Particle Physics and the structure of Space, Time and Matter Tuesday 20 th March Prof. Ken Peach University of Oxford & Royal Holloway University of London

Ken PeachJohn Adams Institute20 March 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 Institute20 March Probing Inner Space 3 basic ways Look at it Heat it Smash it Wavelength Temperature TEnergy E h c/ =kTE=

Ken PeachJohn Adams Institute20 March Remarkable comment All three the same fundamental physics! Uses ‘light’ Uses ‘heat’ TUses ‘probe’ E h c/ =kTE= Photons ‘Photons’        

Ken PeachJohn Adams Institute20 March Scattered electronScattered lepton ConstituentsConstituents Particle Hammers proton electron { ProtonfragmentsProtonfragments Scattered ‘parton’ PhotonPhoton, W, Z

Ken PeachJohn Adams Institute20 March 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 Institute20 March The Particle Physicists “Periodic Table”

Ken PeachJohn Adams Institute20 March The Particle Physicist’s “Periodic Table” u u d d d u Proton Neutron The Chemist’s Periodic Table

Ken PeachJohn Adams Institute20 March 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 Institute20 March 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 Institute20 March 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 Institute20 March CERN from Space

Ken PeachJohn Adams Institute20 March Arial view of the CERN site © CERN

Ken PeachJohn Adams Institute20 March … and what is beneath the surface © CERN

Ken PeachJohn Adams Institute20 March ALEPH A detector for LEP Physics © CERN & PPARC

Ken PeachJohn Adams Institute20 March Some events Ze+e-Ze+e- Z+-Z+- Z   +  - ZqqZqq

Ken PeachJohn Adams Institute20 March More (complicated) events Z   +  -  Z  qqg Z  4 ‘jets’ e+e-W+W-e+e-W+W-

Ken PeachJohn Adams Institute20 March The Large Hadron Collider ATLAS CMS

Ken PeachJohn Adams Institute20 March 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 Institute20 March … but look what we have done to ‘empty space’ It is filled with these ‘fields’

Ken PeachJohn Adams Institute20 March 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 Institute20 March From microscopes to telescopes …

Ken PeachJohn Adams Institute20 March The biggest challenge … the Creation of the Universe! The Big Bang

Ken PeachJohn Adams Institute20 March From the Big Bang to today © CERN

Ken PeachJohn Adams Institute20 March 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 Institute20 March 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 Institute20 March 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 Institute20 March New physics scale Note: The vacuum ‘knows’ about particles already found … and all of the particles still to be found!  i -1 Log 10 [Energy Scale (GeV)] No Grand Unification Unification ! “e/m” “weak” “strong” Supersymmetry? Evolution of the strength of the interactions with increasing energy  3 -1  2 -1  1 -1

Ken PeachJohn Adams Institute20 March The Cosmic Recipe 1.The Hubble Constant [H 0 ] expansion rate of the Universe (~7.5  y -1 ) The Age of the Universe [t 0 ] (12-18  10 9 y) 2.The Temperature[ T 0 ] temperature of the cosmic microwave background today (~2.7 o K) 3.The Critical Density[  c ] just prevents eventual collapse (3H 0 2 /8  G N ~ g/cc) The actual density relative to  c [  ] (0.75  1.25) 4.The relative energy density of free space [   ] [aka the Cosmological Constant] (0.6  0.8) ____________… two related numbers________________ a)The relative total matter density [  m ] [all forms of gravitational matter] (0.15  0.45) b)The relative visible matter density [  B ] [normal ‘baryonic’ matter] (0.005  0.012) ____________… and two more numbers______________ I.The ratio of the electron to proton mass [m e /m p ] (1/1896) II.The fine structure constant [  ] (1/137) ___________________… and …_____________________ 5.The number of dimensions of space-time [d] (=3+1)

Ken PeachJohn Adams Institute20 March Dark Matter Prof. Richard Pogge Huge structures in ‘Empty Space’Rotation Curves for Galaxies

Ken PeachJohn Adams Institute20 March Dark Energy – more properties of the vacuum

Ken PeachJohn Adams Institute20 March The Cosmological Budget -  From the ‘flatness’ of space   1 From the observed galaxies & nucleosynthesis  B   0.01 From rotation curves of galaxies & large scale structure  Matter   0.34 Rate of expansion  Space   0.65

Ken PeachJohn Adams Institute20 March Particle Physics Cosmology 1 bb pair qq pairs very early time The Universe 1 bb pair qq pairs quarks intermediate time 1 bb pair 0 qq pairs quarks late time

Ken PeachJohn Adams Institute20 March … but … The matter-antimatter asymmetry in particle physics so far discovered is too small (by 10 orders of magnitude) –although physics beyond the Standard Model has more sources of matter-antimatter asymmetry … but the vacuum knows that there should be such an asymmetry! –Without this, matter, galaxies, the Sun, the Earth cannot be And neither can we! The Big Bang

Ken PeachJohn Adams Institute20 March 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

Ken PeachJohn Adams Institute20 March 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!