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Author |
T2K Collaboration (Abe, K. et al); Antonova, M.; Cervera-Villanueva, A.; Fernandez, P.; Izmaylov, A.; Novella, P. |
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Title |
Constraint on the matter-antimatter symmetry-violating phase in neutrino oscillations |
Type |
Journal Article |
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Year |
2020 |
Publication |
Nature |
Abbreviated Journal |
Nature |
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Volume |
580 |
Issue |
7803 |
Pages |
339-344 |
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Abstract |
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 1964(1), and CP violation in the weak interactions of quarks was soon established(2). Sakharov proposed(3) 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 leptogenesis(4). Leptonic mixing, which appears in the standard model's charged current interactions(5,6), provides a potential source of CP violation through a complex phase dCP, which is required by some theoretical models of leptogenesis(7-9). 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 experiments(10,11). Until now, the value of dCP 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 dCP that result in a large increase in the observed antineutrino oscillation probability at three standard deviations (3 sigma). The 3 sigma confidence interval for delta(CP), which is cyclic and repeats every 2p, 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. |
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[Berguno, D. Bravo; Ishii, T.; Labarga, L.] Univ Autonoma Madrid, Dept Theoret Phys, Madrid, Spain |
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Nature Publishing Group |
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0028-0836 |
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WOS:000530151300023 |
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no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4388 |
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Author |
T2K Collaboration (Abe, K. et al); Cervera-Villanueva, A.; Escudero, L.; Gomez-Cadenas, J.J.; Izmaylov, A.; Monfregola, L.; Sorel, M.; Stamoulis, P. |
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Title |
Measurement of Neutrino Oscillation Parameters from Muon Neutrino Disappearance with an Off-Axis Beam |
Type |
Journal Article |
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Year |
2013 |
Publication |
Physical Review Letters |
Abbreviated Journal |
Phys. Rev. Lett. |
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Volume |
111 |
Issue |
21 |
Pages |
211803 - 7pp |
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Abstract |
The T2K Collaboration reports a precision measurement of muon neutrino disappearance with an off-axis neutrino beam with a peak energy of 0.6 GeV. Near detector measurements are used to constrain the neutrino flux and cross section parameters. The Super-Kamiokande far detector, which is 295 km downstream of the neutrino production target, collected data corresponding to 3.01 x 10(20) protons on target. In the absence of neutrino oscillations, 205 +/- 17 (syst) events are expected to be detected while only 58 muon neutrino event candidates are observed. A fit to the neutrino rate and energy spectrum, assuming three neutrino flavors and normal mass hierarchy yields a best-fit mixing angle sin(2) (theta(23)) = 0.514 +/- 0.082 and mass splitting vertical bar Delta m(32)(2)vertical bar = 2.44(-0.15)(+0.17) x 10(-3) eV(2)/c(4). Our result corresponds to the maximal oscillation disappearance probability. |
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Address |
[Kitching, P.] Univ Alberta, Dept Phys, Ctr Particle Phys, Edmonton, AB, Canada |
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Amer Physical Soc |
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0031-9007 |
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Notes |
WOS:000327245600004 |
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no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1656 |
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Permanent link to this record |
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Author |
T2K Collaboration (Abe, K. et al); Cervera-Villanueva, A.; Escudero, L.; Gomez-Cadenas, J.J.; Izmaylov, A.; Monfregola, L.; Sorel, M.; Stamoulis, P. |
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Title |
Observation of Electron Neutrino Appearance in a Muon Neutrino Beam |
Type |
Journal Article |
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Year |
2014 |
Publication |
Physical Review Letters |
Abbreviated Journal |
Phys. Rev. Lett. |
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Volume |
112 |
Issue |
6 |
Pages |
061802 - 8pp |
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Abstract |
