1. 1 FK7003 Lecture 17 – Interactions in Matter ● Electromagnetic interactions in material ● Hadronic interactions in material ● Electromagnetic and hadronic showers

2. 2 FK7003 Why we can neglect weak interactions 10 3 10 6 10 9 110 3 10 6 E (TeV) Neutrino interaction lengthi In water/km Probability of interaction ~ 10 -5 / km water at 100 TeV energy 100 billion neutrinos pass through your thumbnail each second but only 1-2 will interact in your body during your lifetime. From lecture 3 Mean distance between interactions of neutrino + water molecule as neutrinos pass through water (interaction length).

3. 3 FK7003 Strategy Energy loss of particles in matter  Electromagnetic energy loss ● Energy loss through collisions (ionisation) ● Radiation loss ● Electromagnetic shower  Hadronic energy loss ● Energy loss through nuclear collisions ● Hadronic shower

4. 4 FK7003 Ionisation energy loss M

5. 5 FK7003 M l Semi-classical derivation (skip)

6. 6 FK7003

7. 7 M

8. 8

9. 9

10. 10 FK7003 Interaction between two particles

11. 11 FK7003 Bethe-Bloch formula (17.23)

12. 12 FK7003 Bethe-Bloch formula

13. 13 FK7003 Measurements of ionisation energy loss e

14. 14 FK7003 Strategy Energy loss of particles in matter  Electromagnetic energy loss ● Energy loss through collisions (ionisation) ● Radiation loss ● Electromagnetic shower  Hadronic energy loss ● Energy loss through nuclear collisions ● Hadronic shower

15. 15 FK7003 Radiation energy loss E0E0 x

16. 16 FK7003 Energy loss of an electron in copper ECEC

17. 17 FK7003 Question

18. 18 FK7003 Strategy Energy loss of particles in matter  Electromagnetic energy loss ● Energy loss through collisions (ionisation) ● Radiation loss ● Electromagnetic shower  Hadronic energy loss ● Energy loss through nuclear collisions ● Hadronic shower

19. 19 FK7003 Photons

20. 20 FK7003 Photon absorption in lead Lead

21. 21 FK7003 1997

22. 22 FK7003 2007 (i) (ii)

23. 23 FK7003 Electromagnetic shower E0E0 E 0 /2 E 0 /4 t=No. X 0 No. e + No. e - No.  No. particles 00101 10112 21214 32338

24. 24 FK7003 Electromagnetic shower Observed electromagnetic shower (next lecture)

25. 25 FK7003 Strategy Energy loss of particles in matter  Electromagnetic energy loss ● Energy loss through collisions (ionisation) ● Radiation loss ● Electromagnetic shower  Hadronic energy loss ● Energy loss through nuclear collisions ● Hadronic shower

26. 26 FK7003 Hadronic energy loss p xx 

27. 27 FK7003 Nuclear shower EM Cascade Nuclear cascade

28. 28 FK7003 A simple model for hadronic scattering in material p   p L 1 2 3 xx

29. 29 FK7003 p   L Interaction Length xx 1 23 p

30. 30 FK7003 Proton-nucleon cross sections p p

31. 31 FK7003 Nuclear interaction length

32. 32 FK7003 Stopping in iron

33. 33 FK7003 Strategy Energy loss of particles in matter  Electromagnetic energy loss ● Energy loss through collisions (ionisation) ● Radiation loss ● Electromagnetic shower  Hadronic energy loss ● Energy loss through nuclear collisions ● Hadronic shower

34. 34 FK7003 Energy loss mechanisms Important energy loss mechanisms for collider experiments (next lecture). ParticleIonisation energy loss Radiation energy loss Hadronic energy loss e + e - pair production e-e- Important only for low energies (<30 MeV) † xx  Important only at high energies (E >several hundred GeV ) † xx Charged hadrons (p,    K  …) Important only at high energies (E > several hundred GeV:    K - ; E> 1 TeV: p ) † x Neutral hadrons (n,K 0 ) xx x Photon xxx † Not important for these lectures

35. 35 FK7003 Summary ● Interactions of particle in material ● Electromagnetic and hadronic energy loss  Ionisation and radiation energy loss (em)  Hadronic energy loss (strong) ● Now ready to design an detector for a collider experiment (next lecture).