Walton, the LHC and the Higgs boson Cormac O’Raifeartaigh (WIT) Albert Einstein Ernest Walton

Overview I. LHC What, why, how II. A brief history of particles From Walton to the Standard Model III. LHC Expectations The Higgs boson Beyond the Standard Model Particle cosmology

The Large Hadron Collider (CERN) N o black holes High-energy proton beams Head-on collision Huge energy density Create short-lived particles E = mc 2 Detection and measurement

Why Explore fundamental structure of matter Investigate inter-relation of forces that hold matter together T = K t = 1x s V = football Study conditions of early universe Test cosmological theory Mystery of dark matter Mystery of antimatter Highest energy density since BB

Cosmology E = kT → T =

How E = 14 TeV (2.2 µJ) λ = hc/E = 1 x m Ultra high vacuum Low temp: 1.6 K LEP tunnel: 27 km Superconducting magnets 600 M collisions/sec (1.3 kW)

Particle detectors 4 main detectors CMS multi-purpose ATLAS multi-purpose ALICE quark-gluon plasma LHC-b antimatter decay

Particle detectors Tracking device measures momentum of charged particle Calorimeter measures energy of particle by absorption Identification detector measures velocity of particle by Cherenkov radiation

recycling 9 accelerators velocity increase? K.E = 1/2mv 2

II Particle physics (1930s) electron (1895) proton (1909) nuclear atom (1911) Rutherford Backscattering what holds electrons in place? what holds nucleus together? what causes radioactivity? Periodic Table: protons (1918) neutron (1932)

Four forces of nature Force of gravity Holds cosmos together Long range Electromagnetic force Holds atoms together Strong nuclear force: holds nucleus together Weak nuclear force: Beta decay The atom

Strong force strong force >> em charge indep (p +, n) short range Heisenberg Uncertainty massive particle 3 charge states Yukawa pion (π) Yukawa

Walton: accelerator physics Cockcroft and Walton: linear accelerator voltage multiplier: 0.5 MV →0.5 MeV Protons used to split the nucleus (1932) Nobel prize (1956) 1 H Li 6.9 → 2 He He 4 Verified mass-energy (E= mc 2 ) Verified quantum tunnelling Cavendish lab, Cambridge

Ernest Walton ( ) Born in Dungarvan Early years Limerick, Monagahan, Tyrone Methodist College, Belfast Trinity College Dublin (1922) Cavendish Lab, Cambridge (1928) Split the nucleus (1932) Trinity College Dublin (1934) Erasmus Smith Professor ( )

New particles (1950s) Cosmic rays Particle accelerators cyclotrons synchrotrons π + → μ + + ν

Particle Zoo (1950s, 1960s) Over 100 particles

Quarks (1960s) new periodic table p +, n not fundamental gauge symmetry prediction of  - SU3 → quarks new fundamental particles UP, DOWN, STRANGE Gell-Mann, Zweig Stanford experiments 1969

Quantum chromodynamics scattering experiments defining property = colour SF = interquark force asymptotic freedom confinement infra-red slavery The energy required to produce a separation far exceeds the pair production energy of a quark-antiquark pair,pair production energy

Quark generations (1970s –1990s) Six different quarks (u,d,s,c,t,b) Six leptons (e, μ, τ, υ e, υ μ, υ τ ) Gen I: all of ordinary matter Gen II, III redundant

Meanwhile… Gauge theory Unified field theory of e and w forces Salaam, Weinberg, Glashow Single interaction above 100 GeV Mediated by W,Z bosons Predictions Weak neutral currents (1973) W and Z gauge bosons (CERN, 1983) Rubbia and van der Meer Nobel prize 1984

The Standard Model (1970s) strong force = quark force (QCD) em + weak force = electroweak matter particles:fermions (spin ½) (quarks and leptons) force carriers:bosons (integer spin) Prediction: W +-,Z 0 boson Detected: CERN, 1983

Standard Model: 1980s correct masses but Higgs boson outstanding key particle: too heavy?

III LHC expectations (SM) Higgs boson Determines mass of other particles GeV Set by mass of top quark, Z boson Search…surprise?

Main production mechanisms of the Higgs at the LHC Ref: A. Djouadi, hep-ph/

Decay channels depend on the Higgs mass: Ref: A. Djouadi, hep-ph/

Ref: hep-ph/ A summary plot:

Expectations II: supersymmetry Unified field theory Grand unified theory (GUT): 3 forces Theory of everything (TOE): 4 forces Supersymmetry improves GUT (circumvents no-go theorems) symmetry of fermions and bosons gravitons: makes TOE possible Phenomenology Supersymmetric particles? Not observed: broken symmetry

Expectations III: cosmology ? 1. Finish SM (Higgs) ? 2. Beyond the SM (SUSY) 3. Missing antimatter? LHCb 4. Nature of dark matter? neutralinos? High E = photo of early U

Particle cosmology

LHCb Tangential to ring B-meson collection Decay of b quark, antiquark CP violation (UCD group) Where is antimatter? Asymmetry in M/AM decay CP violation Quantum loops

Summary Higgs boson Close chapter on SM Supersymmetric particles Open chapter on unification Cosmology Missing antimatter Nature of Dark Matter New particles/dimensions Revise theory

Epilogue: CERN and Ireland World leader 20 member states 10 associate states 80 nations, 500 univ. Ireland not a member No particle physics in Ireland European Organization for Nuclear Research