The T2K experiment has observed electron neutrino appearance in a muon neutrino beam produced 295 km from the Super-Kamiokande detector with a peak energy of 0.6 GeV. A total of 28 electron neutrino events were detected with an energy distribution consistent with an appearance signal, corresponding to a significance of 7.3 sigma when compared to 4.92 +/- 0.55 expected background events. In the Pontecorvo-Maki-Nakagawa-Sakata mixing model, the electron neutrino appearance signal depends on several parameters including three mixing angles theta(12), theta(23), theta(13), a mass difference vertical bar Delta m(32)(2)vertical bar and a CP violating phase delta(CP). In this neutrino oscillation scenario, assuming vertical bar Delta m(32)(2)vertical bar = 2.4 x 10(-3) eV(2), sin theta(2)(23) = 0.5, and vertical bar Delta m(32)(2)vertical bar > 0 (vertical bar Delta m(32)(2)vertical bar < 0), a best- fit value of sin2 theta(2)(13) = 0.140(- 0.032)(+0.038) (0.170(-0.037)(+0.045)) is obtained at delta(CP) = 0. When combining the result with the current best knowledge of oscillation parameters including the world average value of theta(13) from reactor experiments, some values of delta(CP) are disfavored at the 90% C. L. |
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Address |
[Kitching, P.] Univ Alberta, Dept Phys, Ctr Particle Phys, Edmonton, AB, Canada |
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Amer Physical Soc |
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0031-9007 |
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Notes |
WOS:000331951000003 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1701 |
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Permanent link to this record |
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Author |
T2K Collaboration (Abe, K. et al); Cervera-Villanueva, A.; Escudero, L.; Izmaylov, A.; Monfregola, L.; Sorel, M.; Stamoulis, P. |
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Title |
Precise Measurement of the Neutrino Mixing Parameter theta(23) from Muon Neutrino Disappearance in an Off-Axis Beam |
Type |
Journal Article |
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Year |
2014 |
Publication |
Physical Review Letters |
Abbreviated Journal |
Phys. Rev. Lett. |
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Volume |
112 |
Issue |
18 |
Pages |
181801 - 8pp |
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Keywords |
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Abstract |
New data from the T2K neutrino oscillation experiment produce the most precise measurement of the neutrino mixing parameter theta(23). Using an off-axis neutrino beam with a peak energy of 0.6 GeV and a data set corresponding to 6.57 x 10(20) protons on target, T2K has fit the energy-dependent nu(mu) oscillation probability to determine oscillation parameters. The 68% confidence limit on sin(2)(theta(23)) is 0.514(-0.056)(+0.055) (0.511 +/- 0.055), assuming normal (inverted) mass hierarchy. The best-fit mass-squared splitting for normal hierarchy is Delta m(32)(2) = (2.51 +/- 0.10) x 10(-3) eV(2)/c(4) (inverted hierarchy: Delta m(13)(2) = (2.48 +/- 0.10) x 10(-3) eV(2)/c(4)). Adding a model of multinucleon interactions that affect neutrino energy reconstruction is found to produce only small biases in neutrino oscillation parameter extraction at current levels of statistical uncertainty. |
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Address |
[Kitching, P.] Univ Alberta, Dept Phys, Ctr Particle Phys, Edmonton, AB, Canada |
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Amer Physical Soc |
Place of Publication |
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English |
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0031-9007 |
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Notes |
WOS:000339629400005 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1877 |
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Permanent link to this record |
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Author |
T2K Collaboration (Abe, K. et al); Cervera-Villanueva, A.; Escudero, L.; Izmaylov, A.; Sorel, M.; Stamoulis, P. |
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Title |
Measurement of the Inclusive Electron Neutrino Charged Current Cross Section on Carbon with the T2K Near Detector |
Type |
Journal Article |
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Year |
2014 |
Publication |
Physical Review Letters |
Abbreviated Journal |
Phys. Rev. Lett. |
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Volume |
113 |
Issue |
24 |
Pages |
241803 - 7pp |
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Keywords |
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Abstract |
The T2K off-axis near detector ND280 is used to make the first differential cross-section measurements of electron neutrino charged current interactions at energies similar to 1 GeV as a function of electron momentum, electron scattering angle, and four-momentum transfer of the interaction. The total flux-averaged nu(e) charged current cross section on carbon is measured to be <sigma >(phi) = 1.11 +/- 0.10(stat) +/- 0.18(syst) x 10(-38) cm(2)/nucleon. The differential and total cross- section measurements agree with the predictions of two leading neutrino interaction generators, NEUT and GENIE. The NEUT prediction is 1.23 x 10(-38) cm(2)/nucleon and the GENIE prediction is 1.08 x 10(-38) cm(2)/nucleon. The total nu(e) charged current cross-section result is also in agreement with data from the Gargamelle experiment. |
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Address |
[Ariga, A.; Ereditato, A.; Goeldi, D.; Hierholzer, M.; Nirkko, M.; Pistillo, C.; Redij, A.] Univ Bern, Albert Einstein Ctr Fundamental Phys, High Energy Phys Lab, Bern, Switzerland |
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Amer Physical Soc |
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English |
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0031-9007 |
