Annual modulations from secular variations: relaxing DAMA?

Understand

The DAMA collaboration reported an annually modulated rate with a phase compatible with a Dark Matter induced signal.

• We point out that a slowly varying rate can bias or even simulate an annual modulation if data are analyzed in terms of residuals computed by subtracting approximately yearly averages starting from a fixed date, rather than a background continuous in time.
• In the most extreme case, the amplitude and phase of the annual modulation reported by DAMA could be alternatively interpreted as a decennial growth of the rate.
• This possibility appears mildly disfavoured by a detailed study of the available data, but cannot be safely excluded.