HERA e-p scattering events observed in the H1Detector. H1 Events Joachim Meyer DESY

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1 HERA e-p scattering events observed in the H1Detector H1 Events Joachim Meyer DESY

2 The idea The realisation The Physics The events H1 Events Joachim Meyer DESY

3 What we think what happens, when we scatter electrons on protons at HERA Hadrons W Proton Hadrons or neutrino H1 Events Joachim Meyer DESY

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

5 Calorimeter H1 Events Joachim Meyer DESY

6 Principle of particle identification H1 Events Joachim Meyer DESY

7 Principle of particle identification H1 Events Joachim Meyer DESY

8 An event display : What do we see? R-Z view : Hadrons Hadronic calorimeter Hits and reconstructed tracks in tracker e p Electromagnetic calorimeter e e-p interaction point Energy depositions in calorimeter Scattered Electron H1 Events Joachim Meyer DESY

9 Same event in radial view : ep e ' X X Hadronic calorimeter Hits and reconstructed tracks in tracker Energydepositions in calorimeter e H1 Events Joachim Meyer DESY

10 The hits (fired wires) in the tracking chambers Hits = Signals recorded on sense wires Gas volumen with sense wires at HV H1 Events Joachim Meyer DESY

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 Central tracking chambers Electron H1 Events Joachim Meyer DESY

12 .. and the same procedure in R-Z view : Hadrons Electron Central tracking chambers H1 Events Joachim Meyer DESY

13 another event : Curling tracks Here you see the CJC hits including the mirror hits (ambiguity not resolved) Mirror tracks track H1 Events Joachim Meyer DESY

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 H1 Events Joachim Meyer DESY

15 Event : Combined view (R-z, R-Phi, calorimeter energies) ep e ' X Transverse view (R-Phi) e e X Calorimeter energies Side view (R-z) X Electron and hadronic system X balanced in transverse momentum H1 Events Joachim Meyer DESY

16 A very simple event : ep eγ ( p) Photon Proton leaves unseen down the beam pipe Electron H1 Events Joachim Meyer DESY

17 Here an electron and two photons are recorded Electrons easily radiate photons H1 Events Joachim Meyer DESY

18 Photons tend to convert to e+ e- pairs in material ep eγ X... γ e + e Photon X Photon e e+ e- Pair e Chamber material Photon H1 Events Joachim Meyer DESY

19 Another simple event : A elastic dimuon production + ep eµ µ ( p) MUON IRON Muons penetrate thick materials! MUON H1 Events Joachim Meyer DESY

20 An inelastic dimuon production without visible scattered electron + ep ( e)µ µ X + µ + µ X µ X µ H1 Events Joachim Meyer DESY

21 In the forward direction muons are measured by the Forward Toroid Muon Detector µ 1 µ 2 µ 1 µ 2 Forward Toroid Muon Detector H1 Events Joachim Meyer DESY

22 Here it is very visible how electron, muon and photon are distinguished µ γ µ γ e e H1 Events Joachim Meyer DESY

23 Muons also come from the sky This is BACKGROUND, which we do not like! H1 Events Joachim Meyer DESY

24 Interaction of cosmic primaries create showers in the atmosphere, and multimuons reach us here H1 Events Joachim Meyer DESY

25 Cosmic dimuon seen in calorimeter and central track detector H1 Events Joachim Meyer DESY

26 and it can be even more fierce. H1 Events Joachim Meyer DESY

27 Muons interact rarely, but they do Hit pattern in the central track detector (transverse view) H1 Events Joachim Meyer DESY

28 Here a cosmic muon radiates a photon which gets absorbed in the calorimeter. The muon then exits the detector. The radiated energy deposition H1 Events Joachim Meyer DESY

29 An HERA ep event overlayed with a cosmic muon ep event Cosmic muon H1 Events Joachim Meyer DESY

30 There is not only background from cosmics but also from the Proton beam interacting with the restgas P - beam e-p event vertex should be here Event vertex is here H1 Events Joachim Meyer DESY

