Pion absorption above the Δ(1232) resonance

279

376

We report on measurements of neutrino oscillation using data from the T2K long-baseline neutrino experiment collected between 2010 and 2013. In an analysis of muon neutrino disappearance alone, we find the following estimates and 68% confidence intervals for the two possible mass hierarchies: normal hierarchy∶ sin 2 θ 23 ¼ 0.514 þ0.055 −0.056 and Δm 2 32 ¼ ð2.51 AE 0.10Þ × 10 −3 eV 2 =c 4 and inverted hierarchy∶ sin 2 θ 23 ¼ 0.511 AE 0.055 and Δm 2 13 ¼ ð2.48 AE 0.10Þ × 10 −3 eV 2 =c 4 . The analysis accounts for multinucleon mechanisms in neutrino interactions which were found to introduce negligible bias. We describe our first analyses that combine measurements of muon neutrino disappearance and electron neutrino appearance to estimate four oscillation parameters, jΔm 2 j, sin 2 θ 23 , sin 2 θ 13 , δ CP , and the mass hierarchy. Frequentist and Bayesian intervals are presented for combinations of these parameters, with and without including recent reactor measurements. At 90% confidence level and including reactor measurements, we exclude the region δ CP ¼ ½0.15; 0.83 π for normal hierarchy and δ CP ¼ ½−0.08; 1.09 π for inverted hierarchy. The T2K and reactor data weakly favor the normal hierarchy with a Bayes factor of 2.2. The most probable values and 68% one-dimensional credible intervals for the other oscillation parameters, when reactor data are included, are sin 2 θ 23 ¼ 0.528 þ0.055 −0.038 and jΔm 2 32 j ¼ ð2.51 AE 0.11Þ × 10 −3 eV 2 =c 4 .

Section: Nd280 Detector Systematicsmentioning

confidence: 99%

Measurements of neutrino oscillation in appearance and disappearance channels by the T2K experiment with6.6×1020protons on target

Abe¹,

Adam²,

Aihara³

et al. 2015

279

376

“…A large fraction of the secondary π 0 in the background is estimated to arise from π − → π 0 charge exchange (CEX), for which the cross sections are poorly known. The effect of this uncertainty on our measurement is evaluated by changing the CEX cross section within its uncertainty of ±50% [28,35,36], and then re-measuring the cross sections. The uncertainty in the electromagnetic energy scale contributes 2.2% to the error budget, estimated from the fitted mean uncertainty of the data m γγ distribution.…”

Section: Systematic Uncertaintiesmentioning

confidence: 99%

Cross sections forνμandν¯μinduced pion production on hydrocarbon in the few-GeV region using MINERvA

McGivern¹,

Le²,

Eberly³

et al. 2016

Cross sections for ν_{μ} and ν[over ¯]_{μ} induced pion production on hydrocarbon in the few-GeV region using MINERvA FERMILAB-PUB-16-228-NDCross sections for ν µ andν µ induced pion production on hydrocarbon in the few-GeV region using MINERvA Separate samples of charged-current pion production events representing two semi-inclusive channels νµ-CC(π + ) andνµ-CC(π 0 ) have been obtained using neutrino and antineutrino exposures of the MINERvA detector. Distributions in kinematic variables based upon µ ± -track reconstructions are analyzed and compared for the two samples. The differential cross sections for muon production angle, muon momentum, and four-momentum transfer Q 2 , are reported, and cross sections versus neutrino energy are obtained. Comparisons with predictions of current neutrino event generators are used to clarify the role of the ∆(1232) and higher-mass baryon resonances in CC pion production and to show the importance of pion final-state interactions. For the νµ-CC(π + ) (νµ-CC(π 0 )) sample, the absolute data rate is observed to lie below (above) the predictions of some of the event generators by amounts that are typically 1-to-2 σ. However the generators are able to reproduce the shapes of the differential cross sections for all kinematic variables of either data set.

“…This resonant production is simulated using the Rein-Sehgal model [35], the position dependence within the nucleus is calculated with the model from [36], and the scale of the microscopic pion interaction probabilities in the nuclear medium is determined from fits to pion scattering data [37][38][39]. The simulation of primary de-excitation γ-rays from this process is based on measurements of π − absorption-at-rest on H 2 O at CERN [40].…”

Section: Event Simulationmentioning

confidence: 99%

Measurement of the neutrino-oxygen neutral-current interaction cross section by observing nuclear deexcitationγrays

Abe¹,

Adam²,

Aihara³

et al. 2014

We report the first measurement of the neutrino-oxygen neutral-current quasi-elastic (NCQE) cross section. It is obtained by observing nuclear de-excitation γ-rays which follow neutrino-oxygen interactions at the Super-Kamiokande water Cherenkov detector. We use T2K data corresponding to 3 3.01 × 10 20 protons on target. By selecting only events during the T2K beam window and with wellreconstructed vertices in the fiducial volume, the large background rate from natural radioactivity is dramatically reduced. We observe 43 events in the 4 − 30 MeV reconstructed energy window, compared with an expectation of 51.0, which includes an estimated 16.2 background events. The background is primarily non-quasielastic neutral-current interactions and has only 1.2 events from natural radioactivity. The flux-averaged NCQE cross section we measure is 1.55 × 10 −38 cm 2 with a 68% confidence interval of (1.22, 2.20) × 10 −38 cm 2 at a median neutrino energy of 630 MeV, compared with the theoretical prediction of 2.01 × 10 −38 cm 2 .