New Physics at HERA: Implications for e+e- Scattering at LEP2

The impact of virtual leptoquark or R-parity breaking squark exchange as well as generic contact interactions on the production of quark-antiquark pairs in $e^+e^-$ annihilation, in particular at LEP2, is summarized. An exciting possibility of sneutrino formation in $e^+e^-$ scattering is also mentioned.Comment: 4 pages, LaTeX, 3 figures included, uses aipproc.sty and epsfig; Talk presented at the 5th International Workshop on "Deep Inelastic Scattering and QCD" (DIS '97), Chicago, Illinois, USA, April 14-18, 199

A finite element surface impedance representation for steady-state problems

A procedure for determining the scattered pressure field resulting from a monochromatic harmonic wave that is incident upon a layer energy absorbing structure is treated. The situation where the structure is modeled with finite elements and the surrounding acoustic medium (water or air) is represented with either acoustic finite elements, or some type of boundary integral formulation, is considered. Finite element modeling problems arise when the construction of the structure, at the fluid structure interface, are nonhomogeneous and in particular, when the inhomogeneities are small relative to the acoustic wave length. An approximate procedure is presented for replacing the detailed microscopic representation of the layered surface configuration with an equivalent simple surface impedance finite element, which is especially designed to work only at limited frequencies. An example problem is presented using NASTRAN. However, the procedure is general enough to adapt to practically any finite element code having a steady state option

Lepton flavor violation in supersymmetric B-L extension of the standard model

Supersymmetric B-L extension of the Standard Model (SM) is one of the best candidate for physics beyond the SM that accounts for TeV scale seesaw mechanism and provides an attractive solution for the Higgs naturalness problem. We analyze the charged lepton flavor violation (LFV) in this class of models. We show that due to the smallness of Dirac neutrino Yukawa coupling, the decay rates of l_i -> l_j gamma and l_i -> 3 l_j, generated by the renormalization group evolution of soft SUSY breaking terms from GUT to seesaw scale, are quite suppressed. Therefore, this model is free from the stringent LFV constraints usually imposed on the supersymmetric seesaw model. We also demonstrate that the right-sneutrino is a long-lived particle and can be pair produced at the LHC through the B-L gauge boson. Then, they decay into same-sign dilepton, with a total cross section of order O(1) pb. This signal is one of the striking signatures of supersymmetric B-L extension of the SM.Comment: 17 page

Solution sensitivity and accuracy study of NASTRAN for large dynamic problems involving structural damping

Large dynamic problems involving NASTRAN SOLUTION 8 (i.e., the steady state dynamic response option wherein all response quantities vary as e sub i omega t, where omega is the driving frequency and t is time) are considered. Using a submerged steel plate with a viscoelastic layer layer as the bench mark sample, the solution sensitivity and solution accuracy are checked. The solution sensitivity is examined by running the same finite element model on different computers, different versions of NASTRAN, and different precision levels. The solution accuracy is evaluated for these same runs by comparing the NASTRAN results with the exact solution of the same problem

Steady state solutions to dynamically loaded periodic structures

The general problem of solving for the steady state (time domain) dynamic response (i.e., NASTRAN rigid format-8) of a general elastic periodic structure subject to a phase difference loading of the type encountered in traveling wave propagation problems was studied. Two types of structural configurations were considered; in the first type, the structure has a repeating pattern over a span that is long enough to be considered, for all practical purposes, as infinite; in the second type, the structure has structural rotational symmetry in the circumferential direction. The theory and a corresponding set of DMAP instructions which permits the NASTRAN user to automatically alter the rigid format-8 sequence to solve the intended class of problems are presented. Final results are recovered as with any ordinary rigid format-8 solution, except that the results are only printed for the typical periodic segment of the structure. A simple demonstration problem having a known exact solution is used to illustrate the implementation of the procedure

A summary of NASTRAN fluid/structure interaction capabilities

A summary of fluid/structure interaction capabilities for the NASTRAN computer program is presented. Indirect applications of the program towards solving this class of problem were concentrated on. For completeness and comparitive purposes, direct usage of NASTRAN is briefly discussed. The solution technology addresses both steady state and transient dynamic response problems