1964 PRL symmetry breaking papers

In 1964 three teams proposed related but different approaches to explain how mass could arise in local gauge theories. These three, now famous, papers were written by Robert Brout and François Englert,[1][2] Peter Higgs,[3] and Gerald Guralnik, C. Richard Hagen, and Tom Kibble,[4][5] and are credited with the prediction of the Higgs boson and Higgs mechanism which provides the means by which gauge bosons can acquire non-zero masses in the process of spontaneous symmetry breaking.[6] The mechanism is the key element of the electroweak theory that forms part of the Standard Model of particle physics, and of many models, such as the Grand Unified Theory, that go beyond it. The papers that introduce this mechanism were published in Physical Review Letters (PRL) and were each recognized as milestone papers by PRL's 50th anniversary celebration.[7] Additionally, all of the six physicists were awarded the 2010 J. J. Sakurai Prize for Theoretical Particle Physics for this work.[8] Presently, Fermilab's Tevatron and the Large Hadron Collider at CERN are searching for a particle that will constitute evidence for this significant discovery.

Contents

Introduction

A gauge theory of elementary particles is a very attractive potential framework for constructing the ultimate theory. Such a theory has the very desirable property of being potentially renormalizable—shorthand for saying that all calculational infinities encountered can be consistently absorbed into a few parameters of the theory. However, as soon as one gives mass to the gauge fields, renormalizability is lost, and the theory rendered useless. Spontaneous symmetry breaking is a promising mechanism, which could be used to give mass to the vector gauge particles. A significant difficulty which one encounters, however, is Goldstone's theorem, which states that in any quantum field theory which has a spontaneously broken symmetry there must occur a zero-mass particle. So the problem arises—how can one break a symmetry and at the same time not introduce unwanted zero-mass particles. The resolution of this dilemma lies in the observation that in the case of gauge theories, the Goldstone theorem can be avoided by working in the so-called radiation gauge. This is because the proof of Goldstone's theorem requires manifest Lorentz covariance, a property not possessed by the radiation gauge.

Manifest covariance overview

Most students who have taken a course in electromagnetism have encountered the Coulomb potential. It basically states that two charged particles attract or repel each other by a force which varies according to the inverse square of their separation. This is fairly unambiguous for particles at rest, but if one or the other is following an arbitrary trajectory the question arises whether one should compute the force using the instantaneous positions of the particles or the so-called retarded positions. The latter recognizes that information cannot propagate instantaneously, rather it propagates at the speed of light. Now the radiation gauge says that one uses the instantaneous positions of the particles, but doesn't violate causality because there are compensating terms in the force equation. In contrast, the Lorenz gauge imposes manifest covariance (and thus causality) at all stages of a calculation. Predictions of observable quantities are identical in the two gauges, but the radiation gauge formulation of quantum field theory conveniently avoids Goldstone's theorem.[9]

Combined contributions

Each of these papers is unique and demonstrates different approaches to showing how mass arise in gauge particles. Over the years, the differences between these papers are no longer widely understood, due to the passage of time and acceptance of end-results by the particle physics community. A study of citation indices is interesting—more than 40 years after the 1964 publication in Physical Review Letters there is little noticeable pattern of preference among them, with the vast majority of researchers in the field mentioning all three milestone papers.

See also

References

  1. ^ F. Englert, R. Brout (1964). "Broken Symmetry and the Mass of Gauge Vector Mesons". Physical Review Letters 13 (9): 321–323. Bibcode 1964PhRvL..13..321E. doi:10.1103/PhysRevLett.13.321. 
  2. ^ R. Brout, F. Englert (1998). "Spontaneous Symmetry Breaking in Gauge Theories: A Historical Survey". arXiv:hep-th/9802142 [hep-th]. 
  3. ^ P.W. Higgs (1964). "Broken Symmetries and the Masses of Gauge Bosons". Physical Review Letters 13 (16): 508–509. Bibcode 1964PhRvL..13..508H. doi:10.1103/PhysRevLett.13.508. 
  4. ^ G.S. Guralnik, C.R. Hagen, T.W.B. Kibble (1964). "Global Conservation Laws and Massless Particles". Physical Review Letters 13 (20): 585–587. Bibcode 1964PhRvL..13..585G. doi:10.1103/PhysRevLett.13.585. 
  5. ^ G.S. Guralnik (2009). "The History of the Guralnik, Hagen and Kibble development of the Theory of Spontaneous Symmetry Breaking and Gauge Particles". International Journal of Modern Physics A 24 (14): 2601–2627. arXiv:0907.3466. Bibcode 2009IJMPA..24.2601G. doi:10.1142/S0217751X09045431. 
  6. ^ T.W.B. Kibble (2009). "Englert–Brout–Higgs–Guralnik–Hagen–Kibble mechanism". Scholarpedia 4 (1): 6441. doi:10.4249/scholarpedia.6441. http://www.scholarpedia.org/article/Englert-Brout-Higgs-Guralnik-Hagen-Kibble_mechanism. 
  7. ^ M. Blume, S. Brown, Y. Millev (2008). "Letters from the past, a PRL retrospective (1964)". Physical Review Letters. http://prl.aps.org/50years/milestones#1964. Retrieved 2010-01-30. 
  8. ^ "J. J. Sakurai Prize Winners". American Physical Society. 2010. http://www.aps.org/units/dpf/awards/sakurai.cfm. Retrieved 2010-01-30. 
  9. ^ G.S. Guralnik, C.R. Hagen, T.W.B. Kibble (1968). "Broken Symmetries and the Goldstone Theorem". In R. L. Cool, R. E. Marshak. Advances in Particle Physics. 2. Interscience Publishers. pp. 567–708. ISBN 0470170573. http://www.datafilehost.com/download-7d512618.html. 

Further reading

External links