String Theory in the LHC Era J Marsano (marsano@uchicago.edu) 1 - PowerPoint PPT Presentation

String Theory in the LHC Era J Marsano (marsano@uchicago.edu) 1 Friday, April 27, 12

String Theory in the LHC Era 1. Electromagnetism and 5. Supersymmetry Special Relativity 2. The Quantum World 6. Einstein’s Gravity 3. Why do we need the Higgs? 7. Why is Quantum Gravity so Hard? 4. The Standard Model and Beyond 8. String Theory and Unification 9. String Theory and Particle Physics 2 Friday, April 27, 12

We have already encountered essentially 2/3 of the Standard Model Quantum Weak Interactions Electrodynamics - Lecture 2 - Lecture 3 3 Friday, April 27, 12

In lecture 2, we met Quantum Electrodynamics γ e − e − Electrons interact by exchange of a photon Massless force carrier e − e − r 4 π Dimensionless e ∼ coupling 137 Long range force! Julian Richard Sin-Itiro 4 Schwinger Feynman Tomonoga Friday, April 27, 12

n → p + + e − + ν e In lecture 3, we met the Weak Interactions 1 10 − 16 cm � 2 e − � G F ∼ (300 GeV) 2 ∼ p + ` proton ∼ 10 − 13 cm n m proton ∼ 0 . 938 GeV ν e n n Z 0 ν e ν e M W ∼ 80 GeV M Z ∼ 91 GeV 5 Friday, April 27, 12

Quantum Electrodynamics Weak Nuclear Force Weak bosons W ± , Z 0 Photon γ Massless force carrier Massive force carriers Long range force Short range force 1 Range set by Mass of W ± , Z 0 p + γ e − e − n W − e − e − e − ν e 6 Friday, April 27, 12

Building to the Standard Model.... Electromagnetism Leptons Weak (electron, neutrino, and Interactions two similar pairs of particles) 7 Friday, April 27, 12

What about protons and neutrons? ...for that matter what keeps the protons together in the nucleus of an atom? ...we are missing a force... 8 Friday, April 27, 12

p + p + π 0 n n m π 0 ∼ 0 . 135 GeV Hideki Yukawa Yukawa proposed a ‘force carrier’--pion (he didn’t call it that) Very short lived particle How to observe? π 0 → γ + γ τ π 0 ∼ 8 . 4 × 10 − 17 s 9 Friday, April 27, 12

Cosmic Rays! Expose special photographic plates at high altitudes (on mountains or balloons) Cecil Frank Powell 10 Friday, April 27, 12

Particle accelerators Tevatron at Fermilab By the 1960’s, hundreds of particles were discovered that participate in Yukawa’s p p nuclear interaction 11 Friday, April 27, 12

By the 1960’s, hundreds of particles were discovered that participate in Yukawa’s nuclear interaction • ± ± − • η ± − − − • π ± − − − − ± − − • / ψ • π • • − − − − − − ∗ ± • χ • π • φ • • − − − − • χ • η • ρ • ± ∗ • − − − − • • ρ ± • • • − − − • χ • ρ ∗ ± • − − − − • η • ω • − ∗ • • − − − − • η ′ − • ψ η ± − ∗ • The Particle Zoo − − − − − • ψ • • π ± • ∗ sJ − • • − ∗ ± • sJ − − − − χ • φ ∗ • − − − − − • • φ ∗ • − − ± • η − − − − ± − − − − • ψ • • π • − ± − − − • ρ • ± • • − − − − ± • η • ψ • • ∗ − • − − − − • π ρ − • ± − cb ub • • ∗ − • − − • • − ∗ − • • Many ad hoc concepts − − − • − ∗ − − − − • π • ∗ • − − − − − − • η π • ψ ∗ ∗ • ± • introduced to explain decay ∗ • − − − − − • ω − ± − − ρ ∓ − − − − − • • φ • ∗ − − patterns, masses, etc η − − • ρ ∗ − • − − − − − • • η • • χ − • η ∗ • • χ − − ρ ∗ sJ • χ ′ • • ± − − − • ± − • ± − − − − − ρ − • ± − • χ − − • • − • ∗ • Isospin • χ − − − − • π ρ ∗ ± − • − • χ − ∗ • − − − • ± ∗ − − − • − • η • − − − • − − − • ω ± − − − • − − − • ω ∗ • • ‘Strangeness’ ± ∗ • ∗ ± • Charm 12 Friday, April 27, 12

Interesting patterns for particles of similar mass ‘Strangeness’ Charge Groups of 8 Groups of 10 Groups of 1 η 0 Suggestive of underlying mathematical structure 13 Friday, April 27, 12

This underlying structure is related to the mathematics of symmetries 14 Friday, April 27, 12

