First Lecture: Higgs Boson Theory and Introduction Eilam Gross - PowerPoint PPT Presentation


 First Lecture: Higgs Boson 
 Theory and Introduction Eilam Gross 1 Eilam Gross, WIS, SUSY16

About your Lecturer • Eilam Gross, eilam.work@gmail.com • Prof of Particle Physics @ the Weizmann Institute of Science, Rehovot, Israel • Member of the ATLAS collaboration @ CERN • Main Interests : • DATA Analysis (statistics of HEP) • Higgs Physics (Standard Model and Beyond the Standard Model) 2 Eilam Gross, WIS

1895 To the useless electron Eilam Gross, Weizmann Institute of Science 16

1 8 9 5 0 0 1 $

2 0 1 2 ~$ 6,000,000,000

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A Detector Ensemble of measured interactions in a given proton–proton bunch crossing makes up an “event” 7 Eilam Gross, WIS

AT L A S

3000 Physicists Driven by Curiosity

This is the most incredible thing that A R A R E T- S H I R T happened to me in my lifetime Peter Higgs 4 July 2012 0 2 1 5 1 1 0 1 1

S M H I G G S T H EO R Y eilam gross, WIS

Fields and Particles Quantum fields are used to create and annihilate particles at (x,t) In order to “create” a particle one needs to invest an energy equals to its mass E=mc2 The transition of a particle from one (x,t) to another, is called radiation eilam gross, WIS 12

(QED) Field Theory QED was developed in 
 the first half of the 20th 
 century to describe the interaction of 
 matter with light (photons and electrons) QED is based on the phase U(1) symmetry 
 (which ensures conservation of electric charge). ψγ µ D µ ψ = ψγ µ ∂ µ ψ + ie ψγ µ A µ ψ The photon is the guardian of 
 ψ → e ie θ ( x , t ) ψ the local gauge symmetry. The symmetry requires that the photon be massless. The symmetry ensures the renormalizability of the theory, the theory is free of infinities 
 (i.e. the theory “does not predict particles doing things more often than always”) eilam gross, WIS 13

Spontaneous Symmetry Breaking Spontaneously Symmetry Breaking was first introduced by Ginzburg & Landau (1950) 
 (in an attempt to explain 
 superconductivity) The physics of the system 
 (Lagrangian) posses some 
 exact symmetry, but the 
 vacuum (ground state) breaks 
 this symmetry eilam gross, WIS 14

Spontaneous Symmetry Breaking Higgs Potential eilam gross, WIS 15

Spontaneous Symmetry Breaking Nambu (1960) proposed for the first time that SSB is the source of fermion masses in elementary particle physics: “the existence of such a condensate (scalar field) would break the symmetry of the model..... in particle physics, would be a non-Abelian group containing the U(1) group associated with electric charge conservation as a subgroup” eilam gross, WIS 16

Spontaneous Symmetry Breaking Goldstone, Salam and Weinberg (1962) prove formally that massless Bosons must occur whenever a symmetry is broken (Goldstone Theorem). No such massless Bosons were observed experimentally. eilam gross, WIS 17

Spontaneous Symmetry Breaking Peter Higgs (Phys. Lett. July 1964) develops the mechanism by which the massless Goldstone Boson is “eaten” by the photon and the photon becomes massive -> short range (weak) interaction The photon eats 
 the Goldstone Boson 
 and acquires mass. eilam gross, WIS 18

eilam gross, WIS 82 Eilam Gross

The Higgs Mechanism Higgs sends a 3 pages paper to Physics 
 Letter, the paper is rejected. Higgs adds an epilogue to the paper: “it is worth noting that an essential feature of this type of theory is the prediction of incomplete multiplets of scalar and vector bosons” and sends the revised version to PRL. Higgs: “ The referee who, I discovered later, was Nambu, drew my attention to a paper by Englert and Brout that they had just published in Physical Review Letters”. Higgs is asked to cite Englert & Brout and the paper is accepted (August 1964) eilam gross, WIS 20

The Higgs Mechanism Higgs (in a snail mail to me): eilam gross, WIS 21


 
 The Higgs Mechanism Higgs (in a snail mail to me): 
 In my first paper I outlined how to evade the Goldstone theorem. 
 Englert & Brout showed how a gauge field interaction turns Goldstone massless bosons (elementary OR composite) into helicity-0 states of massive spin-1 particles. They strated from Feynmann diagrams and didn’ t discuss the remaining massive spin-0 particles. 
 In my second paper I used Lagarangian field theory explicitly with elementary scalar fields (a‘ la Goldstone) coupled to a gauge field, so the massive spin-0 boson was an obvious feature, to which I drew attention. eilam gross, WIS 22

