The high collision energies reached at the Large Hadron Collider (LHC) at CERN in
proton-proton, proton-lead and, in particular, lead-lead collisions, lead to significant
production rates of fragile objects, i.e. objects whose binding energies are small
compared to the average kinetic energy of the particles produced in the system.
Such objects are, for instance, light (anti-)nuclei and (anti-)hypernuclei.
The most extreme example here is the hypertriton, a bound state of a proton, a
neutron and a lambda, where the separation energy of the lambda is only around 130
keV. These states, from the anti-deuteron up to the anti-alpha nuclei, are
nevertheless created and observed in heavy-ion collisions at the LHC.
Their production yields can even be well described in a statistical-thermal model
approach with only three parameters, namely chemical freeze-out temperature Tch,
volume V and baryo-chemical potential μB. The latter is close to zero at LHC, which
means the ratio of anti-baryons to baryons is close to unity and in continuation also
anti-nuclei and nuclei of the same type are produced in equal amounts. Tch at the
LHC is extracted to be 156 MeV, which is a factor 1000 above the binding energy of
the lambda to the deuteron inside the hypertriton.
In addition, the thermal model can be used to make predictions for the production of
other fragile objects, such as bound states of hyperons and nucleons, or hyperonhyperon
bound states. The data collected at LHC can be used to test the existence of
these bound states.