Effect of quark-mass variation on big bang nucleosynthesis

We calculate the effect of variation in the light-current quark mass, $m_q$, on standard big bang nucleosynthesis. A change in $m_q$ at during the era of nucleosynthesis affects nuclear reaction rates, and hence primordial abundances, via changes the binding energies of light nuclei. It is found that a relative variation of $\delta m_q/m_q = 0.016 \pm 0.005$ provides better agreement between observed primordial abundances and those predicted by theory. This is largely due to resolution of the existing discrepancies for 7Li. However this method ignores possible changes in the position of resonances in nuclear reactions. The predicted 7Li abundance has a strong dependence on the cross-section of the resonant reactions 3He(d,p)4He and t(d,n)4He. We show that changes in $m_q$ at the time of BBN could shift the position of these resonances away from the Gamow window and lead to an increased production of 7Li, exacerbating the lithium problem

Isotope shift factors for the Cd+ 5s 2S1/2→5p 2P3/2 transition and determination of Cd nuclear charge radii

The accuracy of atomic isotope shift factors limits the extraction of nuclear charge radii from isotope shift measurements because determining these factors is experimentally and theoretically challenging. Here, the isotope shift of the Cd+5s2S1/2→5p2P3/2 transition is measured precisely using laser-induced fluorescence from a sympathetically cooled large Cd+ ion crystal. A King-plot analysis is performed based on the new measurement to obtain accurate atomic field shift F and mass shift K factors that have been cross-checked by state-of-the-art configuration interaction plus many-body perturbation theory. The nuclear charge radii (Rch) of Cd100-130 extracted using these F and K values demonstrate a near fivefold precision increase in the neutron-rich region. This work proves that accurate extraction of Rch from isotope shifts is possible. New Rch values reveal hidden discrepancies with previous density functional predictions in the neutron-rich region and pose strong challenges to advancements in nuclear models.SCOPUS: ar.jinfo:eu-repo/semantics/publishe