Who/What/Where is TRIUMF?

Transcription

1 Who/What/Where is TRIUMF? TRIUMF is Canada's National Lab for Particle and Nuclear Physics ~470 staff, ~220 Canadian Scientists, ~380 foreign scientists Joint venture of UBC, SFU, UVic, Alberta, Carleton, Toronto Collaborations with 14+ institutions in Canada, 36+ abroad Happen to be located on UBC campus

2 What do we do? DON'T... Make bombs Generate power Have an assembly line DO... Stellar nuclear synthesis Fundamental Interactions Medical Physics Nuclear structure Material properties Applications of physics

3 WHY? D' ou venons nous? Q ue sommes nous? D' ou allons nous? Physicists ask - Why does the universe and everything in it exist, and why does it look the way it does

4 This Hour has 13 Billion years 1. The Standard Model (briefly) 1. What is everything made of? 2. Big Bang Cosmology (briefly-er) 1. History of the universe 3. Connection between 1) and 2) 4. Creation of the elements 5. (Where TRIUMF fits in)

5 Fundamental particles Idea of a fundamental particle age old started with Democritus (~400BC) atom means indivisible Search for the fundamental constituents of matter, and the fundamental rules governing their interaction is called Particle Physics Techniques have evolved drastically over time

6 Evolution of the fundamental particles fundamental pa rticles are electrons and quarks which have no size Huh? Then how is stuff s olid

7 Fundamental Forces Helium (not to scale) Electromagnetic Force (also binds molecules) ==> P hoton Exchange Strong Force (also binds nuclei) ==> Glu on Ex change Weak Force (important for radioactive decay) ==> W, Z Boson Exchange d u d u p n Forces give matter its structure

8 How do we see p = 500 nm ( m) E = 2.5 ev = nm E = ev

9 Why we build particle accelerators Idea #1 : to see so mething, must touch it with something smaller Idea #2 : in quantum mechanics, higher energy ==> smaller dimensions

10 Tools of the trade particle Light Helium nucleus proton electron Energy [ev] ~1 ~ ~ ~ size ~1 ~ ~ ~ cell other nuclei protons, neutrons quarks what [ m]

11 The Standard Model (on a T-shirt)

12 The other force - Gravity Einstein's General Theory of Relativity G = 8 T g geometrical theory unlike Standard Model Friedmann (1922) said that GR predicts that universe is expanding Edwin Hubble (1929) observed that universe is expanding Hmmm, if universe is expanding, if we run clock backwards, then...

13 The Big Bang Take all the energy in the universe, and start shrinking it into a smaller and smaller volume Average energy gets higher and higher Eventually energy high enough to Break apart atoms, then Break apart nuclei, then Break apart protons, then (think compressing a bicycle pump) etc etc... Eventually get to a point The Big Bang

14 History of the Universe, Part II TRI UM F

15 Big Bang: the moment after A roughly-pretty-good-outline-of-an-idea about what happened t<10-43 seconds: 10-43<t<10-35 seconds: quantum gravity??? As universe 'cooled', gravitation force separated from others ~10-35 seconds : Inflation!! Universe enlarges unimaginably fast From much smaller than a proton to the size of a softball

16 Hot Particle Soup 10-35<t<10-5 seconds somehow fun damental particles are created Strong force separates from the others Then Weak force separates from Electromagnetic W, Z bosons created Soup of quarks, photons, gluons, W, Z, etc... Too energetic to stick together

17 Whence Antimatter? Q: if we started with equal matter and anti-matter, why didn't they just annihilate each other and leave just photons? A: CP Violation i.e. Matter and anti-matter interact (very) slightly differently. Result in small excess of matter NOT TOTALLY UNDERSTOOD

18 Primordial Nucleosynthesis 10-5<t<100 seconds: Most Anti-particles gone Quarks+gluons slow down enough to bind into protons, neutrons, mesons But no nuclei form since deuteron (p+n nucleus) unstable 100 s < t < 300,000 years Deuteron stable, light elements form But only up to 7Li since no stable mass-8 nuclei p, D, 3He, 4He, 7Li

