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

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

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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

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Eilam Gross, WIS, SUSY16


 First Lecture: Higgs Boson 
 Theory and Introduction

Eilam Gross

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Eilam Gross, WIS

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)

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1895 To the useless electron

Eilam Gross, Weizmann Institute of Science 16

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1 8 9 5

$ 1

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2 0 1 2

~$6,000,000,000

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Eilam Gross, WIS

A Detector

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Ensemble of measured interactions in a given proton–proton bunch crossing makes up an “event”

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AT L A S

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3000 Physicists Driven by Curiosity

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A R A R E T- S H I R T

1 1 1 1 5 1 2 This is the most incredible thing that happened to me in my lifetime Peter Higgs 4 July 2012

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eilam gross, WIS

S M H I G G S T H EO R Y

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eilam gross, WIS

Quantum fields are used to create and annihilate particles at (x,t) In order to “create” a particle

  • ne 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

Fields and Particles

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eilam gross, WIS

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). The photon is the guardian of
 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”)

(QED) Field Theory

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ψγ µDµψ = ψγ µ∂µψ + ieψγ µAµψ ψ → eieθ(x,t )ψ

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eilam gross, WIS

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

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eilam gross, WIS

Spontaneous Symmetry Breaking Higgs Potential

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eilam gross, WIS

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”

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eilam gross, WIS

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.

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eilam gross, WIS

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

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The photon eats 
 the Goldstone Boson
 and acquires mass.

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eilam gross, WIS

Eilam Gross

82

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eilam gross, WIS

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)

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The Higgs Mechanism

Higgs (in a snail mail to me):

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eilam gross, WIS

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.

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eilam gross, WIS

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

  • nly its existence! (and it took 47 years to discover it)

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How Elementary Particles Acquire Mass

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gφψψφψ → gφψψ (H + v)ψ = gφψψ Hψ + gφψvψψ mψ = gφψv gφψ ∼ mψ

V


 
 
 The coupling of the Higgs to 
 particles is proportional to the 
 particles’ mass

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How Elementary Particles Acquire Mass

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gφψψφψ → gφψψ (H + v)ψ = gφψψ Hψ + gφψvψψ mψ = gφψv gφψ ∼ mψ


 
 
 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!

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The Standard Model: Quarkd & Leptons

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eilam gross, WIS, November 2011

Branching Ratios

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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)

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

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Higgs @ LEP

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Higgs @ LEP

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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, 
 mH>ECM-MZ-> mH>114 GeV

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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

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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

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L H C L A RG E H A D RO N CO L L I D E R

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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
 council: “LHC is the right
 machine… for the future


  • f CERN”

1997 December CERN
 council approve the single
 stage 14 TeV LHC for 
 completion in 2005

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1st UA1 Z, April 1983

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eilam gross, WIS

Higgs Production @ the LHC

Higgs hardly couples to u & d quarks (which make protons)

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eilam gross, WIS, November 2011

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

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ggF

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eilam gross, WIS, November 2011

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

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VBF

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eilam gross, WIS, November 2011

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

Higgs Production @ the LHC

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AP

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eilam gross, WIS, November 2011

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

Higgs Production @ the LHC

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ttH

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eilam gross, WIS, November 2011

Higgs Production


 
 is x10
 then
 is even
 smaller, yet distinct
 is the smallest and also difficult

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[GeV]

H

M 100 200 300 400 500 1000 H+X) [pb]

  • (pp
  • 2

10

  • 1

10 1 10 = 7 TeV s

LHC HIGGS XS WG 2010

H ( N N L O + N N L L Q C D + N L O E W )

  • p

p qqH (NNLO QCD + NLO EW)

  • pp

WH (NNLO QCD + NLO EW)

  • pp

ZH (NNLO QCD +NLO EW)

  • pp

ttH (NLO QCD)

  • pp
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eilam gross, WIS, November 2011

Higgs Decay Modes

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eilam gross, Bonn, December 2011

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H->bb H->ZZ->4q

For a channel to be usable, we must be able to trigger it Most efficient and clean triggers are photon or lepton based

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The Killing Trigger

For a channel to be usable, we must be able to trigger it Most efficient and clean triggers are photon or lepton based

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Channel Trigger γγ

Diphoton

ττ

Single lepton (+isolated jet),Dilepton

WH

Single lepton

ZH

Single lepton (ATLAS,CMS); Dielectron (CMS)

WW (lνlν) 0-jet

Single lepton (ATLAS, CMS); Dilepton (CMS)

1-jet

Single lepton (ATLAS, CMS); Dilepton (CMS)

VBF*

Single lepton, dilepton

WW** (lνqq) 0-jet

Single lepton

1-jet

Single lepton

ZZ (llll)

Single lepton (ATLAS);
 Single lepton (early data), dilepton (CMS)

ZZ (llνν)

Single lepton (ATLAS); Dilepton (CMS)

ZZ (llqq)

Single lepton

ZZ (llττ) *

Dilepton

* CMS only / ** ATLAS only

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Trigger ripped off the jet channels

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pp

80 µb−1 total (x2) 20 µb−1 60 µb−1 inelastic Jets R=0.4 nj ≥ 1 0.1 < pT < 2 TeV nj ≥ 2 0.3 < mjj < 5 TeV

γ

fid. pT > 25 GeV pT > 100 GeV

W

fid. nj ≥ 0 nj ≥ 1 nj ≥ 2 nj ≥ 3 nj ≥ 4 nj ≥ 5 nj ≥ 6 nj ≥ 7

Z

fid. nj ≥ 0 nj ≥ 1 nj ≥ 2 nj ≥ 3 nj ≥ 4 nj ≥ 0 nj ≥ 1 nj ≥ 2 nj ≥ 3 nj ≥ 4 nj ≥ 5 nj ≥ 6 nj ≥ 7

t¯ t

fid. total nj ≥ 4 nj ≥ 5 nj ≥ 6 nj ≥ 7 nj ≥ 8

t

tot. s-chan t-chan 2.0 fb−1 Wt

VV

tot. ZZ WZ ZZ WZ WW ZZ WZ WW

γγ

fid.

H

fid. H→γγ VBF H→WW ggF H→WW H→ZZ→4ℓ H→ττ total

Vγ

fid. Zγ Zγ W γ

t¯ tW

tot.

t¯ tZ

tot.

t¯ tγ

fid.

Zjj

EWK fid. Zγγ nj = 0 tot. Wγγ nj = 0 tot. VVjj EWK fid. W ±W ± WZ

σ [pb]

10−3 10−2 10−1 1 101 102 103 104 105 106 1011

Theory LHC pp √s = 7 TeV Data 4.5 − 4.9 fb−1 LHC pp √s = 8 TeV Data 20.3 fb−1 LHC pp √s = 13 TeV Data 0.08 − 3.2 fb−1

Standard Model Production Cross Section Measurements

Status: June 2016

ATLAS Preliminary Run 1,2

√s = 7, 8, 13 TeV

Elecroweak measurements are Higgs backgrounds

Good agreement with theory , W, Z, tt become a challenge for theory Systematics dominate

Higgs cross section same order of magnitude as Di-Boson production (WW,WZ,ZZ)

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eilam gross, Bonn, December 2011

ATLAS+CMS Channels Weight

Distinct mass regions γγ, lνlν, 4l, llνν+llqq

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H->γγ H->WW->lυlυ H

  • >

Z Z

  • >

4 l H->ZZ->llυυ