122313966
Chiral SU(2) X SU(2) symmetry in the $pi$K scattering
121196804
CERN beam test of silicon-tungsten calorimeter test module
PIN diode silicon sensors with low leakage current were developed as 4×4 pixel arrays from 5 inch wafers. A test module of silicon-tungsten calorimeter was designed, built using the sensors, and tested with high energy beam of electron, muon, and hadrons for the study of its application at the future linear collider. The construction of the test module and the results of the beam test are discussed.
120126738
Multiparticle Production in the Central Region
The mechanism of multiparticle production in the central region is discussed in the framework of the independent-emission picture and in that of the fragmentation picture. It is argued that the study of a certain moment ratio and distribution ratio may be helpful to differentiate these two pictures. The intersecting-storage-rings multi-$\ensuremath{\gamma}$ experiment of the Brookhaven-Roma Collaboration is discussed in this connection. In order to illustrate some general features of the fragmentation picture, the model recently proposed by Chou and Yang for charge transfer is applied to the multi-$\ensuremath{\gamma}$ production process.
35417982
Dominant two-step process in nuclear fragmentation at high energies.
Definitive measurements of negative {l angle}{ital p}{sub {ital L}}{r angle} in the projectile rest frame are carried out for isotopes produced by fragmentation of relativistic {sup 16}O and {sup 12}C nucleus projectiles. They are analyzed for the evidence of the dominant two-step diffractive excitation processes during the fragmentation. Average energies in the range of 100 MeV or less are explored and the decays of the excited states with lifetimes longer than 10{sup {minus}21} s are investigated.
119301594
Attractor scenarios and superluminal signals in k-essence cosmology
Cosmological scenarios with k-essence are invoked in order to explain the observed late-time acceleration of the Universe. These scenarios avoid the need for fine-tuned initial conditions (the 'coincidence problem') because of the attractorlike dynamics of the k-essence field {phi}. It was recently shown that all k-essence scenarios with Lagrangians p=L(X){phi}{sup -2}, where X{identical_to}(1/2){phi}{sub ,{mu}}{phi}{sup ,{mu}}, necessarily involve an epoch where perturbations of {phi} propagate faster than light (the 'no-go theorem'). We carry out a comprehensive study of attractorlike cosmological solutions ('trackers') involving a k-essence scalar field {phi} and another matter component. The result of this study is a complete classification of k-essence Lagrangians that admit asymptotically stable tracking solutions, among all Lagrangians of the form p=K({phi})L(X). Using this classification, we select the class of models that describe the late-time acceleration and avoid the coincidence problem through the tracking mechanism. An analogous 'no-go theorem' still holds for this class of models, indicating the existence of a superluminal epoch. In the context of k-essence cosmology, the superluminal epoch does not lead to causality violations. We discuss the implications of superluminal signal propagation for possible causality violations in Lorentz-invariant field theories.
18213590
Dark matter in supersymmetric models with axino LSP in Randall-Sundrum II brane model
The axino dark matter hypothesis in RSII brane model is studied. Within the framework of CMSSM we assume that the lightest neutralino or stau is the NLSP, and that the axino production has a single contribution from the NLSP decay. It is found that the axino can play the role of dark matter in the universe and we determine what the axino mass should be for different values of the five-dimensional Planck mass. An upper bound is obtained for the latter.