00 ++

Entanglement of QE and CC 1  Production MiniBooNEK2K 0 ¼ + X 0 ¼ + 1 p + X

Pion Production ‚Data‘ before FSI 1:  1  /  0  after FSI 2:  1  /  0  p after FSI 3:  1  /  QE after FSI 4:  1  /  QE before FSI (‚Data‘) 5:  1  /  QE in vacuum

MiniBooNE CCQE CCQE cross section compared to MiniBooNE background corrected QE ‚data‘, underestimate by ~35% T. Katori, NUINT09 Neutrino Flux too high by 30% ?

MiniBooNE CCQE CCQE Q² distribution CCQE Q² distribution full GiBUU in-med mod., no parameter tuning full GiBUU in-med mod., no parameter tuning M A = 1 GeV M A = 1 GeV in addition: RPA correlations by Nieves et al. PRC 73 (2006) in addition: RPA correlations by Nieves et al. PRC 73 (2006) compared to MiniBooNE „data“: Fermi gas with „modified Pauli blocking“ and M A = 1.35 GeV compared to MiniBooNE „data“: Fermi gas with „modified Pauli blocking“ and M A = 1.35 GeV describes shape but not absolute cross section describes shape but not absolute cross section Grey Band: Data

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

Energy reconstruction via CCQE reconstruction via quasifree kinematics reconstruction via quasifree kinematics E B = 34 MeV CCQE-like = muon, but no pion Rms deviation ~ 15-20% Shift towards lower energies due to misidentified events

Energy reconstruction via CCQE Energy uncertainties affect oscillation mininum and mixing angles

Conclusions Transport theory shows intimate entanglement of QE scattering and pion production, difficulty to isolate elementary processes from in nuclear targets Transport theory shows intimate entanglement of QE scattering and pion production, difficulty to isolate elementary processes from in nuclear targets Experimental (MiniBooNE, K2K) QE and pion nuclear cross sections about 30% too high, compared with theory, inconsistency with NOMAD  deficiency of experimental event generators? too large neutrino flux assumed? Experimental (MiniBooNE, K2K) QE and pion nuclear cross sections about 30% too high, compared with theory, inconsistency with NOMAD  deficiency of experimental event generators? too large neutrino flux assumed? Energy reconstruction has tendency to lower energies, uncertainty about 20%, translates into errors for mixing angles Energy reconstruction has tendency to lower energies, uncertainty about 20%, translates into errors for mixing angles Conclude: state-of-the-art physics-based, well tested event generator is essential to extract meaningful cross sections and neutrino energies Conclude: state-of-the-art physics-based, well tested event generator is essential to extract meaningful cross sections and neutrino energies