New limits on the gravitational Majorana screening from the Zürich G experiment

We analyze the results from an experiment being conducted at the Physik-Institut, Universität Zürich to measure the gravitational constant, and obtain a tight constraint on the Majorana gravitational shielding factor. The limit we obtain is two orders of magnitude lower than the positive results obtained by Majorana in the 1920s and a factor of about 5 better than the constraint obtained by Braginsky in a more modern laboratory experiment. The Zürich experiment is expected in the future to provide a better constraint which is another factor of 10 lower than our present estimate.