Discovering the Unknown at the CERN Large Hadron Collider (LHC) Amy Gladwin University of Arizona
Introduction • High energy physics or particle physics seeks to understand how the universe works at its most basic level • What are the fundamental forces? • What are the fundamental types of particles (matter)? • What is the nature of space and time? Are there additional dimensions? • How can we use these answers to understand how the universe works?
Introduction • What is the universe made of? • Dark energy – 65% • Dark matter – 30% • Baryons (protons and neutrons) – 4% • Stars – 0.5% • Neutrinos – 0.5% • Dark is just another word for “dunno” so, in short, we don’t know what most of the universe is made of!!!
Fundamental Particles • Or another pattern to unravel?
Particle Accelerators • We study nature using high energy collisions between particles • Particle accelerators can be thought of as giant microscopes that are used to study extremely small dimensions • The higher the energy, the smaller the wavelength the higher the resolving power • The higher the energy, the more massive the particles that can be created (E=mc2)
LHC (Large Hadron Collider) • CERN is located near Geneva, Switzerland • The energy of the LHC will be 7 TeV + 7 TeV • But right now it’s 3.5 TeV + 3.5 TeV • The ring circumference is 27 km 8
LHC (Large Hadron Collider) At four points around the ring the two beams are brought together where collisions occur The beams are actually composed of many “bunches” of protons These bunch crossings (collisions) occur every 25 ns At an energy of 7 TeV it takes 90μs for a proton to make one revolution
LHC Bending Dipoles 1232 LHC superconducting dipoles 10
What is the B Field? You might recall from your study of E&M that a particle of momentum p in a uniform magnetic field B undergoes circular motion with radius R The LHC circumference is ~27 km Packing fraction of ~64% gives R~2.8 km Thus B needed for p=7 TeV is ~8.3 T Magnet current at this field is about 12000 A!! Magnet energy at this field is about 8000 J 1 kg of TNT has potential energy of about 5000 J This is amount of energy is substantial 11
First Beam in the LHC • Sept 10, 2008 in the ATLAS control room
September 19th Incident • An electrical arc destroyed the busbars
September 19th Incident • Huge magnet displacements caused by uncontrollable evaporation of liquid helium
LHC Experiments • Particle detectors are used to record the results of these high energy collisions
Particle Detectors • The type of particles produced are identified by how they interact in the various detectors • The momentum of charged particles is determined by their bend in a magnetic field • The energy of most particles (except muons and neutrinos) is determined by their deposited energy in calorimenters
What’s Happening at the LHC? • Since late March, the LHC has been running at 7 TeV • This is only one half the design energy • The LHC is now increasing the beam intensity • By adding more protons per bunch, more bunches, and squeezing the beam • The LHC will run until the end of 2011 • Followed by a year shutdown to fix magnet splice problems • Followed by running at 14 TeV
What’s Happening at ATLAS Now? • http://op-webtools.web.cern.ch/op-webtools/vistar/vistars.php?usr=LHC1 • http://op-webtools.web.cern.ch/op-webtools/vistar/vistars.php?usr=LHC3 • http://atlas-live.cern.ch/
What Do We Hope to Discover? • Some (or none!) of the following • Higgs boson • Supersymmetric particles (dark matter) • Extra spatial dimensions • Gravitons • Evidence for quark substructure • Your bright ideas here • In the best scenario we will discover phenomena that no one to date has predicted or thought of
ATLAS at Arizona • Here at the University of Arizona we are analyzing data from ATLAS being collected now • We are also working on electronics and detectors to be used in the next generation of experiments at the SLHC (Super LHC) • It may seem odd to be working on new electronics for an experiment that has just started to run, but the lead time for developing new ideas and then building and testing them approaches a decade!
FEB (1524 modules) ROD (108 modules) ~10 Gbps 1 12 1 LVL1 FPGA 12 x 1 fibers Pre-Sampler Interface 2 12 FPGA ROB 7 Interface 12 x 7 fibers Front 3 12 FPGA 320 mm 4 t 12 x 4 fibers Middle e x t t e x t t e x t 14 2 12 12 x 2 fibers FPGA Back 280 mm Readout Driver (ROD) • The ROD is used to collect and process data from the liquid argon detector front-end electronics
Readout Driver (ROD) • The ROD must receive and process 1000 Gbits/s = 1Tbit/s !! • Need state-of-the-art optics • Need state-of-the-art FPGAs • And be able to guess what might be available a few years hence • In addition to managing the data, calculations must be performed on the data • And a system architecture developed to handle 200 such ROD cards
Summer Opportunities • While it’s difficult to jump right in and begin working on the ROD design, this summer you will learn basic skills of electronics design including some of • Schematic design • Layout design • FPGA programming • Electronics debugging using external and internal logic analyzers • Data acquisition software • Particle physics at the LHC
Summer Opportunities • Data analysis • If you are a very strong programmer, you may also have an opportunity to analyze LHC data • But this demands strong C++ (or C) programming skills