Measurements of neutrino oscillation in appearance and disappearance channels by the T2K experiment with 6.6 × 1020 protons on target
نویسندگان
چکیده
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 θ23 = 0.514 +0.055 −0.056 and ∆m 2 32 = (2.51± 0.10)× 10−3 eV2/c4 Inverted Hierarchy: sin θ23 = 0.511± 0.055 and ∆m13 = (2.48± 0.10)× 10−3 eV2/c4 The analysis accounts for multi-nucleon 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, |∆m2|, sinθ23, sinθ13, δCP , 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 δCP = [0.15, 0.83]π for normal hierarchy and δCP = [−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% 1D credible intervals for the other oscillation parameters, when reactor data are included, are: sin θ23 = 0.528 +0.055 −0.038 and |∆m 2 32| = (2.51± 0.11)× 10−3 eV/c . PACS numbers: 14.60.Pq ∗ also at J-PARC, Tokai, Japan † also at Institute of Particle Physics, Canada ‡ affiliated member at Kavli IPMU (WPI), the University of Tokyo, Japan § also at Moscow Institute of Physics and Technology and National Research Nuclear University ”MEPhI”, Moscow, Russia ¶ also at JINR, Dubna, Russia ∗∗ also at BMCC/CUNY, Science Department, New York, New York, U.S.A.
منابع مشابه
Latest Results from the K2k Experiment A
The KEK to Kamioka long-baseline neutrino experiment (K2K) is the first accelerator-based experiment with hundreds of km neutrino path length. K2K focuses on the study of the existence of neutrino oscillations in νμ disappearance that is observed in atmospheric neutrinos. With nearly pure muon neutrino beam produced with 5.6 × 10 protons from 12 GeV PS on target, 56 neutrino events have been ob...
متن کاملNeutrino Cross Section Measurements for Long-baseline Accelerator-based Neutrino Oscillation Experiments
Neutrino oscillations are clear evidence for physics beyond the standard model. The goal of next-generation neutrino oscillation experiments is to find a non-zero θ13, the last mixing matrix element for which we only know an upper limit. For this, next-generation long-baseline neutrino oscillation experiments require an order of magnitude better sensitivities. In particular, accelerator-based e...
متن کاملDetermining Neutrino Mass Hierarchy by Precision Measurements in Electron and Muon Neutrino Disappearance Experiments
Recently a new method for determining the neutrino mass hierarchy by comparing the effective values of the atmospheric ∆m measured in the electron neutrino disappearance channel, ∆m(ee), with the one measured in the muon neutrino disappearance channel, ∆m(μμ), was proposed. If ∆m(ee) is larger (smaller) than ∆m(μμ) the hierarchy is of the normal (inverted) type. We re-examine this proposition i...
متن کاملThe Electromagnetic Calorimeter for the T 2 K Near Detector ND 280
The T2K experiment studies oscillations of an off-axis muon neutrino beam between the J-PARC accelerator complex and the Super-Kamiokande detector. Special emphasis is placed on measuring the mixing angle θ13 by observing νe appearance via the sub-dominant νμ → νe oscillation and searching for CP violation in the lepton sector. The experiment includes a sophisticated, off-axis, near detector, t...
متن کاملExtracting Matter Effects , Masses and Mixings at a Neutrino Factory ∗
We discuss and quantify different possibilities to determine matter effects, the value and the sign of ∆m231, as well as the magnitude of sin 2 2θ13 in very long baseline neutrino oscillation experiments. We study neutrino oscillation at a neutrino factory in the νμ → νμ disappearance and νe → νμ appearance channels with and without muon charge identification. One possibility is to analyze the ...
متن کامل