Relativistic effects in the search for new intra-atomic force with isotope shifts

Isotope shift of atomic spectra is considered as a probe of new interaction between electrons and neutrons in atoms. We employ the method of seeking a breakdown of King’s linearity in the isotope shifts of two atomic transitions. In the present work, we evaluate the magnitudes of the nonlinearity using relativistic wave functions and the result is compared with that of nonrelativistic wave functions from our previous work. It turns out that the nonrelativistic calculation underestimates the nonlinearity owing to the new interaction in the mass range of the mediator greater than 1 MeV. Further, we find that the nonlinearity within the standard model of particle physics is significantly magnified by the relativistic effect in the $\text{p}_{1/2}$ state. To get rid of this obstacle in the new physics search, we suggest avoiding $\text{p}_{1/2}$ and that e.g. $\text{p}_{3/2}$ should be used instead.

NEW LIMITS ON TOP SQUARK NLSP FROM ATLAS 4.7 fb-1 DATA

Using the ATLAS 4.7 fb-1 data on new physics search in the jets + [Formula: see text] channel, we obtain new limits on the lighter top squark [Formula: see text] considering all its decay modes assuming that it is the next to lightest supersymmetric particle (NLSP). If the decay [Formula: see text] dominates and the production of dark matter relic density is due to NLSP–lightest supersymmetric particle (LSP) co-annihilation then the lower limit on [Formula: see text] is 240 GeV. The limit changes to 200 GeV if the decay [Formula: see text] dominates. Combining these results it follows that [Formula: see text] NLSP induced baryogenesis is now constrained more tightly.