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Constraint on the matter-antimatter symmetry-violating phase in neutrino oscillations 期刊论文
NATURE, 2020, 580 (7803) : 339-+
作者:  Houben, Lothar;  Weissman, Haim;  Wolf, Sharon G.;  Rybtchinski, Boris
收藏  |  浏览/下载：33/0  |  提交时间：2020/07/03

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.


  
Demonstration of cooling by the Muon Ionization Cooling Experiment 期刊论文
NATURE, 2020, 578 (7793) : 53-+
作者:  Zheng, Wen;  Zhao, Wenjing;  Wu, Meng;  Song, Xinyang;  Caro, Florence;  Sun, Ximei;  Gazzaniga, Francesca;  Stefanetti, Giuseppe;  Oh, Sungwhan;  Mekalanos, John J.;  Kasper, Dennis L.
收藏  |  浏览/下载：21/0  |  提交时间：2020/07/03

The use of accelerated beams of electrons, protons or ions has furthered the development of nearly every scientific discipline. However, high-energy muon beams of equivalent quality have not yet been delivered. Muon beams can be created through the decay of pions produced by the interaction of a proton beam with a target. Such '  tertiary'  beams have much lower brightness than those created by accelerating electrons, protons or ions. High-brightness muon beams comparable to those produced by state-of-the-art electron, proton and ion accelerators could facilitate the study of lepton-antilepton collisions at extremely high energies and provide well characterized neutrino beams(1-6). Such muon beams could be realized using ionization cooling, which has been proposed to increase muon-beam brightness(7,8). Here we report the realization of ionization cooling, which was confirmed by the observation of an increased number of low-amplitude muons after passage of the muon beam through an absorber, as well as an increase in the corresponding phase-space density. The simulated performance of the ionization cooling system is consistent with the measured data, validating designs of the ionization cooling channel in which the cooling process is repeated to produce a substantial cooling effect(9-11). The results presented here are an important step towards achieving the muon-beam quality required to search for phenomena at energy scales beyond the reach of the Large Hadron Collider at a facility of equivalent or reduced wfootprint(6).


  
Pitch Angle Scattering of Upgoing Electron Beams in Jupiter's Polar Regions by Whistler Mode Waves 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2018, 45 (3) : 1246-1252
作者:  Elliott, S. S.;  Gurnett, D. A.;  Kurth, W. S.;  Clark, G.;  Mauk, B. H.;  Bolton, S. J.;  Connerney, J. E. P.;  Levin, S. M.
收藏  |  浏览/下载：19/0  |  提交时间：2019/04/09
pitch angle scattering  Juno  upgoing electron beams  whistler mode  Jupiter  polar cap  
How electron two-stream instability drives cyclic Langmuir collapse and continuous coherent emission 期刊论文
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 2017, 114 (7) : 1502-1507
作者:  Che, Haihong;  Goldstein, Melvyn L.;  Diamond, Patrick H.;  Sagdeev, Roald Z.
收藏  |  浏览/下载：16/0  |  提交时间：2019/11/27
electron beams  nonlinear wave interaction  Langmuir collapse  coherent emission  plasma turbulence