  The LaBr3:Ce scintillator has been widely studied for nuclear spectroscopy
because of its optimal energy resolution (<3%@ 662 keV) and time resolution
(~300 ps). Despite these promising properties, the intrinsic radiation
background of LaBr3:Ce is a critical issue, and pulse shape discrimination
(PSD) has been shown to be an efficient potential method to suppress the alpha
background from the 227Ac. In this paper, the charge comparison method (CCM)
for alpha and gamma discrimination in LaBr3:Ce is quantitatively analysed and
compared with two other typical PSD methods using digital pulse processing. The
algorithm parameters and discrimination efficiency are calculated for each
method. Moreover, for the CCM, the correlation between the CCM feature value
distribution and the total charge (energy) is studied, and a fitting equation
for the correlation is inferred and experimentally verified. Using the
equations, an energy-dependent threshold can be chosen to optimize the
discrimination efficiency. Additionally, the experimental results show a
potential application in low-activity high-energy {\gamma} measurement by
suppressing the alpha background.
