HERA e-p scattering events observed in the H1Detector

1. HERA e-p scattering events observed in the H1Detector Joachim Meyer DESY 2005

2. The idea The realisation The Physics The events Joachim Meyer DESY 2005

3. What we think what happens, when we scatter electrons on protons at HERA Hadrons W Proton Hadrons or neutrino Joachim Meyer DESY 2005

4. The H1 detector at the e-p storage ring HERA p Tracking chambers Calorimeters Instrumented iron system Forward muon detector e Joachim Meyer DESY 2005

5. Calorimeter Joachim Meyer DESY 2005

6. Principle of particle identification Joachim Meyer DESY 2005

7. Principle of particle identification Joachim Meyer DESY 2005

8. An event display : What do we see ? R-Z view : Hadrons Hadronic calorimeter Hits and reconstructed tracks in tracker e p e-p interaction point Electromagnetic calorimeter e Energy depositions in calorimeter Scattered Electron Joachim Meyer DESY 2005

9. Same event in radial view : Hadronic calorimeter X Hits and reconstructed tracks in tracker e Energydepositions in calorimeter Joachim Meyer DESY 2005

10. The hits (fired wires) in the tracking chambers Hits = Signals recorded on sense wires Gas volumen with sense wires at HV Joachim Meyer DESY 2005

11. ..and the result of the pattern recognition program trying to combine the hits to tracks (red lines) : Hadrons Tracks bend in magnetic field : momentum determination Electron Central tracking chambers Joachim Meyer DESY 2005

12. .. and the same procedure in R-Z view : Hadrons Electron Central tracking chambers Joachim Meyer DESY 2005

13. another event : Here you see the CJC hits including the ‘mirror hits’ (ambiguity not resolved) Curling tracks Mirror tracks track Joachim Meyer DESY 2005

14. and here the tracks found by the pattern regognition program successfully fitted to the event vertex Note : The curling tracks seen on the last picture are not vertex-fitted Joachim Meyer DESY 2005

15. Event : Combined view (R-z, R-Phi , calorimeter energies) Transverse view (R-Phi) e e X Calorimeter energies X Side view (R-z) Electron and hadronic system X balanced in transverse momentum Joachim Meyer DESY 2005

16. A very simple event : Photon Proton leaves unseen down the beam pipe Electron Joachim Meyer DESY 2005

17. Here an electron and two photons are recorded Electrons ‘easily’ radiate photons Joachim Meyer DESY 2005

18. Photons tend to convert to e+ e- pairs in material Photon e Photon X e+ e- Pair e Chamber material Photon Joachim Meyer DESY 2005

19. This looks like a di-electron, but is not. A photon converted to a small angle e+ e- pair within the beam pipe e e Conversion point Joachim Meyer DESY 2005

20. Another ‘simple’ event : A elastic dimuon production MUON IRON Muons penetrate thick materials ! MUON Joachim Meyer DESY 2005

21. An inelastic dimuon production without visible scattered electron X X Joachim Meyer DESY 2005

22. Another inelastic dimuon production without visible scattered electron The muons are low energetic and don’t read the iron,they are ‘mips’ in calorimeter X X Joachim Meyer DESY 2005

23. Another inelastic dimuon production without visible scattered electron One muon identified in calorimeter, the other in the iron system X X Joachim Meyer DESY 2005

24. In the ‘forward direction’ muons are measured by the ‘Forward Toroid Muon Detector’ Forward Toroid Muon Detector Joachim Meyer DESY 2005

25. Here it is very visible how electron, muon and photon are distinguished e e Joachim Meyer DESY 2005

26. No detector is perfect : Here the scattered electron enters a nonsensitive region (Phi-crack) of the electromagnetic calorimeter Such an effect has to be recognized in the physics analysis ! e e Electron penetrates into hadronic part of calorimeter Phi-crack in em. calorimeter Joachim Meyer DESY 2005

