Search for exotic mesons at SLAC
The theoretical justification and results from recent experimental searches for backward-produced exotic mesons including two experiments carried out by the collaboration at SLAC are reviewed. The first experiment put upper limits of about 1 to 2 $mu$b for X$sup ++$ $Yields$ (2$pi$, 4$pi$, 6$pi$)$sup ++$ and anti pp$pi$$sup +$$pi$$sup +$ in the reaction $pi$$sup +$ + p $Yields$ X$sup ++$ + n/sub forward/ at 8.4 GeV/c studied with the SLAC 14 inch rapid cycling bubble chamber triggered by a downstream neutron detector. Also the important features of the recently completed second experiment with the SLAC streamer chamber to study the reaction $pi$$sup -$ + p $Yields$ X$sup --$ + p/sub forward/ at 14 GeV/c are discussed. (auth)
Search for exotics produced opposite a forward Λ in 15 GeV/c π+p interactions
We have carried out a search for exotic meson resonances produced in the reaction π+p→K++ + Λ (forward) at 15 GeV/c. We have found no evidence for the existence of resonance-like states in the K++ system, and have obtained 95% confidence level upper limits of 1.7 μb on their production with masses <2.8 GeV, and 2.6 μb with masses between 2.8 GeV and 4 GeV.
New Low-Profile Applicators for Local Heating of Tissues
A new type of low-profile applicator is described giving efficient power transfer to tissue with low leakage. It consists of a resonant element spaced from a ground plane by low-loss material having high relative permittivity and some relative permeability. This combination is covered by similar material which can be placed in direct contact with the tissue to be heated, or separated from it by a water bolus as required. Laboratory measurements using phantom materials show that these applicators are well matched and produce well defined and relatively uniform heating profiles. Applicators having maximum dimensions of 3-15 cm covering the frequency range 1000-100 MHz, respectively, are described. Penetration depths of at least 4 cm at 100-200 MHz are achieved. Tests on anesthetised pigs and some clinical assessment have confirmed the usefulness of this compact low-frequency type of applicator and have shown that performance compares favorably with that of other recently reported types. The design can be optimized for treatment of specific sites, and suitable choice of dimensions and electrical characteristics of the layer material allow the low-profile concept to be extended over a wide range of operating frequencies.