The project of ultracold neutron sources at the PIK reactor with superfluid helium as a moderator

Primordial Nucleosyntheis: theory vs observations

“…The 4 He(αα, γ) 12 C reaction is very sensitive to the position of the "Hoyle state". The corresponding resonance width is very small (a few ∼eV) as compared with the competing reaction 12 C(α, γ) 16 O, dominated by broad (∼100 keV) resonances and subthreshold levels. In Fig.…”

“…They are calculated with, as only experimental input, the neutron lifetime whose experimental value is still a matter of debate [8]. Until very recently, the averaged value of 885.7±0.8 s was recommended by the Particle Data Group, in spite of a new measurement that lead to a significantly different value of 878.5±0.7±0.3 [16]. Newer experimental results and analyses have not yet been able to solve this discrepancy but have motivated a…”

“…The dashed curves represent previous calculations [29] before the re-evaluation [25] of the 3 He(α, γ) 7 Be rate. The dotted and dot-dashed lines corresponds, respectively, to the alternative value [16] of the neutron lifetime and to 4 effective neutrino families.…”

“…1 in [38]). Figure 7 also displays the effect of using a different value of the neutron lifetime (878.5 s [16] instead of 885.7) or an effective number of neutrino families of 4. In both cases, it shifts the temperature at freezeout ( § 2.2), essentially affecting the 4 He primordial abundance without sufficient impact on 7 Li.…”

The quest for an electric dipole moment of the neutron

“…Until now, this instrument remained the workhorse and benchmark in UCNphysics. All other current and next-generation UCN sources [51][52][53][54][55][56][57] are based on the superthermal concept proposed by Pendlebury and Golub in 1975 [58,59]. The principal idea is to use collective excitations of the conversion medium to down-scatter neutrons from higher energies to the UCN energy regime [60].…”