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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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Keywords |
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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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Address |
[Berguno, D. Bravo; Ishii, T.; Labarga, L.] Univ Autonoma Madrid, Dept Theoret Phys, Madrid, Spain |
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Publisher |
Nature Publishing Group |
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English |
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ISSN |
0028-0836 |
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Notes |
WOS:000530151300023 |
Approved |
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); Antonova, M.; Cervera-Villanueva, A.; Fernandez, P.; Izmaylov, A.; Novella, P. |
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Title |
Measurement of the charged-current electron (anti-)neutrino inclusive cross-sections at the T2K off-axis near detector ND280 |
Type |
Journal Article |
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Year |
2020 |
Publication |
Journal of High Energy Physics |
Abbreviated Journal |
J. High Energy Phys. |
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Volume |
10 |
Issue |
10 |
Pages |
114 - 43pp |
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Keywords |
Other experiments |
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Abstract |
The electron (anti-)neutrino component of the T2K neutrino beam constitutes the largest background in the measurement of electron (anti-)neutrino appearance at the far detector. The electron neutrino scattering is measured directly with the T2K off-axis near detector, ND280. The selection of the electron (anti-)neutrino events in the plastic scintillator target from both neutrino and anti-neutrino mode beams is discussed in this paper. The flux integrated single differential charged-current inclusive electron (anti-)neutrino cross-sections, d sigma/dp and d sigma/d cos(theta), and the total cross-sections in a limited phase-space in momentum and scattering angle (p 300 MeV/c and theta <= 45 degrees) are measured using a binned maximum likelihood fit and compared to the neutrino Monte Carlo generator predictions, resulting in good agreement. |
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Address |
[Berguno, D. Bravo; Ishii, T.; Labarga, L.] Univ Autonoma Madrid, Dept Theoret Phys, Madrid, Spain |
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Publisher |
Springer |
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English |
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Series Volume |
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ISSN |
1029-8479 |
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Notes |
WOS:000583585900001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4589 |
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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 |
Neutrino oscillation physics potential of the T2K experiment |
Type |
Journal Article |
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Year |
2015 |
Publication |
Progress of Theoretical and Experimental Physics |
Abbreviated Journal |
Prog. Theor. Exp. Phys. |
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Volume |
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Issue |
4 |
Pages |
043C01 - 36pp |
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Keywords |
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Abstract |
The observation of the recent electron neutrino appearance in a muon neutrino beam and the high-precision measurement of the mixing angle theta(13) have led to a re-evaluation of the physics potential of the T2K long-baseline neutrino oscillation experiment. Sensitivities are explored for CP violation in neutrinos, non-maximal sin(2) 2 theta(23), the octant of theta(23), and the mass hierarchy, in addition to the measurements of delta CP, sin(2) theta(23), and Delta m(32)(2), for various combinations of nu-mode and (nu) over bar -mode data-taking. With an exposure of 7.8 x 10(21) protons-on-target, T2K can achieve 1 sigma resolution of 0.050 (0.054) on sin(2) theta(23) and 0.040 (0.045) x 10(-3) eV(2) on Delta m(32)(2) for 100% (50%) neutrino beam mode running assuming sin(2) theta(23) = 0.5 and Delta m(32)(2) = 2.4 x 10(-3) eV(2). T2K will have sensitivity to the CP-violating phase delta(CP) at 90% C.L. or better over a significant range. For example, if sin(2) 2 theta(23) is maximal (i.e.theta(23) = 45 degrees) the range is -115 degrees < delta(CP) < -60 degrees for normal hierarchy and +50 degrees < delta(CP) < + 130 degrees for inverted hierarchy. When T2K data is combined with data from the NO nu A experiment, the region of oscillation parameter space where there is sensitivity to observe a non-zero delta CP is substantially increased compared to if each experiment is analyzed alone. |
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Address |
[Abe, K.; Hayato, Y.; Ikeda, M.; Iyogi, K.; Kameda, J.; Miura, M.; Moriyama, S.; Nakahata, M.; Nakayama, S.; Sekiya, H.; Shiozawa, M.; Takeda, A.; Tanaka, H. K.; Tomura, T.; Wendell, R.] Univ Tokyo, Inst Cosm Ray Res, Kamioka Observ, Kamioka, Akita, Japan, Email: ichikawa@scphys.kyoto-u.ac.jp |
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Oxford Univ Press Inc |
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English |
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Original Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2050-3911 |
ISBN |
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Notes |
WOS:000355312800005 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
2262 |
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Author |
T2K Collaboration (Abe, K. et al); Cervera-Villanueva, A.; Izmaylov, A.; Novella, P.; Sorel, M.; Stamoulis, P. |
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Title |
Measurement of the single pi(0) production rate in neutral current neutrino interactions on water |
Type |
Journal Article |
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Year |
2018 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
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Volume |
97 |
Issue |
3 |
Pages |
032002 - 13pp |
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Keywords |
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Abstract |
The single pi(0) production rate in neutral current neutrino interactions on water in a neutrino beam with a peak neutrino energy of 0.6 GeV has been measured using the empty set, one of the subdetectors of the T2K near detector. The production rate was measured for data taking periods when the Pempty setD contained water (2.64 x 10(20) protons-on-target) and also periods without water (3.49 x 10(20) protons-on-target). A measurement of the neutral current single pi(0) production rate on water is made using appropriate subtraction of the production rate with water in from the rate with water out of the target region. The subtraction analysis yields 106 +/- 41 +/- 69 signal events where the uncertainties are statistical (stat.) and systematic (sys.) respectively. This is consistent with the prediction of 157 events from the nominal simulation. The measured to expected ratio is 0.68 +/- 0.26(stat) +/- 0.44(sys) +/- 0.12(flux). The nominal simulation uses a flux integrated cross section of 7.63 x 10(-39) cm(2) per nucleon with an average neutrino interaction energy of 1.3 GeV. |
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Address |
[Ariga, A.; Ereditato, A.; Hierholzer, M.; Koller, P. P.; Nirkko, M.; Pistillo, C.; Redij, A.; Wilkinson, C.] Univ Bern, Albert Einstein Ctr Fundamental Phys, Lab High Energy 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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Original Title |
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Series Editor |
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ISSN |
2470-0010 |
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Notes |
WOS:000424057200001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
3472 |
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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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Keywords |
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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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Publisher |
Amer Physical Soc |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
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Original Title |
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Series Volume |
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Edition |
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ISSN |
0031-9007 |
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Notes |
WOS:000327245600004 |
Approved |
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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