Big bang nucleosynthesis with a new neutron lifetime

Abstract

We show that the predicted primordial helium production is significantly reduced when new measurements of the neutron lifetime and the implied enhancement in the weak reaction rates are included in big-bang nucleosynthesis. Therefore, even if a narrow uncertainty in the observed helium abundance is adopted, this brings the constraint on the baryon-to-photon ratio from BBN and the observed helium into better accord with the independent determination of the baryon content deduced from the WMAP spectrum of power fluctuations in the cosmic microwave background, and measurements of primordial deuterium in narrow-line quasar absorption systems at high redshift.

Cosmological constraints on Newton’s constant

“…Increasing Newton's constant enhances the universal expansion rate, and then leads to larger helium and deuterium abundances produced at BBN epoch. We have re-examined this effect including the latest experimental data on the neutron lifetime [15,27]. We found that the experimental value G N (ξ = 1) is now quite consistent with the observed abundances of primordial light elements, and the variation of Newton's constant is tightly constrained to 0.95 < ∼ ξ < ∼ 1.01.…”

Experimental limits on neutron disappearance into another braneworld

“…Constraint from the primordial nucleosynthesis [40] cannot be obtained since the value of a primordial cosmological magnetic vector potential cannot be assessed at present. In addition, constraint from disappearance of bound neutrons in nuclei [41] would need for a rigorous expression of the swapping probability in this case.…”

“…[39]). As a result, ultracold neutron experiments appear as a relevant approach to constrain g (Some other possibilities are not considered for obvious reasons 5 [40,41]). …”

Spin flip loss in magnetic confinement of ultracold neutrons for neutron lifetime experiments

“…(10) holds over the entire remainder, typically 0.01 − 0.1 s, of the motion to the next TP where p(t) is "measured". Equation (10) shows that the result depends only on the local field variables Ω(t) and ω L (t). It does not depend on the path history; from (9), only the phase −iΘ/2 of β(t) does.…”

“…At present, we are confronted by an apparent discrepancy of about three standard deviations between the average τ n from ultracold neutron (UCN) storage experiments and the τ n from cold neutron beam experiments as outlined in the next paragraph. It is the leading source of uncertainty in predictions of the primordial abundance of 4 He [8][9][10].…”