Characterization of nuclear effects in muon-neutrino scattering on hydrocarbon with a measurement of final-state kinematics and correlations in charged-current pionless interactions at T2K

Abstract

This paper reports measurements of final-state proton multiplicity, muon and proton kinematics, and their correlations in charged-current pionless neutrino interactions, measured by the T2K ND280 near detector in its plastic scintillator (C 8 H 8 ) target. The data were taken between years 2010 and 2013, corresponding to approximately 6 × 10 20 protons on target. Thanks to their exploration of the proton kinematics and of imbalances between the proton and muon kinematics, the results offer a novel probe of the nuclear-medium effects most pertinent to the (sub-)GeV neutrino-nucleus interactions that are used in accelerator-based long-baseline neutrino oscillation measurements. These results are compared to many neutrino-nucleus interaction models which all fail to describe at least part of the observed phase space. In case of events without a proton above a detection threshold in the final state, a fully consistent implementation of the local Fermi gas model with multinucleon interactions gives the best description of the data. In the case of at least one proton in the final state, the spectral function model agrees well with the data, most notably when measuring the kinematic imbalance between the muon and the proton in the plane transverse to the incoming neutrino. Within the models considered, only the existence of multinucleon interactions are able to describe the extracted cross section within regions of high transverse kinematic imbalance. The effect of final-state interactions is also discussed.

Pion-proton correlation in neutrino interactions on nuclei

“…The recent development of data analysis techniques [4,5] allows the for separation of QE from non-QE processes in the aforementioned zero-pion (0π) topology. And yet, the remaining RES-referred to as absorbed-pion events in this work-and 2p2h contributions occupy very similar phase space not only in the single-particle kinematics but also in the kinematic imbalance exploited by those techniques [6,7]. Their experimental evidence is the otherwise unaccounted for measured excess of event rates [8,9].…”

Implementation of the SuSAv2-meson exchange current 1p1h and 2p2h models in GENIE and analysis of nuclear effects in T2K measurements

“…However, despite their notable size, such differences would be difficult to observe in any CC0π or inclusive measurement because of the large uncertainty on the 1p1h component which dominates the cross-section. More exclusive measurements, including information of the proton(s) in the final state have been performed in T2K [53] and Minerva [54] in order to enhance the sensitivity to 2p2h and will be discussed in Sec. V.…”

“…Goodness of fit are calculated to be χ 2 RM F = 171.87 (59 bins) and χ 2 SuSA = 168.92 (60 bins), where the latter includes a single extra bin from -1.0 to -0.3 cos θ (not shown). The data points are taken from[53].…”

“…For δφT : χ 2 SuSA = 40.1, χ 2V alencia = 36.8. The data points are taken from[53]. < cosθ µ < 1.000 Comparison of the T2K CC0π measurement of muon-neutrino interactions on Carbon with the SuSAv2-MEC model (1p1h+2p2h) implemented in GENIE in addition to pion-absorption effects from GENIE's Berger-Sehgal model.…”

Nuclear transparency in Monte Carlo neutrino event generators

“…the beam direction. NuWro results are obtained with the SF model known to produce better results then LFG [25]. Due to many adjustments in the FSI model, the results obtained with NuWro 19.02 differ notably from the ones of older versions of NuWro.…”