19 Cosmic Background Radiation At 300,000 years, nuclei capture electrons to become atoms T=3000K Universe now transparent to photons As universe expands, photon wavelength increases Energy decreases Expanding blob of gas Almost all hydrogen Not exactly uniformly distributed Slight density differences

20 STOP!!!Are you pulling my leg? Predict that if 13 billion years go THEN ~3K today Measurement - bang on! Inflation predicts universe smooth and flat tiny CMB deviations --> smooth Also distribution of galaxies Pattern of deviations --> flat General relativity calculation

21 Are you pulling my leg? (part 2) W, Z bosons observed by experiments at CERN, SLAC A TRIUMF experiment helped determine key property of W CP violation detected in 1964 matter/anti-matter asymmetry TRIUMF helped build detector for latest-generation experiment studying this problem Predicted BBN element abundances agree with observation And CMB pattern supports the result

22 What happened next? The Stars formed After ~1 billion years, inhomogeneities in gas clouds 'clump together' by mutual gravitation to common centre Eventually, speed up enough to initiate nuclear fusion reactions Reaction primarily creates more helium from the hydrogen Clusters, galaxies, etc. forming as well

23 Red Giant phase Helium gradually builds up in core Eventually Helium core contracts, outer expands --> Red Giant Energy increases so that Helium can fuse to make Carbon and Oxygen He + 4He 8Be 4 He + 8Be 12C (carbon) 4 He + 12C 16O (oxygen) 4

24 Heavier element synthesis For stars < 10 solar masses process stops at oxygen Becomes nebula+white dwarf H, He, C, and O ejected into space Star > 10 solar masses Enough energy for helium, carbon, oxygen, and silicon fusion Process stops with iron production Iron most tightly bound nucleus Get onion-like structure in star

25 Stellar burning time scales Fuel Major Products Threshold Temperature (K) Hydrogen Helium 4 Million 7 x 106 years Helium Carbon, Oxygen 100 Million 5 x 105 years Carbon Oxygen, Neon, Sodium, Magnesium 600 Million 600 years Oxygen Magnesium, Sulfur, Phosphorous, Silicon 1 Billion 6 months Silicon Cobalt, Iron, Nickel 3 Billion 1 day Duration of stage

26 Heavy Element Synthesis - supernova Stars > 10 solar masses No more fusion after iron produced No more energy to counteract gravitational collapse In seconds, major implosion followed by explosion supernova! Heaviest elements created R-process, s-process

27 What happens to ejected matter? Matter ejected from nebula or supernova eventually recombine from gravitation attraction to form new stars Hydrogen, etc tends to collect in centre Heavier elements tend to the edges New star! Planets! Densest elements end up in... men? We are Star Dust!

28 Are you SURE?? - Yes. Look at the solar surface, interstellar space to determine relative abundances Model stellar evolution and see if you can predict it Study meteorite grains older than solar system RESULT? - very good agreement

29 Nuclear Astrophysics at TRIUMF Agreement NOT perfect, still much to learn TRIUMF ISAC facility studies these stellar reactions Nuclear astrophysics Premiere facility in the world

30 13 billion years later...

31 Summary Historically parallel pursuits of particle physics and cosmology have now converged This is an extremely exciting time for these fields New accelerators and astronomical devices promise great discoveries Getting closer to age-old question... D' ou venons nous? Q ue sommes nous? D' ou allons nous? Answer? We are star dust. (In our own quiet way, TRIUMF is playing a key role)

32 Beyond the Standard Model Standard Model incomplete Building next generation accelerator to test new ideas What about Gravity??? Why so many particles? Neutrinos have MASS! Push back closer to Big Bang extra di mensions branes and s uperstrings TRIUMF taking part in the fun