Extending the Li&Ma method to include PSF information

• A likelihood ratio method for IACT observations of point sources is proposed.
• The method incorporates PSF information and combines ON and OFF observations.
• Toy Monte Carlo samples are used to test several aspects of the technique.
• The method is robust and performs better than counting prescriptions.

The so called Li&Ma formula is still the most frequently used method for estimating the significance of observations carried out by Imaging Atmospheric Cherenkov Telescopes. In this work a straightforward extension of the method for point sources that profits from the good imaging capabilities of current instruments is proposed. It is based on a likelihood ratio under the assumption of a well-known PSF and a smooth background. Its performance is tested with Monte Carlo simulations based on real observations and its sensitivity is compared to standard methods which do not incorporate PSF information. The gain of significance that can be attributed to the inclusion of the PSF is around 10% and can be boosted if a background model is assumed or a finer binning is used.

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