How do we detect particles HSSIPProject presentation Elias

How do we detect particles? HSSIP-Project presentation: Elias Kunze & Julia Nehlin

Electromagnetic interactions: • radiation of a charged particle due to its deceleration caused by an electric field of another charged particle

Electromagnetic showers: Cascade of secondary particles is produced by interacting with dense matter • E as starting point cascade of positrons & photons • acceleration • e. m. radiation! • More photons more e+ e- pairs! • energy loss of e- dominates number decays exponentially!

Electromagnetic showers: Characterization: • Number of p. • Location • Longitudinal distribution • Transverse distribution • If material has a high atomic number greater nuclear charges greater acceleration! We need material with high atomic number!

How can we analyze particle showers?

Detector construction: • Tracking chamber sensing devices determine particles trajectories • Electromagnetic calorimeters we’ll come back to this one… • Hadronic calorimeter measures total energy of hadrons • Muon chamber muons are detected.

Electromagnetic calorimeters: ECAL measures: • the total energy of electrons, e+, photons total absorption • spatial location of energy deposit • direction • • Showers of e+, e- pairs in the material e- are deflected by electric fields radiate photons Photons make e-/e+ pairs cycle Final number: proportional to energy of first p.

Homogeneous calorimeter: Full volume detectors (sensitive) medium for energy and signal • to cause shower development + detect particles Types: • Liquid scintillators • Lead loaded glass • Dense crystal scintillators: Pb. WO 4 (+others) CMS!

Sampling calorimeter: Liquid-Argon calorimeter (ATLAS) • Layers of steel + liquid argon interspaced • Lead gives shower development • Ionisation gaps of liquid argon • Inductive signal registered by copper electrodes Accordion shaped absorbers and electrodes

Geant 4: • Toolkit to simulate interactions of particles with matter • electromagnetic and nuclear passages • Geometry & Tracking • Physics processes and models • Graphics etc. • Fundamental for understanding detector performance

Geant 4: Applications: • High energy & nuclear physics detectors (ATLAS, CMS, LHCb, HARP “…”) • Accelerators and Shielding • Medicine • Radiotherapy (particle beams) • Simulation & scanners (PET scan) • Space • Satellites • Space-environment

Using Geant 4:

Using Geant 4:

Using Geant 4: • Comparison of material at 100 Me. V for ECAL 100 Me. V e 120 100 % 80 60 40 20 0 2 4 6 8 10 12 14 16 18 Pb. WO 4 Z(cm) Pb 20 W

Using Geant 4: • Comparison of particles at 50 Ge. V % Energieabsorbtion in Pb. WO 4 von Teilchen mit 50 Ge. V 100 90 80 70 60 50 40 30 20 10 0 12 13 14 15 16 17 18 19 20 21 Z(cm) e- gamma

ECAL Comparison: Pb. WO 4 Crystals • Energy can be measured more precisely • Quite compact • Not able to measure and compare initial/final energy • Lead-Tungstate looses property with time less transparent Liquid-Argon/Lead • Liquid-Argon is resistant to radiation • Ability to measure where the majority of a particles energy was submitted • Energy that is submitted in lead must be estimated • Large size, compared to CMS

Thank you!