40 research outputs found
A measurement of proton-carbon forward scattering in a proof-of-principle test of the EMPHATIC spectrometer
The next generation of long-baseline neutrino experiments will be capable of
precision measurements of neutrino oscillation parameters, precision
neutrino-nucleus scattering, and unprecedented sensitivity to physics beyond
the Standard Model. Reduced uncertainties in neutrino fluxes are necessary to
achieve high precision and sensitivity in these future precise neutrino
measurements. New measurements of hadron-nucleus interaction cross sections are
needed to reduce uncertainties of neutrino fluxes. We report measurements of
the differential cross-section as a function of scattering angle for
proton-carbon interactions with a single charged particle in the final state at
beam momenta of 20, 30, and 120 GeV/c. These measurements are the result of a
beam test for EMPHATIC, a hadron-scattering and hadron-production experiment.
The total, elastic and inelastic cross-sections are also extracted from the
data and compared to previous measurements. These results can be used in
current and future long-baseline neutrino experiments, and demonstrate the
feasibility of future measurements by an upgraded EMPHATIC spectrometer
Measurement of the charged-current cross sections on water, hydrocarbon, iron, and their ratios with the T2K on-axis detectors
We report a measurement of the flux-integrated charged-current cross sections on water, hydrocarbon, and iron in the T2K on-axis neutrino beam with a mean neutrino energy of 1.5 GeV. The measured cross sections on water, hydrocarbon, and iron are = (0.840(stat.)(syst.))10cm/nucleon, = (0.817(stat.)(syst.))10cm/nucleon, and = (0.859(stat.) (syst.))10cm/nucleon respectively, for a restricted phase space of induced muons: 0.4 GeV/ in the laboratory frame. The measured cross section ratios are = 1.028(stat.)(syst.), = 1.023(stat.)(syst.), and = 1.049(stat.)(syst.). These results, with an unprecedented precision for the measurements of neutrino cross sections on water in the studied energy region, show good agreement with the current neutrino interaction models used in the T2K oscillation analyses
Measurement of neutrino and antineutrino neutral-current quasielasticlike interactions on oxygen by detecting nuclear deexcitation γ rays
Neutrino- and antineutrino-oxygen neutral-current quasielastic-like
interactions are measured at Super-Kamiokande using nuclear de-excitation
-rays to identify signal-like interactions in data from a $14.94 \
(16.35)\times 10^{20}\langle \sigma_{\nu {\rm -NCQE}} \rangle = 1.70 \pm 0.17 ({\rm stat.}) ^{+
{\rm 0.51}}_{- {\rm 0.38}} ({\rm syst.}) \times 10^{-38} \ {\rm cm^2/oxygen}\langle \sigma_{\bar{\nu} {\rm
-NCQE}} \rangle = 0.98 \pm 0.16 ({\rm stat.}) ^{+ {\rm 0.26}}_{- {\rm 0.19}}
({\rm syst.}) \times 10^{-38} \ {\rm cm^2/oxygen}$ with a flux-averaged energy
of 0.68 GeV, for neutrinos and antineutrinos, respectively. These results are
the most precise to date, and the antineutrino result is the first cross
section measurement of this channel. They are compared with various theoretical
predictions. The impact on evaluation of backgrounds to searches for supernova
relic neutrinos at present and future water Cherenkov detectors is also
discussed
Search for electron antineutrino appearance in a long-baseline muon antineutrino beam
Electron antineutrino appearance is measured by the T2K experiment in an accelerator-produced antineutrino beam, using additional neutrino beam operation to constrain parameters of the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixing matrix. T2K observes 15 candidate electron antineutrino events with a background expectation of 9.3 events. Including information from the kinematic distribution of observed events, the hypothesis of no electron antineutrino appearance is disfavored with a significance of 2.40σ and no discrepancy between data and PMNS predictions is found. A complementary analysis that introduces an additional free parameter which allows non-PMNS values of electron neutrino and antineutrino appearance also finds no discrepancy between data and PMNS predictions
Constraint on the matter-antimatter symmetry-violating phase in neutrino oscillations
