The effect of a limited acceptance when measuring fragment momentum distributions from halo nuclei

Momentum distributions of breakup fragments from halo nuclei are useful to test models for halo nuclei and to estimate the extent of the halo. When breakup fragments are emitted with a non-Gaussian distribution an incomplete acceptance can influence the shape of the observed distribution. We obtain analytical results for the change in shape of the observed distribution when fragments are emitted with a Gaussian or Lorentzian distribution and detected with an incomplete acceptance. Finally, we develop a method to estimate the influence of an incomplete acceptance when complex distribution shapes are involved.