Kaons are heavy enough to have an interesting range of decay modes available to them, and light enough to be produced in sufficient numbers to explore rare modes with satisfying statistics. Kaons and their decays have provided at least two major breakthroughs in our knowledge of fundamental physics. They have revealed to us CP violation,l and their lack of flavor-changing neutral interactions w...

The main features of radiation by relativistic electrons are well approximated in the Weizsäcker-Williams method of virtual quanta. This method is best known for its application to radiation during elementary particle collisions, but is equally useful in describing “classical” radiation emitted during the interaction of a single relativistic electron with an extended system, such as synchrotron...

These lectures give a general introduction to supersymmetry, emphasizing its application to models of elementary particle physics at the 100 GeV energy scale. I discuss the following topics: the construction of supersymmetric Lagrangians with scalars, fermions, and gauge bosons, the structure and mass spectrum of the Minimal Supersymmetric Standard Model (MSSM), the measurement of the parameter...

I. The Mists of Scotland S25 II. ‘‘Cosmic Rays Go Downward, Dr. Anderson’’ S25 III. On Making a Particle Take a Photograph of Itself S26 IV. The Slow Discovery of the Mesotron S27 V. The Mesotron is Not the Yukon S28 VI. ‘‘Even a Theoretician Might be Able To Do It’’ S28 VII. The Reservoir of Ideas Runneth Over S29 VIII. ‘‘There is No Excellent Beauty That Hath Not Some Strangeness in the Propo...

In a set of two papers, we propose to study an old-standing problem, namely the electromagnetic interaction for particles of arbitrary spin. Based on the assumption that light-cone helicity at tree level and Q = 0 should be conserved non-trivially by the electromagnetic interaction, we are able to derive all the natural electromagnetic moments for a pointlike particle of any spin. In this secon...

Scattering amplitudes take surprisingly simple forms in theories such as quantum chromodynamics (QCD) and general relativity. This simplicity indicates deep symmetry. Recently, it has become possible to explain some of this symmetry. I will describe these insights and show how to derive amplitudes efficiently and elegantly. Key new ideas involve using complexified momentum, exploring singular b...

The Inönü-Wigner contraction is applied to special relativity and the little groups of the Lorentz group. If the O(3) symmetry group for massive particle is boosted to an infinite-momentum frame, it becomes contracted to a combination of the cylindrical group and the two-dimensional Euclidean group. The Euclidean component becomes the Lorentz condition applicable to the electromagnetic four-pot...

By using a combined amplitude analysis of the γγ→DD̅ and γγ→J/ψω data, we demonstrate that the X(3915), which is quoted as a J(PC)=0(++) state in the Particle Data Group table, is favored by the data to be a J(PC)=2(++) state appearing in both channels, which means that the X(3915) and the X(3930) can be regarded as the same J(PC)=2(++) state. Meanwhile, the data also prefer a large helicity-0 c...

We examine the matrix element of a current with arbitrary number s of four vector indices between one particle states of definite helicity. The conservation of the angular momentum in the brick wall reference frame was used to derive a set of linear relations between the matrix elements. Requiring the helicities of the particles to be conserved asymptotically, we derive a restriction on the spi...