Lo Low-energy energy ne neut utrino rino-nucleus nucleus cross ross se sections ctions N. Jachowicz Ghent University Department of Physics and Astronomy natalie.jachowicz@UGent.be
Low-energy neutrino-nucleus cross sections Intro Neutrino energies Natalie Jachowicz NuInt12, Rio, October 22-27 2012
Low-energy neutrino-nucleus cross sections Intro Neutrino-hadron scattering • little experimental data is available - small cross sections - no monochromatic neutrino beams 208 Pb Uncertainties : • one has to rely on theoretical predictions, • uncertainties induced by model dependence, and more fundamental uncertainties … N.J. et al, PRC66, 065501 (2002) ; E. Kolbe et al, PRC63, 025802 (2001) ; J. Engel et al, PRD67, 013005 (2001) Natalie Jachowicz NuInt12, Rio, October 22-27 2012
Low-energy neutrino-nucleus cross sections Intro What can we learn from these neutrinos ? • Electroweak tests • Nuclear structure information • Astrophysical neutrinos : a.o. core-collapse supernovae • Oscillations • Neutrinonucleosynthesis How can we learn from these neutrinos ? Detect them • Neutrino-electron scattering • Neutrino-hadron scattering Study their interactions : theory + experiment Natalie Jachowicz NuInt12, Rio, October 22-27 2012
Low-energy neutrino-nucleus cross sections Formalism Modeling neutrino-nucleus cross sections @ low energies : Continuum RPA E •Green’s function approach • Skyrme II residual interaction r • ground state : Hartree-Fock single-particle wave functions (Skyrme) • non-relativistic Natalie Jachowicz NuInt12, Rio, October 22-27 2012
Low-energy neutrino-nucleus cross sections Formalism Lepton tensor Hadronic current Natalie Jachowicz NuInt12, Rio, October 22-27 2012
Low-energy neutrino-nucleus cross sections Basic features • Axial contribution dominant Continuum Random Phase 16 O( n 50 MeV , n ’) 16 O * Approximation (CRPA) • Transverse contribution dominant Natalie Jachowicz NuInt12, Rio, October 22-27 2012
Low-energy neutrino-nucleus cross sections Basic features 12 C Natalie Jachowicz NuInt12, Rio, October 22-27 2012
Low-energy neutrino-nucleus cross sections Basic features Higher order multipoles important : 16 O Natalie Jachowicz NuInt12, Rio, October 22-27 2012
Low-energy neutrino-nucleus cross sections Basic features Contribution of different single-particle channels in 12 C Natalie Jachowicz NuInt12, Rio, October 22-27 2012
ν versus anti ν Low-energy neutrino-nucleus cross sections Neutrinos versus antineutrinos 16 O neutrinos antineutrinos Natalie Jachowicz NuInt12, Rio, October 22-27 2012
ν versus anti ν Low-energy neutrino-nucleus cross sections Helicity dependence of the cross section: For neutrinos : S+hA = S-A, is small S-hA = S+A, is large h - h - * dominates 16 O For antineutrinos : S+hA = S+A, is large S-hA = S-A, is small h + h + * dominates Natalie Jachowicz NuInt12, Rio, October 22-27 2012
ν versus anti ν Low-energy neutrino-nucleus cross sections Adding antineutrinos to the picture : • Neutrinos 16 O favor ‘spin down’ nucleon knockout • Antineutrinos mainly induce ‘spin up’ knockout reactions • Polarization differences increase with incoming neutrino energies Natalie Jachowicz NuInt12, Rio, October 22-27 2012
ν versus anti ν Low-energy neutrino-nucleus cross sections The asymmetry and the dissimilarities between neutrinos and antineutrinos are most clear considering the angular cross section : The asymmetry is most prominent for forward nucleon knockout, and remains large over a broad angular range. For the suppressed backward scattering 208 Pb reactions, the asymmetry is completely reversed Natalie Jachowicz NuInt12, Rio, October 22-27 2012
ν versus anti ν Low-energy neutrino-nucleus cross sections Neutrinos 208 Pb Neutrinos Antineutrinos Antineutrinos Natalie Jachowicz NuInt12, Rio, October 22-27 2012
ν versus anti ν Low-energy neutrino-nucleus cross sections Longitudinal pola lariza izatio ion asym ymmetry ry : 16 O • For antineutrinos, A l is large and positive • For neutrinos, A l is large and negative N. Jachowicz, K. Vantournhout, J. Ryckebusch, K. Heyde, PRL 93, 082501 (2004) ; N. Jachowicz, K. Vantournhout, J. Ryckebusch, K. Heyde, PRC71, 034604 (2005). Natalie Jachowicz NuInt12, Rio, October 22-27 2012
M A @ low energies Low-energy neutrino-nucleus cross sections Dependence on M A is very small at very low neutrino energies … 12 C( ν e ,e - ) E ν =50 MeV Natalie Jachowicz NuInt12, Rio, October 22-27 2012
Low-energy neutrino-nucleus cross sections Strangeness Strangeness in the nucleon Axial form factor : Weak vector form factors : Natalie Jachowicz NuInt12, Rio, October 22-27 2012
Low-energy neutrino-nucleus cross sections Strangeness Traditionally : • strangeness contribution to the weak vector formfactors : Parity Violating Electron Scattering (Sample, Happex, G0, …) Correlated ! • strangeness contribution to the axial current : neutrino scattering -vector current contributions are suppressed -no radiative corrections N.J., P. Vancraeyveld, P. Lava, J. Ryckebusch, PRC76, 055501 (2007). Natalie Jachowicz NuInt12, Rio, October 22-27 2012
Low-energy neutrino-nucleus cross sections Strangeness Neutrino cross sections including strangeness • Generally : net strangeness effect vanishes for isoscalar targets • close to particle knockout threshold the influence becomes larger due to binding energy differences between protons and neutrons • differential cross sections differ, energy of reaction products can be CRPA very different 16 O Natalie Jachowicz NuInt12, Rio, October 22-27 2012
Low-energy neutrino-nucleus cross sections Strangeness proton/neutron cross sections • differences up to 20% • opposite effect for protons 16 O and neutrons Natalie Jachowicz NuInt12, Rio, October 22-27 2012
Low-energy neutrino-nucleus cross sections Energy dependence of the cross section Supernova neutrino spectra : Experimentally : Michel spectra : Natalie Jachowicz NuInt12, Rio, October 22-27 2012
Energy dependence of the cross section Low-energy neutrino-nucleus cross sections Supernova neutrino spectra : cumulative folded cross section spectrum< ε >=18MeV, w=.7 spectrum< ε >=18MeV, w=.9 folded cross section ω =12 MeV Natalie Jachowicz NuInt12, Rio, October 22-27 2012
Low-energy neutrino-nucleus cross sections MiniBooNe Experiments at intermediate energies Quasi-elastic processes : Intermediate energies : 100 MeV - … GeV Energy distribution ! Natalie Jachowicz NuInt12, Rio, October 22-27 2012
Low-energy neutrino-nucleus cross sections MiniBooNe Cross sections at low Q 2 Comparison between inclusive cross sections obtained within a relativistic Fermi gas calculation, a relativistic plane wave impulse approximation (RPWIA) approach, a mean-field calculation, and a calculation including CRPA correlations implemented using a Skyrme parametrization as residual interaction. Natalie Jachowicz NuInt12, Rio, October 22-27 2012
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