Many questions in particle physics are related to the existence of particle mass. The “Higgs mechanism,” which consists of the Higgs field and its corresponding Higgs boson, is said to give mass to elementary particles. By “mass” we mean the inertial mass, which resists when we try to accelerate an object, rather than the gravitational mass, which is sensitive to gravity. In Einstein’s celebrated formula E = mc2, the “m” is the inertial mass of the particle. In a sense, this mass is the essential quantity, which defines that at this place there is a particle rather than nothing.
In the history of the universe, particles interacted with the Higgs field just 10-12 seconds after the Big Bang. Before this phase transition, all particles were massless and travelled at the speed of light. After the universe expanded and cooled, particles interacted with the Higgs field and this interaction gave them mass. The BEH mechanism implies that the values of the elementary particle masses are linked to how strongly each particle couples to the Higgs field. These values are not predicted by current theories. However, once the mass of a particle is measured, its interaction with the Higgs boson can be determined.
Over the past few decades, particle physicists have developed an elegant theoretical model (the Standard Model) that gives a framework for our current understanding of the fundamental particles and forces of nature. One major ingredient in this model is a hypotheticals , ubiquitous quantum field that is supposed to be responsible for giving particles their masses This field is called the Higgs field (The Higgs boson is an elementary particle in the Standard Model of particle physics, produced by the quantum excitation of the Higgs field, one of the fields in particle physics theory). As a consequence of wave-particle duality, all quantum fields have a fundamental particle associated with them. The particle associated with the Higgs field is called the Higgs boson.
In 1964, theorists proposed a solution to this puzzle. Independent efforts by Robert Brout and François Englert in Brussels, Peter Higgs at the University of Edinburgh, and others lead to a concrete model known as the Brout-Englert-Higgs (BEH) mechanism. The peculiarity of this mechanism is that it can give mass to elementary particles while retaining the nice structure of their original interactions. Importantly, this structure ensures that the theory remains predictive at very high energy. Particles that carry the weak interaction would acquire masses through their interaction with the Higgs field, as would all matter particles. The photon, which carries the electromagnetic interaction, would remain massless.
This particle is the one missing piece of our present understanding of the laws of nature, known as the Standard Model. This model describes three types of forces: electromagnetic interactions, which cause all phenomena associated with electric and magnetic fields and the spectrum of electromagnetic radiation; strong interactions, which bind atomic nuclei; and the weak nuclear force, which governs beta decay–a form of natural radioactivity–and hydrogen fusion, the source of the sun’s energy. (The Standard Model does not describe the fourth force, gravity.)
“The Higgs particle is connected with the weak force. Electromagnetism describes particles interacting with photons, the basic units of the electromagnetic field”
From experiments, we know that a photon can be no more massive than a thousand-billion-billion-billionth (10 -30) the mass of an electron, and for theoretical reasons, we believe it has exactly zero mass. The W and Z particles, however, have enormous masses: more than 80 times the mass of a proton, one of the constituents of an atomic nucleus.
If one simply postulates that these particles interact with the known elementary particles and have a large mass, the theory is inconsistent.
For example, the Standard Model would predict that the probability of two particles having very high energies colliding with one another would be greater than one, a physical impossibility. To fix this problem, there must be additional particles. The simplest models that explain the masses of the W and Z have only one such particle
We are searching for extensions to the electroweak theory that make it more coherent and more predictive.
“If there is a Higgs boson whose mass is less than that of the Z particle, physicists will discover it over the next two years at the large accelerator in Geneva known as LEP (the Large Electron Positron collider). LEP accelerates electrons and their antimatter twins (positrons) to very high energies, then allows them to collide. If Higgs bosons have larger masses, they might be unveiled at the Fermi National Accelerator Laboratory in Batavia, Ill., by the turn of the century. Otherwise we are very likely to find them at a new accelerator, LHC (the Large Hadron Collider), scheduled to start operation at CERN in 2005. Discovery of the Higgs boson was one of the principal tasks scheduled for the Superconducting Super Collider, which the U.S. Congress canceled in 1993.
“Over the next 15 years, we should begin to find a real understanding of the origin of mass. The interest lies not just in the arcana of accelerator experiments but suffuses everything in the world around us: mass is what determines the range of forces and sets the scale of all the structures we see in nature”.
- American Webpage on Scientific Hibbs Boso
- http://cms.web.cern.ch /news/about_higgs_boson
- Quantum Mechanics and path integrals by Richard P.Feynman and Albert R.Hibbs.
- Path Integrals in Quantum Mechanics , Statistics , Polymer Physics , and Financial Markets.