[HN Gopher] Physicists make most precise measurement ever of neu... ___________________________________________________________________ Physicists make most precise measurement ever of neutron's lifetime Author : mkoc Score : 24 points Date : 2021-10-18 21:17 UTC (1 hours ago) (HTM) web link (www.nature.com) (TXT) w3m dump (www.nature.com) | thriftwy wrote: | Stupid question, do they account for speed dilation on the beam | experiment? The difference in lifetime will translate to 50k km/s | speed of neutrons or roughly 1/6c | perihelions wrote: | From skimming the review paper from OP (the "source:" in the | caption on that error-bar chart), the neutrons in the beam | experiments are thermalized, to a mean velocity of ~2,200 m/s. | So, slower than 1e-5 c. | | https://doi.org/10.3390/atoms6040070 | | (Thermal meaning the neutrons scatter lots of times against | atoms in a solid material, until they reach thermal | equilibrium. ~km/s is a typical Boltzmann velocity for atom- | size things at room temperature). | | (Not a domain expert). | davidhyde wrote: | > Neutrons in beams seem to live longer on average | | Isn't this due to relativistic effects? What percentage of the | speed of light are these beams? | fsh wrote: | Neutron lifetime experiments are done with cold beams (tens of | K). Time dilation is completely negligible. | [deleted] | [deleted] | liquidise wrote: | > [isolated neutrons] decay into protons. During the process, | each decaying neutron emits an electron and an antineutrino. | | > ...detected sparks of light each time a neutron decayed. | | Detecting a spark of light would also require photon(s) to be | emitted, right? Is this not called out because it is a byproduct | of the decay and not part of the decay reaction itself? | sharikous wrote: | No, they don't measure decays. | | They let the neutrons decay for a while and then measure all | the remaining neutrons in the trap by lowering there a | detector. | | This detector has a scintillator so when a neutron is captured | it emits some photons and those are converted to an electric | signal. | | So no. There is no requirement for the neutron to emit an | additional photon during the decay that is measured | LatteLazy wrote: | Yes, the decay will also release some energy in the form of | photons but they didn't mention it. | sharikous wrote: | That's inaccurate, please see my reply to the same comment | a1369209993 wrote: | Neutron decay does not produce photons. Rather, the energy | difference is carried as kinetic energy by the resulting | proton, electron and (anti)neutrino. This _can_ cause light | to be emitted (very shortly) _later_ when those particles | slam into things, but as sharikous notes that doesn 't seem | to be they're talking about here. | [deleted] ___________________________________________________________________ (page generated 2021-10-18 23:00 UTC)