Introduction to Experimental Particle Physics Heavily indebted to 1. Steve Lloyd Queen Mary s College, London 2004 2. Robert S. Orr University of Toronto 2007 3. Z. Vilakazi University of Cape Town -2006 For use of ideas/material from their lectures Among the many books I ve consulted the following were the ones I found most instructive Introduction to High Energy Physics D.H. Perkins Particle Physics B.R.Martin & G.Shaw The Fundamental Particles and Their Interactions William B. Rollnick
Introduction to Experimental Particle Physics Total of 12 Lectures over the next 4 weeks to Provide an understanding of the field of Particle Physics including Its history Techniques deployed mainly experimental but with the necessary mathematics & theory Experimental phenomena, discoveries and their significance
Introduction to Experimental Particle Physics Outline of the Course: 1. The History & Fundamentals 2. Special Relativity & Units 3. Accelerators 4. Detectors 5. Attributes & QPM 6. Forces Electromagnetic 7. Weak Force 8. CP Violation 9. Quantum Chromodynamics 10.ElectroWeak Unification 11.Neutrino Physics 12.Summary of SM & Brief Look Beyond
The Fundamentals Particle Physics studies the deepest elementary constituents of matter and the forces between them. Making use of the two most basic theoretical constructs of Physics Special Relativity Quantum Mechanics to Probe the Structure of Matter Large objects with our Eyes Receiving Light reflected/emitted by the objects limited by the wavelength of the visible range of the e.m. spectrum Go deeper see smaller structures within matter - Need probes (Waves) of much smaller wavelength (de Broglie s Particle-Wave Duality) de Broglie s relationship betweenmomentum (p) & Wavelength (λ): λ = h/p So for p = 1 Gev/c, λ = 1.2 fm with h= 197MeV fm
Different Levels of Matter as we know it:
The History: Up to 1930 known particles: Electron, photon and neutrino (postulated to explain the missing energy in β-decay), proton and neutron (inside Nucleus) The 1st Anti-particle the positron was discovered by Carl Anderson B X
The same year (1932) James Chadwick observes a free Neutron In 1933 Fermi sets out his Theory of Beta Decay n p e - υ e 1935 Yukawa proposes his Meson Hypothesis Nuclear force due to exchange of particles with mass (Mesons). Anderson & Seth Nedermeyer discover the Muon (assumed to be Yukawa s proposed Meson but) was far too penetrating in matter to be the required exchange particle between nucleons AND it decayed to an e ± at rest rather than being absorbed by the nucleus as a meson would be. 1946 Cecil Powell discovers the Charged Pion observing the decay Neutral Pion seen in 1950 decaying to 2 Photons. π + µ + υ µ followed by µ + e + υ µ υ e
1947 Rochester & Butler see Strange long-lived in the Cloud Chamber K + µ + υ µ Neutral K 0 A New quantum Number Strangeness Chamberlain & Segre observe the antiproton in 1955 p p 8 Pions in the final state NO NUCLEON
1960/1970s saw observation of a whole zoo of long and short lived sub-atomic particles
A Real Mess that needed theoretical input to sort it out Gellman and Salam independently proposed an underlying structure the 8-fold way based on quaintly named quarks u, d, s - to explain the zoo of strongly interacting particles theory that led to the prediction of a new particle The Ω- made up of 3 strange quarks
D.H. Perkins
Theoretical Highlights 1950 sees advent of the Quantum Theory of Electromagnetism -QED describing the interaction of charged particles via photon exchange. The Architects: Richard Feynman Julian Schwinger Sin-itiro Tomonaga
Gellman s Quarks were followed in the 1970s with the Theory of Quantum Chromodynamics postulates a) New quantum numbers 3 Colours red, blue & green quarks carry colour b) Strong Interactions occur via exchange of gluons Progress in understanding the Weak Interaction as a manifestation of QED at high Energies - ElectroWeak Interaction exchange particles W +, W - and Z 0 as the Carriers of the Weak Force and the γ the carrier of the electromagnetic Force Sidney Glashow Abdus Salam Steven Weinberg
Back to Experimental Discoveries A new fourth Quark Charm (c) postulated by Glashow, Iliapolous & Maiani in (the GIM mechanism) in 1970 Discovered simultaneously at SLAC (Richter)& Brookhaven (Sam Ting) in 1974
SLAC e + e - Ψ hadrons Brookhaven p + Be J ( e + + e - )+ X dimuons e + e - M=3096MeV, Γ=91 KeV a narrow cc bound state D.H. Perkins
A new third charged Lepton Tau was discovered a year later (1975) at SPEAR (SLAC Positron Electron Collider) Martin Perl e + + e - τ + + τ - with τ + µ + + υ µ + υ τ and τ - e - + υ e + υ τ Event appears as e + + e - µ + + e - µ + e + τ + τ - e - e -
Now 3 charged leptons, 2 neutrinos, 4 - (u,d) (c,s) quarks! Must be another neutrino to go with the Tau And for aesthetic symmetry another pair of quarks with the charged leptons and their neutral partners 1978 sees the discovery of the b-quark (b for beauty/bottom) at Fermilab p p e + e - +.. M=9.46GeV, Γ=53KeV again a narrow bb bound state. Open B-hadrons need 10.58 GeV
Still missing the neutrino to go with the Tau lepton to complete symmetry since Leptons come in pairs Direct Observation ν τ +p τ + + Not Yet? Count the number of massless (low mass < 45 GeV) neutrinos One of the 1st Results to come from CERN LEP Collider Measure the missing width of the Z 0 i.e. to all invisible final states (pairs of neutrinos)
The b-quark must have a partner since quarks come in pairs a 17 year wait 1995 Fermilab discovers the t-quark (Truth/Top) pp WbW b 4-Jet Event Vilakazi 2006
The symmetry of matter is complete 3 pairs of quarks and 3 pairs of leptons What Remains Vector Bosons of Weak & Strong Interactions 1979 The Gluon at PETRA e + e - Collider in Hamburg in 3-Jet events 1983 W Z at CERN at SPS p p Collider at CERN
Various expts (1998 onwards) Search for neutrino oscillation indicate neutrinos NOT massless LEP II (105 GeV e + on 105 GeV e - ) indicates existence of the HIGGS Boson
Basic Building Blocks of Matter (at least ones we know of, so far!) 1) Quarks-------> Hadrons -------> Nuclei 3 Generations of quark-pairs each quark with J P = ½ + - each with a unique new Quantum Number Charge = 2/3 Charge = -1/3 Up-Down u d Protons & Neutrons I = ½ Charm-Strange I = 0 Top-Bottom I = 0 M = 1.5 4.0 MeV c M = 1.15 1.35 GeV C = 1 t M = 174 178 GeV M = 4.0 8.0 MeV s M = 80 130 MeV S = -1 b M = 4.1 4.9 GeV uds light quarks s-quarks with u/d produce strange particles cbt Heavy quarks - T = 1 B = -1
Basic Building Blocks of Matter (Cont.) 2) Leptons Again 3 generations of Lepton-pairs each Lepton with J = ½ Charged Neutral (Neutrino) e (Electron) M = 0.5 MeV, L e = 1 µ (Muon) M = 105.7 MeV, L µ = 1 τ (Tau) M = 1.78 GeV, L τ = 1 ν e M < 3 ev, L e = -1 ν µ M < 0.19 MeV, L µ = -1 ν τ M < 18.2 MeV, L τ = -1 Each pair has a unique Lepton Quantum Number which is conserved within the Standard Model with Zero Mass Neutrinos.