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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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from theory to history

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
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
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 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
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 cont1
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
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
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
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
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
The Possible Mass Of The Higgs

LEP (2003)





the anomaly
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
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
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
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
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.
  • 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.”