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Update on CTA-LST activities in Poland

J. Sitarek, K. Adamczyk, P. Gliwny, D. Sobczyńska, M. Szanecki

20.05.2019, Astroparticle physics in Poland, Warsaw

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LST in CTA● The biggest type of

telescopes in CTA – 23m diameter

● Designed for optimal performance in the energy range of tens of GeV

● 2 x 4 telescopes planned for both CTA sites

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LST sub-consortium

Slide by J. Cortina

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LST status● LST1 prototype construction

finished in La Palma site● First light shower images

obtained in December 2018● Ongoing commissioning in the

next months, testing and optimization of operation parameters

● Next steps: – validation if the prototype can

become a part of the CTA– Construction of the LST2-4 in La

Palma

https://www.cta-observatory.org/lst-prototype-records-its-first-light/

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Polish participation in LST● Development of analysis procedures

for LST readout system based on DRS4 chip: PG, JS

● Development of low-energy focused analysis methods for Cherenkov telescopes using MC simulations: JS, DS, KA, MSz

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Single Electromagnetic Subshowers

● We investigated the images of showers in which nearly all the Cherenkov photons come from a single subcascade (SES)

● Those events behave like gamma-ray showers

p

p0

p+ p-

g g

p0 1

Sub-casc2

Sub-casc3

Sub-casc4

Sub-casc1

p-

muon

JS et al. APh, 97, 1

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LST residual background

● At the energies of a few tens of GeV SES events will constitute the main background of LST

● Very limited rejection of SES events (via estimation of the shower maximum position) is possible

JS et al. APh, 97, 1

Before gamma/hadron separationBefore gamma/hadron separation

After gamma/hadron separation

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Rejection of SES events via height of the first interaction

● We derived a simple geometrical method for reconstruction of the height of the first interaction

● The method can be used for rejection of SES events (and other types of hadronic background)

g

e+e-

g

e+e-

p

Deeper in the atmosphere Hadronic

interaction

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H1st

parameter for sensitivity

● The resolution of the height of the first interaction estimation is poor (about 1 X0), but it still allows a mild gain (~10-20%) in the LST sensitivity at the lowest energies (30-200GeV)

JS et al. APh, 103, 108

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Conclusions

● The first LST finished construction and it is being commissioned now

● Stay tuned for more results