The Birth of the Standard Model Glashow (1961) suggests that the symmetry of the 
 Electro-Weak interaction is SU(2)xU(1) and is broken to U(1) em. But Glashow puts the masses of the force carriers by hand and his theory is therefore non-renormalizable Weinberg (1967) implements Higgs mechanism to 
 Glashow’ s SU(2)xU(1) and writes the second most quoted paper in the history of particle phsyics (>9000 citations). Weinberg predicts that the mass of the weak interaction force carriers is mW=80 GeV and mZ=90 GeV , but it took another 14 years to confirm it experimentally. Yet, the mass of the Higgs Boson was NOT predicted by theory only its existence! (and it took 47 years to discover it) eilam gross, WIS 23


 
 
 How Elementary Particles Acquire Mass g φψ ψφψ → g φψ ψ ( H + v) ψ = g φψ ψ H ψ + g φψ v ψψ m ψ = g φψ v g φψ ∼ m ψ The coupling of the Higgs to 
 particles is proportional to the 
 V particles’ mass eilam gross, WIS 24


 
 
 How Elementary Particles Acquire Mass g φψ ψφψ → g φψ ψ ( H + v) ψ = g φψ ψ H ψ + g φψ v ψψ m ψ = g φψ v g φψ ∼ m ψ The coupling of the Higgs to 
 particles is proportional to the 
 particles’ mass The Higgs Boson production 
 and decay is determined 
 by its coupling The Higgs Boson will therefore 
 decay with a higher probability 
 to the heaviest particle 
 kinematically available The Higgs Mass is unknown! eilam gross, WIS 25

The Standard Model: Quarkd & Leptons eilam gross, WIS 26

Branching Ratios eilam gross, WIS, November 2011 27

Higgs Production The Higgs Boson is a quanta of the Higgs field. To produce a Higgs Boson one needs an energy which at least equals its (unknown) mass Protons and electrons are easy to produce and accelerate. Allas, the Higgs hardly couples to electrons or the light quarks which make the proton (up and down quarks) eilam gross, WIS 28

T H E 1 9 7 6 I G N O B E L PA P E R

Higgs @ LEP eilam gross, WIS 30

Higgs @ LEP May 1981 - the LEP (Large Electron Positron Collider) project is approved November 1989 - first collision recorder by OPAL @LEP November 2000, 11 years after, the LEP collider is shut dow The Higgs was not discovered up to 
 the maximum energy mass available 
 at LEP, and a lower bound 
 was put on its mass, 
 m H >ECM-M Z -> m H >114 GeV eilam gross, WIS 31

L E P L E G A C Y - 1 1 5 G E V H I G G S ? H A R D T O G I V E U P O N T H AT O N E … . . CERN-EP/2001-095 18-Dec-2001

L E P L E G A C Y - 1 1 5 G E V H I G G S ? H A R D T O G I V E U P O N T H AT O N E … . . CERN-EP/2001-095 18-Dec-2001

L H C L A RG E H A D RO N CO L L I D E R eilam gross, WIS

First LHC Birds In 1977, during talks about the LEP1983 project, it was already mentioned that the “new” tunnel could also host a hadron (pp) collider in the large future 1983 - A “dirty” Hadron collider can actually make a great discovery. 
 UA1 and UA2 @CERN discover 
 the W and the Z 1991 December CERN 
 1st UA1 Z, April 1983 council: “LHC is the right 
 machine… for the future 
 of CERN” 1997 December CERN 
 council approve the single 
 stage 14 TeV LHC for 
 completion in 2005 eilam gross, WIS 35

Higgs Production @ the LHC Higgs hardly couples to u & d quarks (which make protons) eilam gross, WIS 36

Higgs Production @ the LHC Higgs hardly couples to u & d quarks (which make protons) To produce a Higgs Boson in P-P collisions 4 processes are used: ggF , VBF , Associate Production and ttH ggF eilam gross, WIS, November 2011 37

Higgs Production @ the LHC Higgs hardly couples to u & d quarks (which make protons) To produce a Higgs Boson in P-P collisions 4 processes are used: ggF , VBF , Associate Production and ttH VBF eilam gross, WIS, November 2011 38

Higgs Production @ the LHC Higgs hardly couples to u & d quarks (which make protons) To produce a Higgs Boson in P-P collisions 4 processes are used: ggF , VBF , Associate Production and ttH AP eilam gross, WIS, November 2011 39

Higgs Production @ the LHC Higgs hardly couples to u & d quarks (which make protons) To produce a Higgs Boson in P-P collisions 4 processes are used: ggF , VBF , Associate Production and ttH ttH eilam gross, WIS, November 2011 40