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Notes |
WOS:000346372300002 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
2049 |
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Permanent link to this record |
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Author |
T2K Collaboration (Abe, K. et al); Cervera-Villanueva, A.; Izmaylov, A.; Sorel, M.; Stamoulis, P. |
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Title |
Measurement of Muon Antineutrino Oscillations with an Accelerator-Produced Off-Axis Beam |
Type |
Journal Article |
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Year |
2016 |
Publication |
Physical Review Letters |
Abbreviated Journal |
Phys. Rev. Lett. |
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Volume |
116 |
Issue |
18 |
Pages |
181801 - 8pp |
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Keywords |
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Abstract |
T2K reports its first measurements of the parameters governing the disappearance of (nu) over bar μin an off-axis beam due to flavor change induced by neutrino oscillations. The quasimonochromatic (nu) over bar μbeam, produced with a peak energy of 0.6 GeVat J-PARC, is observed at the far detector Super-Kamiokande, 295 km away, where the (nu) over bar μsurvival probability is expected to be minimal. Using a data set corresponding to 4.01 x 10(20) protons on target, 34 fully contained mu-like events were observed. The best-fit oscillation parameters are sin(2) ((theta) over bar (23)) = 0.45 and vertical bar Delta(m) over bar (2)(32)vertical bar = 2.51 x 10(-3) eV(2) with 68% confidence intervals of 0.38-0.64 and 2.26-2.80 x 10(-3) eV(2), respectively. These results are in agreement with existing antineutrino parameter measurements and also with the nu(mu) disappearance parameters measured by T2K. |
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Address |
[Ariga, A.; Ereditato, A.; Hierholzer, M.; Nirkko, M.; Pistillo, C.; Redij, A.; Wilkinson, C.] Univ Bern, Albert Einstein Ctr Fundamental Phys, High Energy Phys Lab, Bern, Switzerland |
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Publisher |
Amer Physical Soc |
Place of Publication |
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English |
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0031-9007 |
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Notes |
WOS:000375669300003 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
2666 |
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Permanent link to this record |
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Author |
T2K Collaboration (Abe, K. et al); Cervera-Villanueva, A.; Novella, P.; Izmaylov, A.; Sorel, M.; Stamoulis, P. |
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Title |
Measurement of Coherent pi(+) Production in Low Energy Neutrino-Carbon Scattering |
Type |
Journal Article |
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Year |
2016 |
Publication |
Physical Review Letters |
Abbreviated Journal |
Phys. Rev. Lett. |
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Volume |
117 |
Issue |
9 |
Pages |
192501 - 7pp |
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Keywords |
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Abstract |
We report the first measurement of the flux-averaged cross section for charged current coherent pi(+) production on carbon for neutrino energies less than 1.5 GeV, and with a restriction on the final state phase space volume in the T2K near detector, ND280. Comparisons are made with predictions from the Rein-Sehgal coherent production model and the model by Alvarez-Ruso et al., the latter representing the first implementation of an instance of the new class of microscopic coherent models in a neutrino interaction Monte Carlo event generator. We observe a clear event excess above background, disagreeing with the null results reported by K2K and SciBooNE in a similar neutrino energy region. The measured flux-averaged cross sections are below those predicted by both the Rein-Sehgal and Alvarez-Ruso et al. models. |
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Address |
[Ariga, A.; Ereditato, A.; Hierholzer, M.; Nirkko, M.; Pistillo, C.; Redij, A.; Wilkinson, C.] Univ Bern, Albert Einstein Ctr Fundamental Phys, LHEP, Bern, Switzerland |
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Publisher |
Amer Physical Soc |
Place of Publication |
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English |
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0031-9007 |
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Notes |
WOS:000386903400010 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
2844 |
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Permanent link to this record |
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Author |
T2K Collaboration (Abe, K. et al); Cervera-Villanueva, A.; Izmaylov, A.; Novella, P.; Sorel, M. |
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Title |
Combined Analysis of Neutrino and Antineutrino Oscillations at T2K |
Type |
Journal Article |
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Year |
2017 |
Publication |
Physical Review Letters |
Abbreviated Journal |
Phys. Rev. Lett. |
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Volume |
118 |
Issue |
15 |
Pages |
151801 - 9pp |
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Keywords |
