The discovery of astrophysical neutrino signal by IceCube neutrino telescope has extended the energy frontier of astronomy into Peta-electronvolt energy range. The nature of astronomical sources operating powerful particle accelerators and producing the highest energy neutrinos is currently uncertain. A breakthrough toward understanding of the nature of these sources can be achieved via detection of the gamma-ray counterpart of the astrophysical neutrino signal. The subject of the Master and Thesis work is the search of such counterpart using new observation facility: Large High-Altitude Air Shower Observatory (LHAASO), situated at 4410 m altitude in Sichuan province in China. LHAASO enters its scientific operations phase now and is expected to yield breakthrough discoveries revolutionising our understanding of high-energy Universe over the next several years. The Master and Thesis work will be focused on development of methods of gamma-ray and cosmic ray data analysis, modelling and interpretation aimed at detection of the diffuse emission and/or isolated source gamma-ray counterparts of the astrophysical neutrino signal and ultimately at understanding of the mechanisms of operation of sources producing cosmic rays.