H Y P A T I A

HYbrid Pupil’s Analysis Tool for Interactions in Atlas

http://hypatia.phys.uoa.gr/applet

HYPATIA of Alexandria

•First woman mathematician•Alexandria, Egypt (370-418 A.D.)

Proton – proton Collisions

Beam energy: 3.5, 4 TeV2 x 3.5 TeV = 7 or 8 TeVSome of the particles

produced are unstable and decay instantly

ATLAS•Particle tracks appear as lines on the detectors•The length of each track is determined by particle type•Each particle leaves a trace only on specific detectors according to its type

HY.P.A.T.I.A.

CanvasDisplays events in various forms depending on particle type and user preference. Can do zoom, pan, rotate, pick track etc

HY.P.A.T.I.A.

Track MomentaDisplays the quantities that describe each track (type, momentum, charge, φ, θ)

HistogramsCreated automatically from the tracks of the invariant mass table

HY.P.A.T.I.A.

Invariant MassMain event analysis window.Displays the user selected tracks from various events. Calculates invariant masses.Creates Histograms.

Η → 4ℓ

Laboratory Exercise

Laboratory ExerciseDetection and mass calculation of particles – Real EventsKnown particles:

Z → μ- + μ+ Z → e- + e+

2 tracks, opposite charge, isolated Invariant mass 91,2 GeV Small missing energy ETMiss

J/ψ → μ- + μ+ J/ψ → e- + e+

2 tracks, opposite charge, not diametrical Invariant mass 3 GeV Small missing energy ETMiss<15GeV

Laboratory ExerciseDetection and mass calculation of particles – Real EventsKnown 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)

Laboratory ExerciseIdentification 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

Laboratory ExerciseDetection and mass calculation of particles- Histogram

Laboratory ExerciseDetection and mass calculation of particles –Dimuon spectrum

+???

Discover Higgs!

Laboratory Exercise“Discover Higgs”H → 2 Z → 4lZ → e- + e+ ή Z → μ- + μ+

H 2 e- + 2 e+

H 2 μ- + 2 μ+

Η e- + e+ + μ- + μ+

Isolated tracks 6 GeV pT Cut Invariant mass of 4 tracks (Z boson pairs)

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)

Track examples

Laboratory Exercise

Recap

So, what are we looking for?? Z → e- + e+ or Z → μ- + μ+ 91,2 GeV Y → e- + e+ or Y → 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