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Dissecting the Higgs Discovery: The Anatomy of a 21st Century Scientific Achievement Lauren Tompkins Arthur H. Compton Lectures October 12th, 2013 Lecture 2 Accelerators: Creating new particles out of (very) thin air Nobel Prize! • Higgs and Englert won • the Nobel prize for developing a theory of how particles acquire mass The prize was awarded this year because Atlas and CMS amassed enough evidence to say that the newly discovered particle is a Higgs boson 2 Schedule of Lectures [10/5] Welcome to the Theater: Introduction to the Standard Model and Higgs Boson [10/12] Accelerators: Creating particles out of (very) thin air [10/19] Seeing the Higgs with light [10/26] Guest Lecture: Martin Bauer On Theory [11/2] Seeing the Higgs with heavy particles [11/9] Digesting the Data: Triggering, Data Processing [11/16] Finding the Needle in the Haystack: Data Analysis and Statistics [11/23] What else have we learned from the LHC? [11/30] No Lecture for Thanksgiving [12/7] No Lecture for Physics with a Bang [12/14] What's next for the LHC? 3 Outline • Brief Review of Last Week • Introduction to Accelerators • Why we use accelerators • LHC Overview 4 Last Week 5 Last Week • Standard Model describes the fundamental particles and forces • 3 forces: Strong, Electromagnetic and Weak nuclear • 6 quarks and 6 leptons 5 Last Week • • Standard Model describes the fundamental particles and forces • 3 forces: Strong, Electromagnetic and Weak nuclear • 6 quarks and 6 leptons The Higgs field exists everywhere, all of the time and a particle’s mass is determined by how strongly it interacts with the electron field • The Higgs boson is the physical manifestation of the field x x neutrino top quark x xx x x x x = interaction with Higgs field 5 Loose Strings Comparison to EM Note: In this plot the Y axis is defined such that the energy of the field = 0 at 0 field strength. Energy is always defined relative to some reference point.* *note, this is not strictly true for General Relativity. See this for a discussion 6 Outline • Brief Review of Last Week • Introduction to Accelerators • Why we use accelerators • LHC Overview 7 Accelerators 101 Rhodatron, commercial accelerator • An accelerator is a device which increases the energy of a particle by increasing its speed • Accelerators are used to accelerate: • • electrons, protons and ions Used for a wide variety of applications: • • • • Cancer therapy • “Frontier” physics Ion implantation for electronics LHC Polymer cross-linking in plastics Biology, chemistry, materials science research More info: http://science.energy.gov/~/media/hep/pdf/files/pdfs/accel_for_americas_future_final_report.pdf 8 How acceleration happens • To accelerate an object you need to exert a force on it (F = ma) : • • Electromagnetic force is the only viable option! Can accelerate only charged particles • Electric fields push particles in the direction of the field • Constant field = constant acceleration • Hard to maintain large constant field, so alternating fields are used 9 Accelerating Particles 10 Accelerating Particles 11 Linear Accelerator acceleration regions 12 The trouble with linear accelerators • To achieve high energies, linacs need to be very long • Highest energy one was 2 miles long! (Stanford) • Need to go to circular designs to make compact machines The SLAC linear accelerator 13 Magnetic Fields • To have a circular accelerator • you need to bend charge particles Magnetic fields push charged particles perpendicular to their direction • In a constant magnetic field, charged particles travel in a circular orbit 14 Cyclotron • E.O. Lawrence first combined electric and magnetic fields to produce cyclotron • Nobel Prize 1939 15 Animated Cyclotron 16 Modern Circular Accelerators • Modern accelerators use varying magnetic field strength to bend particles and timed radio frequency to accelerate them in at a fixed radius Acceleration region Magnets Vacuum tube Synchrotron Straight Sections Injector Electromagnets Acceleration region (RF cavities) 17 Outline • Brief Review of Last Week • Introduction to Accelerators • Why we use accelerators • LHC Overview 18 Why accelerate particles? 19 Why accelerate particles? • (Obvious) Answer: to make higher energy particles! 19 Why accelerate particles? • (Obvious) Answer: to make higher energy particles! • Why do we want higher energy particles? 19 Why accelerate particles? • (Obvious) Answer: to make higher energy particles! • Why do we want higher energy particles? • Particle physicist answer: E = mc2 19 Why accelerate particles? • (Obvious) Answer: to make higher energy particles! • Why do we want higher energy particles? • Particle physicist answer: E = mc2 • The real equation: 19 Why accelerate particles? • (Obvious) Answer: to make higher energy particles! • Why do we want higher energy particles? • Particle physicist answer: E = mc2 • E2 = m2c4 + p2c4 • The real equation: 19 Why accelerate particles? • (Obvious) Answer: to make higher energy particles! • Why do we want higher energy particles? • Particle physicist answer: E = mc2 • • E2 = m2c4 + p2c4 • The real equation: A particle’s momentum can be converted into mass 19 Why accelerate particles? • (Obvious) Answer: to make higher energy particles! • Why do we want higher energy particles? • Particle physicist answer: E = mc2 • • E2 = m2c4 + p2c4 • The real equation: A particle’s momentum can be converted into mass 19 Matter out of Energy! 