121568105
PRECISION ELECTROWEAK PHYSICS
118715122
Physics from Tristan
The TRISTAN e + e − storage ring has delivered a total of about 60 pb−1 to each of the three general purpose solenoidal detectors: AMY, TOPAZ and VENUS. The center-of-mass energy range, between 50 and 64 GeV, is where interference effects between the virtual photon and Z0 mediators of the annihilation process are largest. Experiments at TRISTAN study the electroweak interactions, QCD, and search for new phenomena. Among the reported results are: measurements of R; the observation of forward-backward charge asymmetries for e+e− → lepton pairs, \(e^ + e^ - \to b\bar b\), and \(e^ + e^ - \to q\bar q\); limits on lepton compositeness; determinations of \(\Lambda _{\overline {MS} }\); measurements of various multihadron event properties; evidence for differences between quark and gluon jets; the demonstration of the running of αs and the existence of the triple-gluon coupling; and searches for a variety of new particles. This report describes a few selected results from the AMY experiment.
119304627
The evolution of FTK, a real-time tracker for hadron collider experiments
We describe the architecture evolution of the highly-parallel dedicated processor FTK, which is driven by the simulation of LHC events at high luminosity (1034 cm-2 s-1). FTK is able to provide precise on-line track reconstruction for future hadronic collider experiments. The processor, organized in a two-tiered pipelined architecture, execute very fast algorithms based on the use of a large bank of pre-stored patterns of trajectory points (first tier) in combination with full resolution track fitting to refine pattern recognition and to determine off-line quality track parameters. We describe here how the high luminosity simulation results have produced a new organization of the hardware inside the FTK processor core.
18430798
Measuring the top quark mass with m_T2 at the LHC
We investigate the possibility to measure the top quark mass using the collider variable $m_{T2}$ at the LHC experiment. Monte Carlo studies of $m_{T2}$ are performed with the events corresponding to the dilepton decays of $t\bar{t}$ produced at the LHC with 10 $fb^{-1}$ integrated luminosity. Our analysis suggests that the top quark mass can be determined by the $m_{T2}$ variable alone with a good precision at the level of 1 GeV.
67819097
Fast beam-ion instability driven longitudinal damping
In the Pohang Light Source storage ring, we empty 68 buckets of total 468 buckets to cure the conventional ion trapping. However, the fast beam-ion instability is occasionally generated at higher beam current. Immediately after the strong vertical beam shaking due to the fast beam-ion instability, the longitudinal coupled bunch mode instabilities are substantially damped down without any active feedback system. We have described the fast beam-ion instability driven longitudinal damping and its mechanism in the Pohang Light Source storage ring.
119082127
Wigner's Photons
If Einstein's photon is $E = cp = \hbar\omega$, Wigner's photon is its helicity which is a Lorentz-invariant concept coming from the E(2)-like little group for massless particles. In addition, the E(2)-like little group has two translation-like degrees of freedom. What happens to them? They are associated with the gauge degree of freedom. Since the physics of polarized light waves can be formulated within the framework of the Lorentz group, it is now possible to use polarization experiments to study the E(2)-like little group in terms of quantities that can be measured in laboratories.
119339738
Photon spin as a rotation in gauge space
It is shown that the photon spin is associated with the rotational invariance in a two-dimensional space spanned by the two ''translation'' parameters of the E(2)-like little group of the Poincare group. Since the translation in the E(2)-like space is a gauge transformation, the photon spin can be associated with an orbitlike rotation with nonzero radius in the gauge space.
56300970
Representations of the Poincaré group for relativistic extended hadrons
Representations of the Poincare group are constructed from the relativistic harmonic oscillator wave functions which have been effective in describing the physics of internal quark motions in the relativistic quark model. These wave functions are solutions of the Lorentz‐invariant harmonic oscillator differential equation in the ’’cylindrical’’ coordinate system moving with the hadronic velocity in which the time‐separation variable is treated separately. This result enables us to assert that the hadronic mass spectrum is generated by the internal quark level excitation, and that the hadronic spin is due to the internal orbital angular momentum. An addendum relegated to PAPS contains discussions of detailed calculational aspects of the Lorentz transformation, and of solutions of the oscillator equation which are diagonal in the Casimir operators of the homogeneous Lorentz group. It is shown there that the representation of the homogeneous Lorentz group consists of solutions of the oscillator partial diffe...