The Impact of nuclear effect modeling on the cross-section ratio νe/νμ and its impact for future measurements of CP violation
Creators: name: Dieminger, Till
Publisher: name: Zenodo
Year: 2022

description: Long-baseline (LBL) neutrino oscillation experiments search for Charge-Parity (CP) violation in the leptonic sector by precisely measuring the nu_mu -&gt; nu_e and anu_mu→anu_e appearance probabilities.<br> One of the dominant systematic uncertainties on the measurements of CP violation, comes from our modeling of the nu_e/anu_eO cross-section ratio, which is subject to a range of uncertainties related to poorly-constrained nuclear physics processes.<br> Whilst tight constraints on the nu_mu/anu_mu cross-section can be achieved using LBL experiment's near detector data, the lepton mass differences mean that the extrapolation to the nu_e/anu_e is not trivial.Currently running LBL experiments reach a sensitivity to exclude the CP conserving hypothesis of about three standard deviations for a relatively large range of δCP values, hence a more accurate evaluation of the nu_e/anu_e related uncertainties becomes increasingly crucial.<br> Nikolakopoulos et al. showed that a more consistent treatment of final state interactions (FSI) via a distortion of the outgoing nucleon wave function within an Hartree-Fock (HF) mean-field model for charged-current quasi-elastic (CCQE) interactions with continuum random phase approximation (CRPA) corrections leads to significantly different predictions for muon and electron neutrino cross sections at low energy transfers compared to widely used plane wave impulse approximation (PWIA) models, such as SF, usually employed in LBL experiment's interaction simulations.Following up on this work, we show how HF-CRPA predictions of the nu_mu(anu_mu) - nu_e(anu_e) cross-section ratio differs from the widely used models employed in the NEUT and GENIE neutrinLong-baseline (LBL) neutrino oscillation experiments search for Charge-Parity (CP) violation in the leptonic sector by precisely measuring the nu_mu→nu_e and anu_mu→anu_e appearance probabilities.<br> One of the dominant systematic uncertainties on the measurements of CP violation, comes from our modeling of the νe/ν¯¯¯e cross-section ratio, which is subject to a range of uncertainties related to poorly-constrained nuclear physics processes.<br> Whilst tight constraints on the nu_mu/anu_mu cross-section can be achieved using LBL experiment's near detector data, the lepton mass differences mean that the extrapolation to the nu_e/anu_e is not trivial. Currently running LBL experiments reach a sensitivity to exclude the CP conserving hypothesis of about three standard deviations for a relatively large range of δCP values, hence a more accurate evaluation of the nu_e/anu_e related uncertainties becomes increasingly crucial.<br> Nikolakopoulos et al.~cite{Nik} showed that a more consistent treatment of final state interactions (FSI) via a distortion of the outgoing nucleon wave function within an Hartree-Fock (HF) mean-field model for charged-current quasi-elastic (CCQE) interactions with continuum random phase approximation (CRPA) corrections leads to significantly different predictions for muon and electron neutrino cross sections at low energy transfers compared to widely used plane wave impulse approximation (PWIA) models, such as SF, usually employed in LBL experiment's interaction simulations. Following up on this work, we show how HF-CRPA predictions of the nu_mu(anu_mu) - nu_e(anu_e) cross-section ratio differs from the widely used models employed in the NEUT and GENIE neutrino interaction event generators. In a second step, we proceed to estimate the potential impact of such model differences on future measurements of CP-violation by the T2K experiment.o interaction event generators. In a second step, we proceed to estimate the potential impact of such model differences on future measurements of CP-violation by the T2K experiment.