Data Visualization in Particle Physics Past and Presence. Otto Schaile, LMU München Interdisciplinary Cluster Workshop on Visualization, 5 Nov, 2015

Transcription

1 Data Visualization in Particle Physics Past and Presence Otto Schaile, LMU München Interdisciplinary Cluster Workshop on Visualization, 5 Nov, 2015

2 Our current picture of particles and forces 2 elementary Protons and neutrons are composites of 3 quarks bonded by gluons Quarks dont exist as free objects (confinement) Leptons are point like in the Standard Model Higgs gives mass to the elementary particles - Forces between particles are mediated by exchange of bosons (γ, Z, W, Gluon)

3 Why cannot be that all 3 no explanation of dark matter, 4/5 of gravitational matter is yet unknown does not explain the excess of matter compared to antimatter why are masses so different why is Higgs that light what about gravity

4 The birth of particle physics Conrad Röntgen: Discovery of X-Rays (photographic plate) 1896 Antoine Becquerel: Discovers Uranium Rays = radioactivity (emulsion) 1899 J.J.Thomson: Identifies cathode rays as free electrons 1885 C.T.R.Wilson: Cloud formation in saturated water vapor caused by ionisation 1911 C.T.R.Wilson: First working cloud chamber with photographs of tracks from alpha rays

5 Wilsons cloud chamber 5 Detection volume B contains air saturated with water vapor Opening valve C lets air below piston flow into vacuum vessel A Piston is pulled down, volume B is increased and cooled adiabatically Volume B is now in a supersaturated with water vapor Ionizing particles produce condensation nuclei along their path The track of a particle is visible as droplets and can be photographed

6 Wilsons cloud chamber 6 Alpha-Ray picture, Wilson 1912 In the following years Wilsons invention got much more sophisticated and became an important tool for nuclear and particle physics: Cloud chambers with external triggers to select events Diffusion chambers: The supersaturated region is built up by diffusion of alcohol vapor between the warm top (15 ) and a cold bottom(-35 ), no need for the expansion mechanism. Modern diffusion chambers are still used for education and museums. Rutherford: The most original and wonderful instrument in scientific history

7 Discovery of the positron 7 First photograph of an antiparticle by C.D. Anderson, 1932 In the picture the positron enters from below and is bent in a magnetic field In a 6 mm lead plate it looses 40 MeV. The positron was postulated by P. Dirac 1928

8 Nuclear emulsion 8 Thick (1-2 mm = 100 x of films) photosensitive emulsion First used by Bequerel to detect radioactivity of Uranium Advantage: 1000 times higher density than cloud chambers more reactions Simple, can be used in balloon experiments to investigate cosmic rays Evidence for: Kaon 3 Pions Nuclear reaction in ft altitude

9 Bubble chambers, D.A.Glaser Compress a liquid (hydrogene, propane, freon) to produce a superheated state Ions along particle track serve as nuclei for bubbles which are illuminated by flash lights and photographed Density 1000 x of cloud chamber, however not triggerable Excellent spatial resolution (5µm), ideal for complex decay modes Used with particle accelerators compression is synchronized with beam bunches Low rate (typ 10 / second) and no trigger required huge number of pictures BEBC (Big European Bubble Chamber) 6 million Development of scanning tables (ERASME) and manual digitisation Electron RAy Scanning and Measuring Equipment 1973

10 10 Turning images into digits The ERASME scanning and digitisation system Otto Schaile Interdisciplinary Cluster Workshop on Visualization, 5 Nov, 2015

11 11 Turning images into digits Photograph Otto Schaile Reconstruction Interdisciplinary Cluster Workshop on Visualization, 5 Nov, 2015

12 . Discovery of neutral currents 12 Gargamelle, constructed at Ecole Polytechnique Paris 1970, Operated with liquid Freon at CERN with ν - beam in a 2T Magnet

13 13 Turning images into digits - sparkchambers Sparkchambers are descendants of Geiger-Mueller counters (1928) High voltage (20KV) is applied between stacks of gaps Ionizing particles induce discharges which form sparks Sparkchambers can be triggered to select interesting events Sparkchamber in action, Univ. of Cambridge Otto Schaile Interdisciplinary Cluster Workshop on Visualization, 5 Nov, 2015

14 Turning images into digits - CERN 14 In the Omega spektrometer sparks are viewed by a TV Camera (plumbicon) The TV signals are digitized and recorded on magnetic tapes This marks the transition to: Turn digits into images π + p ΛK + π +, OS PhD thesis 1977 Λ pk

15 Electronic imaging devices 15 In the 1970ies electronic devices replace bubble chambers & Co E.g. Multiwire proportional chambers, Charpak 1968 New high resolution computer driven visualization devices: E.g. Merlin: 2 Megatek graphics workstation + VAX 11/780 from DEC Discovery of the Z boson: UA1 at CERN SPS (1983)

16 The OPAL experiment at LEP 16 Exploded view as seen by software Electromagnetic barrel, leadglass blocks Omni Purpose Apparatus for Lep, size about 12x12x12 m Data taking at around 91 GeV to study the Z boson upto 209 GeV to produce WW pairs and look for new particles Maximum energy limited by synchrotron radiation, energy loss/rev : 3 GeV

17 OPAL software 17 Start of Coding 1983 Design tool SASD: Structured Analysis, Structured Design Data flow diagrams Prerequisites: Standard FORTRAN, CERNLIB: ZEBRA, HBOOK 3D Graphics: GPHIGS licensed by G5G/CERN, FORTRAN (F77) binding PHIGS: Programmer s Hierarchical Interactive Graphics System GROPE: Graphic Reconstruction of OPal Events, still used for educational purposes 2012: End of F77 (Linux) End of GPHIGS Replacement of graphics parts: GPHIGS, HBOOK by OpenGL, ROOT graphics

18 Praktikumsversuch Z0 - Zerfall, visualization part 18 What do we want learn / teach (among other): How does a general purpose detector work How can we identify particles How can we deduce the underlying basic interaction The Z0 boson decays into quark-antiquark or lepton-antilepton pairs 20% neutrinos invisible 3.3% electrons tracks, signal in electromagnetic calorimeters 3.3% myons tracks, small signal in calorimeters, signal in myon detectors 3.3% taus decay into leptons,pions (1-5), mean flight path at LEP 2 mm they are always accompanied by an invisible neutrino 70% quarks show up as jets of hadrons ( 10 charged) mostly 2 jets, few % 3 and more (gluon bremsstrahlung)

19 Schematic layout of the Atlas detector 19

20 Atlas, highmass dijet event 20 A high-mass, central dijet event collected in July 2015 (Event , Run ): the two central high-pt jets have an invariant mass of 3.25 TeV, the highest-pt jet has a pt of 1.47 TeV, and the subleading jet has a pt of 1.40 TeV.

21 21 Atlas, a Higgs candidate Event displays of a 2e2µ candidate event with m(4 leptons)=124.3 GeV. The masses of the lepton pairs are 76.8 GeV and 45.7 GeV Otto Schaile Interdisciplinary Cluster Workshop on Visualization, 5 Nov, 2015

22 Atlas, Educational activities 22 At LMU work in progress on F-Praktikumsversuch Higgs discovery

23 23 OPAL, e + e e + e

24 24 OPAL, e + e µ + µ

25 25 OPAL, e + e τ + τ

26 26 OPAL, e + e 3jets