Basics The past Challenges Where to start Detector

Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID Particle Detectors Overview LHC detectors “Events” Final thoughts Dave Barney, CERN (biased towards the CMS detector!) ISEF: Introduction to Particle Detectors 1 David Barney, CERN

Particle Detectors Overview Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts • • What does a particle detector need to do? The first particle detectors The challenges of modern detectors Rising to the challenge - let’s design a detector! • The LHC detectors and components • What might physicists get excited about in a few years from now? ISEF: Introduction to Particle Detectors 2 David Barney, CERN

What we do at CERN: Smash things together and see what happens! Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts ISEF: Introduction to Particle Detectors 3 David Barney, CERN

Spherical Detector Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts ISEF: Introduction to Particle Detectors 4 David Barney, CERN

Basics The past Challenges Where to start? Forward Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts ISEF: Introduction to Particle Detectors 5 David Barney, CERN

What does a particle detector need to do? Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts • Need to determine: – What particles do we see? – Where did they come from and where do they go? – What were their energies and momenta? • In order to understand: – What happened in a collision between particles? – Has something interesting been created? ISEF: Introduction to Particle Detectors 6 David Barney, CERN

The first particle detectors Basics The past Challenges Where to start? Cloud chamber (1911 by Charles T. R. Wilson, Nobel Prize 1927) chamber with saturated water vapour; originally developed to study formation of rain clouds Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Positron loses Final thoughts energy in lead: narrower curvature lead plate upward going positron ISEF: Introduction to Particle Detectors Was used at discovery of the positron (1932 by Carl Anderson, Nobel Prize 1936) 7 David Barney, CERN

The first particle detectors Basics The past Liquid hydrogen “bubble chamber” Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts ISEF: Introduction to Particle Detectors The hydrogen acts as a target (for incoming particles) and a detector 8 David Barney, CERN

The first particle detectors Basics The past Challenges Particle colliding with a proton in liquid hydrogen - A “Bubble Chamber” Many people employed to look through these photos to understand what happened! Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts ISEF: Introduction to Particle Detectors 9 David Barney, CERN

Scanning Photographs Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts ISEF: Introduction to Particle Detectors 10 David Barney, CERN

The first particle detectors Basics Spark Chambers The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts Big one in the CERN microcosm ISEF: Introduction to Particle Detectors 11 David Barney, CERN

The first particle detectors Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” • Phil. Mag. Xiii (1896)392 • Conduction of electricity through gases (Ist ed 1903) • Proc. of Royal Soc. A 81(1908)14 1 • The Geiger-Müller tube – 1928 • Tube filled with inert gas+ organic vapour • Central thin wire (20 – 50 µm) • High voltage between wire and tube Strong increase of E-field close to the wire electron gains more and more energy above some threshold (>10 k. V/cm) electron energy high enough to ionize other gas molecules Final thoughts newly created electrons also start ionizing avalanche effect: exponential increase of electrons (and ions) measurable signal on wire organic substances responsible for “quenching” (stopping) the discharge ISEF: Introduction to Particle Detectors 12 David Barney, CERN

The first particle detectors Basics The past Challenges Where to start? • Geiger-Müller tube just good for single tracks with limited precision (no position information) • Multi Wire Proportional Chamber (MWPC) • (1968 by Georges Charpak, Nobel Prize 1992) Detector Design Tracker Calorimetry Particle ID cathode plane (-) LHC detectors “Events” Final thoughts E anode plane (+), many wires, a few mm apart E charged particle cathode plane (-) Georges Charpak, Fabio Sauli and Jean-Claude Santiard ISEF: Introduction to Particle Detectors 13 David Barney, CERN

The challenges of modern detectors Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts • We don’t really know what we are looking for! • The “interesting” things we are looking for are very rare – Need to make millions of collisions every second! – Cannot use conventional photography – They are also unstable…. . ISEF: Introduction to Particle Detectors 14 David Barney, CERN

Unstable Interesting Particles Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts The interesting things (the dinosaurs!) disappear almost instantly. We “see” the resulting particles – so we have to be like detectives – look at the evidence to see what happened! ISEF: Introduction to Particle Detectors 15 David Barney, CERN

The challenges of modern detectors Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts • Each collision produces many hundreds of particles • The energies/momenta of the particles involved are huge – The detectors are very complex and have many layers – They also need to be big! VERY BIG!! ISEF: Introduction to Particle Detectors 16 David Barney, CERN

The challenges of modern detectors Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts Have to understand this sort of image 40 million times per second! ISEF: Introduction to Particle Detectors 17 David Barney, CERN

A “simple” collision at LHC (simulation) Basics Higgs 4 muons The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID Where are the muons? LHC detectors “Events” Final thoughts Red lines show the muons (cheating!) ISEF: Introduction to Particle Detectors 18 David Barney, CERN

Let’s add a magnetic field! Charged particles bend in the magnetic field Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID The lower the particle momentum (~speed) the more they bend. LHC detectors “Events” Final thoughts Now the muons are clear! ISEF: Introduction to Particle Detectors 19 David Barney, CERN

A typical detector for the LHC #1 Basics The “CMS” detector for LHC The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID Each colour shows a different layer LHC detectors “Events” Final thoughts This is the view along the beam direction ISEF: Introduction to Particle Detectors 20 David Barney, CERN

Let’s design a detector #1 Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” • Start with a magnet! BIG and powerful Final thoughts ISEF: Introduction to Particle Detectors 21 David Barney, CERN

The “Gothic Cathedrals of the 21 st Century” Basics ATLAS The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts ISEF: Introduction to Particle Detectors 22 David Barney, CERN