The charge-conjugation and parity-reversal (CP) symmetry of fundamental particles is a symmetry between matter and antimatter. Violation of this CP symmetry was first observed in 19641, and CP violation in the weak interactions of quarks was soon established2. Sakharov proposed3 that CP violation is necessary to explain the observed imbalance of matter and antimatter abundance in the Universe. However, CP violation in quarks is too small to support this explanation. So far, CP violation has not been observed in non-quark elementary particle systems. It has been shown that CP violation in leptons could generate the matter–antimatter disparity through a process called leptogenesis4. Leptonic mixing, which appears in the standard model’s charged current interactions5,6, provides a potential source of CP violation through a complex phase δCP, which is required by some theoretical models of leptogenesis7,8,9. This CP violation can be measured in muon neutrino to electron neutrino oscillations and the corresponding antineutrino oscillations, which are experimentally accessible using accelerator-produced beams as established by the Tokai-to-Kamioka (T2K) and NOvA experiments10,11. Until now, the value of δCP has not been substantially constrained by neutrino oscillation experiments. Here we report a measurement using long-baseline neutrino and antineutrino oscillations observed by the T2K experiment that shows a large increase in the neutrino oscillation probability, excluding values of δCP that result in a large increase in the observed antineutrino oscillation probability at three standard deviations (3σ). The 3σ confidence interval for δCP, which is cyclic and repeats every 2π, is [−3.41, −0.03] for the so-called normal mass ordering and [−2.54, −0.32] for the inverted mass ordering. Our results indicate CP violation in leptons and our method enables sensitive searches for matter–antimatter asymmetry in neutrino oscillations using accelerator-produced neutrino beams. Future measurements with larger datasets will test whether leptonic CP violation is larger than the CP violation in quarks
Search for light sterile neutrinos with the T2K far detector Super-Kamiokande at a baseline of 295 km
We perform a search for light sterile neutrinos using the data from the T2K far detector at a baseline of 295 km, with an exposure of 14.7ð7.6Þ × 1020 protons on target in neutrino (antineutrino) mode. A selection of neutral-current interaction samples is also used to enhance the sensitivity to sterile mixing.
No evidence of sterile neutrino mixing in the 3 þ 1 model was found from a simultaneous fit to the charged-current muon, electron and neutral-current neutrino samples. We set the most stringent limit on the sterile oscillation amplitude sin2 θ24 for the sterile neutrino mass splitting Δm241 < 3 × 10−3 eV2=c4
Search for CP Violation in Neutrino and Antineutrino Oscillations by the T2K Experiment with 2.2 x 10(21) Protons on Target
The T2K experiment measures muon neutrino disappearance and electron neutrino
appearance in accelerator-produced neutrino and antineutrino beams. With an
exposure of protons on target in neutrino
(antineutrino) mode, 89 candidates and 7 anti- candidates were
observed while 67.5 and 9.0 are expected for and normal mass
ordering. The obtained confidence interval for the violating
phase, , does not include the -conserving cases
(). The best-fit values of other parameters are
and .Comment: 9 pages, 6 figure
Search for neutral-current induced single photon production at the ND280 near detector in T2K
Neutrino neutral-current (NC) induced single photon production is a sub-leading order process for accelerator-based neutrino beam experiments including T2K. It is, however, an important process to understand because it is a background for electron (anti)neutrino appearance oscillation experiments. Here, we performed the first search of this process below 1 GeV using the fine-grained detector at the T2K ND280 off-axis near detector. By reconstructing single photon kinematics from electron-positron pairs, we achieved 95% pure gamma ray sample from 5.738 x 10(20) protons-on-targets neutrino mode data. We do not find positive evidence of NC induced single photon production in this sample. We set the model-dependent upper limit on the cross-section for this process, at 0.114 x 10(-38) cm(2) (90% C.L.) per nucleon, using the J-PARC off-axis neutrino beam with an average energy of similar to 0.6 GeV. This is the first limit on this process below 1 GeV which is important for current and future oscillation experiments looking for electron neutrino appearance oscillation signals