![]() There are also other proposals, many of them more exotic. The simplest models that explain the masses of the W and Z have only one such particle: the Higgs boson. ( 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. If one simply postulates that these particles interact with the known elementary particles and have a large mass, the theory is inconsistent. "The huge masses of the W and Z particles is a puzzle. 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. ![]() 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. In many respects, these particles are similar to photons. In a parallel way, the modern theory of weak interactions describes particles (the W and Z particles) interacting with electrons, neutrinos, quarks and other particles. Electromagnetism describes particles interacting with photons, the basic units of the electromagnetic field. "The Higgs particle is connected with the weak force. It seems to provide a complete description of the natural world down to scales on the order of one- thousandth the size of an atomic nucleus. In the past few years, in high-energy experiments at CERN, the European laboratory for particle physics, near Geneva and at the Stanford Linear Accelerator Center (SLAC), physicists have made precision tests of the Standard Model. Since the 1970s, however, scientists have come to understand the strong and weak forces almost equally well. Until relatively recently, it was the only one which we understood well. "In our daily lives, electromagnetism is the most familiar of these forces. (The Standard Model does not describe the fourth force, gravity.) 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. This particle is the one missing piece of our present understanding of the laws of nature, known as the Standard Model. "Much of today's research in elementary particle physics focuses on the search for a particle called the Higgs boson. One of the main aims of particle physics over the next couple of decades is to prove once and for all the existence or nonexistence of the Higgs boson."Īnother, more extensive response comes from Howard Haber and Michael Dine, both of whom are professors of physics at the Santa Cruz Institute for Particle Physics at the University of California at Santa Cruz: We have not yet truly proved that the Higgs boson exists, however. In other words, if we assume that the Higgs boson exists, we can infer its mass based on the effect it would have on the properties of other particles and fields. We can even take all our data on particle physics data and interpret them in terms of the mass of a hypothetical Higgs boson. "Because the Higgs field would be responsible for mass, the very fact that the fundamental particles do have mass is regarded by many physicists as an indication of the existence of the Higgs field. The particle associated with the Higgs field is called the Higgs boson. As a consequence of wave-particle duality, all quantum fields have a fundamental particle associated with them. One major ingredient in this model is a hypothetical, ubiquitous quantum field that is supposed to be responsible for giving particles their masses (this field would answer the basic question of why particles have the masses they do-or indeed, why they have any mass at all). ![]() "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. Stephen Reucroft in the Elementary Particle Physics group at Northeastern University gives this introductory reply:
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