Add hypertriton, correct ion masses, rename ions
This MR introduces three changes to the ParticleTable:
- Correct the triton, He3 and alpha masses to the latest CODATA values, to follow the corresponding Run2 MR (!123)
- Add a new particle, hypertriton, and it's antiparticle.
- Remove "[0.0]" from the ion names
These changes were introduced for the 2024 data taking for the following reasons: New HLT2 trigger lines to select decays of hypertriton into He3 and a pion will be added. In principle a different particle could be used as a placeholder for hypertriton, but adding it directly seems cleaner. As hypertriton mass, the value from the most precise single measurement (M. Juric (1973), based on emulsion) is taken. For the lifetime, the Lambda0 value is used, as hypertriton is a bound state of a Lambda0, proton and neutron and it's measured lifetime is in agreement with the free Lambda0 lifetime [ref].
There reason for removing "[0.0]" in the ion names is that the decay descriptor of decays into helium (e.g. [hypertriton -> He3[0.0] pi-]cc
) could not be interpreted due to the extra brackets. While there are probably other ways to address this problem directly in the decay descriptor interpreter, renaming the ions seemed to be the simplest solution to me?
(Changed the branch name from hjage_add_ions
to upgrade/hjage_add_ions
)