HERA e-p scattering events observed in the H1Detector H1 Events Joachim Meyer DESY 2005 1
The idea The realisation The Physics The events H1 Events Joachim Meyer DESY 2005 2
What we think what happens, when we scatter electrons on protons at HERA Hadrons W Proton Hadrons or neutrino H1 Events Joachim Meyer DESY 2005 3
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 2005 4
Calorimeter H1 Events Joachim Meyer DESY 2005 5
Principle of particle identification H1 Events Joachim Meyer DESY 2005 6
Principle of particle identification H1 Events Joachim Meyer DESY 2005 7
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 2005 8
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 2005 9
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 2005 10
..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 2005 11
.. and the same procedure in R-Z view : Hadrons Electron Central tracking chambers H1 Events Joachim Meyer DESY 2005 12
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 2005 13
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 2005 14
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 2005 15
A very simple event : ep eγ ( p) Photon Proton leaves unseen down the beam pipe Electron H1 Events Joachim Meyer DESY 2005 16
Here an electron and two photons are recorded Electrons easily radiate photons H1 Events Joachim Meyer DESY 2005 17
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 2005 18
Another simple event : A elastic dimuon production + ep eµ µ ( p) MUON IRON Muons penetrate thick materials! MUON H1 Events Joachim Meyer DESY 2005 19
An inelastic dimuon production without visible scattered electron + ep ( e)µ µ X + µ + µ X µ X µ H1 Events Joachim Meyer DESY 2005 20
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 2005 21
Here it is very visible how electron, muon and photon are distinguished µ γ µ γ e e H1 Events Joachim Meyer DESY 2005 22
Muons also come from the sky This is BACKGROUND, which we do not like! H1 Events Joachim Meyer DESY 2005 23
Interaction of cosmic primaries create showers in the atmosphere, and multimuons reach us here H1 Events Joachim Meyer DESY 2005 24
Cosmic dimuon seen in calorimeter and central track detector H1 Events Joachim Meyer DESY 2005 25
and it can be even more fierce. H1 Events Joachim Meyer DESY 2005 26
Muons interact rarely, but they do Hit pattern in the central track detector (transverse view) H1 Events Joachim Meyer DESY 2005 27
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 2005 28
An HERA ep event overlayed with a cosmic muon ep event Cosmic muon H1 Events Joachim Meyer DESY 2005 29
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 2005 30
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 2005 31
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 2005 32
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 2005 33
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 2005 34
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 2005 35
Most events are much more complicated : Very high track multiplicity Small visible energy in calorimeter H1 Events Joachim Meyer DESY 2005 36
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 2005 37
Another event with detailed track measurement in the CST CST : R-z view CST : R-Phi view H1 Events Joachim Meyer DESY 2005 38
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 2005 39
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 2005 40
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 2005 41
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 2005 42
.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 10 18 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 2005 43
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 2005 44
Here the forward scattered electron radiates a very energetic photon ep e ' Xγ electron photon electron photon electron photon H1 Events Joachim Meyer DESY 2005 45
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 2005 46
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 2005 47
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 2005 48
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 2005 49
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 2005 50
Also CC events exhibit multijet structures ν H1 Events Joachim Meyer DESY 2005 51
In this CC event the Jet is very broad H1 Events Joachim Meyer DESY 2005 52
A CC event with a photon radiated from the incident electron ep νγx γ γ H1 Events Joachim Meyer DESY 2005 53
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 2005 54
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 2005 55
A dijet event with very high dijet-mass H1 Events Joachim Meyer DESY 2005 56
Here a THREE-JET-EVENT J1 J2 J1 J2 J3 J3 H1 Events Joachim Meyer DESY 2005 57
A very high three-jet mass H1 Events Joachim Meyer DESY 2005 58
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 2005 59
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 2005 60
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 2005 61
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 2005 62
Sometimes strange features show up : Muonic Electromagnetic Neutral behavior Explanation?? H1 Events Joachim Meyer DESY 2005 63
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 2005 64
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 2005 65
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 2005 66
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 2005 67
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 2005 68
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 2005 69
In this event an even more massive e+ e- pair.. : What physics is that? H1 Events Joachim Meyer DESY 2005 70
A collinear electron pair Such events we were used to see at the electron-positron collider PETRA H1 Events Joachim Meyer DESY 2005 71
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 2005 72
There are also dilepton events with different lepton types : Electron and muon e e muon muon H1 Events Joachim Meyer DESY 2005 73
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 2005 74
Summary H1 Events Joachim Meyer DESY 2005 75
The Method: e p scattering Nobel prize 2004 Cartoon The Data H1 Events Joachim Meyer DESY 2005 76
Physics Results examples : Protonstructure : Quarks and Gluons Electroweak Unification..and many more.. H1 Events Joachim Meyer DESY 2005 77
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 2005 78
and thanks to HERA. H1.. the worlds most powerful microscope x 10 18 m H1 Events Joachim Meyer DESY 2005 79