Buxton & District U3A Science Discussion Group “Higgs Boson – what is it?” John Estruch 19 October 2012

Buxton & District Science Discussion Higgs Boson What is it? What difference will finding it make to my life? How much did it cost to look for it? Was it worthwhile?

Buxton & District Science Discussion What are we going to talk about A little bit of history The standard model The Large Hadron Collider (LHC) So what does it mean?

Buxton & District Science Discussion When I did my O and A levels Forces Gravity Electricity & Magnetism Particles Electrons Protons Neutrons Heard of but didn’t study until university Relativity (very fast) Speed of light invariant Can’t exceed light speed Energy/mass equivalence Quantum Mechanics (very small) Energy “quantised” Wave-particle duality Uncertainty principle Pauli exclusion principle Classical Physics (pre-1900) Beginning of modern Physics

Buxton & District Science Discussion What was next in Modern Physics? New Forces Strong Nuclear Force Glues nucleus together 100 times stronger than electromagnetism Very short range Weak Nuclear Force Explains β radiation times weaker than electromagnetism Very short range New Particles (created in accelerators) Leptons Includes electron Feel electromagnetic & weak forces (& gravity) only Hadrons Includes proton Feel electromagnetic, weak & strong forces (& gravity)

Buxton & District Science Discussion An aside Where did the Physicists get the particle names from: Atom – Proton – Electron – Hadron – Lepton – Quark – from Latin atomus "indivisible particle," from Greek atomos "uncut, unhewn; indivisible," from Greek “protos” meaning “first” from “electric” meaning “resembling amber” from Greek “hadros” meaning “thick, bulky” from Greek “leptos” meaning “small, slight” from “Three quarks for Muster Mark” in James Joyce's Finnegans Wake meaning ???????

Buxton & District Science Discussion What are we going to talk about A little bit of history The standard model The Large Hadron Collider (LHC) So what does it mean?

Buxton & District Science Discussion What is the standard model A “quantum field theory” which: Was gradually developed by many people during the 1960s and 1970s Incorporates three of the four forces: Electromagnetic Weak Strong Describes the sub-atomic particles Quarks (which make up the hadrons) Leptons “Gauge Bosons” which “mediate” the forces (they “carry” the force)

Buxton & District Science Discussion The Higgs mechanism Also known as Englert-Brout-Higgs-Guralnik-Hagen-Kibble mechanism Developed around Without it the theory models only “massless” particles Implies a new massive boson “the Higgs leads to all the matter in the universe” – hence “the God Particle” Press love it Physicists hate it

Buxton & District Science Discussion Is the Standard Model a good theory? Yes Describes well particles & behaviour known at the time Predicted particles subsequently found: – Tau (1975), Tau neutrino (2000) – Bottom quark (1977) – W +,W -, Z 0 (1983) – Top quark (1995) But it’s not the final answer Does not incorporate gravity Cannot explain large amount of “dark matter” / “dark energy” required for current cosmological theories Some claim it is “inelegant” The big test Does the Higgs Boson exist? Is the Higgs Field real?

Buxton & District Science Discussion What are we going to talk about A little bit of history The standard model The Large Hadron Collider (LHC) So what does it mean?

Buxton & District Science Discussion Why particle accelerators? Only lightest of each type of particle exists in a “low energy” environment (i.e. electron, proton, neutron) If a heavier particle exists it quickly tends to a lower energy state (i.e. decays to a lighter particle) Heavier particles can exist in high energy environments (e.g. Shortly after Big Bang) If we accelerate particles to high energy & collide them we can briefly bring heavier particles into existence

Buxton & District Science Discussion LHC Largest accelerator to date 27km circumference tunnel 2 beams of protons circulate in opposite directions at 11,000 revs per second Beams cross at 4 points – protons can collide here Energy enough to create particles 7,000 times heavier than proton Operates at °C (1.9 K) – colder than space Vacuum of Atm – less gas than the moon Consumes 120MW of electric power (6 x Buxton) Cost about £2.6bn

Buxton & District Science Discussion Detectors Higgs Boson will decay before it leaves beam pipe – so we can’t see it. So we look for the shower of particles it produces. Detector records data about particles. Complex computer models figure out what came from the collision Atlas 45m long, 25m high, 7,000 tons 3,000 physicists, 174 universities, 38 countries 3,200 terabytes of data per year

Buxton & District Science Discussion Another aside BEBC (Big European Bubble Chamber) The apparatus I used for my PhD Now sits in CERN Microcosm Museum, in the garden On this visit in 2003 the guide said “that was how they did experiments in the olden days”

Buxton & District Science Discussion So what have they found? July Atlas & CMS teams each announce: Found a boson with mass between 125GeV/C 2 and 126GeV/C 2 which is “consistent with” the/a Higgs Boson Actually they have also done a lot of other physics but that isn’t very newsworthy.

Buxton & District Science Discussion What are we going to talk about A little bit of history The standard model The Large Hadron Collider (LHC) So what does it mean?

Buxton & District Science Discussion Will the Higgs Boson change my life? No! (not in the short term) No cure for cancer No solution to world hunger No solution to global warming No new mobile phones

Buxton & District Science Discussion Is there any value in pure science? Standard model is where Quantum Mechanics was years ago: Esoteric Public know very little about it No immediate practical use But Quantum Mechanics led to: Most modern Chemistry & Biochemistry – Materials, medicines etc. Understanding of DNA (according to Francis Crick) MRI Scanners Transistor, silicon chip, CRT tubes, (imagine no TV, no computers, no electronics!) etc.

Buxton & District Science Discussion More than pure Physics Technology developments from CERN/LHC: IT developments: – WWW – 1991 – LHC Computing Grid 2005 Technology Developments – Superconducting magnets – Large scale high vacuum Control systems: – You try keeping many bunches with 1 billion protons each moving in opposite directions in 6.3 cm pipes in 27km circuit at % of the speed of light without touching the sides and making sure they cross in exactly the right places. Lots more…….

Buxton & District Science Discussion Questions?