Constraints for weakly interacting light bosons from existence of massive neutron stars

Theories beyond the standard model include a number of new particles, some of which might be light and weakly coupled to ordinary matter. Such particles affect the equation of state of nuclear matter and can shift admissible masses of neutron stars to higher values. The internal structure of neutron stars is modified provided the ratio between coupling strength and mass squared of a weakly interacting light boson is above g(2)/mu(2) similar to 25 GeV-2. We provide limits on the couplings with the strange sector, which cannot be achieved from laboratory experiments analysis. When the couplings to the first family of quarks is considered, the limits imposed by the neutron stars are not more stringent than the existing laboratory ones. The observations on neutron stars give evidence that the equation of state of the beta-equilibrated nuclear matter is stiffer than expected from many-body theory of nuclei and nuclear matter. A weakly interacting light vector boson coupled predominantly to the second family of the quarks can produce the required stiffening.