Introduction to Particle Physics Saturday July 3 rd 2010 APPEAL, Oxford Prof. Ken Peach

Ken PeachJohn Adams Institute3 July What is ‘Particle Physics’? The Particle Physics (or ‘High Energy Physics’) ‘Mission’ –identify the fundamental constituents of matter –describe the interactions (forces) between them A long and honourable history –Constituents ‘Earth, Fire, Air and Water’ of the Greeks ‘Atoms’ of Democretus and Lucretius –Forces Gravity (Newton) Electricity (Coulomb) A significant achievement of the 20 th century –The electron (JJ Thomson, 1897) –The top quark (CDF & D0, 1995) –QED, QCD, electro-weak (gravity)

Ken PeachJohn Adams Institute3 July An important equation  U=0 “U” is “the equation of state of the Universe”! Of course, we do not know what U is … but we can try to find out what U contains U = U known + U unknown U known is the result of experiment U unknown is the object of theory

Ken PeachJohn Adams Institute3 July Probing Inner Space 3 basic ways Look at it Heat it Smash it Wavelength Temperature TEnergy E h c/ =kTE=

Ken PeachJohn Adams Institute3 July Remarkable comment All three the same fundamental physics! Uses ‘light’ Uses ‘heat’ TUses ‘probe’ E h c/ =kTE= Photons ‘Photons’        

Ken PeachJohn Adams Institute3 July Scattered electronScattered lepton ConstituentsConstituents Particle Hammers proton electron { ProtonfragmentsProtonfragments Scattered ‘parton’ PhotonPhoton, W, Z

Ken PeachJohn Adams Institute3 July The Particle Physicist’s “Periodic Table” u u d d d u Proton Neutron The Chemist’s Periodic Table

Ken PeachJohn Adams Institute3 July HiggsBosonHiggsBoson? Force Carriers Z Z boson W W boson  photon g gluon Generations of matter Generations of matter  tau   -neutrino b bottom t top III  muon   -neutrino s strange c charm II e electron e e-neutrino d down up uI Leptons Quarks Particles and their Interactions Each with its own ‘antiparticle’ © Brian Foster

Ken PeachJohn Adams Institute3 July The Standard Model … After G Barbieri, ICHEP04

Ken PeachJohn Adams Institute3 July The Standard Model The Parameters 6 quark masses –m u, m c, m t –m d, m s, m b 3 lepton masses –m e, m , m  2 vector boson masses –M w, M Z (m , m g =0) 1 Higgs mass –Mh–Mh 3 coupling constants –G F, ,  s 3 quark mixing angles –  12,  23,  13 1 quark phase – –  Neutrino masses set to 0!

Ken PeachJohn Adams Institute3 July The Standard Model in action Take a process e + e -     - 4  2 /3s a is the fine structure constant s is the (C.of.M Energy) 2 (neglecting masses and √s<<M Z )

Ken PeachJohn Adams Institute3 July What still remains to be done? The origin of mass –“Hunting the Higgs” The origin of the forces –Strong, electro-weak & gravity, or just one fundamental force The origin of “Dark Matter” (& Dark Energy) –Accounting for most of the mass of the universe The origin of cosmological matter-antimatter asymmetry –Why does the universe today consist only of matter, not equal amounts of matter and antimatter Fundamental questions in particle physics that are equally fundamental questions in cosmology

Ken PeachJohn Adams Institute3 July High Precision Frontier Known phenomena studied with high precision may show inconsistencies with theory High Energy Frontier New phenomena (new particles) created when the “usable” energy > mc 2 [×2] How will we do it? 2 routes to new knowledge about the fundamental structure of the matter

Ken PeachJohn Adams Institute3 July How do we know all this? © CERN Matter & antimatter annihilate into energy Go to the highest energy See what happens Energy (MeV) ,000 10,000 1, e u,d s  c b  W Z t leptons quarks Weak Bosons Higgs?