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Abstract |
T2K reports its first results in the search for CP violation in neutrino oscillations using appearance and disappearance channels for neutrino-and antineutrino-mode beams. The data include all runs from January 2010 to May 2016 and comprise 7.482 x 10(20) protons on target in neutrino mode, which yielded in the far detector 32 e-like and 135 mu-like events, and 7.471 x 10(20) protons on target in antineutrino mode, which yielded 4 e-like and 66 mu-like events. Reactor measurements of sin(2) 2 theta(13) have been used as an additional constraint. The one-dimensional confidence interval at 90% for the phase delta(CP) spans the range (-3.13,-0.39) for normal mass ordering. The CP conservation hypothesis (delta(CP) = 0, pi) is excluded at 90% C.L. |
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Address |
[Ariga, A.; Ereditato, A.; Nirkko, M.; Pistillo, C.; Redij, A.; Wilkinson, C.] Univ Bern, LHEP, Albert Einstein Ctr Fundamental Phys, Bern, Switzerland |
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Publisher |
Amer Physical Soc |
Place of Publication |
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English |
Summary Language |
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0031-9007 |
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Notes |
WOS:000399957800006 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
3104 |
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Permanent link to this record |
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Author |
T2K Collaboration (Abe, K. et al); Antonova, M.; Cervera-Villanueva, A.; Fernandez, P.; Izmaylov, A.; Novella, P. |
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Title |
Search for CP Violation in Neutrino and Antineutrino Oscillations by the T2K Experiment with 2.2 x 10(21) Protons on Target |
Type |
Journal Article |
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Year |
2018 |
Publication |
Physical Review Letters |
Abbreviated Journal |
Phys. Rev. Lett. |
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Volume |
121 |
Issue |
17 |
Pages |
171802 - 9pp |
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Keywords |
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Abstract |
The T2K experiment measures muon neutrino disappearance and electron neutrino appearance in accelerator-produced neutrino and antineutrino beams. With an exposure of 14.7(7.6) x 10(20) protons on target in the neutrino (antineutrino) mode, 89 nu(e) candidates and seven anti-nu(e) candidates are observed, while 67.5 and 9.0 are expected for delta(CP) = 0 and normal mass ordering. The obtained 2 sigma confidence interval for the CP-violating phase, delta(CP), does not include the CP-conserving cases (delta(CP) = 0, pi). The best-fit values of other parameters are sin(2) theta(23) = 0.526(-0.036)(+0.032) and Delta m(32)(2) = 2.463(-0.070)(+0.071) x 10(-3) eV(2)/c(4). |
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Address |
[Labarga, L.] Univ Autonoma Madrid, Dept Theoret Phys, Madrid 28049, Spain |
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Publisher |
Amer Physical Soc |
Place of Publication |
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English |
Summary Language |
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Series Volume |
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Series Issue |
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ISSN |
0031-9007 |
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Conference |
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Notes |
WOS:000448172000004 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
3773 |
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Permanent link to this record |
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Author |
T2K Collaboration (Abe, K. et al); Antonova, M.; Cervera-Villanueva, A.; Fernandez, P.; Izmaylov, A.; Novella, P. |
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Title |
Search for Electron Antineutrino Appearance in a Long-Baseline Muon Antineutrino Beam |
Type |
Journal Article |
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Year |
2020 |
Publication |
Physical Review Letters |
Abbreviated Journal |
Phys. Rev. Lett. |
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Volume |
124 |
Issue |
16 |
Pages |
161802 - 8pp |
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Keywords |
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Abstract |
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 2.40s 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. |
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Address |
[Bravo Berguno, D.; Labarga, L.] Univ Autonoma Madrid, Dept Theoret Phys, Madrid, Spain |
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Publisher |
Amer Physical Soc |
Place of Publication |
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English |
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ISSN |
0031-9007 |
ISBN |
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Area |
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Expedition |
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Conference |
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Notes |
WOS:000527135200004 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4379 |
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Permanent link to this record |