31 Scattering of the HERA-proton on a nucleus of the restgas. The nucleus is dissociates into lots of protons (positive tracks) and neutrons H1 Events Joachim Meyer DESY

32 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 H1 Events Joachim Meyer DESY

33 Back to HERA -e-p scattering events : A very forward Dimuon event These muons are decay products of the famous J/Psi particle ep ( e)( p) J / Ψ Muons bent in the magnetic field of the forward toroid magnet J / + Ψ µ µ H1 Events Joachim Meyer DESY

34 Another event where the J/Psi particle decays into two muons (this time backward ) Muon Iron ep ( e)( p) J / Ψ J / + Ψ µ µ Muon H1 Events Joachim Meyer DESY

35 The J / Ψ particle has a sister the Ψ + µ Central Tracker + µ π π µ + π ep e( p)ψ + π e µ Backward calorimeter Ψ ' Ψπ + π + Ψ µ µ e H1 Events Joachim Meyer DESY

36 Most events are much more complicated : Very high track multiplicity Small visible energy in calorimeter H1 Events Joachim Meyer DESY

37 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 H1 Events Joachim Meyer DESY

38 Another event with detailed track measurement in the CST CST : R-z view CST : R-Phi view H1 Events Joachim Meyer DESY

39 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 H1 Events Joachim Meyer DESY

40 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 H1 Events Joachim Meyer DESY

41 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 H1 Events Joachim Meyer DESY

42 Back to the Deep-Inelastic-Electron-Proton-Scattering (DIS) ep e ' X 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! H1 Events Joachim Meyer DESY

43 .and here its even more virulent. ep e ' X The squared momentum transfer is 2 Q 50000GeV 2, this corresponds to a space resolution of x m e e Jet Notice : The hadronic system X is a well collimated bundle of particles. This is called JET Jet Jets are the footprints of the quarks and gluons H1 Events Joachim Meyer DESY

44 A NC-DIS event with two jets ep e ' Jet 1 Jet 2 e Jet2 Jet2 e Jet1 Jet1 J1 e J2 H1 Events Joachim Meyer DESY

45 Here the forward scattered electron radiates a very energetic photon ep e ' Xγ electron photon electron photon electron photon H1 Events Joachim Meyer DESY

46 Another ep ' e Xγ event, but here the scatted electron and photon are far apart It is likely that here the photon is of hadronic origin (prompt photon) X γ e H1 Events Joachim Meyer DESY

47 There is also a chance that two photons are radiated : ep e ' Xγ 1 γ 2 e γ 2 γ γ 2 1 e γ 1 H1 Events Joachim Meyer DESY

48 A new event class : In this event the hadrons X are NOT balanced by an electron! ep νx The Neutrino does not leave a trace in the detector Hadrons X This is a different type of DIS event It is pure weak interaction. ν It is a Charged Current (CC) event ν H1 Events Joachim Meyer DESY

49 The CC event with the highest recorded transverse momentum 2 Q ep νx The quark on which the electron scattered had nearly all of the proton momentum H1 Events Joachim Meyer DESY

50 This is a CC event with a pronounced two-jet structure ep νj 1 j 2 ν j1 j2 j1 j2 H1 Events Joachim Meyer DESY

51 Also CC events exhibit multijet structures ν H1 Events Joachim Meyer DESY

52 In this CC event the Jet is very broad H1 Events Joachim Meyer DESY

53 A CC event with a photon radiated from the incident electron ep νγx γ γ H1 Events Joachim Meyer DESY

54 This CC event shows a muon separated from the jet µ µ This could be a muon produced in the semileptonic decay of a charm quark H1 Events Joachim Meyer DESY

55 Another event class : Photoproduction Here two jets are visible, but the scattered electron is not recorded, it leaves the detector under very small scattering angle Jet 1 e Needles of energy Jet 2 H1 Events Joachim Meyer DESY

