# V-shaped Cherenkov images of magnetically-separated gamma-rays

## TL;DR

This paper investigates V-shaped Cherenkov images caused by magnetically-separated gamma-ray events, proposing a new geometrical energy estimation method and analyzing its potential to improve CTA measurements.

## Contribution

It introduces a novel geometrical method for energy estimation of V-shaped Cherenkov images and evaluates its effectiveness alongside classical methods.

## Key findings

- V-shaped images result from geomagnetic deflection of early particle pairs
- The new geometrical method provides an independent energy estimate
- Combining methods can help validate systematic uncertainties

## Abstract

Cherenkov Telescope Array (CTA) is an upcoming instrument that will start a new generation of atmospheric Cherenkov telescopes. CTA is expected not only to provide an unprecedented sensitivity in the tens of GeV to hundreds of TeV range, but also to considerably improve the systematic uncertainties of the measurements. We study the images registered by Cherenkov telescopes from low energy gamma rays with its first interaction in the upper parts of the atmosphere. The images show a characteristic separation due to the deflection of the first e- e+ pair in the Geomagnetic Field. We evaluate the performance of the standard stereoscopic analysis for such events. We derive also a novel method for energy estimation of V-shaped events based purely on geometrical properties of the image. We investigate the potential of combining the classical energy estimation and the novel method for independent validation of the systematic shifts in the energy scale of Cherenkov telescopes and discuss the limitations of such analysis.