56232513
Search for physics beyond the standard model via a polarization-asymmetry correlation experiment on In-107
We report on a new precision measurement of the longitudinal polarization of positrons emitted by polarized 107In nuclei. Preliminary results yield a lower limit of 303 GeV/c2 for the mass of a possible, predominantly right-handed, W gauge boson, if interpreted in the framework of the manifest, left-right symmetric model. In more general left-right symmetric models our result is complementary to those from muon decay experiments and to results from searches for a similar particle in collider experiments. Our data also provide new results on possible tensor contributions to the weak interaction.
56232513
Search for physics beyond the standard model via a polarization-asymmetry correlation experiment on In-107
We report on a new precision measurement of the longitudinal polarization of positrons emitted by polarized 107In nuclei. Preliminary results yield a lower limit of 303 GeV/c2 for the mass of a possible, predominantly right-handed, W gauge boson, if interpreted in the framework of the manifest, left-right symmetric model. In more general left-right symmetric models our result is complementary to those from muon decay experiments and to results from searches for a similar particle in collider experiments. Our data also provide new results on possible tensor contributions to the weak interaction.
32448171
Limits on right-handed charged weak currents from a polarization-asymmetry correlation experiment with 107In.
A new technique, based on relative measurements of the longitudinal polarization ([ital P]) of positrons emitted in two opoosite directions with respect to the nuclear polarization ([ital R]=[ital P][sup [minus]]/[ital P][sup +]), is used to provide constraints on extensions of the standard model ([ital R][sub 0]). The first result, i.e., [ital R]/[ital R][sub 0]=0.926[plus minus]0.041, was obtained with [sup 107]In. Interpreted in the framework of left-right symmetric models and assuming no mixing, it provides a 90% C.L. lower limit of 225 GeV/[ital c][sup 2] for the mass of a possible right-handed charged [ital W] gauge boson, reducing the mass range allowed by other semileptonic experiments.
118642962
Black brane viscosity and the Gregory-Laflamme instability
We study long wavelength perturbations of neutral black p-branes in asymptotically flat space and show that, as anticipated in the blackfold approach, solutions of the relativistic hydrodynamic equations for an effective p + 1-dimensional fluid yield solutions to the vacuum Einstein equations in a derivative expansion. Going beyond the perfect fluid approximation, we compute the effective shear and bulk viscosities of the black brane. The values we obtain saturate generic bounds. Sound waves in the effective fluid are unstable, and have been previously related to the Gregory-Laflamme instability of black p-branes. By including the damping effect of the viscosity in the unstable sound waves, we obtain a remarkably good and simple approximation to the dispersion relation of the Gregory-Laflamme modes, whose accuracy increases with the number of transverse dimensions. We propose an exact limiting form as the number of dimensions tends to infinity.