27. Here a photon converts and the e+ e- pair enters an insensitive region of the em. calorimeter (z- and Phi-cracks) Phi-crack e e z-crack Converted photon Joachim Meyer DESY 2005

28. Muons also come from the sky …… This is BACKGROUND, which we do not like ! Joachim Meyer DESY 2005

29. Interaction of cosmic primaries create showers in the atmosphere, and multimuons reach us here Joachim Meyer DESY 2005

30. Cosmic dimuon seen in calorimeter and central track detector Joachim Meyer DESY 2005

31. Another cosmic dimuon … wires in iron system pads in iron system Muon radiates Joachim Meyer DESY 2005

32. …and it can be even more fierce …. Joachim Meyer DESY 2005

33. Muons interact rarely, but they do Hit pattern in the central track detector (transverse view) Joachim Meyer DESY 2005

34. Here a cosmic muon radiates a photon which gets absorbed in the calorimeter. The muon then exits the detector. The radiated energy deposition Joachim Meyer DESY 2005

35. A HERA ep event overlayed with a cosmic muon Such an effect has to be recognized in the physics analysis ! ep event Cosmic muon Joachim Meyer DESY 2005

36. There is not only background from cosmics but also from the Proton beam interacting with the restgas P - beam Event vertex is here e-p event vertex should be here Joachim Meyer DESY 2005

37. Scattering of the HERA-proton on a nucleus of the restgas. The nucleus dissociates into lots of protons (positive tracks) and neutrons Joachim Meyer DESY 2005

38. Another kind of beam-related background : Protons lost in the ring create showers and muons from decaying pions accompany the beam and may be visible in the detector Beamhalo muons Joachim Meyer DESY 2005

39. Here a NC event is overlayed by a beam halo muon Such an effect has to be recognized in the physics analysis ! Joachim Meyer DESY 2005

40. Back to HERA -e-p scattering events : A very forward Dimuon event These muons are decay products of the famous J/Psi particle Muons bent in the magnetic field of the forward toroid magnet Joachim Meyer DESY 2005

41. Another event where the J/Psi particle decays into two muons (this time ‘backward’) Muon Iron Muon Joachim Meyer DESY 2005

42. The particle has a sister the Central Tracker e Backward calorimeter e Joachim Meyer DESY 2005

43. Most events are much more complicated : Very high track multiplicity Small visible energy in calorimeter Joachim Meyer DESY 2005

44. The Central Silicon Detector (CST) measures hits very precisely (10 micrometer). search for secondary vertices of heavy quark (charm,bottom) decays : Zoom in …. H1 Central Tracker Secondary Vertex CST CST Reconstruction Joachim Meyer DESY 2005

45. Another event with detailed track measurement in the CST CST : R-z view CST : R-Phi view Joachim Meyer DESY 2005

46. Tracks seen in the Forward Silicon Track Detector (FST) FST Forward Direction CST CJC 1 CJC 2 The FST allows to cover very small forward angles Joachim Meyer DESY 2005

47. Often there is activity in forward direction around the beam pipe : that are the ‘left overs’ of the ‘broken’ proton Electron scattered under small angle into backward calorimeter Joachim Meyer DESY 2005

48. But in 10% of all cases there is no forward activity : the proton stays intact, and disappears down the beam pipe e-tagger p e e-tagger Joachim Meyer DESY 2005

49. Back to the Deep-Inelastic-Electron-Proton-Scattering (DIS) X X e Incident e 27 GeV e Scattered e The electron is scattered back by 160 degree and got an energy of 300 GeV. Very virulent scattering ! Joachim Meyer DESY 2005

50. .and here its even more virulent. , this corresponds to a space resolution of The squared momentum transfer is e Notice : The hadronic system X is a well collimated bundle of particles. This is called JET e Jet Jets are the ‘footprints’ of the quarks and gluons Jet Joachim Meyer DESY 2005