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The Discovery of the Higgs Boson. Christian Smith Charles Jay Jeremy Umphress Robert Farrar. From Theory To History:. Physics 3313-001 Dr. Jaehoon Yu University of Texas at Arlington December 4, 2013.

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The Discovery of the Higgs Boson

Christian Smith

Charles Jay

Jeremy Umphress

Robert Farrar

From Theory To History:

Physics 3313-001

Dr. Jaehoon Yu

University of Texas at Arlington

December 4, 2013

Today’s Presentation:

  • The History of the Higgs Particle

    • The need for broken symmetry

    • The Higgs mechanism as the solution

    • Complications with theory

  • Experimental Process

    • How to look for the Higgs

    • Zoning in on the mass of the Higgs

    • Criterion for the Higgs

    • Discovery of the Higgs boson

  • The Discovery and Future

    • What this discovery means for Physics

    • What is next?

Why Do We Need Broken Symmetry?

  • If everything were symmetric, all the particles would be canceled out by their anti-particles.

  • The imbalance allows the existence of the particles that constitute our existence.

  • What breaks this symmetry of particle – anti-particle creation?

The Higgs Mechanism

  • The original theory of broken symmetry was proposed by Sheldon Glashow in 1960. Though he was unsure of what caused this breakage.

    • “The mass of the charged intermediaries must be greater than the K-meson mass, but the photon mass is zero-surely this is the principle stumbling block in any pursuit of the analogy between hypothetical vector mesons and photons. It is a stumbling block we must overlook.” (Glashow)

  • Roughly four years later Higgs, Englert and Brout propose a mechanism that would account for this breaking of symmetry.

The Higgs Mechanism (cont.)

  • In the standard model of Physics all our elementary particles are massless.

  • We know from experimentation that they have mass, where does this mass come from?

  • Higgs-Englert-Brout Mechanism would give these particles their mass, thus allowing for the breaking of symmetry.

  • How do the objects interact with the Higgs field?

  • How do they obtain their mass from this field?

The Higgs Mechanism (cont.)

  • At the Big Bang, all the fundamental particles were pure energy.

  • Within the first second, the universe cooled and the Higgs field was formed.

  • Each of the fundamental particles interact with this field differently, slowing them down.

  • The greater the interaction with the Higgs field, the greater the mass.

  • Particles like photons and gluons do not interact with the Higgs field, while W and Z bosons and top quarks interact heavily with the Higgs Field.

Complications With The Theory

  • Though the mechanism had been proposed, the Higgs field must have an associated particle in order to observe its existence.

  • The mass of this particle was not determined in the theory, which means that the mass of the Higgs boson could vary widely.

How To Generate A Higgs

  • Particles must be massive enough to have enough energy to form Higgs Bosons.

  • Top Quarks are the preferred particles, but are not commonly found in nature.

  • Top quarks can be formed through the collision of gluons.

  • Gluons and up and down quarks are found in protons, so by the collision of protons we can collide gluons.

  • How do we see the Higgs?

Higgs Production

  • Two gluons are collided to form top quarks which are then used to generate a Higgs.

  • Higgs decays into W-boson pair. Which then decays to photons.

  • Higgs decays in bottom quark pair. Which then decays to photons.

How To Look For The Higgs (cont.)

  • Accounting for events and what could generate them.

    • Formation of γγ, photon pairs. (UC Berkley)

    • Formation of 4 electrons or muons. (UC Berkley)

    • Formation of W-Boson Pairs. (Dreiner)

  • Determining the mass of the particle that would generate the different events.

  • Ruling out known particles that would generate other events.

  • Looking for the “anomaly.” (BBC)

The Possible Mass Of The Higgs

LEP (2003)





The Anomaly

  • 2012 data run was focused in the mass range between 114 GeV and 145 GeV.

  • Data collected from both CMS (Bottom Left) and ATLAS (Bottom Right) show anomalies between 120-130 GeV.

Matching The Higgs To Results

  • Higgs must have enough mass to create a bottom quark pair, photon pair or W-Boson pair.

  • Higgs must have an integer spin of zero. So angular distribution of products is equally probable in all directions. (CERN)

  • Must have positive parity. Does not distinguish between left and right. (CERN)

  • Must be electrically neutral (unaffected by electric or magnetic fields).

Discovery Of The Higgs Particle

  • On July 04, 2012 CERN announced the results of the data that had been collected between 2010-11 and analyzed.

  • The ATLAS and CMS experiments independently observed statistical anomalies at 126 GeV (ATLAS) and 124 GeV (CMS).

  • The results showed a 5-sigma standard deviation (1 in 350 million), this means that there was a 1 in 350 million possibility that the event was caused by background noise. (CMS-CERN)

Future Of The Higgs

  • Increase in our understanding of the fundamental particles and their creation.

  • Other theories propose the existence of multiple Higgs, leading into further exploration of nature.

  • Coupling between matter and the Higgs and the Higgs and dark matter could allow for the observation of dark matter.

What We Have Covered Today

  • The History of the Higgs Particle

    • The need for broken symmetry for the existence of particles.

    • The Higgs mechanism as the solution to break the symmetry

    • Complications with theory with the lack of mass of the Higgs

  • Experimental Process

    • How to look for the Higgs by finding the results of its decompositions

    • Zoning in on the mass of the Higgs by various experiments

    • Criterion for the Higgs particle: spin, parity and mass

    • Discovery of a Higgs boson

  • The Discovery and Future

    • Furthered understanding of nature

    • Study of dark matter and existence of other Higgs Bosons.

Q & A


  • Abbiendi, G, et al. “Search for the Standard Model Higgs Boson at LEP.” ALEPH, DELPHI, L3, OPAL Collaborations. (2003)

  • BBC. Jan 09, 2012. “The Hunt For The Higgs.”

  • CERN Press Office. March 14, 2013. “New Results Indicate that particle discovered at CERN is a Higgs boson.”

  • CMS Experiment, CERN. July 04, 2012.

  • Dreiner, H. “Particle Physics: A Higgs is a Higgs.” Nature Physics. NS-9. 268-9. (2013)

  • FermiLab Press Release. July 26, 2010. “FermiLab experiments narrow allowed mass range for Higgs Boson.”

  • FermiLab Press Release. August 22, 2011. “LHC experiments eliminate more Higgs hiding spots.”

  • Glashow, S. “Partial Symmetries of Weak Interactions.” Nuclear Physics. NP-22. 579-588. (1961)

  • UC Berkley. July 13, 2012. “The Higgs Boson Explained.”

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