  ANAIS is a direct dark matter detection experiment aiming at the confirmation
or refutation of the DAMA/LIBRA positive annual modulation signal in the low
energy detection rate, using the same target and technique. ANAIS-112, located
at the Canfranc Underground Laboratory in Spain, is operating an array of
3$\times$3 ultrapure NaI(Tl) crystals with a total mass of 112.5 kg since
August 2017. The trigger rate in the region of interest (1-6 keV) is dominated
by non-bulk scintillation events. In order to discriminate these noise events
from bulk scintillation events, robust filtering protocols have been developed.
Although this filtering procedure works very well above 2 keV, the measured
rate from 1 to 2 keV is about 50% higher than expected according to our
background model, and we cannot discard non-bulk scintillation events as
responsible of that excess. In order to improve the rejection of noise events,
a Boosted Decision Tree has been developed and applied. With this new
PMT-related noise rejection algorithm, the ANAIS-112 background between 1 and 2
keV is reduced by almost 30%, leading to an increase in sensitivity to the
annual modulation signal. The reanalysis of the three years of ANAIS-112 data
with this technique is also presented.
