中文版 | English

在结果中检索

GSTDTAP

浏览/检索结果: 共3条，第1-3条 帮助

已选(0)清除 条数/页：   排序方式：
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：30/0  |  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.


  
Synchrotron infrared spectroscopic evidence of the probable transition to metal hydrogen 期刊论文
NATURE, 2020, 577 (7792) : 631-+
作者:  Zhuang, Zhe;  Yu, Jin-Quan
收藏  |  浏览/下载：33/0  |  提交时间：2020/07/03

Hydrogen has been an essential element in the development of atomic, molecular and condensed matter physics(1). It is predicted that hydrogen should have a metal state(2)  however, understanding the properties of dense hydrogen has been more complex than originally thought, because under extreme conditions the electrons and protons are strongly coupled to each other and ultimately must both be treated as quantum particles(3,4). Therefore, how and when molecular solid hydrogen may transform into a metal is an open question. Although the quest for metal hydrogen has pushed major developments in modern experimental high-pressure physics, the various claims of its observation remain unconfirmed(5-7). Here a discontinuous change of the direct bandgap of hydrogen, from 0.6 electronvolts to below 0.1 electronvolts, is observed near 425 gigapascals. This result is most probably associated with the formation of the metallic state because the nucleus zero-point energy is larger than this lowest bandgap value. Pressures above 400 gigapascals are achieved with the recently developed toroidal diamond anvil cell(8), and the structural changes and electronic properties of dense solid hydrogen at 80 kelvin are probed using synchrotron infrared absorption spectroscopy. The continuous downward shifts of the vibron wavenumber and the direct bandgap with increased pressure point to the stability of phase-III hydrogen up to 425 gigapascals. The present data suggest that metallization of hydrogen proceeds within the molecular solid, in good agreement with previous calculations that capture many-body electronic correlations(9).


  
Resource recovery and low carbon transitions: The hidden impacts of substituting cement with imported 'waste' materials from coal and steel production 期刊论文
GLOBAL ENVIRONMENTAL CHANGE-HUMAN AND POLICY DIMENSIONS, 2018, 53: 146-156
作者:  Millward-Hopkins, Joel;  Zwirner, Oliver;  Purnell, Phil;  Velis, Costas A.;  Iacovidou, Eleni;  Brown, Andrew
收藏  |  浏览/下载：20/0  |  提交时间：2019/04/09
Biomass  Carbon accounting  Coal ash  Complex value  Concrete  Resource recovery  Solid waste