The Fermi Model BNL HET amp; NT PAGE费米型 BNL HET amp；NT页.pptVIP

Sally Dawson, BNLIntroduction to the Standard ModelTASI, 2006 Introduction to the Standard Model Review of the SU(2) x U(1) Electroweak theory Experimental status of the EW theory Constraints from Precision Measurements Theoretical problems with the Standard Model Beyond the SM Why are we sure there is physics BSM? What will the LHC and Tevatron tell us? Lecture 1 Introduction to the Standard Model Just the SU(2) x U(1) part of it…. Some good references: Chris Quigg, Gauge Theories of the Strong, Weak, and Electromagnetic Interactions Michael Peskin, An Introduction to Quantum Field Theory Sally Dawson, Trieste lectures, hep-ph/9901280 Science Timeline Large Hadron Collider (LHC) proton-proton collider at CERN (2007) 14 TeV energy 7 mph slower than the speed of light cf. 2TeV @ Fermilab ( 307 mph slower than the speed of light) Typical energy of quarks and gluons 1-2 TeV LHC is Big…. ATLAS is 100 meters underground, as deep as Big Ben is tall The accelerator circumscribes 58 square kilometers, as large as the island of Manhattan LHC Will Require Detectors of Unprecedented Scale What we know The photon and gluon appear to be massless The W and Z gauge bosons are heavy MW=80.404 ? 0.030 GeV MZ =92.1875 ? 0.0021 GeV There are 6 quarks Mt=172.5 ?2.3 GeV Mt all the other quark masses There appear to be 3 distinct neutrinos with small but non-zero masses The pattern of fermions appears to replicate itself 3 times Why not more? Abelian Higgs Model Why are the W and Z boson masses non-zero? U(1) gauge theory with single spin-1gauge field, A? U(1) local gauge invariance: Mass term for A would look like: Mass term violates local gauge invariance We understand why MA = 0 Abelian Higgs Model, 2 Add complex scalar field, ?, with charge –e: Where L is invariant under local U(1) transformations: Abelian Higgs Model, 3 Case 1: ?2 0 QED with MA=0 and m?=? Unique minimum at ?=0 Abelian Higgs Model, 4 Case 2: ?2 0 Minimum energy state at: Abelian Hi