Suppose 31 flavors was really ‘3 flavors’ fUdge ripple cookie Dough Strawberry You and I decide to buy two sundaes but the flavors are chosen at random Mine Yours How many possibilities? 3 3 = 9 × flavors flavors 15 Friday, April 27, 12

fUdge ripple cookie Dough Strawberry Suppose instead that both are for me Mine Also mine = 9 3 3 × flavors flavors These 2 Less than 9 distinct U D combinations are combinations... effectively the same D U how many? 16 Friday, April 27, 12

fUdge ripple cookie Dough Strawberry Mine Also mine We can enumerate all possibilities = 9 3 3 × flavors flavors UU UD+DU DD US+SU = 6 SS DS+SD This set of 6 possibilities is closed under relabeling of flavors 17 Friday, April 27, 12

fUdge ripple cookie Dough Strawberry Mine Also mine Mathematicians like to divide the 9 combinations into groups that do not mix with one another under relabeling = 9 3 3 × flavors flavors UU UD+DU UD-DU DD US+SU US-SU SS DS+SD DS-SD Symmetric under interchange Antisymmetric under interchange 18 Friday, April 27, 12

fUdge ripple cookie Dough Strawberry Mine Also mine Mathematicians like to divide the 9 combinations into groups that do not mix with one another under relabeling = 9 3 3 × flavors flavors UU UD+DU UD-DU DD US+SU US-SU SS DS+SD DS-SD Symmetric under interchange Antisymmetric under interchange 3 6 + = 9 18 Friday, April 27, 12

fUdge ripple cookie Dough Strawberry Mine Also mine If we have a set of states made of 2 things that come in 3 flavors = 9 3 3 × flavors flavors 3 x 3 = 6 + 3 Expect a grouping according to this is not quite what we see in the particle zoo.... 19 Friday, April 27, 12

Interesting patterns for particles of similar mass ‘Strangeness’ Charge Groups of 8 Groups of 10 Groups of 1 η 0 Suggestive of underlying mathematical structure 20 Friday, April 27, 12

Interesting patterns for particles of similar mass 10 + 8 + 8 + 1 = 27 = 3 x 3 x 3 ‘Strangeness’ Charge Groups of 8 Groups of 10 Groups of 1 η 0 Suggestive of underlying mathematical structure 20 Friday, April 27, 12

Interesting patterns for particles of similar mass 10 + 8 + 8 + 1 = 27 = 3 x 3 x 3 ‘Strangeness’ Charge Groups of 8 Groups of 10 Groups of 1 η 0 Suggestive of underlying mathematical structure 20 Friday, April 27, 12

Interesting patterns for particles of similar mass 10 + 8 + 8 + 1 = 27 = 3 x 3 x 3 ‘Strangeness’ Charge Groups of 8 Groups of 10 Groups of 1 η 0 Suggestive of underlying mathematical structure 20 Friday, April 27, 12

fUdge ripple cookie Dough Strawberry You and I invite a friend to join us for the sundae... Now how many combinations? Mine Yours Our friend’s 3 3 3 = 27 × × flavors flavors flavors 21 Friday, April 27, 12

Permutation Groups UUU, UUD, UDU, DUU, UUS, USU, SUU Consider all 27 possible DDD, DDU, DUD, UDD, DDS, DSD, SDD, permutations of sundaes SSS, SSU, SUS, USS, SSD, SDS, DSS, UDS, USD, DUS, DSU, SUD, SDU Mathematicians divide the 27 combinations into groups that do not mix under relabeling 3 x 3 x 3 = 27 = 10 + 8 + 8 + 1 UUU+DDD+SSS 10 ‘symmetric’ combinations UUU UUD+... USS+... DDD UUS+... DDS+... UDS+... SSS UDD+... DSS+... 22 Friday, April 27, 12

Interesting patterns for particles of similar mass ‘Strangeness’ Charge Groups of 8 Groups of 10 27 = 10 + 8 + 8 + 1 Particles display pattern consistent being made of three things that come in three flavors 23 (mesons too if you think of 3 as product of 3 0 s ) Friday, April 27, 12

‘The Eightfold Way’ Murray ‘Strangeness’ Charge Gell-Mann Suppose each of these particles is composed of 3 ‘quarks’ 3 ‘flavors’ of quark up, down, strange Very useful organizational principle that gives order to the ‘particle zoo’ 24 Friday, April 27, 12

‘The Eightfold Way’ Murray Gell-Mann The Ω − was not previously known Gell-Mann predicted its existence and its mass 25 Friday, April 27, 12

‘The Eightfold Way’ Murray ‘Strangeness’ Charge Gell-Mann Quarks introduced as a mathematical tool suggested by symmetry structure and particle mass patterns Are they real? 26 Friday, April 27, 12

Is my favorite particle fundamental or composite? γ γ e − e − e − e − p + p + e − e − Appears that energy is Energy is conserved not conserved Scattering is ‘elastic’ Scattering is ‘inelastic’ 27 Friday, April 27, 12

Is my favorite particle fundamental or composite? γ e − e − Some initial energy deposited in proton p + structure p + Appears that energy is γ e − e − not conserved Scattering is ‘inelastic’ u u d p + 28 Friday, April 27, 12