H Y P A T I A HY brid P upil’s A nalysis T ool for I nteractions in A tlas

1. H Y P A T I AHYbrid Pupil’s Analysis Tool for Interactions in Atlas http://hypatia.phys.uoa.gr/applet

2. HYPATIA of Alexandria First woman mathematician Alexandria, Egypt(370-418 A.D.)

4. Proton – proton Collisions • Beam energy: 3.5, 4 TeV • 2 x 3.5 TeV = 7 or 8 TeV • Some of the particles produced are unstable and decay instantly

5. ATLAS Particletracksappear as lines on the detectors Thelengthof each track is determined by particle type Each particle leaves a traceonly on specific detectors according to its type

7. HY.P.A.T.I.A. Canvas Displays events in various forms depending on particle type and user preference. Can do zoom, pan, rotate, pick tracketc

8. HY.P.A.T.I.A. Track Momenta Displays the quantities that describe each track (type, momentum, charge, φ, θ) Histograms Created automatically from the tracks of the invariant mass table

9. HY.P.A.T.I.A. Η → 4ℓ Invariant Mass Main event analysis window. Displays the user selected tracks from various events. Calculates invariant masses. Creates Histograms.

10. Laboratory Exercise

11. Laboratory Exercise Detection and mass calculation of particles – Real Events Known particles: Z → μ- + μ+ Z → e- + e+ 2 tracks, opposite charge, isolated Invariant mass 91,2GeV Small missing energy ETMiss J/ψ → μ- + μ+ J/ψ → e- + e+ 2 tracks, opposite charge, not diametrical Invariant mass 3GeV Small missing energyETMiss<15GeV

12. Laboratory Exercise Detection and mass calculation of particles – Real Events Known particles: Υ → μ- + μ+ Υ → e- + e+ 2 tracks, opposite charge Invariant mass 9,5 GeV Small missing energy ETMiss Background events Usually one lepton (W boson decay) Leptons from quark decays are in jets (non-isolated tracks) Cosmic rays : diametrical tracks on both detector views Large missing energy ETMiss (because of neutrinos)

13. Laboratory Exercise Identification of electrons - muons e : charged particles, usually isolated that leave a trace in the E/M calorimeter μ : charged particles that leave a trace in the muon chambers

14. Detection and mass calculation of particles- Histogram Laboratory Exercise

15. Detection and mass calculation of particles – Dimuon spectrum Laboratory Exercise +???

16. Discover Higgs!

17. Laboratory Exercise “Discover Higgs” H → 2 Z →4l Z → e- + e+ή Z → μ- + μ+ H  2 e- + 2 e+ H  2 μ-+ 2 μ+ Η  e- + e++ μ- + μ+ Isolated tracks 6 GeVpT Cut Invariant mass of 4tracks (Z boson pairs)

18. Laboratory Exercise “Discover Higgs” H → 2 γ Photons do not carry charge Photons have 0 mass Photons leave NO tracks Photons deposit energy on the E/M Calorimeter Converted photons γ  e- e+(Invariant mass ≈ 0)

19. Track examples

28. Laboratory Exercise

37. Recap

38. So, what are we looking for?? • Z → e- + e+or Z → μ- + μ+91,2 GeV • Y→ e- + e+orY→ μ- + μ+ 9,5 GeV • J/ψ→ e- + e+or J/ψ→ μ- + μ+3,1 GeV • Unknown particles→ e- + e+or→ μ- + μ+ • H → 2 Z →4l (very few events)?GeV For all the above enter tracks which have sum of charge=0 • H → 2 γ? GeV • Background