rpp2010-rev-standard-model

Rpp2010-rev-standard - 10 Electroweak model and constraints on new physics 1 10 ELECTROWEAK MODEL AND CONSTRAINTS ON NEW PHYSICS Revised Study 10.1

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
10. Electroweak model and constraints on new physics 1 10. ELECTROWEAK MODEL AND CONSTRAINTS ON NEW PHYSICS Revised November 2009 by J. Erler (U. Mexico) and P. Langacker (Institute for Advanced Study). 10.1 Introduction 10.2 Renormalization and radiative corrections 10.3 Low energy electroweak observables 10.4 W and Z boson physics 10.5 Precision flavor physics 10.6 Experimental results 10.7 Constraints on new physics 10.1. Introduction The standard electroweak model (SM) is based on the gauge group [1] SU(2) × U(1), with gauge bosons W i μ , i =1 , 2 , 3, and B μ for the SU(2) and U(1) fac- tors, respectively, and the corresponding gauge coupling constants g and g ± . The left-handed fermion Felds of the i th fermion family transform as doublets Ψ i = µ ν i ± i and µ u i d ± i under SU(2), where d ± i j V ij d j ,and V is the Cabibbo- Kobayashi-Maskawa mixing matrix. (Constraints on V and tests of universality are d i s cu s s edinR e f .2andinth eS e c t i onon“Th eCKMQu a rk -M ix in gM a t r .Th e extension of the formalism to allow an analogous leptonic mixing matrix is discussed in the Section on “Neutrino Mass, Mixing, and ±lavor Change”.) The right-handed Felds are SU(2) singlets. In the minimal model there are three fermion families and a single complex Higgs doublet φ ³ φ + φ 0 ´ which is introduced for mass generation. After spontaneous symmetry breaking the Lagrangian for the fermion Felds, ψ i ,is L F = X i ψ i µ i ± m i gm i H 2 M W ψ i g 2 2 X i Ψ i γ μ (1 γ 5 )( T + W + μ + T W μ i e X i q i ψ i γ μ ψ i A μ g 2cos θ W X i ψ i γ μ ( g i V g i A γ 5 ) ψ i Z μ . (10 . 1) θ W tan 1 ( g ± /g ) is the weak angle; e = g sin θ W is the positron electric charge; and A B cos θ W + W 3 sin θ W is the (massless) photon Feld. W ² ( W 1 iW 2 ) / 2and Z ≡− B sin θ W + W 3 cos θ W are the massive charged and neutral weak boson Felds, K. Nakamura et al. ,JPG 37 , 075021 (2010) (http://pdg.lbl.gov) July 30, 2010 14:36
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 10. Electroweak model and constraints on new physics respectively. T + and T are the weak isospin raising and lowering operators. The vector and axial-vector couplings are g i V t 3 L ( i ) 2 q i sin 2 θ W , (10 . 2 a ) g i A t 3 L ( i ) , (10 . 2 b ) where t 3 L ( i ) is the weak isospin of fermion i (+1 / 2for u i and ν i ; 1 / d i and e i )and q i is the charge of ψ i in units of e . The second term in L F represents the charged-current weak interaction [3,4]. For example, the coupling of a W to an electron and a neutrino is e 2 2sin θ W h W μ μ (1 γ 5 ) ν + W + μ νγ μ (1 γ 5 ) e i . (10 . 3) For momenta small compared to M W , this term gives rise to the e±ective four-fermion interaction with the Fermi constant given (at tree level, i.e. , lowest order in perturbation theory) by G F / 2= g 2 / 8 M 2 W .
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 06/07/2011 for the course PHYS 4132 taught by Professor Kutter during the Spring '11 term at University of Florida.

Page1 / 54

Rpp2010-rev-standard - 10 Electroweak model and constraints on new physics 1 10 ELECTROWEAK MODEL AND CONSTRAINTS ON NEW PHYSICS Revised Study 10.1

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online