Transporting and constructing the CMS solenoid Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts ISEF: Introduction to Particle Detectors 23 David Barney, CERN

“Swivelling the CMS solenoid” Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts ISEF: Introduction to Particle Detectors Coil is constructed vertically but needs to be horizontal! 24 David Barney, CERN

Inserting the CMS solenoid into the yoke Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts ISEF: Introduction to Particle Detectors 25 David Barney, CERN

Standing in the CMS solenoid – at 100 K! CMS solenoid is 13 m long, 6 m diameter and provides a magnetic field of 4 teslas when a current of ~19500 Amps is passed down it – coil is made of superconducting niobium-titanium and operates at 269 o. C Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts With the return yoke it weighs around 12000 tonnes! ISEF: Introduction to Particle Detectors 26 David Barney, CERN

Basics Tracking Detectors The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID To measure the direction and momenta of charged particles LHC detectors “Events” Final thoughts Thin sensors – do not disturb the trajectories of the particles: must go on the inside of the detector ISEF: Introduction to Particle Detectors 27 David Barney, CERN

A basic “Tracker” Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts Multiple thin layers of, for example, silicon sensors ISEF: Introduction to Particle Detectors 28 David Barney, CERN

Example Silicon Detector Construction Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts 25 mm thick wires ultrasonically bonded ISEF: Introduction to Particle Detectors 29 David Barney, CERN

CMS Tracker Basics The past Challenges Many layers of silicon sensors Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts Silicon sensors are reverse-biased diodes. Electrons & holes created in the extended depletion region due to the passage of a charged particle make a signal ISEF: Introduction to Particle Detectors 30 David Barney, CERN

Basics Calorimeters The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID To measure the energies of different types of particle LHC detectors “Events” Final thoughts Electromagnetic Calorimeters – sensitive to photons, electrons, positrons Hadronic Calorimeters – sensitive to “hadrons” (particles containing quarks) such as protons, neutrons, pions etc. The calorimeters “stop” the incoming particles so must go outside of the “tracker” ISEF: Introduction to Particle Detectors 31 David Barney, CERN

A basic “sampling” calorimeter Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts Total # of particles is proportional to energy of incoming particle Light materials (green) produce a signal proportional to the number of charged particles traversing ISEF: Introduction to Particle Detectors 32 David Barney, CERN

ATLAS tile calorimeter Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts ISEF: Introduction to Particle Detectors 33 David Barney, CERN

CMS Electromagnetic Calorimeter Crystals Basics The past Challenges Lead tungstate (Pb. WO 4) crystals nearly as dense as lead! Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts Crystals initiate showers and produce light ISEF: Introduction to Particle Detectors 34 David Barney, CERN

Let’s design a detector #3 Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID • Need to identify the different types of particle • Combination of signals in the tracker and calorimeters can identify many particles LHC detectors “Events” Final thoughts • Also have dedicated sensors for muons – These are the only particles that travel all the way through the calorimeters without stopping ISEF: Introduction to Particle Detectors 35 David Barney, CERN

Muon Detectors – e. g. RPCs Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID • RESISTIVE PLATE CHAMBERS • Place resistive plates (Bakelite or window glass) in front of the metal electrodes • Sparks cannot develop because the resistivity and capacitance will allows only a very localized discharge • Large area detectors can be made • Fast – k. Hz/cm 2 LHC detectors “Events” Final thoughts ISEF: Introduction to Particle Detectors 36 David Barney, CERN

Muon Detectors Basics The past Challenges ATLAS 1200 muon chamber with 5500 m 2 Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” CMS muon detectors in magnet yoke Final thoughts Muon detectors ISEF: Introduction to Particle Detectors 37 37 David Barney, CERN

Particle Identification Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts ISEF: Introduction to Particle Detectors 38 David Barney, CERN

LHC Detectors Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts 39 ISEF: Introduction to Particle Detectors 39 David Barney, CERN

LHC Detectors Basics ATLAS CMS The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts ISEF: Introduction to Particle Detectors ALICE LHCb 40 David Barney, CERN

The two giant detectors for the LHC Basics ATLAS The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts CMS ISEF: Introduction to Particle Detectors 41 David Barney, CERN

Lowering CMS underground Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts ISEF: Introduction to Particle Detectors 42 David Barney, CERN

The “Gothic Cathedrals of the 21 st Century” Basics The ATLAS detector 100 m underground The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts ISEF: Introduction to Particle Detectors 43 David Barney, CERN

In the CMS cavern Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts ISEF: Introduction to Particle Detectors 44 David Barney, CERN

What might a real Higgs event look like? 2 muons Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts 2 electrons ISEF: Introduction to Particle Detectors 45 David Barney, CERN

The physicist’s gold! Basics The past IF the Higgs particle exists & IF it has a mass around 130 Ge. V Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts ISEF: Introduction to Particle Detectors This is the signal we will see after about a year of running! 46 David Barney, CERN

Some final thoughts on the technology Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts • The LHC detectors are the most complex scientific instruments ever made • A typical LHC detector has about 100 million individual sensors (c. f. a typical digital camera with ~6 Mpixels) – But it takes a “digital photo” 40 million times every second! • The detectors have to operate for at least ten years with little or no intervention • Technology – sensors and electronics – are cutting-edge ISEF: Introduction to Particle Detectors 47 David Barney, CERN

People Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts • CMS and ATLAS have about 2500 collaborators each, including more than 1000 students! • They come from all over the world - about 80 countries • We have been working on these detectors for the past ~15 years – and they haven’t even started operation yet! ISEF: Introduction to Particle Detectors 48 David Barney, CERN