《中子物理学实验》由会员分享，可在线阅读，更多相关《中子物理学实验（52页珍藏版）》请在金锄头文库上搜索。
1、arXiv:nucl-ex/0612022v1 20 Dec 2006 Experiments in Fundamental Neutron Physics Jeff rey S. Nico National Institute of Standards and Technology Physics Laboratory Gaithersburg, MD 20899 W. Michael Snow Indiana University and Indiana University Cyclotron Facility Department of Physics Bloomington, IN
2、47408 December 20, 2006 Contents 1INTRODUCTION1 1.1Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 1.2Neutron Optics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 1.3Neutron Sources. . . . . . . . . . .
3、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 2NEUTRON DECAY AND STANDARD MODEL TESTS6 2.1Theoretical Framework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6 2.2Neutron Lifetime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4、 . . . . . . . . .9 2.3Angular Correlation Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 3SEARCHES FOR NONSTANDARD T AND B VIOLATION16 3.1EDM Theoretical Framework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 3.2Electric Dipole Moment
5、Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 3.3T-violation in Neutron Beta Decay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 3.4 D- and R-coeffi cient Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 3.5T Viola
6、tion in Neutron Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 3.6Neutron-antineutron Oscillations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 4NEUTRON-NUCLEON WEAK INTERACTIONS22 4.1Overview. . . . . . . . . . . . . . . . . . . . . . . . .
7、. . . . . . . . . . . . . . . . . . . . . .22 4.2Theoretical Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23 4.3Parity-Odd Neutron Spin Rotation and Capture Gamma Asymmetries . . . . . . . . . . . . .24 4.4Test of Statistical Theories for Heavy Nuclei Matri
8、x Elements . . . . . . . . . . . . . . . . . .26 5LOW ENERY QCD TESTS27 5.1Theoretical Developments in Few Nucleon Systems and the Connection to QCD. . . . . . .28 5.2Precision Scattering Length Measurements Using Interferometric Methods . . . . . . . . . . .28 5.3Neutron-electron Interaction . . .
9、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30 5.4Neutron Polarizability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31 5.5Ultrahigh Resolution Gamma Spectroscopy and Metrology with Neutrons . . . . . . . . . . .31 6NEUTRONS IN ASTROPHYSICS A
10、ND GRAVITY32 6.1Big Bang Nucleosynthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32 6.2Stellar Astrophysics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32 6.3Gravitationally-induced Phase Shift. . . . . . . . . . . . . . . . . .
11、. . . . . . . . . . . . . .33 6.4UCN Gravitational Bound States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 7SUMMARY34 8ACKNOWLEDGMENTS35 i 1INTRODUCTION 1.1Overview The fi eld of neutron physics has become an integral part of investigations into an array of important issue
12、s that span fi elds as diverse as nuclear and particle physics, fundamental symmetries, astrophysics and cos- mology, fundamental constants, gravitation, and the interpretation of quantum mechanics. The experiments employ a diversity of measurement strategies and techniques - from condensed matter a
13、nd low temperature physics, optics, and atomic physics as well as nuclear and particle physics - and address a wide range of issues. Nevertheless, the fi eld possesses a certain coherence that derives from the unique properties of the neutron as an electrically neutral, strongly interacting, long-li
14、ved unstable particle that can be used either as the probe or as an object of study. This review covers some of the important new contributions that neutrons have made in these diverse areas of science. By “fundamental” neutron physics we mean that class of experiments using slow neutrons that prima
15、rily address scientifi c issues associated with the Standard Model (SM) of the strong, weak, electromagnetic, and gravitational interactions and their connection with issues in astrophysics and cosmology. Neutrons experience all known forces in strengths that make them accessible to experimentation.
16、 It is an amusing fact that the magnitude of the average neutron interaction energy in matter, in approximately 1T magnetic fi elds, and over a one meter fall near the surface of the Earth is the same order of magni- tude ( 100neV). This coincidence leads to interesting and occasionally bizarre strategies for experiments that search for gravitational eff ects on an elementary particle. The experiments include measurement of neutron-decay parameters, the use of parity violation to isolate the we
