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.
Monte Carlo simulations of magnetovolume instabilities in anti-Invar systems
We perform constant pressure Monte Carlo simulations of a spin-analogous model which describes coupled spatial and magnetic degrees of freedom on an fcc lattice. Our calculations qualitatively reproduce magnetovolume effects observed in some rare earth manganese compounds, especially in the anti-Invar material YMn2. These are a sudden collapse of the magnetic moment which is connected with a huge volume change, and a largely enhanced thermal expansion coefficient.