56 A dijet event with very high dijet-mass H1 Events Joachim Meyer DESY

57 Here a THREE-JET-EVENT J1 J2 J1 J2 J3 J3 H1 Events Joachim Meyer DESY

58 A very high three-jet mass H1 Events Joachim Meyer DESY

59 Here 5 jets are visible, there is no limit in the number. J5 J1 J4 J3 J2 Quarks radiate gluons, which in turn may radiate gluons or produce quarkantiquark pairs. All turn (if energetic enough) to visible jet structures H1 Events Joachim Meyer DESY

60 The jets can be so energetic that they are not absorbed in the main calorimeter but leak out into the instrumented iron yoke. Leakage Energy H1 Events Joachim Meyer DESY

61 It happens that a jet is associated to only a single charged particle Explanation : -statistical fluctuation? -physics reason Tau Lepton? τ πν H1 Events Joachim Meyer DESY

62 We also record events with an unbalanced jet associated to a single particle. Are these events with isolated tau-mesons and missing transverse momentum? H1 Events Joachim Meyer DESY

63 Sometimes strange features show up : Muonic Electromagnetic Neutral behavior Explanation?? H1 Events Joachim Meyer DESY

64 The most exciting issue : Are there new phenomema, we don t expect? We have seen ' ep e X ep But this looks like µ DIS - events X (As such forbidden in HEP Standard Model) Muon Muon Fluctuating background or sign of new physics? X X H1 Events Joachim Meyer DESY

65 A similar event, but here muon and hadronic jet are not back-to-back : clear evidence for unobserved particle (neutrino?)? H1 Events Joachim Meyer DESY

66 Similar event, but here also the scattered electron is visible. This allows to reconstruct the invariant mass of the muon-neutrino-system. It turns out to be 82 GeV. That s close to the W mass. e µ µ e ν ν ep exw... W µν H1 sees more events than expected from this reaction. New physics? H1 Events Joachim Meyer DESY

67 Here only an unbalanced electron is visible. This topology is predominantly expected for ep ( e)( X ) W... W eν e e H1 Events Joachim Meyer DESY

68 Jet1 Jet1 Jet2 The W decays also into quark-antiquark producing two jets. The jet-jet-mass is 80 GeV, just the known W-mass. Jet2 H1 Events Joachim Meyer DESY

69 The W particle has a sister, the Z, of 90 GeV mass, decaying into lepton pairs Z 0 e + e H1 Events Joachim Meyer DESY

70 In this event an even more massive e+ e- pair.. : What physics is that? H1 Events Joachim Meyer DESY

71 A collinear electron pair Such events we were used to see at the electron-positron collider PETRA H1 Events Joachim Meyer DESY

72 Here a positron and 2 electrons are recorded. Presumably the scattered electron and a pair created in the interaction Note : All electrons are well confined in the electromagnetic part (green) of the calorimeter H1 Events Joachim Meyer DESY

73 There are also dilepton events with different lepton types : Electron and muon e e muon muon H1 Events Joachim Meyer DESY

74 A pair of tau-mesons with the scattered electron ep e( p)τ + τ + µ + µ τ τ + π µ + π ν + π ν e 3π 3π H1 Events Joachim Meyer DESY

75 Summary H1 Events Joachim Meyer DESY

76 The Method: e p scattering Nobel prize 2004 Cartoon The Data H1 Events Joachim Meyer DESY

77 Physics Results examples : Protonstructure : Quarks and Gluons Electroweak Unification..and many more.. H1 Events Joachim Meyer DESY

78 All this became possible thanks to the work of the H1 members Some members of the H1 Collaboration Work at the innermost parts of the H1 detector H1 Events Joachim Meyer DESY

79 and thanks to HERA. H1.. the worlds most powerful microscope x m H1 Events Joachim Meyer DESY