Ken PeachJohn Adams Institute3 July Arial view of the CERN site © CERN

Ken PeachJohn Adams Institute3 July ALEPH A detector for LEP Physics © CERN & PPARC

Ken PeachJohn Adams Institute3 July Some events Ze+e-Ze+e- Z+-Z+- Z   +  - ZqqZqq

Ken PeachJohn Adams Institute3 July More (complicated) events Z   +  -  Z  qqg Z  4 ‘jets’ e+e-W+W-e+e-W+W-

Ken PeachJohn Adams Institute3 July The Standard Model Where are we?  ? ? Neutrino Oscillations need a neutrino mass term  i  M ij  j Why are the strong, electromagnetic and weak interactions like they are?

Ken PeachJohn Adams Institute3 July New physics scale Energy evolution of the interaction strength  i -1 Log 10 [Energy Scale (GeV)] No Grand Unification Unification ! “e/m” “weak” “strong” Supersymmetry?  3 -1  2 -1  1 -1

Ken PeachJohn Adams Institute3 July The Large Hadron Collider ATLAS CMS

Ken PeachJohn Adams Institute3 July ATLAS Z 0 event

Ken PeachJohn Adams Institute3 July ATLAS W +  e + event

Ken PeachJohn Adams Institute3 July ATLAS 4-jet event

Ken PeachJohn Adams Institute3 July ATLAS – a potential problem

Ken PeachJohn Adams Institute3 July A CMS event

Ken PeachJohn Adams Institute3 July First data Before discovering new things, need to “discover” the old things, just to be sure that we understand the new instruments.

Ken PeachJohn Adams Institute3 July From microscopes to telescopes …

Ken PeachJohn Adams Institute3 July The biggest challenge … the Creation of the Universe! The Big Bang

Ken PeachJohn Adams Institute3 July Particle Physics and Cosmology The Higgs potential … Primordial ripples Fundamental mode Geometry Potential wells compression baryons Rarefaction… etc WMAP Data, Verde, LP03 the particle spectrum … and the unknown … Illustrations from Muryama, LP03 should explain

Ken PeachJohn Adams Institute3 July Galaxy formation The state of the Universe Time (sec) Temperature ( o K) The Big Bang Biology Solar System forms Atoms form Chemistry begins Today 3 x s 3 o K Neutron lifetime nucleosynthesis Protons, neutrons & nuclei form W & Z production Particle physics

Ken PeachJohn Adams Institute3 July Summary We have a wonderful “model” to describe the particle world –but it is not a theory it describes but does not explain –and has “missing links” What about gravity? Why 3 forces? Why 3 generations? How does the matter-antimatter asymmetry arise? Why 3 space and 1 time dimension? Are there more dimensions? … (fortunately) still a lot to learn!

Ken PeachJohn Adams Institute3 July

Ken PeachJohn Adams Institute3 July What is the Vacuum? Dictionary Definitions: An entirely (or very nearly) empty space Chambers 20 th Century 1.Emptiness of space; space unoccupied by matter 2.(a) A space entirely empty of matter (b) A space empty of air, esp. one from which the air has been artificially withdrawn 3.An empty space; a portion of space (left) unoccupied or unfilled with the usual or natural contents OED My definition: That which remains when everything else is taken away

Ken PeachJohn Adams Institute3 July The problem of mass The Standard Model relies on –Relativity +Quantum mechanics Relativistic Quantum Field Theory –Each particle has an associated all-pervasive ‘field’  (x,t) –Symmetry There is no ‘special place’ in the Universe There are no ‘preferred directions’ in space-time There is ‘local autonomy’ for the particle fields –Produces a beautiful theory –… with all particles massless! Adding mass violates the beautiful symmetries The Higgs Mechanism –Fill space-time with another (Higgs) field  (x,t) A new type of force with special properties –… that give mass to the particles …and leaves a signature behind …– the Higgs Boson!

Ken PeachJohn Adams Institute3 July Origin of Mass ? m=0, v = speed of light No Higgs field 00 00H H H H V 0 With Higgs field

Ken PeachJohn Adams Institute3 July … but look what we have done to ‘empty space’ It is filled with these ‘fields’

Ken PeachJohn Adams Institute3 July The vacuum … 1.‘knows’ about all particles that exist …and that can exist 2.‘knows’ about all forces that exist …and that can exist 3.has more energy (x 10) than all normal matter in the universe …we are cosmologically less significant than ‘empty space’ 4.created the Universe …as we know it today 5.made more matter than antimatter … and so created the conditions that allow us to exist! Remember The vacuum is the most complicated thing in the Universe