20 Relativity! • The closer a • particle gets to the speed of light, it’s total energy dramatically increases! We win a lot by small increases in velocity! Relativistic energy Classical energy (wrong) http://www.phys.unsw.edu.au/einsteinlight/jw/module5_equations.htm 21 So, we accelerate particles to give them more energy and from energy, we can create new particles, like the Higgs! 22 23 Outline • Brief Review of Last Week • Introduction to Accelerators • Why we use accelerators • LHC Overview 24 The LHC • Located near Geneva, Switzerland • Pan-european project with significant North American and Asian contributions 25 • Tunnel is 27 km long, ~100m below the earth. • Collides protons at a center of mass energy of 14 TeV! 26 Specs 27 • 9600 magnets Specs 27 • 9600 magnets • Specs Bending magnets: 1232 dipoles (most of the total magnet mass) 27 • 9600 magnets Specs • Bending magnets: 1232 dipoles (most of the total magnet mass) • Focussing and correcting magnets make up the rest 27 • 9600 magnets Specs • Bending magnets: 1232 dipoles (most of the total magnet mass) • • Focussing and correcting magnets make up the rest Cooled to 1.7 degrees above absolute 0 using superfluid helium 27 • 9600 magnets Specs • Bending magnets: 1232 dipoles (most of the total magnet mass) • • Focussing and correcting magnets make up the rest Cooled to 1.7 degrees above absolute 0 using superfluid helium • 8 RF cavities per beam 27 • 9600 magnets Specs • Bending magnets: 1232 dipoles (most of the total magnet mass) • • Focussing and correcting magnets make up the rest Cooled to 1.7 degrees above absolute 0 using superfluid helium • 8 RF cavities per beam • 2 Million V @ 400 MHz 27 • 9600 magnets Specs • Bending magnets: 1232 dipoles (most of the total magnet mass) • • Focussing and correcting magnets make up the rest Cooled to 1.7 degrees above absolute 0 using superfluid helium • 8 RF cavities per beam • • 2 Million V @ 400 MHz Wall plug: 120V @ 60Hz 27 • 9600 magnets Specs • Bending magnets: 1232 dipoles (most of the total magnet mass) • • Focussing and correcting magnets make up the rest Cooled to 1.7 degrees above absolute 0 using superfluid helium • 8 RF cavities per beam • • 2 Million V @ 400 MHz Wall plug: 120V @ 60Hz • All in a vacuum system 27 • 9600 magnets Specs • Bending magnets: 1232 dipoles (most of the total magnet mass) • • Focussing and correcting magnets make up the rest Cooled to 1.7 degrees above absolute 0 using superfluid helium • 8 RF cavities per beam • • 2 Million V @ 400 MHz • Beam vacuum is 10-13 of earth’s atmosphere! Wall plug: 120V @ 60Hz • All in a vacuum system 27 Dipoles • 35 tonnes each • 14.3 m long • 8.3 Tesla field • • Earth’s field: 5x10-5 T • Medical MRI machines: 1.5-3T Refrigerator magnet: 1x10-3 T 28 Magnetic field of LHC dipoles 29 From the inside 30 Why so cold? 31 Why so cold? • To generate high magnetic field you need high electric current 31 Why so cold? • To generate high magnetic field you need high electric current • Currents produce magnetic fields 31 Why so cold? • To generate high magnetic field you need high electric current • Currents produce magnetic fields • In normal metals, high current = high resistance 31 Why so cold? • To generate high magnetic field you need high electric current • Currents produce magnetic fields • In normal metals, high current = high resistance • Very hot! Needs lots of power 31 Why so cold? • To generate high magnetic field you need high electric current • Currents produce magnetic fields • In normal metals, high current = high resistance • Very hot! Needs lots of power • Enter superconductivity! 31 Why so cold? • To generate high magnetic field you need high electric current • Currents produce magnetic fields • In normal metals, high current = high resistance • Very hot! Needs lots of power • At very low temperatures, some metals loose all resistance • Enter superconductivity! 31 Why so cold? • To generate high magnetic field you need high electric current • Currents produce magnetic fields • In normal metals, high current = high resistance • Very hot! Needs lots of power • At very low temperatures, some metals loose all resistance • Can have (in theory) infinite current! • Enter superconductivity! 31 Picture of Superconductivity http://www.abc.net.au/science/articles/2011/07/20/3273635.htm 32 The accident.... • 19 Sep 2008 damaged ~50 magnets • Delayed start until late 2009! 33 November 2009: First Collisions! 34 • The LHC is the 5th accelerator in the a chain • Start with a bottle of hydrogen • First use a linear accelerator • Followed by 3 small(ish!) circular accelerators to get protons to 450 x rest energy • LHC take protons from 450x rest energy to 7000x rest energy • ~3000 bunches of 1011 protons at once 35 36